Intraoral Radiographic Principles and Techniques 31 A B Figure 2.20 (A) Horizontal bitewings. (B) Vertical bitewings. Bite-wing radiographs are typically produced with the size 2 receptor in a horizontal orientation, but in situations where the alveolar crests have receded, horizontal bite-wings may fail to reveal the alveolar crests. Reorienting the receptor into a vertical position (vertical bitewing) will capture the apically positioned alveolar crests on the image (Figure 2.20A,B). Method Figure 2.21 Clockwise from left, stick on bite tabs, cardboard bite tab loops and RINN XCP-DS (digital) The seven basic steps used to produce intraoral bitewing instrument. (Images courtesy of B. Rakiewicz, images, as outlined earlier, are applied to produce BAA, RBP, DPES, Faculty of Dentistry, University of the bite-wing radiographs. Toronto, 2011.) Receptor holders The type of holder is selected and attached appropriately to the receptor. To produce a bite-wing radiograph, the receptor must be held in position. Several types of receptor When using the bitetab loop, the receptor is hori- holders are available for use with film type or zontally inserted into the loop so that the loop digital receptors. wraps around it and the horizontal tab is cen- tered, extending outward from the active side Cardboard bitetabs loops of the receptor. Stick on bitetabs Rinn XCP and XCP-DS bite-wing instrument (Figure 2.21).
32 General Principles and Techniques Stick on bitetabs are attached and centered on Figure 2.22 Acquiring a bitewing radiograph. (Image the plastic sleeve or outer plastic covering of courtesy of B. Rakiewicz, BAA, RBP, DPES, Faculty of the active side of the receptor. Dentistry, University of Toronto, 2011.) Rinn XCP and XCP-DS bite-wing instruments the occlusal surfaces of the teeth. The patient is support the correctly inserted receptor to instructed to close their teeth together into their provide rigid stabilization and an aiming ring natural biting position. The operator holds the for the PID. horizontal component during closing so that the receptor position is maintained. It is important to correctly attach the bite-wing holder to the receptor. If the horizontal extension Aiming the PID is not centered, the resulting image will exhibit a disproportionate amount of each arch and may Vertical angulation therefore limit the usefulness of the radiograph. With the patient’s head stable against the head- rest and oriented so that the occlusal plane is Attaching the holder so that the horizontal parallel to the floor when in occlusion, the ver- extension is on the incorrect (nonactive) side places tical plane of the maxillary and mandibular the receptor backward in the mouth, producing posterior teeth are aligned at a small angle. an image that is reversed, resulting in mounting In order for the X-ray beam to strike the errors, which can lead to confusion and potential receptor at a 90-degree angle (perpendicular), errors in treatment. Film type receptors placed the PID must be rotated to approximately +10 backward will produce a lighter (less dense) image degrees (Figure 2.10). This allows accurate rep- with a geometric superimposition of the embossed resentation of the teeth on the image, with lead foil along one side. maximal overlapping of the buccal and lingual cusps and surfaces of the alveolar crest. Receptor positioning Horizontal angulation There are four standard locations for positioning The X-ray beam is directed through the inter- bite-wing radiographs; two on either side of the proximal contacts of the adjacent teeth in the dental arch. These include the anterior (premolar) view. In this way the beam will strike the recep- bite-wing radiograph and the posterior (molar) tor at a 90-degree angle (perpendicular), pro- bite-wing radiograph (Figure 2.20A,B). viding a clear view of the interproximal regions free of any superimpositions. If the horizontal The anterior bitewing is positioned so that the angulation of the beam directed incorrectly, the distal aspect of the canine is captured in the resulting image will display superimpositions image. The posterior bitewing is positioned more dis- tally in the arch ensuring that the distal aspect of the last erupted molar is evident in the view. When all four radiographs are prescribed, the maxillary and mandibular crowns of all of the pos- terior teeth are imaged simultaneously. To insert the receptor with its holder into posi- tion, the patient is instructed to open their mouth while the operator slides the base of the receptor into the lingual aspect of the mandibular arch. The receptor should be aligned parallel and rest against the mandibular teeth. All bite-wing holders have a horizontal portion that extends buccally between
Intraoral Radiographic Principles and Techniques 33 (overlap) of the adjacent proximal surfaces of Standard occlusal radiographs position the the teeth, and therefore make evaluation of receptor within the plane of occlusion (between the these areas more problematic. occlusal surfaces of the maxillary and mandibular teeth), as opposed to the lingual or palatal position- In general, when exposing the anterior or pre- ing of the periapical radiograph. Occlusal radio- molar bitewing, the horizontal angulation of the graphs may be used alone or as an adjunct to other PID should position the central ray at approxi- imaging modalities to provide the practitioner mately 30-degrees from the mid-sagittal plane with valuable diagnostic information. or aimed toward the inner canthus of the eye. Types of Occlusal Radiographs For the posterior or molar bitewing, the hori- Periapical type occlusal radiographs (Figure zontal angulation of the PID should position 2.23) the central ray at approximately 60 degrees Maxillary anterior occlusal from the mid-sagittal plane or aimed toward Maxillary lateral occlusal the outer canthus of the eye. Mandibular anterior occlusal The central ray is directed toward the center of Cross-sectional type occlusal radiographs the receptor. Imagining the central ray project- (Figure 2.24) ing through the bite tab of the holder (when Maxillary cross-sectional (vertex) correctly positioned) ensures centering from occlusal the top to bottom of the receptor. Instructing Mandibular cross-sectional (standard) the patient to “keep their teeth together and occlusal grin” allows the operator to visualize the mesial Anterior edge of the receptor and direct the central ray Posterior (lateral) to the midpoint of the receptor in the mesial distal plane (Figure 2.22). Uses for Periapical Type Occlusal Radiographs Larger imaging field, allowing more com- The occlusal radiograph plete visualization of a structure or lesion As an alternative to intraoral periapical Occlusal radiographs use size 4 receptors that are radiographs in patients with limited opening larger in size than standard periapical receptors to or severe gag reflexes create two distinct occlusal categories. To examine the alveolar processes for the location and extent of fractures These include the following: To produce large periapical type images of the anterior teeth in pediatric patients, using Periapical type occlusal radiographs, which are a size 2 receptor larger versions of standard periapical views, providing visualization of a greater area. PID Uses for cross-sectional type occlusal radiographs angulations are based on the principles of the To locate supernumerary, impacted, or un bisecting angle technique. erupted teeth To locate foreign bodies Cross-sectional type occlusal radiographs provide To provide information about the relation- an image of a region in a different imaging ship of structures in the axial plane plane (at right angle) to that of the periapical To examine the buccal and lingual cortices radiograph, thereby allowing visualization of for expansion, destruction, or the presence of objects and structures in the axial plane. PID a periosteal reaction angulation is directed parallel to the long axis To locate and provide information extent of of the teeth, perpendicular to the active surface fractures of the receptor. The seven basic steps used to produce intraoral Each category can be further subdivided by the images, as outlined earlier, are applied to produce location of the receptor, imaging specifically the anterior or lateral regions of the maxillary or man- dibular arches.
