138 Chapter 10 Figure 10.29 Histological and immunohistochemical demonstration of ankylosis in a secondarily retained first mandibular molar. The radiograph demonstrates the left first mandibular molar in a child 11 years of age. Note that there appears to be a resorption process occurring interradicularly (red arrow). This process is schematically shown in the drawing to the left of the radiograph. To the right of the radiograph, three histological sections are shown. The black arrows indicate the borderline between dentin and bone tissue. This borderline is characterized by a wavy contour indicating former resorption of dentin. In section B, the arrow points to bone tissue within the dentin. Such ankylotic processes were seen in several parts of the root complex, but there were areas without ankylosis as well. This is demonstrated in the two lower left immunohistochemical sections. In these sections, innervation is marked by NGFR for innervation. In the left section (no ankylosis), brown markings indicate positivity for nerve tissue located along the innermost part of the peri-root sheet. To the right (with ankylosis), the NGFR reaction is disorganized and does not lie near either the bone tissue (uppermost part) or the dentin (lowermost part). Source: Reproduced with kind permission of L. Kieffer-Kristensen. Figure 10.30 Histological section and two radiographs of a secondarily retained first molars. (Left) The histological section demonstrates hypercementosis which is a condition often seen in secondarily retained molars which were found in addition to the ankylotic processes. It could be hypothesized that the hypercementosis is a secondary process occurring on the nonerupting root surface but this cannot be proven. (Upper right) A radiograph of a first molar where hypercementosis and ankylosis were discovered. (Lower right) A maxillary second molar, secondarily retained where hypercementosis also occurred.
Tooth eruption and alveolar bone formation 139 imperfecta. Some teeth are unable to erupt and do not respond to orthodontic treatment. See Chapter 5 for further details. Ectodermal dysplasia Ectodermal dysplasia is also characterized by delayed eruption (Figure 10.43). For further detail, see Chapter 5. Different conditions affect/disrupt different layers in the peri root sheet. These affected layers are the ectomesenchyme/fiber layer and the ectoderm/Malassez’ epithelial layer. Linear scleroderma en coup de sabre This condition can affect the dental arch locally with tooth malformations and/or retardation in eruption (Figure 10.44). For more information, see Chapter 14. Segmental odontomaxillary/mandibular dysplasia Figure 10.31 Arrested eruption of canines and premolars. (Upper) Section Segmental odontomaxillary/mandibular dysplasia arises within a of an orthopantomogram demonstrating arrested eruption of the canine restricted region of the jaw, occurring in both the mandible and and premolars due to a local disruption of the innervation to these teeth in the maxilla. Agenesis may occur in the affected area as well as the maxillary field. These teeth could not be orthodontically removed. The deviations in tooth morphology and eruption deviations. It is green line marked C/P indicates the canine/premolar innervation path to characteristic for the bony tissue to be dysplastic and the alveolar the maxillary field. (Lower) Arrested eruption of the first premolar in the process typically appears swollen. This condition occurs most right side of the mandible. There was no explanation for this eruption commonly in females in the left side of the maxilla. deviation. Note the vertical margin of the alveolar process which indicates ankylosis of the first premolar. The condition is characterized by a localized, dysplastic development of the jaw bone, involving mostly the molar and premolar fields and the teeth within them. There is no explan ation for this regional bone defect. A regional swelling is observed with a broader alveolar process than normal (Figure 10.45). There can be a groove in the palate medial from the defect which represents an area without appositional bone growth (see Figure 10.45). This means that the defect is not resorption of bone but rather nonapposition of bone. In the area of a segmental maxillary/mandibular dysplasia, agenesis of teeth can be observed as well as teeth with a deviant morphology and slow ectopic eruption. In several of these cases, the skin covering the affected jaw area also appears abnormal (Figure 10.46). It is suggested that a dysplastic maxillary region is caused by a defect in the cells migrating to the maxillary and palatal fields. An overview of different examples of segmental odontomaxillary/ mandibular dysplasia is illustrated in Figure 10.46. Eruption and heredity Figure 10.32 Arrested eruption of the incisors, canine, and premolars in It is believed that eruption time and pattern can be inherited. In the right side of the maxilla. In this case, the etiology was an innervation primary failure of tooth eruption with a restricted regional disruption due to mumps in childhood. Note the schematic drawing of the arrested eruption of premolars and molars, the genotype respon innervation to the incisors marked by an orange line (I) and to the canine/ sible for eruption deviation has been discovered. In 25% of cases, premolars marked by a green line (C/P). the eruption disturbance is caused by a single gene mutation affecting parathyroid hormones. There is little other information on specific genotypes related to nonsyndromal eruption deviations.
140 Chapter 10 Figure 10.33 Primary failure of eruption observed in an adult patient. This severe eruption problem occurs in this patient bilaterally. (Upper) Orthopantomogram demonstrating severe internal and external resorption processes in premolars and molars. The etiology behind the occurrence of severe resorption in patients with primary failure of eruption is not known. (Lower left) Intraoral view demonstrating the open bite in the right side. (Lower right) Profile radiograph illustrating the vertical occlusal gap posteriorly from the canines. Figure 10.34 Unilateral primary failure of eruption. The images are identical and demonstrate lateral open bite. Inserted in the right image are schematically drawn innervation paths to the jaw fields. The green lines indicate innervation to the canines and premolars. The blue lines indicate innervation to the molars. Primary failure of eruption can be inherited and can, in such cases, be the result of a mutation in a parathyroid hormone receptor gene. More often, however, the cause is not known. The marking of the innervation might draw attention to a local disturbance in the premolar and molar jaw regions. However, this is speculative at this stage.
Tooth eruption and alveolar bone formation 141 Figure 10.35 Bilateral primary failure of eruption in the primary/early mixed dentition. Inset in the upper right corner is an intraoral photograph of the occlusion in the left side. Inset in the upper left corner is a histological section from a primary molar demonstrating the straight borderline between the bone (B) and the dentin (D). There is no periodontal membrane between the two tissue types. There are also no resorption lines which are usually observed in ankylotic teeth. A periodontal membrane might have existed between the two layers earlier on, but why it has disappeared is not clear. Figure 10.36 Section from an orthopantomogram demonstrating eruption of seemingly rootless mandibular premolars in the right side. Inset is a histological section of the first premolar without a root. The section is immunohistochemically treated with NGFR for marking of innervation. A brown line appears along the apical edge which indicates the presence of a membrane similar to a root membrane with the ability to “lift” the tooth. The enamel is not visible due to decalcification. The explanation behind eruption of a tooth without a root is that the root length in itself does not influence the eruption process but rather the root membrane which is the driving force behind eruption. Figure 10.37 Radiographs demonstrating how severe virus attack involving hospitalization has disturbed tooth formation and eruption. (Left) A dental radiograph from a child who has been treated for meningitis. The canine (yellow star) has the same appearance in this radiograph as it had two years before. The region never developed further. (Center) An orthopantomogram from a child approximately nine years of age. The radiograph has a film error in the left side (black vertical column). In the right side of the maxilla, arrested formation of the incisors, premolars, and first molar appears after a severe virus attack. Note also that the shape of the pulp chamber in the first molar differs from the pulp chamber in the contralateral tooth. The development of the canine and molars continued after a dormant period but maturation in these teeth was delayed in comparison to the contralateral teeth. The incisors and premolars had to be removed. Transplantation of the second mandibular premolars to the right side of the maxilla, combined with orthodontic treatment, was successful. (Right) The dental cast demonstrates the underdevelopment of the maxillary right side. This disturbance in the dentition and in the jaw bone was associated with hearing loss in the right ear due to a severe mumps infection. The hearing loss was partially regained after eight months but will never completely heal. This case demonstrates the interrelationship between regions with the same innervation (ears, jaws, and teeth), and the importance of thorough anamnesis.
142 Chapter 10 Figure 10.40 An orthopantomogram from a child 11 years of age with cherubism (genotype 4p16.3). Note the cyst formation in the mandible and the ectopic eruption of the second mandibular molars. This condition occurs in several degrees of severity. The case demonstrated belongs to the milder category. Eruption problems in both dentitions Figure 10.38 Two radiographs demonstrating nonshedding of the Eruption problems can occur in the primary dentition alone or in primary molars and canines in cases with completely formed the permanent dentition alone. However, it has often been permanent premolars and canines. This condition occurs often in recognized that many eruption problems occur in both denti connection with skin diseases but can also occur without this tions for the same individual (Figures 10.47, 10.48, and 10.49). connection. Furthermore, nonshedding can be a symptom of hyper-IgE This means that there must be some distinct similarities in the syndrome (in which, among other organs, the lungs are involved). two dentitions which have an influence on the eruption distur (Upper) Note the fully formed premolars and canines in the permanent bances. This is a subject that needs further study. dentition at the age of 16 years. These and also the second molars have not erupted. (Inset) Photo of a cheek displaying the affected skin condition. (Lower) In this case, the premolars have also fully formed but have not erupted at the age of 15 years. The second molars are also not erupted. Ectopia of the maxillary canines is present which is a characteristic trait in this condition. Figure 10.39 Sections from orthopantomograms demonstrating that there Figure 10.41 Radiographs from two different children with amelogenesis must be an inheritable factor in cases with nonshedding primary molars imperfecta. (Upper) The two dental films illustrate arrested eruption of the and canines and fully erupted premolars and canines. (Upper) Section canines and incisors in the mandible and maxilla. (Lower) The from an orthopantomogram demonstrating the mandibular dentition in a orthopantomogram illustrates eruption deviations for the permanent female patient 17 years of age. She is sister to the patient in the lower molars, permanent canines, and premolars. radiograph. (Lower) Section from an orthopantomogram demonstrating the mandibular dentition from the brother of the above-mentioned female patient at age 16 years. He has fully formed premolars and nonshedding of the corresponding primary molars.
Tooth eruption and alveolar bone formation 143 Figure 10.42 Section from an orthopantomogram of a child nine years of age with amelogenesis imperfecta. The eruption of the first permanent molar is delayed. Note the very thin enamel. Localized abnormal alveolar bone formation In some cases, a tooth erupts without activating the alveolar bone growth sufficiently, resulting in a deep trench around the tooth. An example is shown in Figure 10.50. The explanation for this phenomenon is unknown. Abnormal growth of the alveolar bone can also occur in just one side of the tooth, as can be observed in juvenile periodontitis. Juvenile periodontitis: theory and heredity Figure 10.44 Photograph and a section from an orthopantomogram of a Juvenile periodontitis is a heritable disease in which alveolar bone child eight years of age with linear scleroderma en coup de sabre. (Upper) is missing anteriorly to the first molars and posteriorly to the Note the alopecia localized to the parasagittal field. In the coup de sabre, maxillary lateral incisors in the initial stages (Figure 10.51). The there is a connective tissue and skin deviation. In this patient, this initial bone defects are not caused by bacterial infection. Later in deviation stretches from the scalp to the face and can also be observed in the process, periodontitis may arise but in the initial stages, the the dentition where tooth morphology is abnormal and eruption abnormality is regarded as a bone growth defect. It occurs during deviations occur. (Lower) A section from an orthopantomogram puberty, when the alveolar bone growth is intensive. The bone demonstrating the abnormal tooth development including eruption level in the alveolar pocket mesial to the first molar, where problems in the parasagittal region. The red arrow demonstrates the juvenile periodontitis is often diagnosed, is slanted. The slanted connection between the scalp and the dentition. Source: Hørberg et al. (2015). Reproduced with permission of Springer. position occurs because the bone level is normal around the second premolar which has had normal alveolar bone growth, while the level is deeper anteriorly to the first molar which has not undergone normal alveolar bone growth. The same slanted bone position can be seen in secondary retention of a molar (see Figure 10.29). Why the first molars do not have the ability to activate the alveolar bone growth is not known. Interestingly, the areas of the initial bone deficit are the same areas where agenesis is most often observed. It can be hypothesized that both condi tions can be caused by disturbances in innervation posteriorly in the developmental field involved. Figure 10.43 Tooth film from a patient approximately 11 years of age with Hypophosphatasia and Papillon–Lefèvre ectodermal dysplasia-like symptoms in the skin, hair, and eyebrows. Note Abnormal alveolar bone formation and/or bone resorption have the arrested eruption of the first permanent molar. also been observed in hypophosphatasia. In this condition, tooth loss occurs in the primary dentition due to a lack of alveolar bone
144 Chapter 10 Figure 10.45 Regional odontodysplasia demonstrated in two different patients. The dysplasia regions are in the left maxillary and left palatine fields. It is characteristic for localized dysplasia to appear as a swollen alveolar bone process. (Upper left) An intraoral photograph from a child approximately six years of age with a dysplasia region in the left maxillary field. (Upper right) A schematic drawing of the jaw fields in the maxilla. (Lower) A dental cast and an intraoral photograph from the same patient at the age of 14 years (left) and 18 years (right). Note the swollen alveolar process in the left side of the maxilla in the cast and note the cavity in the palate most visible on the intraoral photograph. This cavity displays an area of the palate where appositional growth has not occurred. The relationship between the palate and the alveolar bone corresponds to the extent of the field from the alveolar bone to the midpalatal suture (illustrated also in the schematic drawing). Therefore the entire field is affected in this regional odontodysplasia condition. Figure 10.46 Two orthopantomograms demonstrating regional dysplasia Figure 10.47 Sections from two orthopantomograms from the same child in the maxilla and the mandible. (Upper) Eruption problems in the left illustrating arrested eruption in the primary dentition and the permanent maxilla due to regional maxillary dysplasia. (Lower) Regional mandibular dentition. (Upper) At the age of seven years, the radiograph shows that the dysplasia is rare. In this radiograph, the condition is observed in the second primary molar in the mandible was arrested in eruption. (Lower) canine/premolar field in the right side of the mandible where the canine At the age of 12 years, the radiograph demonstrates that the first and first premolar are arrested in eruption and the second premolar is not permanent molar in the mandible is arrested in eruption. present. Inset in the radiograph are examples of skin changes (left) and bone tissue deviation (right) which occur in these regional dysplasia types.