34 General Principles and Techniques AB C Figure 2.23 (A, B, and C) Periapical type occlusal radiographs (from top left): (A and B) Maxillary anterior and lateral occlusal radiographs; (C) Mandibular anterior occlusal radiograph (bottom). all of the different types of occlusal radiographs. of occlusal radiography, the considerations for The major differences when comparing occlusal to their prescription, and the techniques involved in other types of intraoral radiography are found in creating these views. With proper consideration, the size of the receptor, its positioning, and the aim occlusal radiographs are a viable prescription of the PID. option (Tables 2.2 and 2.3). All of the different occlusal views provide Extraoral uses for occlusal radiographs important and valuable information that is useful for specific diagnostic challenges. In endodontics, The occlusal radiograph can be used in an extraoral occlusal radiographs are an infrequently prescribed orientation in certain situations. This variation category of radiograph. They require the purchas- of occlusal radiography positions the receptor in ing and maintenance of the size 4 receptors (film different extraoral locations, determined by the or digital sensors) along with their single use required imaging plane and region of interest. plastic sleeves (used for digital systems), as required for infection control. In addition, it is important to understand and apply the principles
A BC Figure 2.24 (A, B, and C) Cross-sectional type occlusal radiographs (top row): (A) Maxillary occlusal radiograph (Vertex); (from bottom left): (B and C) Mandibular posterior and anterior occlusal radiographs. Table 2.2 Periapical-type occlusal radiograph. Maxillary Mandibular Active side Maxilla Lateral Mandible directed toward Anterior Long side centered on midline, parallel to labial Receptor position Long side centered on Long side parallel to buccal surfaces of incisors midline, parallel to labial surfaces of posterior teeth −55° from plane of receptor Vertical angulation surfaces of incisors Long axis of PID Horizontal +55–65° +55–65° perpendicular to front edge angulation Long axis of PID Long axis of PID of receptor perpendicular to front perpendicular to front edge Central ray edge of receptor of receptor Through mid-sagittal plane Guide Through mid-sagittal plane Through contacts in premolar Through chin Anatomical guide region Through middle of nose Through inner canthus of eye 35 Adapted from Cash and Perschbacher (2010b). DPES Professional-Occlusal Radiographs.
36 General Principles and Techniques Table 2.3 Cross-sectional type occlusal radiograph. Maxillary Mandibular Active side directed Maxilla Mandible toward Anterior Receptor position Long side centered on −100° from the plane of Posterior midline, parallel to labial receptor Vertical angulation surfaces of incisors Open end of PID parallel Perpendicular to receptor Horizontal angulation +110° (Through long axis to receptor Central ray of max incisors) Open end of PID parallel Guide Open end of PID parallel Through mid-sagittal plane to receptor to receptor Under chin Lateral and parallel to Through mid-sagittal plane mid-sagittal plane Through inferior border Anatomical guide Through top of head in of mandible anterior region The Profile Occlusal technique. In some ways, the receptor–structure The receptor is positioned on the side, and at relationship limits these views. The X-ray beam the level of interest, resting against the cheek, attenuates a multitude of various anatomical and parallel to the sagittal plane. The receptor structures prior to exposure of the receptor, result- can be stabilized in position using a wooden ing in poor image resolution due to numerous tongue depressor taped to a bite block. The superimpositions. Various types of extraoral imag tongue depressor is positioned laterally, within ing techniques are available to provide many the occlusal plane (patient bites on it). The bite different imaging views. In the practice of end- block supports the receptor, maintaining its odontics, extraoral imaging is mostly reserved to position. The PID is positioned toward the the panaoramic radiograph. These radiographs opposite cheek, with the central ray directed are taken regularly to evaluate the relationship perpendicular and toward the center of the of the mandibular canal to the apical region and receptor. For the horizontal angulation, the for presurgical assessment to allow visualization open end of the circular PID is aligned parallel of the sinus floor where evaluation of trabecular to the receptor. This produces a lateral view height and integrity is required for preimplant (similar to a lateral cephalometric radiograph), consideration. allowing visualization of relationship details in the anterior-posterior plane (Figure 2.25). The panoramic radiograph Extraoral radiography The panoramic radiograph presents an image of the maxilla, mandible, and their surrounding Extraoral radiographs position the receptor outside structures on a single large radiograph (Figure of the oral cavity to produce images with a greater 2.26). It is a very technique-sensitive radiograph field of view. They provide important information that requires optimal conditions to produce a high- about the relationship of structures, while utilizing quality radiograph. The patient is prepared by a less invasive and potentially more comfortable removing all metallic objects that may attenuate
Intraoral Radiographic Principles and Techniques 37 the X-ray beam. They are covered with a lead ing screens that increase receptor sensitivity. CCD apron and directed to stand in position. They are receptors are a permanent component within the instructed to bite onto a bite stick attached to panoramic machine and therefore do not require the machine, which positions their jaw within an the use of a cassette or erasure preparation prior to imaginary focal trough. When objects are posi- use. In contrast, storage phosphor sensors must be tioned within the focal trough, and a panoramic prepared for exposure by ensuring that any prior image is exposed, the image produced is a good image(s) are erased. This can be achieved using the representation of the object, with minimal dis computer software associated with the panoramic tortions or magnifications. Both film type and unit. digital sensors are used in panoramic radiography. Film and storage phosphor receptors are encased The patient should stand tall, extending their within a specialized cassette containing intensify- neck, providing maximal extension of the cervical spine. Optimal positioning places the midline of Figure 2.25 Extraoral positioning of an occlusal receptor the anterior teeth centered and biting into the provides a lateral view of the maxilla in this profile view. groove of the bite block. Horizontal and vertical light lines are used as guides to ensure that the axial and sagittal planes are correctly positioned (Figure 2.27). The ala-tragus line should parallel the horizontal light line, while the canine light line should be aligned vertically through the maxillary canine. Incorrectly positioning the patient outside of the focal trough will produce a distorted image. Supports are adjusted snuggly against the temples to reinforce stability. The patient is instructed to maintain position without any movement, press their tongue against their hard palate, and close their lips. The operator exits the room and activates and holds the preset exposure button. The receptor and X-ray source rotate around the patient. When com- plete, the operator re-enters the operatory releas- ing the patient from position within the panoramic unit and removes the cassette (when used) to process the receptor. Figure 2.26 A panoramic radiograph.
38 General Principles and Techniques Figure 2.27 The use of light lines as guides when Langland, O., Langlais, R., and Preece, J. (2002) Priniciples positioning a patient for a panoramic radiograph. (Image of dental imaging, 2nd ed. Williams and Wilkins, Balti- courtesy of A. Cormier, BSc, MScBMC, DPES, Faculty of more: Lippincott. Dentistry, University of Toronto, 2011.) Lim, K.C. and Teo, C.S. (1986) Some problems encoun- References tered in endodontic radiography. Ann Acad Med Sin- gapore, 15(3), 320–325. American Dental Association. (2011) The selection of patients for dental radiographic examinations. U.S. Saunders, W.P., Chestnutt, I.G., Saunders, E.M. (1999) Food and Drug Administration Home Page. N.p., n.d. Factors influencing the diagnosis and management of Web. June 21. teeth with pulpal and periradicular disease by general dental practitioners. Part 2. Br Dent J, 187, 548–554. www.fda.gov/Radiation-EmittingProducts/ RadiationEmittingProductsandProcedures/ Versteeg, C., Sanderink, G., and der Stelt, P.V. (1997) Effi- MedicalImaging/MedicalX-Rays/ucm116504.htm cacy of digital intra-oral radiography in clinical den- tistry. J Dent, 25(3–4), 215–224. Chandler, N.P., Koshy, S. (2002) Radiographic practices of dentists undertaking endodontics in New Zealand. White, S.C. and Pharoah, M.J. (2009) Oral Radiology Prin- Dentomaxillofac Radiol, 31, 317–321. ciples and Interpretation, 6th ed. Mosby, St. Louis. Fava, L.R. and Dummer, P.M. (1997) Periapical radio- Further reading graphic techniques during endodontic diagnosis and treatment. Int Endod J, 30(4), 250–261. Cash, M. and Perschbacher, S. (2008) DPES professional- periapical radiographic technique-long cone parallel- Haring, J.I. and Jansen, L. (2000) Dental Radiography Prin- ing [homepage on the Internet]. [cited May 31, 2011]. ciples and Techniques, 2nd ed. Saunders, Philadelphia. Available from: University of Toronto, Faculty of Den- tistry, Department of Oral Radiology Web site: Kazzi, D., Horner, K., Qualtrough, A.C., Martinez- sp.dentistry.utoronto.ca/dpes/pro/procs/Periapi- Beneyto, Y., and Rushton, V.E. (2007) A comparative cal%20Radiographic%20Technique%20-%20Long%20 study of three periapical radiographic techniques for Cone%20Paralleling.aspx endodontic working length estimation. Int Endod J, 40(7), 526–531. Epub April 24, 2007. Cash, M. and Perschbacher, S. (2010a) DPES professional- bitewing radiographic technique [homepage on the Internet]. [cited May 31, 2011]. Available from: Univer- sity of Toronto, Faculty of Dentistry Web site: sp. dentistry.utoronto.ca/dpes/pro/procs/Bitewing%20 Radiographic%20Technique.asp Cash, M. and Perschbacher, S. (2010b) DPES professional- occlusal radiographs [homepage on the Internet]. [cited June 17, 2011]. Available from: University of Toronto, Faculty of Dentistry Web site: sp.dentistry. utoronto.ca/dpes/pro/procs/Occlusal%20Radio- graphs.aspx Perschbacher, S. and Cash, M. (2009) DPES professional- panoramic radiographic technique [homepage on the Internet]. [cited June 20, 2011]. Available from: Univer- sity of Toronto, Faculty of Dentistry Web site: sp.dentistry.utoronto.ca/dpes/pro/procs/Pan- oramic%20Radiographic%20Technique.aspx
3 Special Situations Bettina Basrani Pregnancy should not be cause for concern. A UK epidemio- logic study of a cohort of 7375 mothers did not find Oral radiography is safe for pregnant patients pro- a significant association between use of dental vided that protective measures such as high-speed X-ray scans and low birth weight or preterm deliv- film and lead apron and a thyroid collar are used. ery. In addition, a case-control study found no No increase in congenital anomalies or intrauterine overall increased risk of childhood brain tumors growth retardation has been reported for X-ray after exposure to prenatal abdominal X-ray scan, radiation exposure during pregnancy totaling less which produces many times higher radiation expo- than 5–10 cGy, and a full-mouth series of dental sure than dental X-ray scans. (Michalowicz et al., radiographs results in only 8 × 10–4 cGy (National 2008) Council on Radiation Protection and Measure- ments, 2003). A bitewing and panoramic radio- Radiation therapy graphic study generates about one-third the radiation exposure associated with a full-mouth Patients with a malignancy in the oral cavity or series with E-speed film and a rectangular colli- perioral region often receive radiation therapy for mated beam (Freeman and Brand, 1994). Patients the treatment of their disease. Although such who are concerned about radiography during patients are often apprehensive about receiving pregnancy should be reassured that in all cases additional exposure, dental exposure is insignifi- requiring such imaging, the dental staff will prac- cant when compared with what they have already tice the ALARA (As Low as Reasonably Achiev- received. able) principle and that only radiographs necessary for diagnosis will be obtained (Carlton et al., 2000). In addition to the clinical examination, a thor- ough radiographic examination is crucial to The estimated fetal dose in a single dental expo- determine the presence of inflammatory periapi sure is 0.01 mrad. It is known that doses less than cal abnormalities, periodontal status, other dental 5 rad are not associated with increased congenital disease, and tumor invasion of mandibular or malformations; therefore, dental X-ray scans Endodontic Radiology, Second Edition. Edited by Bettina Basrani. © 2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc. 39
40 General Principles and Techniques maxillary bone. A panoramic radiograph plus the gag reflex, a number of cranial nerves as well selective periapical and/or bitewing films should as sympathetic and parasympathetic nerves par- be available for dental assessment previous to ticipate. Gag reflexes may be initiated by psycho- radiotherapy. Consultation with the patient’s phy- logical factors as well as by tactile stimulation. sician on the timing, nature (external beam radio- Anxiety and awareness of a previous gagging therapy or radioactive implant), and features problem may heavily influence the severity of the (location and size of treatment fields, radiotherapy condition. fractionation and total dose) of the radiotherapy is essential for overall risk assessment and schedul- Recommendations for suppressing and reduc ing of any required dental intervention. (White and ing gag reflexes during intraoral radiographic Pharoah, 2009) examination Gag reflexes 1. Gain confidence of the patient by demonstrat- ing a professional and confident behavior and Gag reflexes occur in most patients as a natural by demonstrating technical competence. reaction to tactile stimulation of the soft palate, base of the tongue and parts of the pharynx. In 2. The operator explains the procedure. some patients, these reflexes are so predominant 3. The patient rinses the mouth with ice-cold that dental procedures such as impression making, dry field maintenance, and placement of dental water. X-ray films intraorally are made difficult. In 4. Salt is placed on the patient’s tongue. extreme cases, adequate examination and dental 5. The patient is requested to initiate deep and treatment of these patients may be impossible (Bassi et al., 2004). audible respiration. 6. The patient holds his/her breath The gag reflex is a normal defense mechanism, 7. Film placement is done quickly and in a in preventing foreign bodies from entering the trachea. During the reflex, the shape of the pharynx gentle and nonirritating manner, with expo- and its openings are altered by spasmodic muscle sure follows immediately to film placement contractions. 8. The attention of the patient is distracted by a. Biting vigorously on the bite block Characteristic elements of the gagging behavior b. Looking fixedly at a point in the room have been described as follows: (1) puckering the c. Concentrating on breathing control (e.g., lips or attempting to close the jaws, (2) elevating and furrowing the tongue, (3) elevation of the soft by counting seconds) palate, (4) contraction of the anterior and posterior d. Performing slow muscular activities pillars of the fauces, (5) elevation, contraction, and retraction of the larynx and closure of the glottis, requiring concentration (e.g., alternately (6) forcing air through the closed glottis, producing raising legs to a horizontal position) the characteristic retching sound, (7) excessive sali- 9. Fingers in the mouth are avoided vation, lacrimation, and sweating, (8) respiratory 10. Film holders are used muscle spasm, and (9) vomiting (Kumar et al., 11. Tissue edge of the film packet is moistened by 2011). holding it in a stream of cold water 12. The patient is asked to swallow immediately The regions most sensitive to stimuli that prior to film insertion produce the gag reflex are the fauces, base of the 13. Surface anesthesia tongue, palate, uvula, and posterior pharyngeal wall. Sensory nerves forming afferent pathways for The frequency of gagging during full-mouth impulses to the reflex center in the medulla oblon- radiography was evaluated in 478 patients. Gagg gata are the trigeminal, glossopharyngeal, and ing was observed in 13% of the patients. The vagus (cranial nerves V, IX, and X). At the release frequency of gagging differed significantly in of the complex muscular and secretory elements of groups radiographed by trained radiologists and by students (9% and 26%, respectively). Gagging occurred in all regions but most frequently in the maxillary molar area. The technical skill, authority, and self-confidence of the operator were major factors of importance in preventing and suppress-
Special Situations 41 ing gag reflexes in dental radiography (Sewerin, more common in early adult life and can increase 1984). in size. In some older people, the size of the tori may decrease due to bone resorption. Palatal tori Torus are usually a clinical finding with no treatment necessary. It is possible for ulcers to form on the Mandible torus area of the tori due to repeated trauma. Also, the tori may complicate the fabrication of dentures. If Mandible (or mandibularis) Torus is a bony growth removal of the tori is needed, surgery can be done in the mandible along the surface nearest to the to reduce the amount of bone present (Neville tongue. Mandibular torus is usually present near et al., 2002) the mandibular premolars and above the location of the mylohyoid muscle’s attachment to the man- Radiographic examination dible. The prevalence of mandibular torus ranges from 5% to 40%. In 90% of cases, there is a torus on Radiographically, mandibular and palatal torus both the left and right sides, making this finding a appears as radiopaque masses, often obliterating bilateral condition. details of the teeth and the maxillary sinus. For a large palatal torus, the spongy layer appears as a Mandibular torus is more common in Asian less dense radiopaque mass compared with the and Inuit populations, and slightly more common compact layer. (Seah, 1995) in males. In the United States, the prevalence is 7–10% of the population. It is believed that man- Patients with physical disabilities dibular torus is caused by several factors. They are more common in early adult life and are associated Patients with physical disabilities may require with bruxism. The size of the torus may fluctuate special handling during a radiographic examina- throughout life, and in some cases the torus can be tion. These patients usually are cooperative and large enough to touch each other in the midline of eager to assist. Members of the patient family often mouth. Consequently, it is believed that mandible help in holding the films (White and Pharoah, torus is the result of local stresses and is not solely 2009). due to genetic influences. Mandibular torus is usually found during a clinical examination and no Patients with trismus treatment is necessary. Ulcers may form on the torus due to trauma. The torus may also complicate Trismus is defined in Taber’s Cyclopedic Medical the fabrication of dentures. If removal of the torus Dictionary as a tonic contraction of the muscles of is needed, surgery can be done to reduce the mastication. In the past, this word was often used amount of bone, but the torus may return in cases to describe the effects of tetanus, also called “lock- where nearby teeth still receive local stresses. jaw.” More recently, the term “trismus” has been (Neville et al., 2002) used to describe any restriction to mouth opening, including restrictions caused by trauma, surgery Palatal torus or radiation. This limitation in the ability to open the mouth can have serious health implications, Palatal torus or Torus palatinus is a bony protru- including reduced nutrition due to impaired mas- sion on the palate. Palatal torus is usually present tication, difficulty in speaking, and compromised on the midline of the hard palate. Most palatal tori oral hygiene. In persons who have received radia- are less than 2 cm in diameter, but their size can tion to the head and neck, the condition is often change throughout life. Prevalence of palatal tori observed in conjunction with difficulty in swallow- ranges from 9% to 60%. Palatal tori are more ing (Garnett et al., 2008). Causes of limited mouth common in Asian and Inuit populations, and twice opening can be temporary or permanent. The most more common in females. In the United States, the prevalence is 20–35% of the population. They are