Tooth eruption and alveolar bone formation 145 Figure 10.48 Sections from two orthopantomograms from the same child illustrating arrested eruption in the primary dentition and the permanent dentition. (Left) At the age of eight years, a radiograph was taken of arrested eruption in the second primary molar in the right side of the mandible. (Right) At the age of 14 years, arrested eruption of the first permanent molar in the right side of the maxilla was verified. (Figure 10.52). The condition can also provoke root resorption. Referral to a pediatric endocrinologist is needed. In the Papillon–Lefèvre condition, exfoliation of teeth occurs (Figure 10.53). Figure 10.50 Radiographs illustrating premature opening of the follicles. It seems that the teeth erupt without activating the alveolar bone growth sufficiently. The etiology behind this anomaly is not known. (Upper) This orthopantomogram is from a child 11 years of age with a follicular opening which has occurred earlier than normal. It is seen in the mandible as well as in the maxilla. (Lower) This section of an orthopantomogram from a 10-year-old child also demonstrates a premature follicular opening from the mandibular canines. The first premolar in the right side has a forked root. Why analyze the etiology behind abnormal eruption? Figure 10.49 Two orthopantomograms from the same patient It is important to be aware of the etiology of the eruption demonstrating severe eruption problems in the left side of the maxilla and deviation because this determines treatment. mandible in both the primary and permanent dentition. The condition is a • In ectopia where a developmental field is not involved, treat unilateral primary failure of eruption. (Upper) Arrested eruption appears at the age of seven years in the left mandibular second primary molar and ment of eruption deviations can normally be performed. the second primary molar in the left side of the maxilla. (Lower) Arrested • Concerning primary arrest in eruption where the etiology is eruption of the left permanent maxillary molar occurs at the age of 11 years. abnormal function of the crown follicle, timely surgical expo sure of the crown is usually an appropriate treatment for provoking eruption. However, this requires that appropriate space is available. • Concerning secondary retention where the tooth is ankylosed, arrested eruption cannot be treated orthodontically. Secondary retention can occur in all molars within a molar field. • In segmental odontomaxillary/mandibular dysplasia, the cause of retention lies in the osseous tissue and this condition cannot be treated. However, eruption does proceed gradually. • In hyper-IgE syndrome, it is important to extract the primary molars before apical root closure of the premolars. Eruption deviations in syndromes and dysplasia can sometimes be guided/treated and sometimes not.
146 Chapter 10 Figure 10.51 Radiographs and schematic drawings illustrating the alveolar bone level in juvenile periodontitis and in secondary arrested eruption. The illustration demonstrates two different situations close to the first molar root in which the alveolar bone cannot form normally and an oblique/vertical ridge is formed on the alveolar process. In the one case, the molar erupts without initiating alveolar bone formation. In the other, eruption is prohibited and the alveolar bone cannot grow. (Upper) Two radiographs from two different young patients demonstrating an oblique, almost vertical alveolar bone level (red arrows) between the first permanent molar and the second premolar in the mandible (left) and in the maxilla (right). (Lower) The center illustration shows the oblique, almost vertical bone level in juvenile periodontitis marked by the red line. It is presumed that the alveolar bone apposition during pubertal growth (see also Chapter 5) occurs close to the premolar but not close to the molar. Thus, it is suggested that juvenile periodontitis initially is a growth defect in the alveolar bone and secondarily an infection. This also explains the regional specific occurrence of this type of periodontitis. The right illustration shows a similar oblique, almost vertical bone level which is observed in secondary retention of the molars, where the molar affected by secondary retention has ankylosed. Figure 10.52 Radiographs demonstrating early alveolar bone loss and loss of teeth in the front regions of the mandible and the maxilla which could be a sign of hypophosphatasia. The orthopantomogram (right) is from a child five years of age who shed the incisors before the root of the permanent incisor had started formation. The inserted figures (left) are from two different children aged 3½ years (upper) and five years (lower) who have abnormal loss of alveolar bone.
Tooth eruption and alveolar bone formation 147 Figure 10.53 Sections of two orthopantomograms form a child with Papillon–Lefèvre syndrome at the age of 2½ years (left) and three years (right). The patient is sibling to the patient case demonstrated in Figure 5.8. The teeth appear to have exfoliated in the front. This figure does not illustrate an eruption problem but a problem in the alveolar process which is obvious around the primary maxillary canines. • In primary failure of tooth eruption, conventional treatment is Becktor KB, Becktor JP, Karnes PS, Keller E. Craniofacial and dental not possible. Orthognathic (jaw) surgery might be a treatment manifestations of Proteus syndrome: a case report. Cleft Palate option in some cases. Craniofac J 2002;39 (2):233–245. Highlights and clinical relevance Becktor KB, Kjær I, Koch C. Tooth eruption, epithelial root sheath and craniofacial profile in hyper-IgE syndrome: report of two cases. Eur J • Eruption deviations can occur throughout the entire dentition. Paediatr Dent 2001;4:185–190. • It is important to elucidate heredity when evaluating possible Becktor KB, Reibel J, Vedel B, Kjær I. Segmental odontomaxillary treatment plans. dysplasia: clinical, radiological and histological aspects of four cases. • It is the etiology-based diagnostics that determine whether it is Oral Dis 2002;8:106–110. possible to treat the eruption deviation in question. For Becktor KB, Steiniche K, Kjær I. Associations between ectopic eruption example, primary retention of a permanent molar can be of maxillary canines and first molars. Eur J Orthod 2005;27:186–189. treated so that the tooth reaches the occlusal level while secondary retention of a molar cannot be treated in the Begtrup A, Grønastød H, Christensen IJ, Kjær I. Predicting lower third same way. molar eruption on panoramic radiographs after cephalometric com • Eruption deviations which often are difficult or impossible to parison of profile and panoramic radiographs. Eur J Orthod treat include, for example, arrested eruption after trauma, 2013;35:460–466. secondary retention of molars, teeth within a segmental, dysplastic region, some inherited deviations, and primary Caspersen LM, Christensen IJ, Kjær I. Inclination of the infraorbital failure of eruption. canal studied on dry skulls expresses the maxillary growth pattern: a new contribution to the understanding of change in inclination of Further reading ectopic canines during puberty. Acta Odontol Scand 2009;67:341–345. Bang E, Kjær I, Christensen LR. Etiologic aspects and orthodontic Ely NJ, Sheriff M, Cobourne MT. Dental transpositions as a disorder of treatment of unilateral localized arrested tooth development com genetic origin. Eur J Orthod 2006;28:145–151. bined with hearing loss. Am J Orthod Dentofac Orthop 1995;108:154–161. Frazier-Bowers SA, Koehler KE, Ackerman JL, Proffit WR. Primary failure of eruption: further characterization of a rare eruption dis Becker A, Chaushu S. Dental age in maxillary ectopia. Am J Orthod order. Am J Orthod Dentofac Orthop 2007;131 (5):e1–11. Dentofacial Orthop 2000;117:657–662. Fujiyama K, Yamashiro T, Fukunaga T, Balam TA, Zheng L, Takano- Becktor KB, Bangstrup MI, Rølling S, Kjær I. Unilateral primary or Yamamoto T. Denervation resulting in dento-alveolar ankylosis associ secondary retention of permanent teeth, and dental malformations. ated with decreased Malassez epithelium. J Dent Res 2004;83:625–634. Eur J Orthod 2002;24:205–214. Hørberg M, Lauesen SR, Daugaard-Jensen J, Kjær I. Linear scleroderma en coup de sabre including abnormal dental development. Eur Arch Paediatr Dent 2015;16 (2):227–231. Kenrad J, Vedtofte H, Andreasen JO, Kvetny MJ, Kjær I. A retrospective overview of treatment choice and outcome in 126 cases with arrested eruption of mandibular second molars. Clin Oral Invest 2011;15:81–87. Kjær I. Can the location of tooth agenesis and the location of initial bone loss seen in juvenile periodontitis be explained by neural develop mental fields in the jaws? Acta Odontol Scand 1997;55:70–72.
148 Chapter 10 Kjær I. Phenotypic classification of 90 dentitions with arrested eruption Neville BW, Damm DD, Allen CM, Bounot JE. Oral and maxillofacial of first permanent mandibular maxillary molars. Semin Orthod pathology. WB Saunders, Philadelphia, 1995. 2010;16:172–179. Nielsen SH, Becktor KB, Kjær I. Primary retention of first permanent Kjær I. Can the reduced level of alveolar bone in the initial stages of mandibular molars in 29 subjects. Eur J Orthod 2006;28:529–534. juvenile periodontitis anterior to the first molar be explained as arrest in alveolar bone growth? Dental Hypotheses 2013;4:44–49. Njio B, Kjær I. The development and morphology of the incisive fissure and the transverse palatine suture in the human fetal palate. J Kjær I. Mechanism of human tooth eruption: review article including a Craniofac Genet Dev Biol 1993;13:24–34. new theory for future studies on the eruption process. Scientifica 2014; Article ID 341905. Parner ET, Heidmann JM, Kjær I, Væth M, Poulsen S. Biological interpretation of the correlation of emergence times of permanent Kjær I, Nolting D. Immunohistochemical PGP 9.5 positivity in human teeth. J Dent Res 2002;81:451–454. osteoblasts may indicate that compensatory and dysplastic cranio facial growth are under control by peripheral nerves. Orthod Cra Rincon JC, Young WG, Bartold PM. The epithelial cell rests of Malassez niofac Res 2008;11:196–200. – a role in periodontal regeneration? J Periodont Res 2006;41:245–252. Kjær I, Fink-Jensen M, Andreasen O. Classification and sequelae of Risom L, Christoffersen L, Daugaard-Jensen J, et al. Identification of six arrested eruption of primary molars. Int J Paediatr Dent novel PTH1R mutations in families with a history of primary failure of 2008;18:11–17. tooth eruption. PLoS One 2013;8 (9):e74601. Koch G, Poulsen S. (eds). Pediatric dentistry. A clinical approach, 2nd Rune B, Sarnaes KV. Root resorption and submergence in retained edn. John Wiley, Chichester, 2009. deciduous second molars. Eur J Orthod 1984;6:123–131. Larsen HJ, Sørensen HB, Artmann L, Christensen IJ, Kjær I. Sagittal, Vedtofte H, Andreasen JO, Kjær I. Arrested eruption of the permanent vertical and transversal dimensions of the maxillary complex in lower second molar. Eur J Orthod 1997;21:31–40. patients with ectopic maxillary canines. Orthod Craniofac Res 2010;13:34–39. Wise GE, He H, Gutierrez DL, Ring S, Yao S. Requirement of alveolar bone formation for eruption of rat molars. Eur J Oral Sci Marks SC, Schroeder HE. Tooth eruption: theories and facts. Anat Rec 2011;119:333–338. 1996;245:374–393. Yao S, Wise GE. In vivo expression of classic PKC isoforms in the rat Melfi RC, Alley K.E. (eds). Permar’s oral embryology and microscopic dental follicle as related to tooth eruption. Connect Tissue Res anatomy, 10th edn. Lippincott Williams and Wilkins, Philadelphia, 2004;45:216–221. 2000. Yao S, Pan F, Prpic V, Wise GE. Differentiation of stem cells in the dental follicle. J Dent Res 2008;87:767–771.