42 General Principles and Techniques obvious effect of trismus is difficulty in opening growth can give the impression of a narrow palate the mouth. but should be distinguished separately. The term “gothic palate” is used to indicate that the roof of If the trismus is temporary, the dental treatment the palate is not round but rather has an inverted and intraoral radiographs need to be postponed V-shape, and therefore, only the upper part of the until the condition will improve. palate is narrow. A technique to place the radiograph in the mouth Taking peripaical radiographs in patients with a of the patient with limited mouth opening is the narrow palate can be a challenge. Cotton rolls can following (White and Pharoah, 2009): to be used to try to make the film parallel to the X-ray tube as possible. Or occlusal films can be 1. Place the film in haemostatic pliers. used (White and Pharoah, 2009). 2. Place the film in the mouth of the patient in an References horizontal position. 3. Turn the film in the vertical position. Bassi, G.S., Humphris, G.M., and Longman, L.P. (2004) 4. Use smaller size films. The etiology and management of gagging: a review of 5. Take occlusal films. the literature. J Prosthet Dent 91(5), 459–467. Patients where the floor of the mouth is Carlton, R.R., Adler, A.M., and Burns, B. (2000) Principles nondepressible of Radiographic Imaging, 3rd ed. Thompson Delmar Learning, Clifton Park, NY. These patients have a high insertion of the mylo- hyoid muscle. Both muscles mylohioides uniting Freeman, J.P. and Brand, J.W. (1994) Radiation doses of constitute the muscular substance of the floor of commonly used dental radiographic surveys. Oral the mouth. This is a muscle plane with parallel Surg Oral Med Oral Pathol, 77(3), 285–289. fibers, which beginning in the mylohyoid line of mandible medially directed raphe ending in a Garnett, M.J., Nohl, F.S., Barclay, S.C. (2008) Management tendon that extends from the inner surface of the of patients with reduced oral aperture and mandibu- chin to the body of the hyoid bone, through a lar hypomobility (trismus) and implications for opera- midline along the boundaries between the two tive dentistry. Br Dent J, 204(3), 125–131. mylohyoid. The back of the muscle attaches to the hyoid body. Kumar, S., Satheesh, P., Savadi, R.C. (2011) Gagging. N Y State Dent J, 77(4), 22–27. Placing a periapical radiograph in the area of the lower premolars or canine when the floor of the Seah, Y.H. (1995) Torus palatinus and torus mandibu- mouth is high can be impossible. Occlusal, panorex, laris: a review of the literature. Aust Dent J, 40(5), or Cone Beam Computed tomography (CBCT) 318–321. radiographs should be considered instead of peri- apical films (White and Pharoah, 2009). Michalowicz, B.S., DiAngelis, A.J., Novak, M.J., Buchanan, W.P., Apapanou, P.N., and Mitchel, D.A. Narrow palatal (2008) Examining the safety of dental treatment in pregnant women. J Am Dent Assoc, 139(6), 685–695. Palatal width is measured as the distance between the maxillary first permanent molar on the right National Council on Radiation Protection and Measure- and left sides, at the palatal cervical line, using a ments (2003) Recommendations on limits for exposure specific device. Palate width is typically assessed to ionizing radiation. Bethesda, Md. NCRP, 1987. subjectively in routine clinical practice. Narrowing NCRP report no. 91., Katz VL. Prenatal care. In: J.R. is often associated with a high palate, but this Scott, R.S. Gibbs, B.Y. Karlan, and A.F. Haney, eds., should be assessed separately. Gingival over- Danforth’s Obstetrics and Gynecology, 9th ed. Lippin- cott, Williams and Wilkins, Philadelphia, pp. 1–20. Neville, B.W., Damm, D., Allen, C., and Bouquot, J. (2002) Oral & Maxillofacial Pathology, 2nd ed. Saunders, Medical University of South Carolina, Charleston. Sewerin, I. (1984) Gagging in dental radiography I. Oral Surg Oral Med Oral Pathol, 58(6), 725–728. White, S.C. and Pharoah, M.J. (2009) Oral Radiology, 6th Edition Principles and Interpretation. Mosby Elsevier, St. Louis.
4 Intraoral Digital Imaging Ernest W. N. Lam Intraoral radiography with digital sensors should a second or 60 Hz. This means that the waveform be considered the primary radiographic technique repeats itself between successive peaks or troughs, in endodontics. Should digital intraoral radiogra- every 1/60th of a second. When the waveform phy not provide adequate diagnostic information reaches its peak, electrons flow from the tungsten for the clinician, occlusal radiography and small filament inside the X-ray tube to the tungsten field, high-resolution cone beam computed tomog- target where the X-rays are generated. X-rays are raphy (CT) may be used to supplement periapical generated throughout the entire positive cycle of images. The purpose of this chapter will be to the waveform, every 1/120th of a second; during review intraoral digital imaging sensor technology the trough, no X-rays are generated. as it applies to endodontics. There are inherent inconsistencies or errors in Intraoral digital imaging the timing systems of X-ray machines, and these may be more pronounced with shorter exposure Intraoral imaging is performed using an alternat- times. For less sensitive film-based image receptors ing current (AC) or direct current (DC) X-ray unit that in the past relied on longer exposure times, the with a focal spot size of between 0.4 mm and pulsed nature of the X-ray beam was not signifi- 0.7 mm, operating between 60 kVp and 70 kVp cantly impacted by inconsistencies in the timing using a filament current of between 4 mA and or generation of each waveform. For more sensi- 7 mA, and an X-ray target-to-exit distance of at tive film-based or digital sensors that use very least 12 in. short exposure times, inconsistencies may be more noticeable. For example, for very short exposure Contemporary X-ray systems use either an AC times of say 0.1 or 0.2 second, an inconsistency of or DC generator in the X-ray housing to produce the waveform that disrupts X-ray production for X-rays. The AC waveform can be visualized as 0.02 or 0.03 second may substantially reduce image being sinusoidal in nature with regular peaks and density. In an attempt to lessen this problem, troughs (Figure 4.1), and a periodicity of 1/60th of manufacturers have developed DC or constant potential systems that incorporate technology that Endodontic Radiology, Second Edition. Edited by Bettina Basrani. © 2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc. 43
44 General Principles and Techniques peak beam produces less penumbra or edge unsharp- ness around an object, creating an image that is trough theoretically sharper with better defined edges. Figure 4.1 Active current (AC) waveform. This trace Other factors that affect X-ray beam divergence demonstrates the peaks and troughs of the AC waveform. include the distance between the focal spot and the The duration of one cycle of the waveform (peak-to-peak or exit point of the X-ray beam from the X-ray colli- trough-to-trough time) is 1/60th of a second. The frequency mator and collimator shape. Some intraoral X-ray of the waveform is therefore 60 Hz. systems employ distances as short as 8 in. Shorter focal spot-to-exit point distances also create a more Figure 4.2 Constant or direct current (DC) X-ray tube divergent X-ray beam in comparison to those that heads increase the frequency to some 70,000 Hz (70 kHz) use longer collimation, for example, 12 or 16 in. (black trace). As a result of the ultra-high frequency of the Although 16-in. collimators may be difficult to waveform, the output of radiation attains an almost find, most intraoral X-ray machine manufacturers steady-state peak. have, as an option, collimators that result in a 12-in. focal spot-to-exit point distance. increases the frequency of the AC waveform from 60 Hz to near 70,000 Hz (i.e., 70 kHz) (Figure 4.2, Rectangular collimation in which the exit field of black line). Consequently, X-ray generation the X-ray beam is not substantially larger than the becomes almost steady state (Figure 4.2, red line). size of an American National Standards Institute DC systems also theoretically contribute to lower (ANSI) number 2 size sensor limits the size of the effective radiation doses. Because the voltage gen- X-ray field on the patient. The use of rectangular erated is always at or near its peak, less lower collimation limits not only reduces the skin energy, less-penetrating, or “soft” radiation is pro- entrance dose of the X-ray beam by as much as duced, and consequently, less radiation is absorbed two-thirds, which is substantial, but the amount of by superficial tissues such as skin. The practical X-ray scatter as well (Velders et al., 1991). decrease in patient dose has not, however, been well documented. Both operating peak kilovoltage (kVp) and fila- ment current (milliamperage [mA]) affect the The size of the focal spot or tungsten target may quality and/or quantity of the X-ray photons pro- also impact the quality of the image. A smaller duced. While increasing both peak kilovoltage and focal spot diameter (0.4 mm vs. 0.7 mm) theoreti- milliamperage increases the total bolus of X-ray cally produces less divergence of the X-ray beam photons produced, only peak kilovoltage affects from focal spot to receptor. A less divergent X-ray the quality of the photons; that is, the distribution of lower energy, less penetrating photons and higher energy, more penetrating photons. As well, higher peak kilovoltage X-ray beams impact on image contrast by affecting the number of gray values that are visible. For viewing subtle changes in tooth or bone mineralization, lower peak kilo- voltage settings that produce greater short scale (high image) contrast are preferable. X-ray filament current affects only the number of X-ray photons produced. Therefore, lowering either or both peak kilovoltage and milliamperage will necessitate a concomitant increase in exposure time to maintain image density within the diagnostic range. Digital sensors There are three competing intraoral digital receptor technologies: solid-state charge-coupled device