CHAPTER 11 Root and crown resorption: normal and abnormal pattern including syndromes Tooth resorption theory The most recent resorption studies demonstrate that different types of idiopathic resorption can be explained from the com The etiology behind external root resorption may be known, but position of the peri-root sheet layers (see Chapter 5). Changes in may also be unknown. Known etiology can occur after tooth these tissue layers lead to inflammation. This inflammatory trauma. In such cases, resorption is caused by inflammation in the process is believed to initiate root resorption and is comparable pulp and/or the periodontal tissue. Permanent tooth roots can to the inflammatory process provoked by trauma and orthodon also be affected by resorption caused by pressure, for example, tic forces. from erupting teeth, from orthodontic appliance or from tumors. It is presumed that these pressure changes create an inflammatory As the hypothesis is based specifically on the ectodermal/ condition in the periodontal membrane that induces the root mesodermal, and neuroectodermal tissues, these specific layers resorption process. Both apical and cervical resorption can arise. will receive special attention. Resorption with unknown etiology is called idiopathic resorption. Most collum resorptions are idiopathic resorptions. Ectodermal tissue The ectodermal tissue layer in the peri-root sheet is formed by the Permanent dentitions with idiopathic resorptions and resorp epithelial cells of Malassez. These are the red cell groups in tions due to an erupting maxillary canine are demonstrated in Figure 5.7. The ectodermal tissue layer affects both the tooth Figure 11.1. morphology and apparently also the occurrence of idiopathic resorptions in ectodermal diseases. Root resorption is a normal physiological process in the primary teeth, in which the root gradually disappears due to It is well known that the ectoderm (oral mucosa) forms the resorption. What begins this process is not known, and what early tooth bud. It later composes the inner layer in the dental causes the primary tooth root to undergo resorption but not the follicle and the cells of Malassez along the root surface (see permanent tooth is a question currently under debate (see Chapter 4). This ectodermal layer influences the tooth morphol Figure 11.1). A way to elucidate this paradox is to compare ogy. The orthopantogram in Figure 7.16 illustrates red contours the periodontal membrane in primary teeth with the periodontal expressing the structures influenced by the ectoderm. membrane in permanent teeth. This was demonstrated in Chapter 6. When these periodontal membranes are compared, Different ectodermally derived morphologies of incisors and the main difference in the peri-root sheets (the part of the molars from dentitions which are susceptible to root resorption membrane close to the root) is the structure, location, and are shown in Figure 11.2. The figure is reprinted from a national morphology of the Malassez’ tissue layer. Former studies have study involving pretreatment panoramic and profile radiographs demonstrated that innervation also appears within the Malassez’ from 107 patients who had developed excessive root resorption epithelium. In the primary dentition, this epithelial layer is less during orthodontic treatment (more than one-third of one or prominent than in the permanent teeth shortly after eruption. more roots had been resorbed). Approximately 90 of the patients When resorption occurs in the primary root, the Malassez’ had more than three of the following morphological signs: epithelium and ectomesenchyme layer disappear while the invaginations, short roots, deviant root morphology, collum innervation appears less destinctive. resorption, crown malformations, ectopia, and agenesis. These were considered to be predominantly ectodermal signs. The Accordingly, a theory behind root resorption is that the peri conclusion drawn is that ectodermally derived abnormal tooth root sheet protects the root against resorption and that the morphology might be a sign of root resorption susceptibility. composition of a normal peri-root sheet in the permanent However, this study also showed that 17 out of 107 patients did dentition is necessary for preventing root resorption. not display these ectodermal, morphological signs, implying that Etiology-Based Dental and Craniofacial Diagnostics, First Edition. Inger Kjær. © 2017 John Wiley & Sons, Ltd. Published 2017 by John Wiley & Sons, Ltd. 149
150 Chapter 11 Figure 11.1 An overview of radiographs and histological sections demonstrating unexplainable and explainable root resorption. (Upper left) Orthopantomogram from a 16-year-old patient before orthodontic treatment. This treatment was refused due to severe root resorption without a known etiology. (Upper right) An enlargement of the maxillary incisors from the orthopantomogram on the left. It is obvious that severe resorption has occurred and that this was the reason for refused treatment. (Lower left) This dental film is from a 22-year-old patient who had never received orthodontic treatment. The dentition was radiographed and the diagnosis was a progressive root resorption. A serum investigation revealed normal calcium and phosphorus levels. The etiology behind this condition was never found. Source: Courtesy of Dr Peter du Hoang. (Lower center) A dental radiograph demonstrating severe resorption of the central maxillary incisor due to eruption of an ectopic maxillary canine. (Lower right) Histological sections of an extracted permanent incisor (a case similar to the lower center case). The large picture shows the remains of the incisor root. The large arrow points in the direction in which the canine erupted and caused the tooth root to be resorbed (upper right small histo-section). The interesting observation here is that the mesial root surface has several root resorption lacunae (arrow), but this surface has not been influenced directly by resorption from the canine. A resorption lacuna is shown in the lower right small histo-section. This dentohistological analysis shows that the resorbed tooth root had a disposition for root resorption (arrow). From this analysis, it can be hypothesized that there are tooth roots that are more resistant to root resorption than others. there are backgrounds for susceptibility to resorption without 12 patients showed plump roots that were combined with ectodermal origin. resorptive changes in the condyle and with open bite (Figure 11.5). Open bite has formerly been associated with root resorp Ectodermal dysplasia is a condition in which root resorption tion. These signs are all ectomesenchymal in origin. The conclu occurs (Figure 11.3). Other diseases such as tuberous sclerosis sion is that ectomesenchymally derived abnormal tooth with skin problems (Figure 11.4) are conditions also prone to morphology might also be a sign of root resorption susceptibility. root resorption. Tuberous sclerosis is a dominant hereditary disease (genotype deviation in chromosome 9q34 or 16p13) in One general mesodermal bone disease with root resorption as which cervical resorption is a characteristic symptom. a known complication is osteitis deformans (Paget’s disease in bone) (Figure 11.6). In this condition, root resorption begins at Mesodermal or ectomesenchymal tissue the collum and plump roots are observed. Osteogenesis imper- The ectomesenchymal tissue layer in the peri-root sheet (green in fecta, hypophosphatasia, and hypocalcemia are also examples of Figure 7.17) affects both the tooth morphology and the occur- mesodermal diseases where root resorption occurs. rence of idiopathic resorption in diseases. Neuroectodermal tissue In the drawing of an early tooth bud formation, the green areas The neuroectodermal layer is the innermost layer of the peri are the mesodermal or ectomesenchymal areas which later odontal peri-root sheet close to the root (see Figure 5.7). Whether compose the pulpal tissue and the middle layer of the peri- this layer or the peripheral nerves influence the tooth morphol root sheet. If this layer is malfunctioning or disrupted, the ogy is not known. The jaw innervation has been mapped in morphology of the teeth has a characteristic appearance: short several studies and is illustrated in Chapter 2. plump roots and obliteration of the pulp chambers. Collum resorptions and a vertical open bite can be characteristic symp- A recent study of two cases has demonstrated that peripheral toms as well. In the national study on root resorption mentioned, nerves also play a role in root resorption. These resorptions were
Root and crown resorption 151 Figure 11.3 A section from an orthopantomogram demonstrating the maxillary dentition from a 14-year old-patient with one type of ectodermal dysplasia. Note the absence of the permanent lateral incisors, canines, and premolars. One molar has complete taurdontia. In this case, the persisting primary dentition has severe root resorption. Figure 11.2 The morphological characteristics for dentitions where root whooping cough bacteria. The other case was a patient diagnosed resorption can occur during orthodontic treatment. It is characteristic that with aggressive/idiopathic resorption in a frontonasal incisor there must be more than three deviations in the dentition before it can be field. In that case, the resorption was caused by meningitis virus deemed at risk for resorption. The morphological characteristics for the (Figure 11.8). The virus attack had disturbed the peripheral incisors are deviant and short roots, narrow crowns, and invaginations. In nerves and the incisors were affected by resorption within fields. the molars, the symptoms are short, slender, and taurodontic roots (specifically a short distal root of the first mandibular molar). Source: Kjær With these two examples of collum resorption, the clinical (1995). idiopathic classification of these conditions was changed. In both cases, the resorption types were innervation induced and occurred in limited fields defined by the innervation of different branches of the peripheral nerves. It is presumed that the virus and bacteria disturb the myelin sheaths along the peripheral nerves and that demyelinization provokes inflammation and later resorption along the tooth root starting at the collum. The destruction due to resorption stays within the affected fields. This is schematically illustrated in Figure 5.7. In summary, pathological tissue changes in the ectodermal, ectomesenchymal, and neuroectodermal layers cause root resorption. first categorized as idiopathic (Figure 11.7). After follow-up and Resorption in the primary dentition treatment over a course of six years, one of these cases revealed a whole new explanation for innervation-induced resorption lim Pattern of resorption ited to four jaw fields where innervation was destroyed after Resorption of a primary tooth can occur during the eruption of an underlying permanent tooth (see Figure 5.2). It is believed that Figure 11.4 Images from a patient with tuberous sclerosis which is a dominant, hereditary disease (chromosome 9q34 or 16p13). (Far left) Note the severe skin condition of the forehead. (Center left) The radiograph demonstrates both internal and external resorption of the mandibular incisors starting at the collum occurring at the time of referral. (Center right) The intraoral photograph shows that many teeth had already been extracted due to resorption before the radiograph of the incisors was taken. It is believed that the Malassez’ epithelium is affected in this patient and that this might be a component of the etiology behind the resorption condition. (Far right) Two radiographs of the maxillary canine (upper) and the mandibular first molar (lower) before extraction. Source: Kjær (2013). Reproduced with permission of Elsevier.
152 Chapter 11 Figure 11.5 Radiographs demonstrating that the ectomesenchyme also plays a role in the resorption process. In this case, there is an open bite which is visible in the profile radiograph. The four dental films to the right show collum resorption (upper center), plump roots (upper right and lower center), and apical resorption of the incisors (lower center and right). It is therefore not only the ectodermally based morphology (invagination and taurodontia) but also the mesenchymal formations that can be predisposed to root resorption during orthodontic treatment. Source: Kjær (1995). the permanent tooth provokes the resorption process. Mean permanent successor. Too early resorption of the primary root, while, resorption of a primary root can also occur in cases with compared to the maturity and eruption state of the permanent agenesis of the permanent successors (Figure 11.9). In cases with tooth, can occur but also aggressive resorption of the crown of the multiple agenesis, severe resorption of the primary dentition has primary tooth has been observed. Examples of this abnormal been observed. This is believed to be related to the abnormal resorption and repair of primary roots appear in Figure 11.10. ectodermal condition also causing multiple agenesis. Resorption Former studies have documented an interrelationship between of primary roots occurs in regions without the presence of abnormal resorption in the primary dentition and morphological permanent teeth (see Figure 11.9). deviations in the permanent dentition known to be signs of susceptibility to root resorption (Figure 11.11). This means that The ectodermal tissue layer in the peri-root sheet of the the primary dentition in some cases may predict resorption in the primary teeth is proposed to be less protective against resorption. permanent dentition. The etiology behind this interrelationship This has formerly been regarded as an inexplicable phenomenon is presumed to be an abnormality in the ectoderm. of idiopathic resorption. Histological analysis in Figure 11.10 demonstrates this. This figure also demonstrates how resorption Shedding times lacunae are repaired by ectomesenchyme and how the innerva Shedding in the primary dentition is a normal physiological tion layer close to the root is reestablished. process occurring in close relation to the eruption of the suc ceeding permanent tooth. The resorption pattern observed in the primary root under going resorption can also be deviant in cases where there is a Figure 11.6 These are old radiographs demonstrating abnormal resorption in Paget’s disease (osteitis deformans) which is an ectomesenchymal deviation. It is believed that the ectomesenchymal tissue layer in the peri-root sheet could be involved in external resorption in this disease. The dentin, which also has a mesenchymal origin, could be involved. This is seen in the internal resorption. Source: Smith (1978). Reproduced with permission of Elsevier.
Root and crown resorption 153 Figure 11.7 Radiographs and a histological section demonstrating severe regional resorption provoked by whooping cough bacteria. The patient was hospitalized as a child due to this infection. (Upper) Eight years later, the resorption observed in the radiographs of the mandibular incisors (far left) and maxillary premolar and molar (center left) was imaged at the age of 19 years. Treatment of these severe resorptions was not possible at that time and the teeth were extracted one by one. A central mandibular incisor is demonstrated after extraction (center right). The extracted incisor was investigated histologically (far right), and deep, severe resorption lacunae were observed (arrows). (Lower) The orthopantomogram was taken at the age of 26 years when the resorption processes had ceased and the implants had been inserted (oral surgeon: Nils Worsaae). Note that the resorption followed the innervation path in the maxilla and did not cross the midline in the mandible. Only the incisor field was affected. Early shedding Chapter 10 (see Figures 10.38 and 10.39). These dentitions The shedding of primary teeth can occur early and is considered develop premolars or canines that do not have the ability to pathological as in hypophosphatasia (Figure 11.12). shed the primary dentition. This means that the primary roots are not resorbed. The treatment is to extract the primary teeth at a Late shedding or nonshedding time when the premolars and permanent canines are still at a There are three conditions to be discussed regarding primary maturity stage before root closure. Some of these conditions teeth not undergoing root resorption. cannot be explained while other symptoms suggest the hyper-IgE condition, in which ectodermal structures such as skin, lungs, In the first condition, the succeeding permanent tooth cannot and tympanic membranes can be affected. The etiology behind resorb the overlying primary tooth. This is described in Figure 11.8 These illustrations demonstrate how a meningitis virus can result in resorption started as collum resorption. (Left) In the upper lip, there is a retracted area which corresponds to the area of change in the sensitivity in the upper lip and ala nasi. This patient had meningitis at 10 years of age. (Center) The dental film demonstrates the incisors before (left) and after (right) the meningitis attack. Resorption occurred corresponding to the marked area in the face, first on the central incisor and then the lateral incisor. (Right) The orthopantomogram demonstrates the situation in the front before the lateral incisor was extracted. Later, implants were inserted.
154 Chapter 11 Figure 11.9 Dental films and an orthopantomogram demonstrating abnormal resorption of primary molars marked by yellow stars. (Upper left) Resorption at the time when root formation of the permanent successor had just started. (Upper right) Complete crown resorption before shedding. (Center left) Complete resorption of the roots in a primary molar without a successor. (Center right) Complete root resorption of primary molars with successors which are not yet in their eruptive state. (Lower) Abnormal resorption pattern of the primary molars in the maxilla and the mandible. Figure 11.10 Three histological sections from various primary tooth roots demonstrating resorption lacunae (R) and repair of these. The resorption process disturbs the peri-root sheet tissue layers which are predominantly reestablished by ectomesenchymal fibers and innervation. The Malassez’ epithelium seems to be sparse. (Left) This section illustrates that the resorption lacuna (R) has been filled up with bone. The section is immuno-marked for ectoderm and marks a single Malassez’ epithelium island (arrow). (Center) In this section, the resorption lacuna (R) has also been filled up with bone. The section is immuno-marked for ectomesechyme and the brown tissue layer shows that the ectomesenchyme has again taken its normal position in the peri-root sheet (arrow). (Right) In section, the resorption lacuna (R) has also been filled up. The section is marked by NGFR for innervation (arrow). The brown color demonstrates that the innervation has been reestablished in the peri-root sheet. Source: Bille et al. (2009). Reproduced with permission of Taylor & Francis Publishing Group.
Root and crown resorption 155 Figure 11.11 Four dental films from the same patient illustrating resorption with unknown etiology. (Upper) The patient was seven years old at the time of the radiograph. The first mandibular molars had normal morphology. Note the abnormal resorption pattern seen in the primary molars. (Lower) These two radiographs were taken four years later at age 11 years. The first mandibular molars now have severe resorption of their distal roots. There has been no specific treatment for this patient, including orthodontic treatment. the condition of nonshedding is believed to be accumulation of (nontaurodontic), nonresorbed roots and a normal occlusal level epithelial tissue in the bifurcation of the primary teeth. It might when the observation period starts. For the permanent dentition, also be the inability of the ectodermal layer of the crown follicle to it is characteristic that, except for the one premolar, all other initiate resorption. permanent teeth, often including the third molars, are present. The second condition in which a primary tooth does not The third condition involves late shedding of the incisors in undergo resorption involves a primary tooth without a succeed prepubescent children. This is a rare condition which can be ing permanent tooth (Figure 11.13). The primary tooth is not worrying to parents and children, but the cause is still unknown. resorbed but remains a part of the dentition late into adulthood. The shedding occurs later in puberty. Figure 11.14 shows a 10 This has been observed in dentitions with only one premolar year-old boy who still has primary incisors. Late shedding often missing and where the primary molar has long, separated appears within a family which may point to a genetic cause. Figure 11.12 Radiographs of a child diagnosed with hypophosphatasia. (Left) An orthopantomogram was taken at the age of three years. All the incisors have been resorbed and exfoliated. (Right) At 3½ years, this radiograph of the mandibular primary central incisors was taken. Shortly after, the central incisors exfoliated. The lateral primary incisors have already exfoliated.
156 Chapter 11 Figure 11.13 Dental films from two patients (upper and lower) where the primary mandibular second molar has persisted into adulthood. In both patients, agenesis of the second premolar was the only deviation observed in the dentition. All permanent molars had long, nontaurodontic roots. Both patients had a skeletal deep bite and it was decided to let the primary molar persist as a semi-permanent solution. (Upper) The left dental film was taken at 8½ years of age. The right film was taken at 42 years of age. (Lower) The left dental film was taken at 12 years of age and the right at 41 years of age. These radiographs demonstrate how a primary molar can persist in a premolar region when the occlusal level is the same as the occlusal level of the surrounding teeth and when the roots of the persistent tooth only experience minor resorption. Resorption in the permanent dentition trauma, pressure from erupting teeth, a growing cyst, etc. (Figure 11.15). It has also been reported that pressure from When does resorption occur in normally orthodontic appliances in some cases can provoke root resorp developed individuals? tion in normally developed individuals. Resorption in the permanent dentition is a severe clinical prob- lem. Traditionally, resorption is a process that occurs because of An important process in orthodontic treatment is careful analysis of the dentition in relation to treatment planning. There are dentitions that express idiopathic resorptions to a great extent without former exposure to orthodontic appliances. Examples are shown in Figures 11.1 and 11.15. It is not known why idiopathic resorptions occur or if they even are resorptions. They could express malformations or arrested tooth formation. However, it can be presumed that the dentition has a congenital tendency to this pathological process. Such idiopathic resorptions are further aggrevated by orthodontic treatment. This is essential knowledge for any decision making about orthodontic treatment options. Figure 11.14 This orthopantomogram demonstrates the dentition from a Dentitions especially susceptible to root child 10 years of age where the permanent incisors have not erupted. The resorption first molars are fully erupted. The explanation for this deviation in Dentitions especially susceptible to root resorption are those that eruption time can be found in the different innervation pathways to the create a foundation for the resorption theory proposed in the different tooth groups (see Chapter 2). beginning of this chapter. These dental phenotypes will be summarized.