Intraoral Digital Imaging 45 AB C Figure 4.3 Intraoral charge-coupled device (CCD) size 2 sensor (Kodak 6100, Carestream, Rochester, NY). A. Sensitive surface; B. Back surface with wire connection; C. Side profile. (CCD), complementary metal-oxide semiconduc- visible light is then converted into electrons by a tor (CMOS), and photostimulatable phosphor fiber optic plate, and finally, the electrons are cap- (PSP). The different technologies all capture patient tured in the CCD or CMOS element of the sensor. anatomy on a two-dimensional, 2 by 2 matrix of The number of electrons captured is directly pro- picture elements or pixels. portional to the number of X-ray photons that exits the patient and strikes the sensor surface. Although All sensor types are capable of displaying up to CCD and CMOS sensors differ in the manner in 16,384 shades of gray, from white to black, with which the electrons are captured and converted to each shade of gray represented by a value between an electronic signal, a discussion of the specific 0 and 16,383. Such sensors are referred to as 14-bit electronic requirements of the two sensors is sensors (214 = 16,384). Interestingly, most computer beyond the scope of this chapter. monitors that display black and white images are only capable of displaying 256 shades of gray or 28, In contrast, PSP plates (Figure 4.4A,B) consist of and the human eye is only capable of differentiat- a photoluminescent material consisting of a mixture ing between 64 shades of gray or 24. of different barium fluorohalides containing trace amounts of europium. Europium is incorporated All digital sensors convert X-ray information to as an activator or luminescence center. This mate- electronic information, but they do so in different rial is mounted on a polyester support. X-rays ways. The components of the CCD (Figure 4.3A–C) arriving on the surface of the PSP sensor liberate and CMOS sensors are encased in a sealed plastic electrons from europium atoms, and the escaping case, typically with an electrical connection to a electrons become entrapped in the halide lattice. computer. The thickness of this case may range Following exposure, the PSP plate is fed into a between 4 mm and 7 mm (Farman and Farman, machine that contains a laser that scans the plate, 2005). For CCD and CMOS sensors, X-ray photons releases the electrons, converting them to a propor- exiting the patient are converted to visible light tionate number of light photons that are collected photons by a scintillator within the sensor. The
46 General Principles and Techniques A BC Figure 4.4 Intraoral photostimulatable phosphor (PSP) ANSI size 2 sensor (Air Techniques, Melville, NY) and plate reader. A. Sensitive surface; B. Nonsensitive back surface; C. Plate reader. and assigned a numerical value like the CCD or ANSI 4 receptor is not available. One resultant CMOS sensor (Figure 4.4C). effect of the smaller active surface area of CCD and CMOS sensors is that compared with PSP sensors CCD and CMOS receptors are substantially and conventional film, more images may be more costly than PSP receptors, costing in the required to cover a particular area within the jaws range of thousands of dollars versus the hundred (Berkhout et al., 2003). The thickness and rigidity dollar range or less for each PSP receptor. Despite of CCD and CMOS sensors make them more dif- the lower cost of PSP receptors, regular replace- ficult to position in children and adults with small ment is necessary as the active surface of the plate mouths, in particular when making bisecting-the- may be damaged by scratches or abrasions gener- angle images (Wenzel and Møystad, 2001b). And ating images that may be nondiagnostic (Bedard indeed, the CCD and CMOS wire sensors may con- et al., 2004). found this all the more. One manufacturer does, however, have a wireless CCD sensor, but it is com- Like conventional film, PSP receptors are avail- paratively bulky (Figure 4.3C). able in ANSI sizes 0, 1, 2, and 4, and the entire surface of the receptor is active. In contrast, less With regard to radiation effective dose to the than 80% of the CCD or CMOS sensor surface is patient, it has been reported that the mean dose active due to the electronics contained within the reduction when using digital sensors is between sensor. A CCD or CMOS sensor the size of the
Intraoral Digital Imaging 47 55% compared with ANSI D speed film (Wenzel hemostat or the commercially available Snap-R- and Møystad, 2001a). Indeed, the reduction may Ray. The use of the patient’s own fingers is not also be less than expected if more images are considered an acceptable alternative to the use of required to adequately cover a particular region of a film-holding device if the patient’s finger(s) fall the jaws (Bahrami et al., 2003), or remaking of within the X-ray beam. images is required due to the constraints already alluded to for CCD and CMOS sensors. Unlike the paralleling technique where the receptor is placed parallel or nearly parallel to the Finally, image resolution and display may be long axis of a tooth, the receptor is placed at an considerations for clinicians. The median resolu- angle relative to the long axis of the tooth. Should tion of CCD and CMOS sensors has been reported the incident X-ray beam strike the tooth at 90 in in vitro studies to be approximately 11 line pairs degrees to its buccal surface, the projected image per millimeter (lp/mm). This compares with of the tooth on the receptor will appear elongated. approximately 8 lp/mm for PSP sensors. The Alternatively, should the incident X-ray beam newest generation of CCD and PSP sensors have strike the receptor plane at 90 degrees, the tooth recently achieved tested resolutions of greater than will appear foreshortened. In both cases, one can 20 lp/mm and 13 lp/mm, respectively, rivaling expect errors should measurements be required. In conventional film (>22 lp/mm) (Farman and practice, errors associated with misjudgments in Farman, 2005). By comparison, the human eye is tooth or X-ray beam angulation may be more pro- capable of resolving 8 lp/mm, unaided. It has also nounced in the anterior regions of the jaws where been reported that the PSP sensor has greater the incisors are more prominently proclined com- receptor latitude, allowing it to capture a greater pared with the more posterior parts of the jaws number of gray shades compared with CCD/ where the teeth appear more upright in their alveo- CMOS sensors. lar processes. In general, digital images are more easily In addition to periapical radiography, some managed after exposure compared with film, and occlusal radiographic techniques may also rely on the time-savings that dentists who use digital the use of bisecting-the-angle radiography. Classi- systems experience is significant; 36 min/day for cally, occlusal radiography has relied primarily on CCD/CMOS users (range, 10–120 minutes) and the use of large, ANSI 4-sized receptors although 25 min/day for PSP users (5–120 minutes). The ANSI 2 receptors have been used as well. Due to decrease in savings from PSP users is likely due, in the larger sized receptors, larger regions of the jaws part, to the scanning process required of the sensor can be captured on a single image, rather than on plates (Figure 4.4C) (Berkhout et al., 2002). two or more smaller individual images. More importantly, however, by placing the receptor on After an image is captured, software enhance- the occlusal surfaces of the teeth and using oblique ment of the images can be performed, although X-ray beam angulations, it may be possible to changes to image contrast and density appear to examine different aspects of the jaws not possible the most widely used applications. It should, with periapical radiography. however, be noted, that there is little published evidence that suggests modifying an image using Cross-sectional occlusal radiography is com- software has a biological correlate. monly used in the mandible for demonstrating the effects of space-occupying pathoses on the contour Bisecting-the-angle and occlusal of the mandible, including effects on the buccal radiography and lingual cortices. In the anterior maxillae and mandible, an ANSI 4 receptor used with a bite Bisecting-the-angle radiography is performed block mounted on a wooden tongue depressor can when a position-indicating device (PID) is not used also demonstrate buccal cortical expansion. This or cannot be used to make intraoral images using novel technique permits the user to demonstrate the paralleling technique. Typically, the receptor is changes to the anterior buccal contour of the maxil- held in place by a device that can be stabilized by lae or mandible in an extraoral examination that the patient. Such devices have included a simple uses the higher resolution capabilities of an intra- oral sensor (Figure 4.5).
48 General Principles and Techniques Figure 4.5 Occlusal-on-a-stick image of a simple bone cyst References associated with a region of osseous dysplasia. The image shows a mixed radiolucent/radiopaque abnormality in the Bahrami, G., Hagstrøm, C., and Wenzel, A. (2003) Bite- anterior mandible that has not only expanded the anterior wing examination with four digital receptors. Dento- mandible, but has also produced a thinning of the anterior maxillofac Radiol, 32, 317–321. and inferior cortices of the mandible. Bedard, A., Davis, T.D., and Angelopoulos, C. (2004) Storage phosphor plates: how durable are they as a digital dental radiographic system? J Contemp Dent Pract, 5, 57–69. Berkhout, W.E., Sanderlink, G.C., and Van Der Stelt, P.F. (2002) A comparison of digital and film radiography in Dutch dental practices assessed by questionnaire. Dentomaxillofac Radiol, 31, 93–99. Berkhout, W.E., Sanderlink, G.C., and Van Der Stelt, P.F. (2003) Does digital radiography increase the number of intraoral radiographs? A questionnaire of Dutch dental practices. Dentomaxillofac Radiol, 32, 124–127. Farman, A.G. and Farman, T.T. (2005) A comparison of 18 different x-ray detectors currently used in dentistry. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 99, 485–489. Velders, X.L., van Aken, J., and van der Stelt, P.F. (1991) Absorbed dose to organs in the head and neck from bitewing radiography. Dentomaxillofac Radiol, 20, 161–165. Wenzel, A. and Møystad, A. (2001a) Experience of Nor- wegian general dental practitioners with solid state and phosphor detectors. Dentomaxillofac Radiol, 30, 203–208. Wenzel, A. and Møystad, A. (2001b) Decision criteria and characteristics of Norwegian general dental practitio- ners seeking digital radiography. Dentomaxillofac Radiol, 30, 197–202.
5 Radiographic Considerations Before the Endodontic Treatment Is Initiated Calvin D. Torneck Introduction Anatomy of dental tissues A correct diagnosis is the foundation of an effective Teeth are composed primarily of dentin, with an treatment plan, and in endodontics, the dental enamel cap over the coronal portion and a thin radiograph is an indispensable diagnostic tool. layer of cementum over the root surface. Tooth Interpreting images on a radiograph requires an enamel is the hardest and most highly mineralized understanding of anatomy, tissue physiology and substance of the body and with dentin, cementum, pathophysiology, and radiographic physics. It is and dental pulp is one of the four major parts of for this reason that these topics will be briefly the tooth. reviewed in this chapter dealing with the radio- graphic expression of endodontic disease. Further- Enamel more, they will be discussed as they relate to two-dimensional or standard radiography. While Enamel appears more radio-opaque than other three-dimensional radiography, as generated by tissues because of its 90% mineral component that cone beam tomography, has been shown to be causes greater attenuation of X-ray photons. more effective in imaging endodontic disease than standard radiography (Patel et al., 2009; Scarfe Dentine et al., 2009), it has yet to achieve wide acceptance in everyday clinical practice. This is not to imply The dentine will have 70% mineral content. It is that it is not in use in some dental practices, only less radio-opaque than enamel; its radio-opacity is that the current expense associated with its pur- similar to bone, and the enamel–dentinal junction chase and the special knowledge associated with appears as a distinct interface separating these two the interpretation of its images has limited its use. structures (Torneck, 1998). At present, it is found primarily in dental specialty offices and teaching institutions. Endodontic Radiology, Second Edition. Edited by Bettina Basrani. © 2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc. 49
50 General Principles and Techniques dƌĂďĞĐƵůĂƌďŽŶĞ ĞŵĞŶƚƵŵ Dentin ĞŶƟŶ ZŽŽƚĂŶĂů Dentin WƵůƉ WƵůƉŚĂŵďĞƌ WƵůƉ ůŝŐĂ WĞƌŝŽĚŽŶƚĂůůŝŐĂŵĞŶƚ WƵůƉ,ŽƌŶ ůǀĞŽůĂƌďŽŶĞ Figure 5.1 Anatomy of the tooth and supporting tissues. A (Reprinted from Torneck and Torabinejad, 2002, with permission from Elsevier Ltd.) Dentine-pulp complex WƵůƉ,ŽƌŶ WƵůƉŚĂŵďĞƌ The dentin–pulp complex, the periodontium and ZŽŽƚĂŶĂů the bone of the maxilla and mandible constitute the endodontic tissues (Figure 5.1). The dentin–pulp B complex is a specialized connective tissue with dentin-forming capabilities that define what is Figure 5.2 A. Divisions of the pulp space of maxillary referred to radiographically as the pulp space incisor. B. Divisions of the pulp space of mandibular molar. (Figure 5.2A,B). The pulp space, in turn, is divided into the pulp chamber or coronal pulp space, and coronally are called lateral canals. Lateral canals the root canal, or radicular pulp space. The dentin– vary in size from very small (0.1 mm) to sizes that pulp complex receives its blood supply via chan- approach that of the apical foramen (0.4 mm). nels that extend through the dentin wall of the Varying methods in identifying the presence of tooth root from the periodontium (Torneck, 1998). lateral canals in anatomical studies have led to The major channel is called the apical foramen and varying reports in their incidence. Suffice it to say is located at or near the anatomical end of the root that most teeth have one or more canals of this type or apex. It is usually, but not exclusively, the largest and that they can play a significant role in the of the vascular channels. However, despite its spread of endodontic infection from the root canal relatively large size when compared to the other to the surrounding tissues. There are rare occasions vascular channels, it is difficult to image on a radio- when large lateral canals can be detected in pre- graph for most adult teeth. The other vascular treatment radiographs, but in most of cases, they channels present in the dentin are referred to as are only detected after endodontic treatment, when accessory and lateral canals. These are found at they become filled with radio-opaque root canal different sites along the root surface, as well as in cement or a core material (Figure 5.3A,B). the furcation area of multirooted teeth. Channels in close proximity to the apical foramen are often called accessory canals while those located more
Radiographic Considerations Before the Endodontic Treatment Is Initiated 51 AB Figure 5.3 A. Lateral lesion associated with lateral canal (arrow) imaged in diagnostic radiograph. B. Lateral canal filled with root canal filling material as seen immediately post treatment. Periodontium Figure 5.4 Dental supporting tissues as imaged radiographically. The periodontium is a complex of hard and soft tissue that supports the tooth in the jaw during absence, a sign of disease. In partially developed function. The soft tissue is a combination of spe- (newly erupted) teeth where apex formation cialized collagen fibers and a loose connective and periodontal development are incomplete, the tissue containing progenitor cells, fibroblasts, apical region still contains residual soft tissue ele- blood vessels, and nerves. Alternatively called the ments of the dental papilla and the dental follicle periodontal ligament, this appears as a radiolucent (Figure 5.5). In the radiograph, this combination of space that extends around the periphery of the root when the tooth is imaged radiographically (Figure 5.4). The collagen fibers of the ligament are embed- ded in mineralized tissue on both sides of the space. On the tooth side the anchorage is by cemen- tum, a bone-like mineralized tissue that normally covers the entire root surface, and on the opposite side by the alveolar bone (bundle bone) that lines the bone socket in the jaw. Because alveolar bone is denser than the trabecular bone that comprises the inner structure of the jaw, it appears more radio-opaque than trabecular bone when imaged. This relative opacity is highlighted by the radiolu- cent appearance of the soft tissue ligament. The name given to alveolar bone radiographically is lamina dura. Although not always detectable in the radiograph due to variances in the way the tooth may be imaged, its continuity in mature teeth is interpreted as a sign of periodontal health, and its