Root and crown resorption 157 Figure 11.15 Three dental films from a patient who suffered unexpected resorption. In the root pulp of all the teeth in the radiographs, obliteration occurs. The incisor roots (left and center) are rounded apically and the left lateral incisor is completely resorbed. It is likely that pressure from the canine is the cause but there is no apparent space problem in the region. Note the right mandibular incisors which are obliterated in the root pulp. This might be a sign of susceptibility to root resorption. Case reports have documented that resorption occurs in reaction similar to an inflammatory response (Figure 11.19). This diseases such as osteitis deformans and syndromes such as inflammatory reaction is healed by resorptive cells which also Down’s syndrome and ectodermal dysplasia. The reason for cause resorption of the root surface. In ectodermal dysplasia, a the diverse factors which provoke resorption has long been a similar etiology can explain resorption in these cases. In Down’s mystery. It is proposed that dentitions especially susceptible to syndrome, where among other symptoms the skin, hair, nails, root resorption are those with malfunctions of the peri-root and glands are also affected (all structures with ectodermal sheet. When looking at the issue from this perspective, there is a origin), the sporadic occurrence of root resorption can also be common explanation for these diverse factors such as trauma, explained (Figure 11.20). Also tuberous sclerosis with skin pressure, and illness, which can provoke resorption (Figures affections involves collum resorption. 11.16 and 11.17). But there are still unexplained cases of unexpected root resorption, which might possibly be caused Mesodermal deficiency by the composition of the dentin (Figure 11.18). In patients with plump roots, pulp obliterations, and open bite, the (ecto)mesenchymal tissue is involved. If this middle layer The etiology behind root resorption can be explained as a of the peri-root sheet is abnormal (see Figure 5.7), then an disturbance in any of the three main tissue layers. In the peri “imbalance” in tissue signaling between the protective root root sheet, a disturbance in just one layer may disturb the sheet layers may result. In this way, deviations in the meso interaction between the three layers. The interrelationship dermal functions can create a reaction in the peri-root sheet between the three layers protecting the root is considered when exposed to pressure. This reaction can provoke an essential for understanding the strength of the root surface. inflammation-like response that heals by resorption, including Thus abnormality in one layer can disturb this inter resorption of the root. This could also be the case in diseases relationship and cause a reaction similar to an inflammation such as osteitis deformans, osteogenesis imperfecta, and which provokes resorption. The three layers in the peri-root hypophosphatasia, which all have a mesodermal etiology. It sheet are the ectoderm (Malassez’ epithelium), the ectome is also possible (but not documented) that the composition of senchyme (mesoderm), and the innervation which appear the dentin and cementum might influence the resorption together as a layer close to the root (see Figure 5.7). process. Ectodermal deficiency Innervation deficiency The abnormal phenotypic morphology that lies behind tauro Regional resorptions in the developmental fields of the jaws have dontic roots, short roots, and invaginations is caused by abnor recently been documented. These regional resorption processes mal ectoderm. As the ectodermal epithelium in the Malassez’ occur after virus attack. The virus attack destroys the myelin tissue layer is presumed to protect the root against resorption, it is sheaths which again influence the peri-root sheet. Virus attacks understandable that deviations in the ectodermal tissue layer can, from meningitis, as well as bacterial attacks from whooping under certain conditions such as orthodontic pressure, cause a
158 Chapter 11 Figure 11.16 Four dental films from two different patients demonstrating how a trauma can provoke root resorption. (Upper) These two radiographs illustrate how a trauma to the incisors can result in root fracture (arrows). Resorption occurs at the site of the fracture. (Lower) These dental films illustrate a coronal fracture of the incisors resulting in root resorption (arrow). cough, have lead to severe regional resorption activity, as Root resorption and heredity: short roots or described in this chapter. resorbed roots? It is often difficult to determine if a root has always been short This overview focusing on the etiology behind root resorption or if it was once a long root that has undergone resorption, as makes it possible to understand why different inborn and demonstrated in Figure 11.18. It may also be a short root acquired conditions can provoke root resorption. It also aids due to arrest in development. These questions can only be understanding of how resorption can occur in normally devel- answered if earlier radiographs of the patient in question oped individuals with only minor morphological deviations in exist Figure 11.11. the dentition.
Root and crown resorption 159 Figure 11.17 Radiographs illustrating how erupting permanent teeth can unexpectedly resorb other permanent teeth. (Upper left) The root of the left maxillary central incisor (yellow star) has been nearly completely resorbed by a supernumerary tooth in the region. (Upper center) Pressure from the left permanent maxillary canine has almost completely resorbed the permanent lateral incisor (yellow star) during eruption. Note deep invagination in the permanent lateral incisor and the central incisor which have been resorbed distally. (Upper right) The second mandibular permanent molar in the left side has resorbed the permanent first molar during eruption (yellow star). (Lower) An orthopantomogram taken before orthodontic treatment indicating severe resorption in the permanent dentition. The resorption has been initiated by pressure from erupting permanent teeth, especially in the molar regions, but unexpected apical resorption has also occurred in all other teeth. This is seen apically in the maxillary incisors and in the canines without pressure from erupting teeth. Note the short, distal root of the first permanent mandibular molars. This is a very severe case of idiopathic, unexplainable root resorption. When seeing a first-time patient with short roots (which appear to be resorbed) without former radiographs or ortho dontic treatment, the only option is to ask about root resorption in the family and possible x-rays from other family members. Two examples of short roots and resorption tendency in families without orthodontic treatment are demonstrated in Figures 11.21 and 11.22. In such a case it may be that the characteristics of these three tissue layers are genetically inherited. Heritability of these qualities is a topic not yet explored. Figure 11.18 Orthopantomogram from a child 13 years of age taken Figure 11.19 A schematic drawing demonstrating tissue reactions on the before orthodontic treatment. Having seen this radiograph, the surface of the root which provoke resorption. The root dentin is marked gray orthodontist suggested that orthodontic treatment should be postponed and has a fracture (black line). The fracture creates bleeding in the peri-root due to the very short roots and apparently ongoing resorption. The sheet (B) (see Chapter 5). The bleeding starts a resorption process which orthodontist suggested an observation period during which it could be spreads to the root dentin where resorption lacunae form (wavy contour, determined whether the resorption was progressive. marked with arrow). Source: Kjær (2014). Reproduced with permission of Wolters Kluwer.
160 Chapter 11 Figure 11.20 Dental films from a child with Down’s syndrome illustrating short roots. It cannot be determined whether the roots are congenitally short or whether they are short due to ongoing resorption (a wide space for the periodontium is seen). Bilaterality Prevention of root resorption in the permanent Unilateral resorption occurs in cases where resorption has been dentition initiated by, for example, a virus attack on the innervation. Virus Prevention of resorption during treatment is an ultimate goal in attacks can spread through an innervation field and through the orthodontics. This is unfortunately not always possible. Our entire unilateral side but never pass over the midline (see knowledge of the resorption process is still limited and the nature Figure 11.7). Bilateral occurrence of resorption is often seen of resorption differs from individual to individual. in association with idiopathic resorption cases which might have an ectodermal or ectomesenchymal origin. Whether the resorp Factors of importance for preventing root resorption during tion condition appears unilaterally or bilaterally can be an treatment are thorough anamnesis, knowledge of the family indicator of its etiology. history of illness and dental treatment, including resorption and information about former clinical and radiographic Root resorption in syndromes, dysplasia, and investigations. disruptions Syndromes Idiopathic root resorption occurs not only in the primary There is little research in the area of resorption in syndromes, but dentition but also in the permanent dentition. Why a distal root it is well known that Down’s syndrome has a resorptive aspect in of a first molar starts to resorb and shorten without a known the dentition (see Figure 11.20). cause is still not understood (see Figure 11.11). There are cases Dysplasia A recent report illustrates three cases of ectodermal dysplasia of which two have multiple agenesis and one does not.The purpose was to observe how orthodontic treatment, even with good precautions and gentle use of force, could provoke undesirable root resorption (Figure 11.23). Disruptions Figure 11.21 Sections from two orthopantomograms (mother and child) Disruption occurs in association with a virus attack on the demonstrating hereditary short roots and root resorption. (Upper) innervation (see earlier) and in connection with bacterial infec Radiograph from the child at nine years of age demonstrating total tions such as leprosy and whooping cough (see Figure 11.21). resorption of the permanent maxillary lateral incisor roots during eruption Characteristic for leprosy are sharply pointed incisors due to of the canines. Note short roots on the central incisors and first premolars. Mycobacterium leprae occupying the moist environment of the (Lower) The same radiographic section from the child’s mother illustrating floor of the nasal cavity. In severe cases, the tooth root is nearly short roots in the incisors and the premolars. completely missing. It is important to recognize that this condi tion can be categorized as arrested tooth formation and as resorption.
Root and crown resorption 161 Figure 11.22 Dental films from two sisters demonstrating hereditary short root anomaly of the central maxillary incisors. with inborn short root anomalies in which the short root is Clinical investigation includes a description of the tooth congenital and not a sequela due to resorption (see Figure 11.22). eruption and the size, shape, and color of the teeth. If possible, A short root could possibly also be a result of drug interference. knowledge of the salivary secretions is useful. A radiological This is an area of odontology which needs to be elucidated. Short, study involves the analysis of all known tooth and jaw abnor malformed roots are also observed after treatment for leukemia, malities. If a radiographic investigation reveals severely short when the roots can be short as an acquired phenomenon roots, abnormal tooth morphology and/or plump roots and unrelated to resorption (see Chapter 8). taurodontic root shapes, then orthodontic treatment must be considered although one must proceed with caution and the Clinically, it is important to observe the skin, hair, and nails. treatment plan should be evaluated regularly. Observation of normal developmental aspects such as body height, body proportions, olfactory senses, hearing, and sight Prevention involves a high degree of attentiveness to a large is also important. The parents should be asked about their dental number of factors, some of which are new. If one or several health and about possible disorders in the family (see factors are present, treatment may provoke resorption. However, Figure 11.21). The dental history of siblings may also be signifi even if these factors are present, the dentition may be able to resist cant (see Figure 11.22). resorption. Research in this specific field is urgently needed. Figure 11.23 An orthopantomogram of a child with ectodermal dysplasia. Orthodontic treatment was performed to gather the central maxillary incisors which originally had a large diastema. The arch was attached to the canines (presumably primary canines). Inserted are the appearances of the canine roots after a very short treatment period. This type of resorption is apparently caused by an ectodermal deviation in the Malassez’ epithelium in the peri-root sheet.
162 Chapter 11 Figure 11.24 Demonstration of unexplainable internal resorption in the primary and permanent dentition. (Upper left) Dental film from a child six years of age demonstrating a complete internal resorption of the crown and part of the root. (Upper right) Clinically, this internal resorption is observed as a “pink tooth.” (Lower left) Unexplainable internal resorption of a mandibular canine. Note the root pulps in the incisors appear to be partially obliterated. Whether this is a condition combined with internal resorption in the canine is not known but the possibility should be considered. (Lower right) Disintegration of the crown pulp in a first mandibular permanent molar, indicating the start of internal resorption. Note that the root pulps in the teeth present are partially obliterated. The etiology behind this condition is not known. Other examples of resorption Aggressive resorption Aggressive root resorption is an extreme and inexplicable form of Postemergence resorption resorption which is demonstrated in young patients in Internal crown and/or root resorptions are relatively rare and Figure 11.26. Resorption of the distal root of the first permanent normally associated with physical trauma or caries-related pul molar is often also observed, also without explanation (see pitis in primary or permanent incisors. The treatment involves Figure 11.26). endodontic therapy; in severe cases, extraction is needed. Exam ple are demonstrated in Figure 11.24. Preemergence resorption Resorption of the roots of unerupted teeth is often a result of Collum resorption regional pathological processes or ectopic eruption from neigh Unexpected, inexplicable collum resorptions can occur in both boring teeth. dentitions in premolars and molars. Resorption often starts at the collum. Examples are demonstrated in Figure 11.25. It is inter Crown resorption before emergence esting that such resorption also occurs in dentitions with primary Certain types of resorption of permanent unerupted tooth crowns failure of eruption (see Chapter 10). have been described in case reports and also demonstrated in
Root and crown resorption 163 Figure 11.25 Demonstration of unexplainable collum resorption in the primary and permanent dentition. (Upper left) Collum resorption in the mandibular primary molar in the right side (arrow). (Upper right) Collum resorption in the maxillary first molar in the right side. This radiograph is from the same child as the radiograph at upper left. The resorption process occurs apically to the gingiva and can therefore not be confused with caries or resorption, provoked by orthodontic appliances. (Lower) Radiographs from three cases, demonstrating aggressive collum resorptions in permanent first mandibular molars. Etiology is not known. textbooks. Histological studies of unerupted teeth with intra- The purpose of presenting these crown resorptions is to make coronal resorption have shown that the change in the dentin is dental professionals aware of preeruptive intracoronal resorp caused not by caries but by resorption from invagination of tion on teeth before emergence. Specialists in orthodontics are odontoclasts through minor defects in the enamel. often the first to analyze the radiographs of unerupted permanent teeth. It is important to consult an endodontist for a treatment According to a recent study of 13 patients, the mandibular plan for teeth with intracoronal resorption before emergence. second molar appears to be most often affected, but second Decisive for the orthodontic treatment plan is the endodontist’s maxillary molars, canines, and premolars in both jaws can also be evaluation of whether the tooth can be preserved and the affected (Figure 11.27). The patients all showed unexpected and prognosis for the tooth. After this evaluation, the orthodontist severe resorption of the dentin in the unemerged permanent can determine a treatment plan. Each patient requires an indi tooth crowns. Complete resorption of the crown might occur vidual treatment plan. within a year or two (see Figure 11.27). It cannot be verified from radiographs in this study whether there is a developmental defect Treatment of teeth with preeruptive intracoronal resorption in the enamel, as has previously been documented histologically varies greatly. In some cases, the defect can be repaired with a in case reports. In a patient with amelogenesis imperfecta, in filling while other cases may require tooth extraction. The type of which the enamel is known to be defected, preeruptive intra- treatment chosen is based on the severity, the stage at the time of coronal resorption may occur (Figure 11.28). This relationship diagnosis, and the dentition in general. The condition is rare and supports the theory that the crown follicle’s resorptive cells can it is therefore important to share treatment experience between migrate into the dentin through the defective enamel. The dentin professionals. might be hypomineralized, but no evidence for this was found in this study. Hypomineralized dentin is not the cause but might in Conclusion part explain the rapid progression of the resorption process. Another suggestion could be that the patients studied had As a conclusion to this chapter, it is important to recall abnormal development of the crown follicle. This aspect should that idiopathic resorptions (resorptions without a known be investigated further in future studies.
164 Chapter 11 Figure 11.26 Demonstrations of unexplainable and grotesque resorptions that occur unexpectedly in young patients. (Upper left) Two radiographs demonstrating complete root resorption of permanent molars in a 17-year-old patient with no known history of disease. (Upper right) Completely resorbed roots of a right maxillary first molar in an 18-year-old patient with no known history of disease. (Middle left) The third mandibular molar without roots and a short distal root of the first and second mandibular molars in an 18-year-old patient with seemingly normal health. (Middle right) This radiograph is from the same patient as in the two lower radiographs. The patient is 21 years old. The maxillary first molar has partly resorbed roots. (Lower) These two dental films of mandibular molars show short distal roots of the first molar. These are from the same patient as the radiograph at the middle right position. cause) can occur in both the primary and the permanent How to analyze the etiology behind dentition of the same individual. Examples of resorptions in abnormal root resorption in the primary teeth are shown in Figure 11.29. Abnormal resorp- permanent dentition tions in the primary dentition appears to be a sign of later, otherwise unexpected resorption in the permanent denti- The steps in analyzing the etiology behind root resorption are: tion. However, this subject also needs to be further 1 perform an individual general and dental anamnesis elucidated. 2 retrieve a general and dental anamnesis for the family
Root and crown resorption 165 Figure 11.27 Overview of types of development in intracoronal resorptions occurring before tooth emergence in otherwise normal dentitions. The etiology behind intracoronal resorption is not completely understood. It is well known that the crown follicle of the erupting tooth has the ability to resorb overlying bone tissue. If there is a gap in the enamel covering the crown, the resorptive capacity of the crown might be able to penetrate the gap and resorb the dentition. This concept is supported by the dentition observed in amelogenesis imperfecta patients who can have this kind of intracoronoal resorption (see Figure 11.28). (Upper) Three dental films demonstrating developmental stages before emergence, during emergence, and after emergence. Note the rapid arising of an intercoronal resorption in the left mandibular second permanent molar. (Middle) Three dental films in chronological order from age 13, 13½, and 15 years demonstrating developmental stages of intracoronal resorption in the right permanent mandibular second molar. The last image shows a complete collapse of the crown. (Lower far left and center left) In the intraoral photograph, it appears that the mandibular canine has just erupted without a crown. The radiograph demonstrates the crownless canine. (Lower center right) A dental film of a completely resorbed crown of the second mandibular premolar before eruption. (Lower far right) A complete intracoronal resorption of the second permanent maxillary molar in the right side. Source: Kjær et al. (2012a). Reproduced with permission of Elsevier. Figure 11.28 Section of an orthopantomogram from a child nine years of age with amelogenesis imperfecta. Note the absence of a normal enamel contour. In this case, intracoronal resorption is observed before emergence in the crown of the first permanent mandibular molar. It is believed that this resorption occurs because the resorptive capacity within the crown follicle has been able to penetrate the defective enamel and thus to resorb the dentine.
166 Chapter 11 Figure 11.29 This figure demonstrates deviant resorption in the primary dentition in a child seven years of age. All permanent first molars have resorbed parts of the roots and crowns of the primary second molars during eruption. Inserted is a blue figure illustrating this type of abnormal resorption in the primary dentition. Abnormal resorption in the primary dentition of a patient is an indicator that resorption might also occur in the permanent dentition. Studies have shown that there is an association between resorption in the permanent and primary dentition in a given individual. The etiology behind the occurrence in both dentitions could be found in the peri-root sheet. 3 focus on the resorption patterns in the primary and permanent • Idiopathic resorption patterns exist without a known explan dentition of the individual ation both in single teeth and in the entire dentition. 4 determine whether the resorption is an ectodermal trait (not Further reading within fields) or whether it occurs in one or several restricted fields (nerve/ectomesenchymal etiology). Highlights and clinical relevance Bille MLB, Kvetny MJ, Kjær I. A possible association between early apical resorption of primary teeth and ectodermal characteristics of the • It is well known that external factors can provoke root resorp permanent dentition. Eur J Orthod 2008;30:346–351. tion. It is also known that resorption can occur idiopathically without known explanation. Bille MLB, Nolting D, Kjær I. Immunohistochemical studies of the periodontal membrane in primary teeth. Acta Odontol Scand • What occurs on the root surface and why it occurs is discussed 2009;67:382–387. in this chapter. Bille MLB, Nolting D, Kvetny MJ, Kjær I. Unexpected early apical • It is the peri-root sheet covering the root which can explain resorption of primary molars and canines. Eur Arch Paediatr Dent earlier unknown resorption patterns. 2007;8:144–149. • The layers of the peri-root sheet can also explain why resorp Bille MLB, Thomsen B, Andersen TL, Kjær I. Immunolocalization of tion may occur in healthy individuals with few morphological RANK and RANKL along the root surface and in the periodontal devations in the dentition. membrane of human primary and permanent teeth. Acta Odontol Scand 2012;70:265–271. • Preemergence crown resorption is demonstrated in the molars, premolars, and canines Blackwood HJJ. Resorption of enamel and dentine in the unerupted tooth. Oral Surg Oral Med Oral Pathol 1958;11:79–85. • It is important to notice deviated resorption patterns in both the primary and permanent dentition. Brice GL, Sampson WJ, Sims MR. An ultrastructural evaluation of the relationship between epithelial rests of Malassez and orthodontic root • It is also important to notice the characteristic permanent resorption and repair in man. Aust Orthod J 1991;12:90–94. tooth morphologies. Gunraj MN. Dental root resorption. Oral Surg Oral Med Oral Pathol • Consider the individual and their family’s history in order to Oral Radiol Endod 1999;88:647–653. avoid provoking root resorption mechanically. Resorption seems to be inheritable. Ith-Hansen K, Kjær I. Persistence of deciduous molars in cases with agenesis of second premolars. Eur J Orthod 2000;22:239–243. • Some patterns of resorption look like provoked resorption, but are idiopathic resorptions with no former orthodontic Kjær I. Morphological characteristics of dentitions developing excessive treatment. root resorption during orthodontic treatment. Eur J Orthod 1995;16:25–234. Kjær I. External root resorption – different aetiologies explained from the composition of the human root-close periodonatal membrane. Dent Hypotheses 2013;4:75–79.
Root and crown resorption 167 Kjær I. Root resorption – focus on signs and symptoms of importance for Klambani M, Lussi A, Ruf S. Radiolucent lesion of an unerupted avoiding root resorption during orthodontic treatment. Dent Hypoth mandibular molar. Am J Orthod Dentofac Orthop 2005;127:67–71. eses 2014;5 (2):47–52. Neville BW, Damm DD, Allen CN, Bouqout JE. Oral and maxillofacial Kjær I. Sella turcica morphology and the pituitary gland – a new pathology. WB Saunders, Philadelphia, 1995. contribution to craniofacial diagnostics based on histology and neuroradiology. Eur J Orthod 2015;37:28–36. Skaff DM, Dilzell WW. Lesions resembling caries in unerupted third molar. Oral Surg Oral Med Oral Pathol 1983;56:338. Kjær I, Nielsen MH, Skovgaard LT. Can persistence of primary molars be predicted in subjects with multiple tooth agenesis? Eur J Orthod Smith NH. Monostotic Paget’s disease of the mandible presenting with 2008;30:249–253. progressive resorption of the teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1978;46:246–253. Kjær I, Steiniche K, Kortegaard U, et al. Preeruptive intracoronal resorption observed in 13 patients. Am J Orthod Dentofac Orthop Talic NF, Evans CA, Daniel JC, Zaki AE. Proliferation of epithelial rests 2012a;142:129–132. of Malassez during experimental tooth movement. Am J Orthod Dentofac Orthop 2003;123:527–533. Kjær I, Strøm C, Worsaae N. Regional aggressive root resorption caused by neuronal virus infection. Case Rep Dent 2012b; Article ID 693240.
CHAPTER 12 Apparently normal nonsyndromic dentitions are phenotypically different: the interrelationship between deviations in the dentition and craniofacial profile Introduction Eruption In the past few years, it has become clear that eruption patterns In previous chapters (8–11), the focus has been on individual also can be inherited. Examples are demonstrated in Chapter 10. dental deviations. Meanwhile, one dental deviation rarely occurs as a single deviation in the dentition. There are often several Resorption deviations in a single affected dentition. This can be found in the Heredity is still a relatively new concept in relation to resorption. literature cited and is demonstrated in previous chapters. Resorption in permanent dentitions with short root anomaly is demonstrated in a sibling pair in Figure 12.3. The association In dentitions with agenesis, there are often other dental between resorption in a child and short root occurrence in the deviations with the same etiological background. There may parent is demonstrated in Figure 11.21. also be deviations in the jaws and/or cranium. In this chapter, the association between dental deviations and between dental and Heredity in the dentition and in the craniofacial profile is a vast craniofacial deviations will be highlighted by examples. research area which is currently undergoing substantial devel opment. How a genotype affects the phenotype is still not fully Heredity and the dentition understood. This book focuses on phenotypes and may be able to provide background for improving the understanding of the Agenesis and supernumerarity genotype/phenotype interrelationship. Chapters 2–4 describe It is well known that there is a heredity factor in the occurrence of the relationship between different tissues involved in tooth tooth agenesis. The genetic factor has long been recognized and formation while Chapter 6 describes the same tissues and their pedigrees have been published illustrating the occurrence of this involvement in eruption.The information in these chapters condition through several generations of the same families. enables us to understand how an ectodermal deviation can affect Several genes have been shown to be involved in this pathological both the tooth formation process and the eruption and resorp condition, including MSX1, PAX9, AXIN2, and WNT10A, tion processes of the dentition. The same can be applied to the among others. An example of a rare, inheritable, canine agenesis involvement of the innervation and the ectomesenchymal layer. condition is demonstrated in Figure 12.1. Supernumerarity also It has been suggested that various genes can affect the function of occurs within families (see Chapter 9). the three tissue types (see Figure 4.3). Morphology Dentitions with agenesis of single teeth Tooth morphology is also an inheritable trait. It is well known that narrow teeth and agenesis often occur in the same families Dentitions with agenesis of one or two teeth do not always while broader teeth are more often associated with families in contain other dental deviations. Deviations in the craniofacial which agenesis does not occur. An example of two siblings, one skeleton are not specifically associated with agenesis of few teeth. with a macrodontic incisor and one with a supernumerary incisor, demonstrates this association in Figure 12.2. As previously mentioned, agenesis of a maxillary lateral incisor can mean that the contralateral incisor is a conical, Etiology-Based Dental and Craniofacial Diagnostics, First Edition. Inger Kjær. © 2017 John Wiley & Sons, Ltd. Published 2017 by John Wiley & Sons, Ltd. 168
Apparently normal nonsyndromic dentitions are phenotypically different 169 Figure 12.1 Orthopantomograms from two brothers born six years apart. The upper radiograph from the youngest brother displays a rare case of canine agenesis (affecting three canines and one second premolar). The lower radiograph from the older brother displays agenesis of the maxillary canines and one second premolar. Together, these cases demonstrate that very rare forms of agenesis can be inherited. Figure 12.2 Two brothers born two years apart both with a dental deviation in the maxillary front. (Left) The intraoral photograph shows a macrodontic right central incisor as well as a broad left central incisor. The profile radiograph of the same individual (lower left) shows a bimaxillary prognathia. (Right) The intraoral photograph shows supernumerary central incisors in the older brother. The deviations in the dentitions of these two boys are associated with the craniofacial profile and illustrate how broad teeth and supernumerarity can be interrelated (and inherited). They also demonstrate how the dentition and profile are interrelated.
170 Chapter 12 Figure 12.3 Dental films from a sister (upper) and brother (lower) born three years apart. (Upper) The dental films from the older sister show totally unexpected root resorption of the lateral in the left dental film while this is slightly less severe in the right dental film. Note the short, tapered root morphology of the central incisors which is a sign of resorption. (Lower) The left dental film from the younger brother was taken as a preventative measure. At the time of the radiograph, resorption of the incisors was not apparent but 2½ years later (right radiograph) resorption was registered on the right maxillary lateral incisor. narrow tooth. If there is agenesis of a single premolar, then the Dentitions with multiple tooth agenesis contralateral tooth is often delayed in maturation (see Chapter 9). Agenesis of a single second molar is often but In dentitions where several teeth are congenitally missing, not always associated with agenesis of the contralateral molar. other dental deviations are a regular finding. This could, for Agenesis of one or more canines often occurs in a dentition example, be narrow teeth, shovel-shaped incisors, invagination with just minor deviations which can also occur in dentitions of incisors, taurodontic molars, and short, pointed premolar that are considered to be normally developed (see Figure 12.1). roots (Figure 12.4). Severe idiopathic resorption of primary The cranial base angle seems to be enlarged in patients with teeth can often also be observed. The different factors point to a canine ectopia. common etiology behind the different deviations.