52 General Principles and Techniques Figure 5.5 Dental papilla as seen anatomically and radiographically at apex of developing incisor. (Histology reprinted from Torneck and Torabinejad, 2002, with permission from Elsevier Ltd.) soft tissues is imaged as a circumscribed apical radiolucency without the presence of a of lamina dura. This radiolucency gradually diminishes as root development progresses and disappears when development of the periodontium is complete. The presence of the radiolucency at the apex of a devel- oping tooth can easily be misinterpreted as an area of apical inflammation so it is prudent to support a clinical diagnosis with additional tests before treatment is undertaken. It also makes the early detection of apical inflammation when present, difficult in teeth where root development is incom- plete (Torneck 1986). Cementum Figure 5.6 Maxillary premolars and molars demonstrating hypercementosis of the roots. Note interproximal bone loss, The cementum present on the root surface has a areas of calculus deposition, and pulp stones in pulp mineral content similar to that of dentin and bone chamber of molar teeth. and is therefore difficult to differentiate radio- graphically from these two other tissues. An excep- it can result in bizarre anatomical changes at the tion may be times when the periodontium is root apex that can make endodontic management healthy and excessive cementum has been formed of a root canal infection difficult. Generalized on one or more of the root surfaces. This produces hypercementosis is also seen in association with a benign condition called hypercementosis (Figure fibro-osseous disease, but in such cases, there is 5.6). Its endodontic significance lies in the fact that
Radiographic Considerations Before the Endodontic Treatment Is Initiated 53 also a change in the architecture of the bone sur- References rounding the teeth that facilitates interpretation of the image. Nanci, A. (2008) Periodontium. In: A. Nanci, ed., pp. 239–267. Ten Cate’s Oral Histology. Mosby, St. Louis. As previously mentioned, the presence of the periodontal ligament creates a continuous peri- Patel, S. et al. (2009) Detecting periapical bone defects in radicular radiolucent space about the tooth root human jaws. Int Endod J, 42, 506–515. when the tooth is properly imaged. The space nor- mally averages 0.15–0.38 mm in width in young Scarfe, W.C. et al. (2009) Use of cone beam computed adults, with the smallest diameter usually present tomography in endodontics. Int J Dent, 2009, 1–20. at mid root. It does, however, vary in accordance Online article ID 634567, 20 pgs. doi:10.1155/2009/ with age and averages 0.21 mm in 11- to 16-year- 634567 olds and 0.15 mm in 51- to 67-year-olds (Nanci, 2008). When lamina dura is not clearly discernable Torneck, C.D. (1986) Endodontic management of par- in the dental radiograph, the presence of a peri- tially developed teeth. In: N. Levine, ed., Current Treat- odontal space of uniform and normal width also mment in Dental Practice. Saunders, Philadelphia. can be used as a determinant of periodontal health, and conversely, its attenuation as a sign of disease. Torneck, C.D. (1998) Dentin–pulp complex. In: A.R. Ten As in all aspects of interpretive radiology, the Cate, ed., Oral Histology, 5th ed., pp. 150–196. Mosby, use of magnification and multiple views usually St. Louis. proves helpful in properly interpreting informa- tion present in the radiograph. Torneck, C.D. and Torabinejad, M. (2002) Biology of the dental pulp and periradicular tissues. In: R. Walton and M. Torabinejad, eds., Principles and Practice of End- odontics, 3rd ed., pp. 4–26. Mosby, St. Louis.
6 Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics Jeffrey M. Coil An anomaly is a marked deviation from normalcy, radiodensity stemming from the cusp of the pre- especially as a result of congenital or hereditary molar crown tip before eruption (Figure 6.2B–D), defects. Recognition and endodontic treatment of which can influence orthodontic treatment plan- dental abnormalities can present a challenge to ning (McCulloch et al., 1997). As a tooth is erupt- every practitioner. Radiographic evaluation during ing, this extra cusp can also be seen radiographically a consultation visit is a key element in the pretreat- as well as clinically (Figure 6.2E) ment assessment of a patient’s “degree of diffi- culty” (CAE, 1998). Determination of the complexity Dens invaginatus of treatment and assessment of the physical nature and condition of a tooth to be treated allows the This malformation of teeth usually affects maxil- practitioner to better prepare before treatment lary lateral incisors, and is considered to be an commences. invagination of the dental papilla during develop- ment. Although the etiology remains unclear, this Dens evaginatus tooth abnormality has been described for hundreds of years (Hulsmann, 1997). Various types of this The dens evaginatus is a developmental anomaly invaginated tooth anomaly were characterized that manifests clinically as an extra cusp appearing by Oehlers (1957). He categorized this malforma- on the occlusal surface of premolar teeth between tion to occur in three different forms as shown in the buccal and lingual cusps (Figure 6.1). This pro- Figure 6.3. jection of enamel can interfere with tooth eruption and occlusion. This tubercle is usually worn down The first type of dens invaginatus, Class I, is a or broken off, which can result in pulp exposure, minor form of an invagination that occurs within and subsequent pulp necrosis and periradicular the crown of the tooth, and does not extend beyond periodontitis (Figure 6.2A). Radiographically, this the cementalenamel junction (CEJ). It can be seen condition may be recognized by examining the radiographically as an invagination in the vicinity of the cingulum (Figure 6.4). Endodontic Radiology, Second Edition. Edited by Bettina Basrani. © 2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc. 54
Figure 6.1 Projection of the extra cusp on the occlusal surface of the lower bicuspid tooth is seen clinically. (Image courtesy of Dr. Raymond Greenfeld.) A (a) A (b) Figure 6.2 A. (a) Periapical lesion associated with the mandibular right premolar tooth. A slight thickening of enamel is seen in the center of the crown near the occlusal surface in the vicinity of the evagination. (b) Clinical view of lower right posterior teeth. The dens evaginatus tubercle has been either broken off or worn down on this second premolar tooth. 55
A (c) A (d) B (a) B (b) Figure 6.2 (Continued) (c) Occlusal view of the worn tubercle. (d) Magnified view of (c). B. (a) Panorex film showing multiple dens evaginatii of unerupted mandibular premolar teeth. Note the thin radiodensity of enamel near the center of the crown near the occlusal surface. All four unerupted mandibular premolar teeth show this radiolucency stemming from their cusps. Such radiodensities exhibiting this condition are not easily seen on the maxillary premolar teeth. (b) Clinical photo after mandibular premolar teeth have erupted, showing dens evaginatus occurring in all four lower premolar teeth (Images courtesy of Dr. Angelina Loo). 56
C (a) C (b) C (c) Figure 6.2 (Continued) C. Panorex films showing (a) pre- and (b) posteruption states of this patient’s dentition. (c) Breakage of the tubercle on the lower right second premolar tooth necessitated a pulp cap and restoration of this tooth (Images courtesy of Dr. Angelina Loo). 57