Apparently normal nonsyndromic dentitions are phenotypically different 171 Figure 12.5 Average craniofacial morphology in a group of children missing between five and 12 teeth each and a group of children missing between 13 and 21 teeth each. Note the difference in the cranial base angle, jaw prognathia, and facial height in the two groups. Source: Nodal et al. (1994). Figure 12.4 Orthopantomograms demonstrating different morphological collums in the first molars (see Figure 12.4, center radiograph). characteristics in three patients with multiple agenesis. (Upper) The patient Other types of dentitions with multiple agenesis can have other has screwdriver-shaped incisors, the primary molars are arrested in types of morphological deviations such as conical and screw- eruption and the permament mandibular molars (presumably first molars) driver-shaped incisors, as well as taurodontism. have an ectopic location. (Center) The permanent maxillary first molars are barrel shaped without a narrowing in the cervical area. Furthermore, Dentitions with macrodontic maxillary the primary tooth roots are completely resorbed. (Lower) The permanent central incisors molars are completely absent in this dentition. Some premolars and incisors are also missing. Notice the narrow shape of the maxillary lateral A macrodontic incisor is located in the frontonasal field. An incisors. The radiographs are examples of how agenesis and morphology example of this condition is provided in Figure 12.2. Macro are interrelated with eruption and resorption. dontia is more common in males and crowding occurs in the maxillary incisors and canines. Other dental deviations are not a In multiple tooth agenesis cases, the craniofacial profile is regular finding. However, deviations in the osseous frontonasal commonly characterized by a reduced cranial base angle and segment can be observed, revealing that this entire field is retrognathia of the maxilla and mandible and short anterior dimensionally larger than normal (Figure 12.6). facial height (Figure 12.5). There is a high risk of resorption of permanent teeth during orthodontic treatment. The absence of Dentitions with supernumerary teeth teeth is associated with a poorly developed alveolar process because the alveolar process develops in accordance with the The teeth in dentitions with supernumerary teeth are generally tooth eruption process (see Figure 6.12). This means that tooth broad and often all teeth are present, including the third replacement with, for example, implants is associated with molars. The roots of the teeth are long and root resorption is complications due to lack of alveolar bone. Dentitions with multiple agenesis including agenesis of the maxillary canine and first premolar are characterized by broad
172 Chapter 12 Figure 12.6 Two identical radiographs from a patient with macrodontia illustrating the various cephalometric measurements that can be used to measure the identifiable structures within the frontonasal field. Studies of macrodontia have shown that the nasal bone (na – n) is longer than normal, the thickness of the frontal bone (fo – fi) is increased, the sella turcica (st – sd) is longer than normal in the anteroposterior aspect, the cranial base angle (n – s – ba) is increased, the length of the anterior cranial fossa (n – s) is increased, and the height and length of the maxilla (n – sp, sp – pm) are also increased. In summary, the frontonasal segment is enlarged in patients with macrodontia. Source: Kenrad et al. (2013). Figure 12.7 Radiographs demonstrating supernumerarity in the permanent dentition of a patient approximately 18 years of age. (Left) Orthopantomogram visualizing a supernumerary mandibular premolar and a supernumerary molar in the right side of the maxilla. Note that the teeth are broad and that all the teeth including the third molars are present. (Right) Profile radiograph demonstrating an increased incisor inclination in this patient. rare (Figure 12.7). Supernumerary teeth may occur in greater or Buccal ectopia lesser numbers. In some cases, however, supernumeraries and Teeth in this type of dentition are rarely morphologically devi agenesis of teeth occur simultaneously. It can be presumed that ated. The teeth are broad, and agenesis is rare. This ectopia type dentitions with supernumerary teeth that occur with and without appears to be due to a problem of reduced space in the dental agenesis are the result of two different etiologies. Supernumerary arch. teeth occur in cleidocranial dysplasia – see Chapter 15 for craniofacial appearance. Palatal ectopia In this type of dentition, morphological deviations are often Supernumerary teeth can occur sporadically or as a symptom present throughout the dentition. Some cases have malforma of a syndrome. If they occur sporadically, it does not normally tions only in the incisors while others have deviations in the influence the skeletal profile. incisors and the molars. It is interesting to notice that palatal ectopia occurs more frequently in females than in males and Dentitions with ectopic canines that there is extra space in the dental arch in dentitions with several malformations. This means that the etiology behind First, it is important to distinguish between buccally ectopic the palatal ectopia is not a question of space but rather a canines and palatally ectopic canines. Also, cases with one or two question of reduced eruption capacity in the peri-root sheet palatinal canines should be categorized. and the maxilla.
Apparently normal nonsyndromic dentitions are phenotypically different 173 Figure 12.8 Schematic drawings illustrating the resorption of a maxillary lateral incisor due to pressure from an erupting canine. (Upper) These drawings illustrate the shortening of the left permanent maxillary incisor (22) due to eruption of the canine (23). In the drawing to the right, the degree of resorption is compared to the length of the nonresorbed, contralateral incisor root (12). In a study of root resorption due to ectopic canine eruption, the degree of resorption prior to orthodontic treatment (root length of the lateral) (light purple) was compared to the degree of resorption after treatment (dark purple). It appears from this study that the natural resorption process continues even after an orthodontic appliance is inserted. Source: Reproduced with kind permission of E. Sigurdardottir. From a treatment perspective, it can be seen that palatally profile. As a result, valuable international research on this topic is ectopic canines located close to the incisors can resorb the lateral ongoing. and/or central incisors during eruption. Resorption proceeds apically in the incisors and continues siginificantly after ortho Dentitions with transpositions dontic treatment of the ectopic canine has started (Figure 12.8). This is yet another sign of a possible congenital deviation in the Transposition can occur both unilaterally and bilaterally. A peri-root sheet which might be related to the ectoderm and recent study of dentitions with transposition of the maxillary should be considered in treatment planning. canine demonstrated that patients with canine transposition also had a significant increase in the incidence of agenesis and Palatal ectopia occurs both unilaterally and bilaterally taurodontic root morphology. Other dental anomalies such as (Figure 12.9). The etiology behind these two variations of palatal peg-shaped laterals were more frequent occurrences. Skeletal ectopia appears to be of different origins. There seems to be an morphology appears to be normal in most transposition cases. association between bilateral ectopia and skeletal deviations in In a pilot sudy on bilateral transposition, craniofacial deviations the maxillary/palatine fields (specifically premolar and molar were described (Figure 12.10). The observed changes were malformations) while the unilateral deviation has an etiology an enlargement of the cranial base angle and bimaxillary which is more localized and connected to malformations in the retrognathia. incisor region. There are many conflicting opinions concerning the etiology of palatal ectopia and the effect on the craniofacial
174 Chapter 12 Dentitions with arrested eruption of primary molars Arrested primary molars are regarded as a single finding, but they can occur in all fields. If an arrested primary molar is ankylosed, then it should be extracted. If it is not extracted, it will negatively affect the succeeding permanent tooth, the alveolar process, and possibly neighboring teeth as well. This condition can result in a change in occlusion and severely abnormal alveolar process development (see Chapter 10). The deeper in the alveolar process a primary molar is retained, the earlier the disturbance in the eruption has occurred, and the greater the risk of the succeeding permanent tooth germ being malformed and malpositioned. It is estimated that the earliest occurrences of arrested eruption of primary molars arise before the age of three. Figure 12.9 Orthopantomograms demonstrating unilateral, maxillary, Dentitions suitable for tooth canine ectopia (upper) and bilateral, maxillary, canine ectopia (lower). In transplantation both cases, the dentition appears normal with single taurodontic teeth. It is not recommended to transplant a permanent tooth to a recipient site where agenesis has occurred and where the primary molar has been impacted. If such transplantation is performed, there is a great likelihood that the transplanted tooth will become ankylosed. One study concludes that there is an increased risk of ankylosis when the permanent tooth is transplanted to a primary tooth site where the primary tooth was in infraposition (Figure 12.11). This observation may be decisive for treatment planning, especially in young individuals in whom excessive growth of the alveolar process is expected after transplantation. The etiology is not known. A possible etiological explanation might be found in the nature of the periodontal membrane (which is similar in the primary impacted tooth and the perma nent tooth undergoing transplantation) or the explanation could be abnormality in the bone structure or bone physiology at the recipient site. An ankylosed permanent molar cannot erupt in the postemergence growth period and the resulting discrepancies in the occusal level might create a functional problem. Accordingly, a dentition suitable for tooth transplantation is one in which ankylosis has not occurred at the transposition site. Dentitions with arrested eruption of permanent teeth In this section, three types of arrest in the permanent dentition will be discussed. Figure 12.10 A schematic drawing demonstrating a normal craniofacial Primary retention profile (red) and the craniofacial profile in seven patients all with bilateral Primary retention occurs often in dentitions that have normal transposition of the maxillary canines and first premolar (green). This was development, normal tooth morphology, and normal cranio a preliminary study describing the enlargement of the cranial base angle facial profile. However, deviations can be observed locally in the and bimaxillary retrognathia in the bilateral transposition cases. Source: alveolar process. Danielsen et al. (2015). Reproduced with permission of Springer.
Apparently normal nonsyndromic dentitions are phenotypically different 175 Figure 12.11 Three dental films illustrating recipient sites from a tooth transplanted to a second premolar region where agenesis occurs. (Left) The primary second molar appears with normal root length and normal occlusal level. This is an ideal recipient site for a transplanted tooth. (Center) The primary second molar appears to be arrested in eruption. The roots are needle-like and the alveolar bone is steep (nearly vertical) on either side of the tooth. This is not an optimal transplant recipient site. (Right) This film shows a maxillary third molar which has recently been transplanted to a second premolar recipient site. In this case, the transplantation site was optimal, meaning that the conditions for a successful transplant were good. Secondary retention mandibular gonial angle, and an enlarged mandibular alveolar Individuals with secondary arrested eruption of the permanent prognathia. Also the maxillary incisors’ inclination was less than lower second molar have a frequent occurrence of morphological in the reference group. Local space problems in the jaw can also tooth anomalies such as root deflections, invaginations, and be associated with secondary molar retention. taurodontism. However, secondary retention may also occur in dentitions without other known deviations. Cephalometric Primary failure of tooth eruption studies have demonstrated that individuals with secondary In these dentitions, there is often unilateral or bilateral open bite retention of the second mandibular permanent molars have a stretching posteriorly from the canines. The alveolar processes mandibular prognathia which is less than normal, a small and jaw bones are severely underdeveloped and unexpected, Figure 12.12 Radiographs demonstrating the association between plump root morphology and skeletal open bite. In this case, collum resorption of the permanent maxillary first molar also occurred but is not visible in the radiographs. Collum resorption from this case is illustrated in Figure 11.25 in the upper right corner of the figure.
176 Chapter 12 inexplicable resorption can occur in the molars. The explanation • There is a connection between dental deviations and cranio for the interrelationship between severe eruption problems and facial morphology and between dental deviations and alveolar severe resorption has not yet been elucidated. See Chapters 10 process morphology. and 15 for more information on the dentition and craniofacial profile in patients with primary failure of tooth eruption. • These relationships can be used in an assessment of etiological background and treatment planning. Dentitions with persistence of a primary molar in adulthood • Do not focus solely on the deviation at hand, but evaluate the entire dentition, remembering also to evaluate the primary A single primary molar in childhood with a normal occlusal level dentition. and without any resorption can persist until adulthood under special circumstances. The reported conditions require a denti • Treatment options and outcomes for a “strong” dentition (a tion without dental malformations and with only one permanent dentition with all teeth present and without deviations) differ tooth congenitally missing (see Figure 11.13). The third molar is from the treatment planning and outcomes for a “weak” also often present. dentition (a dentition with several instances of agenesis and or other deviations). • Transplantation has greater success in a “strong” dentition than in a “weak” dentition. Dentitions with idiopathic collum Further reading resorption Bokelund M, Andreasen JO, Christensen SS, Kjær I. Autotransplanta Idiopathic collum resorption in the permanent dentition often tion of maxillary second premolars to mandibular recipient sites occurs in cases where there has been idiopathic collum resorp where the primary second molars were impacted, predisposes for tion in the primary dentition (see Chapter 11). This condition is complications. Acta Odont Scand 2013;71:1464–1468. not clearly elucidated, but it is important to be aware of the association between idiopathic collum resorptions in the two Danielsen JC, Karimian K, Ciarlantini R, Melsen B, Kjær I. Unilateral dentitions. Collum resorption appears to be a sign for progressive and bilateral dental transpositions in the maxilla – dental and skeletal root resorption during orthodontic treatment, but progressive findings in 63 individuals. Eur Arch Paediatr Dent 2015;16:467–476. resorption can also occur in cases not treated orthodontically. Collum resorption often occurs in dentitions with plump roots Kenrad A, Christensen IJ, Kjær I. Craniofacial morphology of the and skeletal open bite (Figure 12.12). frontonasal segment in patients with one or two macrodontic maxil lary central incisors. Eur J Orthod 2013;35:329–334. Highlights and clinical relevance Nodal M, Kjær I, Solow B. Craniofacial morphology in patients with multiple congenitally missing permanent teeth. Eur J Orthod 1994;16:104–109. Sørensen HB, Artmann L, Larsen HJ, Kjær I. Radiographic assessment of dental anomalies in patients with ectopic maxillary canines. Int J Paediatr Dent 2009;19:108–114. • There is an association between dental deviations in the primary and permanent dentitions.
CHAPTER 13 Craniofacial syndromes and malformations: prenatal and postnatal observations In this chapter, we focus on syndromes and malformations for Concerning tooth development, a deciduous central incisor was which both prenatal and postnatal screenings have been con demonstrated midaxially in the intermaxillary suture in a cebo ducted to detect abnormalities in the hard tissue. Craniofacial cephalic fetus (Figure 13.3). development and dental development are well-integrated pro cesses. In some syndromes and malformations, the dentition In the sella turcica, the anterior wall is completely or partially provides the essential characteristics for recognition of the absent and the pituitary gland is malformed (Figure 13.4). Also in condition. the sella/pituitary region, the severity of malformation is strictly related to the external features. The vertebral column has in most Holoprosencephaly/solitary median cases a normal morphology. Histological studies have shown that maxillary central incisor (SMMCI) the nasal cavity and nasal septum are severely malformed – most syndrome pronounced in cyclopia and less pronounced in midline cleft (Figure 13.5). Holoprosencephaly (Greek for one brain hemisphere) is a con dition in which the brain has a nonseparated prosencephalon. The malformations in holoprosencaphaly are restricted to From a craniofacial point of view, it is interesting that the face tissues and organs located within the fan-shaped tissue mass also lacks a midline structure. which composes the frontonasal field (Figure 13.6). The field stretches from the pituitary gland/anterior wall of the sella Prenatal turcica and externally to the lowermost part of the forehead Severe holoprosencephalic conditions are lethal. The hemispheres and to the tissues between the eyes, the nose, and the axial part of of the cerebrum are not divided midaxially. This nonseparation the upper lip. The crista galli, the midline aspects of the cere can occur in just a small area or more extensively along the brum, and the nasal septum are also located within this tissue midaxis. The fact that the cerebrum is not clearly divided at the mass. Caudally, the frontonasal field is limited by the palate midaxis means that the falx cerebri, which separates the hemi (Figure 13.7). The frontonasal tissue segment is triangular in spheres and is attached to the crista galli, has not developed. This shape and looks like a fan from above (see Figure 13.7). If the condition causes the following cranial deviations: entire fan is missing, then the eyes are close-set and the most • absence or reduced size of the crista galli (process of the severe degree of cyclopia occurs. If the fan is half-sized, missing only the axial area, then there is just one nostril (cebocephaly). If ethmoid bone) only the most axial part of the fan is missing, the resulting • absence or maldevelopment of the nasal septum. condition is SMMCI. There are different grades of severity of holoprosencephaly The brain is malformed in different grades of severity from which are expressed in the facial features as well as in the united (nonseparated) hemispheres to partly divided hemi underlying bone and brain. spheres (Figure 13.8). In the face, these deviations are cyclopia (extremely close-set Only the less severe holoprosencephalic fetuses can survive. eyes), short or absent nasal bones, absence of the protruding nose These have only minor degrees of the holoprosencephalic exter (ethmocephaly), less severe deviation such as one nostril (cebo nal features, such as close-set eyes and deviations in the contours cephaly), midline cleft and short lip (midline cleft) (Figure 13.1). of the philtrum. Postnatal SMMCI syndrome exemplifies a In holoprosencephaly, the lip contour is malformed and there is a condition which can occur with or without the abnormal brain midpalatal vault (swelling). The palate is narrow and the vault is formation. most pronounced in cyclopia, while it is not present in midline cleft (Figure 13.2). Thus, the severity of the extraoral structures is Postnatal strictly correlated with the severity of the intraoral structures. Only the mild forms of holoprosencephaly are viable. These are mostly median cleft and short lip cases. The mildest form is SMMCI syndrome which involves skeletal deviations which are Etiology-Based Dental and Craniofacial Diagnostics, First Edition. Inger Kjær. © 2017 John Wiley & Sons, Ltd. Published 2017 by John Wiley & Sons, Ltd. 177
178 Chapter 13 Figure 13.1 Facial appearances of four human fetuses GA between 15 and 19 weeks with various severities (in order from most to least severe) and types of holoprosencephaly. (Far left) Type: Cyclopia. This face is characterized by cyclopia and a proboscis (yellow star) above the cyclopic eye, as well as absence of the nose. (Center left) Type: Ethmocephaly. The eyes are very close-set. In some ethmocephalic fetuses, a proboscis appears as demonstrated in this photograph (yellow star). This is an inconsistent finding, however. A nose has not developed. (Center right) Type: Cebocephaly. In this face, they eyes are also close-set. A nose has formed but has only one nostril (arrow). The upper lip contour is abnormally straight. (Far right) Type: Midline cleft. In this face, the eyes appear to have a normal interocular distance. The nose is formed and a midline cleft exists (arrow). When comparing these four faces, it is obvious that the frontonasal field is absent in cyclopia. In the proboscis, histological sections have demonstrated traces of cartilaginous tissue which should have formed the nasal cavity. The cebocephalic fetus (with a nose) contains more of the frontonasal field than the ethmocephalic fetus. less severe but comparable to the midaxial deviations seen in narrow, often with a deviation in the nasal septum and absence of holoprosencephaly (Figures 13.9 and 13.10). Characteristic for the anterior nasal spine, and the sella turcica is diminutive, the dentition is the presence of only one, undivided maxillary sometimes with an inclination in the anterior wall (Figure central incisor. This tooth is symmetrical along the midaxis (see 13.14; see also Figure 13.12). Chapter 8). In the primary dentition, there is also one central deciduous incisor (Figures 13.11 and 13.12). The primary and In a very rare condition called solitary median maxillary lateral permanent incisors can have one root or an apically split root, incisor (SMMLI), there is only one maxillary incisor (Figure appearing with two apices (see Chapter 8). As in holoprosence- 13.15). This is a midaxially located, symmetrical, lateral incisor phaly, the child lacks the midaxial facial structures which results and this condition involves the absence of a broad axial tissue in a short, malformed nasal bone, reduced ocular distance, a segment which stretches from the midaxial lateral incisor to the tubular nose, absence of the philtrum, deviations in the lip pituitary gland. This condition, in which a single symmetrical contour, absence of the superior labial frenulum, absence of lateral incisor is bordered by two maxillary canines, can be the incisive papilla, and presence of a midpalatal vault (Figure combined with hypopituitarism. The missing axial area within 13.13; see also Figures 13.11 and 13.12). The nasal cavity is also the frontonasal field is larger in the SMMLI condition than in the SMMCI condition. Figure 13.2 Demonstration of four palates seen from the occlusal view. The palates are from four types of holoprosencephalic human fetuses (demonstrated in Figure 13.1) in the same order. (Far left) The palate from a human fetus with cyclopia has a circular shape characterized by a midaxial vault (arrows). (Center left) A palate from an ethmocephalic human fetus is characterized by a deep vault midaxially and a palate shape which is rounded but has more parallel buccal edges than the palate in cyclopia. (Center right) A palate from a cebocephalic human fetus. The palate has a more recognizable palate formation but is still more narrow posteriorly. (Far right) In a palate from a midline cleft human fetus, the palatal defect follows the midline. In combined cleft lip and palate, the defect does not follow the midline – it reroutes towards the lateral incisor in either one or both sides. The etiology behind midline cleft and combined cleft lip and palate is completely different. In midline cleft-holoprosecephaly, the frontonasal field (formerly named the premaxilla) is completely absent. The nasal septum can be seen through the midline cleft in the photograph.
Craniofacial syndromes and malformations 179 Figure 13.3 These figures illustrate the absence of the midpalatine suture in the incisor region on a human fetus (left) and a child approximately three years of age (right). (a) A horizontal, histological section of the anterior part of the palate from a cebocephalic, holoprosencephalic human fetus. The anterior face points upward in the figure. The section illustrates a primary central maxillary incisor tooth bud located midaxially (D). Posteriorly to this tooth bud (below in the figure), the midpalatine suture appears (M). Bilaterally from the midpalatine suture, the incisive fissures appear (I). Accordingly, this section demonstrates that the midpalatine suture only exists until it reaches the tooth bud from behind. In the alveolar bone (B) anterior to the tooth, there is no suture. Usually, the interincisal part of the midpalatine suture approaches the anterior maxillary alveolar bone (B) but this is not the case in this condition. (b) A magnetic resonance image from a child with SMMCI demonstrating a horizontal view of the cranium at the palatal level. The white arrow points to the primary central maxillary incisor and the dark arrows point to the midpalatine suture which does not continue to the incisive region. The scan illustrates the midaxial location of the primary central maxillary incisor. Patients affected with SMMCI are often girls who are short In SMMCI, craniofacial cephalometric analysis demonstrates in stature (Figure 13.16). Growth hormone supply can be that the length of the anterior cranial fossa, expressed as the recommended due to abnormal pituitary gland function. Brain distance from the fixed point nasion (n) to the fixed point sella scanning can reveal interdigitations of the hemisphere mid- (s), is significantly shorter than in normally developed children axially (Figure 13.17). This is an example of a craniofacial (Figure 13.18). In a 3D analysis of the palate, it can be observed syndrome where the individual symptoms can all be found in how the central incisor lies midaxially in relation to the mid- the midaxial region of the maxilla and in the anterior cranial palatine suture. An orthopantomographic analysis of the denti fossa which includes some of the frontal squama and the tion of a child with SMMCI demonstrates that the only anterior part of the hemipsheres (see Figure 13.7). The skeletal malformation in the dentition is this single maxillary incisor symptoms all appear within the frontonasal developmental (see Figure 13.12). field. In conclusion, the findings in prenatal holoprosencephaly and Embryologically, the deviations all arise from a malfunction in in postnatal SMMCI are in accordance with one another. the early telencephalic region rostrally between the hemispheres of the CNS (see Figure 13.7). Also, the growth retardation could Orthodontic treatment of SMMCI depends on the sagittal, be related to the abnormal development of the pituitary gland. vertical, and transverse deviations observed in each individual. The adenopituitary gland, which is the anterior part of the There are, in short, two treatment options. One involves extrac pituitary gland, is abnormal and developmentally dependent tion of the medial central incisor and mesial movement of the on the neuropituitary gland, located midaxially in the brain. laterals which are later morphologically shaped as central incisors. Another orthodontic treatment plan could be extraction of one
180 Chapter 13 Figure 13.4 Midsagittal, histological sections of the cranial base through the sella turcica, from a cyclopic and a cebocephalic human fetus. The anterior face points to the left. A schematic drawing illustrates the morphology of the sella turcica and the positioning of the adenopituitary gland tissue (red) and the neuropituitary gland (yellow). (Left) Section from a cyclopic fetus. It is characteristic that the dorsum sellae (D) and the posterior part of the floor (F) in the sella have a normal morphology. An arrow indicates the rostral end of the notochord which has a normal appearance. The anterior wall and anterior part of the floor are completely absent. There are cartilaginous remnants (C) which might indicate a severe malformation in the region anteriorly to the sella turcica. N indicates the neuropituitary gland and A indicates the adenopituitary gland tissue which is normally located in a pit in the floor of the sella. In this case, with absence of the anterior sella floor, the adenopituitary tissue is observed in both the sella and the pharynx. (Center) Section from a cebocephalic fetus. In this case, the sella turcica has formed but the cartilaginous area (C) anterior to the sella is malformed. The dorsum sellae (D) is broad but with a normal location. In this section, the pituitary gland does not appear. The bone formation of the sella has begun in the floor region (F) as it would under normal conditions. An arrow indicates the rostral end of the notochord which has a normal appearance. (Right) Schematic drawing showing an example of the sella turcica in holoprosencephaly. Note the normal posterior wall of the sella, the malformed anterior wall, and the ossified posterior floor (white dots) while a hole/channel exists in the region of the anterior floor. The adenopituitary gland is displaced as indicated and the neuropituitary gland has its normal location in the sella turcica. The notochord is not drawn. The drawing illustrates the normal development of the body axis to the middle of the floor in the sella. Neurologically, the infundibulum cerebri maintains its usual function. The malformed areas are all anterior to the sella turcica. Source: Kjær (2015). premolar to create space for a new central incisor. This can be Cerebellar hypoplasia/cri-du-chat difficult due to the often narrow palate. Maxillary suture expan- syndrome sion is not recommemded in these cases because the anterior part of the midpalatine suture (intermaxillary suture) is not present. In Prenatal some cases, orthodontic treatment is not needed and the dentition In cerebellar hypoplasia and pons malformation, a bony defect is as well as the extraoral appearance is acceptable with one central often observed in the basilar part of the occipital bone (Figure incisor in the maxilla. Body growth control and referral to an 13.19). The malformations in these cases are all within the cerebellar endocrinologist are important for pubertal development. or occipital field and are caused by a malfunction of the rostral Figure 13.5 Frontal, histological sections through the nasal cavities of three holoprosencephalic fetuses between 15 and 19 weeks GA. (Left) From a cyclopic fetus. The nasal cavity appears disorganized with many small and irregular lumens. (Center) From a cebocephalic fetus. In this section, the nasal cavity appears as one space not divided by a nasal septum. A diminutive nasal septum (arrow) appears in the roof of the cavity. (Right) From a midline cleft fetus. In this section, the nasal cavity appears as a broad space with a malformed septum. The cut is not completely in the frontal plane, but slightly skewed.
Craniofacial syndromes and malformations 181 Figure 13.6 Profile radiographs from four holoprosencephalic fetuses GA 15–19 weeks. The cranium of each fetus has been sectioned midsagittally into two parasagittal blocks. Each of these blocks was radiographed separately to avoid overlapping of structures from the parasagittal block. The sections seen in these four images are one block from each of the four holoprosencephalic fetuses. Each includes the forehead, nose area, maxilla, and cranial base. For comparison, the area radiographed prenatally represents the same area which can be analyzed postnatally on profile radiographs. (Far left) Profile radiograph of a cyclopic fetus. The maxilla appears as a compact mass. In the cranial base, the basilar part of the occipital bone is visible (white arrow). The posterior part of the corpus of the sphenoid bone is marked with a red arrow. Pr marks the proboscis. Inset is a diagram illustrating the frontonasal segment of the face which is severely malformed in holoprosencephalic cases. (Center left) Profile radiograph from an ethmocephalic fetus. Note the proboscis (Pr), the compact maxillary bony mass which is a malformed maxilla, the basilar part of the occipital bone (white arrow) and the posterior part of the sphenoid bone corpus (red arrow). Three vertebral bodies are also present. (Center right) Profile radiograph from a cebocephalic fetus. In this case, the nasal bone (N) is visible and the maxilla appears as a compact mass despite a somewhat recognizable nasal cavity over the mass. The basilar part of the occipital bone is marked with a white arrow and the posterior part of the sphenoid bone corpus with a red arrow. A split vertebral body is observed. (Far right) Profile radiograph from a midline cleft fetus. In this radiograph, there is no compact maxillary mass. The palate is marked P and the nasal bone N. The basilar part of the occipital bone is marked with a white arrow and the sphenoid bone corpus with a red arrow. In this case, the posterior and anterior parts of the sphenoid bone corpus are fused in the sphenoid bone. The presence of the anterior sphenoid corpus indicates a more mature fetus compared to the three others. These images illustrate that the basilar part of the occipital bone and the posterior part of the sphenoid bone are normal in all the cases. These structures represent the rostral part of the notochord belonging to the occipital field which is unaffected. In this condition, all the malformations occur anteriorly to the posterior sphenoid corpus. The severity of bone malformations decreases from cyclopia to midline cleft. Figure 13.7 Illustrations demonstrating the area affected in a holoprosencephalic fetus in the brain (left) and in the cranial base (right). (Left) The drawing indicates the early brain formation in the embryonic period. The telencephalon, yellow, includes the brain hemispheres (I and II). The diencephalon, blue (III); the mesencephalon, orange; the metencephalon and myelencephalon (also called the rhombencephalon), green (IV); the spinal cord, light orange (lowermost part in the drawing). Source: Drews (1995). Reproduced with permission of Thieme Publishing Group. The red triangle indicates the part of the brain which lies anteriorly to the pituitary gland and which is affected to varying degrees of severity in holoprosencephaly. If tissue does not exist within the triangle, the most severe type of holoprosencephaly is produced. Holo = one, prosencephalon = forebrain; the name holoprosencephaly thus refers to “one, nonseparated forebrain” which is the case in this condition. The prosencephalon is composed of the telencephalon and the diencephalon. (Right) The interior cranial base viewed from above in a normal human fetus approximately 16 weeks GA. The red triangle indicates the part of the cranial base which supports the part of the brain indicated in the red triangle in the left illustration. The black arrow points to the crista galli which is the attachment area for the falx cerebri which separates the hemispheres. If the bone tissue within the triangle is not present, the crista galli and falx cerebri do not form and the prosencaphalon is “nonseparated.” The etiology behind intellectual disability in the most severe cases of surviving holoprosencephalic patients is this brain defect. In less severe cases, the brain might be partly nonfused.
182 Chapter 13 Figure 13.8 External view and brain morphology in a nonviable ethmocephalic human fetus. (Left) The frontal view of the face is characterized by a short interocular distance and a proboscis located between the eyes. The nose is absent while the prolabium is diminutive and without a philtrum. Source: Keeling (1994). Reproduced with permission of Elsevier. (Center) The lateral view of the same fetus. Note the backward tilted forehead and the smaller, deformed neurocranium. (Right) A posterior view of the brain in the same fetus. Notice how the hemispheres are nonseparated midsagittally and how the cerebellum (C) is not covered by the bilateral cerebral hemispheres as in normal brain development. The development of the cerebellum appears to have been normal. The cerebellum forms in the axial plane and is located in the occipital field (also called the cerebellar field). This field is not disturbed in this condition (see Figure 13.6). Source: Keeling (1994). Reproduced with permission of Elsevier. notochord. The cranial deviations include malformation in the clivus region and in the posterior wall of the sella turcica. Postnatal Cri-du-chat syndrome is an example of a syndrome with a cerebellar malformation. Patients are intellectually disabled. The posterior wall of the sella turcica is thick with a wide base and a reduced cranial base angle is observed cephalometri cally (Figure 13.20). The face is broad and the distance between the eyes is greater than normal, but without other malformations. Analysis of this condition has demonstrated that the occipital field is involved in cri-du-chat, specifically the ninth and tenth cranial nerves – n. glossopharyngealis and n. vagus. These nerves connect the cerebellar region to the laryngeal area. This expresses Figure 13.9 Schematic drawing illustrating how the area of facial Figure 13.10 Illustration of a child with SMMCI which can be combined malformation (black area within the face) is related to the skeletal with holoprosencephaly in the mildest form. The condition can also occur malformations found in the face, jaws, and cranial base (partly without association to holoprosencephaly. Note the close-set eyes, the illustrated in Figure 13.6). The green color marks the bones that are upper lip without a philtrum, and the less prominent nose. present and the red line indicates the position of the notochord before ossification. The most severe case (cyclopia) is demonstrated in the upper left corner and the least severe case (short lip) is demonstrated in the lower right corner. Between these two conditions are the decreasing degrees of severity from left to right (ethmocephaly with and without proboscis, cebocephaly, midline cleft). The three cases marked with black stars are able to survive with this condition. An awareness of the more severe malformations within the same diagnostic spectrum enables a better insight into the etiology-based diagnostics of newborns with congenital malformations. Source: Kjær et al. (1991). Reproduced with permission of BMJ Publishing Group Ltd.
Craniofacial syndromes and malformations 183 Figure 13.11 An intraoral photograph and three dental films of the primary dentition in SMMCI. (Left) In the maxillary arch, there is one primary central incisor. This has a square-like shape and appears to be composed of the two distal halves of two primary central incisors. A mirror was inserted into the mouth so that the oral surface of the maxillary dentition as well as the midaxial tissue vault (V) in the palate could be observed. (Right) These three dental films from the age of four years to the age of six years demonstrate the single, axially located, primary central incisor (I) in two of the radiographs. Note that the root is broad and that the succeeding tooth (S) is also a single permanent central incisor. In the center radiograph, two narrow crowns which are united in a “fused” root appear. This is a rare and mild case of SMMCI in which the condition is first discovered in the dentition during eruption of the single permanent central incisor. Figure 13.12 (Upper figures) The permanent dentition in SMMCI observed intraorally and radiographically. (Left) Two intraoral photographs demonstrating the presence of one single central maxillary incisor. The superior labial frenulum is absent (upper) and a mirror inserted in the mouth visualizes the midsagittal vault observed in the palate marked by an arrow (lower). Notice that there are no papillae incisivae anteriorly in the palate. (Right) An orthopantomogram demonstrating the midsagittally located, single central incisor in the maxilla. Notice also that all other teeth are normally developed and normally located. Because of the absent midaxial tissue, there is not only just one central incisor but also a very narrowly formed nasal cavity and close-set eyes. (Lower figures) An orthopantomogram of two seemingly fused maxillary central incisors. The patient has a minor cleft in the lip. A dental film of the maxillary central incisors is inset in the upper right corner. In the upper left corner, there is an intraoral photograph of the patient just before shedding of the primary incisors. The primary incisors appear as two individual teeth and the roots at this late stage appear fused. This is a case of abnormal development in the frontonasal segment. An asymmetrical nasal cavity is also observable.
184 Chapter 13 Figure 13.15 Demonstration of an extremely rare condition called solitary median maxillary lateral incisor (SMMLI). (Upper left) A midaxially located, single, lateral, symmetrical tooth between two maxillary canines in the primary dentition. (Lower left) A section from an orthopantomogram showing that the permanent dentition also contains one, midaxially located, single, lateral, symmetrical incisor. (Right) A schematic drawing indicating the maxillary incisor region in SMMLI. In this condition the central lateral incisor (L) is bordered by two canines (C). This means that the amount of tissue that normally includes the central incisors and one lateral incisor and extends posteriorly to the sella turcica is absent. The tissue from the incisive alveolar bone to the sella turcica involving the anterior cranial fossa and the midaxial part of the brain is therefore missing. Figure 13.13 Lip contours observed in the SMMCI condition. The prolabium of the upper lip has a characteristic shape which also appears in Figure 13.10. Figure 13.14 Profile radiograph of a child with SMMCI. There is Figure 13.16 A height and weight increment in a child with SMMCI from retrognathia of the maxilla and a morphological change in the sella turcica. the age of 11 to 17 years. At the age of 12½ years, the patient was treated The sella turcica in the profile radiograph is enlarged in the upper right with growth hormone. The beginning of treatment is marked by an arrow figure. The normal shape of the sella turcica at this age is displayed for in the upper growth curve. The figure shows that the child’s height was comparison in the lower right figure. below the normal range (green area) before growth hormone treatment and that growth was normalized during the treatment period. The lower figure shows the weight which was within the normal range both before and after the treatment was received. Source: Kjær et al. (2010). Reproduced with permission of Thieme Publishing Group.
Craniofacial syndromes and malformations 185 Figure 13.17 Scan from a child with SMMCI. Frontal section a deviation in the anterior wall of the sella turcica. This neuro demonstrating the interdigitalization of the frontal part of the cerebral osteological aspect confirms that the notochord controls devel hemispheres (arrows). Source: Kjær et al. (2010). Reproduced with opment of not only the CNS (e.g. closure of the neural tube) but permission of Thieme Publishing Group. also craniofacial bone tissue. Histological investigations have revealed severe malformation in the sella turcica region in spina the neural crest field involved in the cri-du-chat condition (see bifida cases, and minor malformations in cranial encephaloceles. Figure 13.20). Pharyngeally located adenopituitary gland tissue occurs in all fetuses (Figure 13.23). Myelomeningoceles/spina bifida and hydrocephalus Occipital encephaloceles (cranium bifidum) is a condition in which the cerebellum bulges out in the neck region. Parietal and Prenatal frontal encephaloceles occur in the cranium. These often appear Myelomeningoceles along the body axis occur as a nonclosure of bilaterally as two swellings on either side of the midaxis. In the the neural tube with an outbulging of CNS tissue. These celes can lower aspects of the cerebrum, celes can occur through the occur along the vertebral column from the lumbar region to the ethmoid bone and are thus called ethmoidal encephaloceles. occipital region (Figures 13.21 and 13.22). Finally, there are axial transsphenoidal encephaloceles, which can be found in the sphenoid body region (Figures 13.24 and What can these severe prenatal myelomeningoceles and ence 13.25). Some myelomeningoceles and encephaloceles occur as phaloceles teach us about cranial development? malformations where the genotype is unknown. In some cases, myelomeningoceles occur as part of a syndrome. Firstly, bone malformations can occur in the spinal region where the celes are located, but more significantly, there is always Hydrocephalus can occur in connection with myelomeningo celes. In this case, the sella turcica is large and sometimes the floor of the sella is malformed, with a channel between the internal and external cranial bases. In these cases, the pituitary gland is ectopically, pharyngeally located (see Figure 13.24). Hydrocephalus can also occur prenatally due to ventricular malformations and without the presence of a myelomeningocele condition. Malformations in the sella turcica region are also observed in these cases (see Figure 13.24) Postnatal In postnatal spina bifida cases where outbulging of the CNS does not occur, the condition may be associated with hydro cephalus. The common treatment is a shunt in the ventricles of the brain (see Figure 13.25). This reduces the internal cranial Figure 13.18 A cephalometric drawing and a profile radiograph of a child with SMMCI. (Left) The letters n, f, br, I, opc, ba and s are cephalometric reference points. The distance between these reference points is used to illustrate the various sizes of the neurocranium. The blue lines indicate normal length, the orange lines indicate reduced length, and the green line (measuring the anterior cranial fossa) indicates a significantly shorter length than normal. The cephalometric measurements in this figure support the fact that the SMMCI condition is expressed in the frontonasal field and that the cranial lengths depending on the frontonasal field are also affected. (Right) The green line indicates the length of the anterior cranial which is significantly shorter in SMMCI. Source: Tabatabaie et al. (2008). Reproduced with permission of John Wiley & Sons.
186 Chapter 13 experimentally that the same genes might be expressed in the lumbosacral region as in the cranium. As an example, the expression of Pax9 has been demonstrated along the body axis as well as in the cranial region (Figure 13.26). This suggests a correspondence between two locations but does not explain the detailed association between spina bifida and the anterior wall deviations of the sella turcica. In a group of children with myelomeningocele/spina bifida, morphological changes were observed in the anterior wall of the sella turcica (see Chapter 2). In hydrocephalus, the sella turcica appears larger than normal (see Figure 13.26). Before shunt treatment, indivudals with hydrocephalus devel oped grotesque cranial shapes due to the enormous intracranial pressure (Figure 13.27). Observations on the prenatal and post natal aspects of myelomeningoceles are in accordance with one another. Figure 13.19 Radiograph of the front maxillary complex and cranial base Down’s syndrome (trisomy 21) seen in the profile of a human fetus 16 weeks GA with cerebellar hypoplasia. Note that the basilar part of the occipital bone is malformed Prenatal with a notch (arrow) in the region opposite the cerebellum. This indicates In prenatal studies of Down’s syndrome, the cranium, spine, and that there is a correlation between bony development and cerebellar hand have been analyzed. The cranium is characterized by an development in the occipital/cerebellar field. The presence and enlarged cranial base angle, short or absent nasal bones and often a morphology of other bony structures are normal in this stage of midpalatal cleft in the posterior aspects of the palate. Minor development. malformations occur in the sella turcica, especially with an incli nation of the anterior wall. Pituitary gland tissue can appear in the pressure and prevents cranial deformation. Investigations have submucosa of the pharynx (Figure 13.28). The cerebellar field, also drawn attention to the fact that congenital malformations in known as the occipital field, can be cephalometrically smaller in the the axial skeleton located far from the cranial base may sagittal dimensions that in a genotypically normal fetus. The manifest in the cranial base as well. The pathogenetic rela osseous symptoms in the spine are in most cases confined to tionship between these malformations can be found in the the cervical spine region. Only in the most severe cases can the early embryonic development. It has been demonstrated Figure 13.20 Radiographs and a schematic drawing of the structures involved in cri-du-chat syndrome. (Left) A profile radiograph of a child six years of age. Note the broad dorsum sellae (arrow). (Center) Two sections of radiographs demonstrating the sella turcica in cri-du-chat syndrome with a characteristic, very broad dorsum sellae (arrow). (Right) Schematic drawing illustrating the interrelationship between the cerebellum (diminutive and malformed in cri-du-chat syndrome), the posterior wall of the sella turcica, the clivus, and the larynx. This field is innervated by the ninth and tenth cranial nerves. Source: Kjær and Niebuhr (1999). Reproduced with permission of John Wiley & Sons.
Craniofacial syndromes and malformations 187 Figure 13.21 A myelomeningocele observed in a human fetus. The morphology. In the hand, the medial phalangeal bone in the fifth condition is combined with hydrocephalus. Source: Keeling (1994). finger is diminutive and malformed. Down’s syndrome patients Reproduced with permission of John Wiley & Sons. are often of short stature. The sella turcica formed in cartilage has anteriorly and posteriorly diverging walls and sometimes more entire spine be malformed. The types of malformations seen before severe abnormalities (Figure 13.31). In the dentition, agenesis is 20 weeks GA are double vertebral bodies and absent bodies (Figure very common, occurring more frequently in the mandible than in 13.29). The length of the hand is normal during the first half of the the maxilla and most often on the left side (see Chapter 9). The fetal period, whereas the length of the individual bones is reduced. highly significant differences were primarily found in the occur The sequence of ossification of the phalangeal bones is also normal, rence of agenesis of the mandibular central incisors followed by except for the fifth finger, where the middle phalangeal bone ossifies the maxillary lateral incisors and second premolars, and the later or does not ossify. Also in the medial phalangeal bone of the mandibular second premolars (Figure 13.32). second finger malformation can be observed, but to a lesser degree. The pattern of agenesis observed in Down’s syndrome in Postnatal regions where the innervation pathways end within the jaw The characteristic craniofacial symptoms are short nasal bones, fields could be related to the PNS; some aspects may also be retrognathia of the maxilla, a large cranial base angle, and related to deviations in the ectomesenchyme (abnormal carti lowering of the caudal region of the occipital squama (Figure laginous tissue) (Figure 13.33). It is interesting that the high 13.30). In the cervical vertebrae, there are changes in size and prevalence of agenesis in the anterior mandibular area occurs in the same region in which the teeth erupt later than normal (see Chapter 10). This might indicate the importance of the innerva tion for both the formation and the eruption of teeth. The teeth present are often small and deviations occur in the eruption sequence (see Chapter 10). Furthermore, ectopically erupting teeth and resorption occur unexpectedly. In conclusion, the skeletal findings in prenatal and postnatal Down’s syndrome are in accordance with one another. Turner’s syndrome Prenatal The prenatal characteristics for fetuses with Turner’s syndrome are a broad neck with an extra costal bone attached to the seventh cervical vertebra (Figure 13.34). The cranial base is short and the cranial base angle is larger than normal (Figure 13.35). The maxillary prognathia is reduced and the nasal bone short. There are no other significant morphological deviations in the prenatal cranium. The dimensions of the cranial complex and of the hand/finger dimensions show that the bone lengths in relation to the size of the fetus are generally smaller when compared to normally developing fetuses. The hand is short and the distal phalangeal bones are small and pointed. The vertebral bodies appear normal in the initial stages of development. Postnatal The cranium in Turner’s syndrome has a cephalometrically enlarged cranial base angle (see Figure 13.35). There is also a lowering of the caudal part of the occipital squama. The first vertebra, the atlas, has a characteristic morphology as it is both short and thin. The teeth are generally smaller than normal and the pulp chambers are reduced in size (Figure 13.36). Figure 13.22 Cranial encephalocele demonstrated prenatally and Fragile X syndrome postnatally. (Left) A parietal encephalocele. Source: Kjær et al. (1996). Reproduced with permission of Taylor & Francis. (Right) Based on this Prenatal profile radiograph of a child, the diagnosis of ethmoidal encephalocele was The ossification sequences of bone components in the vertebral confirmed by a neurologist. The encephalocele is marked by two arrows. column, the facial skeleton, the cranial base, and the limbs are
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