D (a) D (b) Figure 6.2 (Continued) D. (a) Panorex film exhibiting dens evaginatus on both unerupted lower second premolar teeth. (b) Clinical view of erupted teeth exhibits the protruding dens evaginatus along the lingual ridge of the buccal cusp of the lower right second premolar tooth. Note the “target-like” appearance of this worn tubercle indicative of enamel (outer) and dentin (inner) components. The occlusal surface of the left second premolar has a worn tubercle also, but it does not have this same appearance indicating only an enamel involvement (Images courtesy of Dr. Angelina Loo). 58
E (a) E (b) Figure 6.2 (Continued) E. (a) Panorex film showing an erupting lower right first premolar tooth. A typical dens evaginatus seen as a radiodensity stemming from the clinical crown is evident. (b) Clinical view of this partially erupted tooth shows an obvious tubercle associated with the clinical crown (Images courtesy of Dr. Angelina Loo). 59
(a) (b) (c) Figure 6.3 Categories of dens invaginatus as characterized by Oehlers (Oehlers, 1957). (a) Class I is an invagination that is limited to the crown of the tooth. (b) Class II invaginations extend beyond the CEJ into the root, but end as a blind sac. (c) Class III invaginations extend deeper into the root and communicate with the external root surface and may extend to the apical root third. Note that none of these invaginations directly communicate with the pulp. (Images courtesy of Dr. Raymond Greenfeld.) Figure 6.4 Dens invaginatus Class I. Radiodense projections are seen emanating from the cingulum of these maxillary central incisor teeth. (Images courtesy of Dr. Raymond Greenfeld.) 60
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 61 (a) (b) Figure 6.5 Dens invaginatus Class II. (a) Double invagination of the upper left maxillary incisor tooth extending below the CEJ. (b) Invagination near the incisal edge of the upper right maxillary lateral incisor extends below the CEJ and appears directly adjacent to the root canal space. (Images courtesy of Dr. Raymond Greenfeld.) Deeper forms of invagination that cross the CEJ there is usually no immediate communication with and invade the root, yet still end in a blind sac, are the pulp. Figure 6.8Ba shows a maxillary lateral categorized as Class II. Such invaginations are incisor tooth with apical periodontitis resulting shown in Figure 6.5. These invaginations may or from infection originating from an invagination. may not communicate with the pulp. Radiographi- The pulp responded normally to thermal testing. A cally, these may appear as a “dens in dente” (tooth recall radiograph shows healing of the apical peri- within a tooth), although this is a misnomer. It is odontitis, and clinical examination revealed that recognized as a pear-shaped invagination emanat- the pulp continued to respond normally to pulp ing from the crown of the tooth (Figure 6.6). There testing procedures. is a constriction at the beginning of the invagina- tion on the surface of the tooth, before it expands Fusion deeper into the root. It may appear that the invagi- nation goes into the pulp because of the superim- Fusion is the result of the union of two separate position of the invagination over the root canal tooth germs. If contact occurs early in develop- (Figure 6.7a). Food, bacteria, and debris may get ment, before calcification begins, two teeth may be packed into the opening of the invagination, result- united to form one large tooth (Figures 6.9 and ing in caries and communication with the pulp. 6.10). Radiographically, this can be seen as one large Sealing off the invagination with a bonded resin is root and root canal system, while having a mal- shown in Figure 6.7b,c. formed crown (Figure 6.11). Such clinical presenta- tions have significant orthodontic implications. Still more severe forms on the invagination, pen- etrating to communicate with the external root Contact of teeth after calcification begins can surface and extending to the apical root third, can result in incomplete fusion, where there may be have quite a malformed appearance (Figure 6.8A). a union of the roots only (Figure 6.12A). The Although this Class III invagination is extensive,
Figure 6.6 Ground section of a tooth exhibiting dens invaginatus Class II. This image shows how this malformation appears like a tooth within a tooth, “dens in dente” (Image courtesy of Dr. Ravindra Shah). (b) (a) (c) Figure 6.7 (a) Dens invaginatus Class II. Radiographically, the invagination is superimposed over the root canal in this upper right lateral incisor tooth. The pulp in this tooth responds normally to thermal testing. (b) Pre- and (c) posttreatment using an acid etched and bonded resin to seal off the invagination. 62
A (a) A (b) B (a) B (b) Figure 6.8 A. Dens invaginatus Class III. (a) Pre- and (b) posttreatment radiographs showing an upper left lateral incisor tooth with associated periradicular radiolucency. This tooth responded normally to pulp testing procedures before and after treatment of this invagination (images courtesy of Dr. Raymond Greenfeld). B. A complex anomaly involving dens invaginatus Class III and either fusion or gemination. Notice that the preoperative radiolucency of the upper left lateral incisor (a), resolved after treatment of the invagination (b). This tooth responded normally to pulp testing procedures before and after treatment of this invagination. (Images courtesy of Dr. Raymond Greenfeld.) 63
(a) (b) Figure 6.9 (a) Clinical view of fused mandibular anterior teeth. (b) Fusion involves both the crown and root, as seen here. (Images courtesy of Dr. Ravindra Shah.) Figure 6.10 Fused teeth are seen clinically here. (Image courtesy of Dr. Ravindra Shah.) (a) (b) Figure 6.11 Fusion. Radiographically evident are one large root and one large root canal system. Malformation of the crown has significant orthodontic considerations. 64
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 65 (d) (c) Figure 6.11 (Continued) AB Figure 6.12 A. to D.Fusion of the roots only of this extracted tooth seen here. (Image courtesy of Dr. Ravindra Shah.) B. Fusion of erupted tooth seen radiographically, and possible fusion of unerupted tooth. Note the radiographic appearance of malformed crowns for both the erupted and unerupted teeth. (Image courtesy of Dr. Ravindra Shah.) radiograph shown in Figure 6.12B shows fusion of not respond to pulp testing procedures. Root canal teeth in both the deciduous and permanent denti- treatment was initiated and completed for tooth tions. Note the malformed crowns in both the #1-2, and osseous healing is seen after 4 months erupted and nonerupted teeth. (Figure 6.13e–g), in addition to the sinus tract healing. The appearance of infections and radiolucent bone in the region of fused teeth can increase the C-shaped canals level of diagnostic difficulty. Figure 6.13a,b shows a sinus tract opening over tooth #21 which was C-shaped canals are a result of fusion of roots traced using a gutta percha point. The radiolu- within a given tooth germ. C-shaped canal sys cency associated with the fused tooth #1-1 could be tems most commonly occur in mandibular second mistaken for the origin of this chronic abscess molar teeth. Mandibular second molars having (Figure 6.13c,d). However, pulp testing of the ante- rior teeth in this region revealed that tooth #1-2 did
Figure 6.13 Fused tooth, sinus tract,. and nonvital adjacent tooth made this endodontic diagnosis difficult. (a) Clinical view of sinus tract opening adjacent to malformed upper right central incisor tooth. (b) Sinus tract exploration with gutta percha point appeared to suggest that the malformed tooth was endodontically involved. (c) Periapical radiolucency extended between upper right lateral and central incisor teeth. (d) Normal bone was present in periapical region of upper left central and lateral incisor teeth. (e) Thermal pulp testing of maxillary anterior teeth revealed that the upper right lateral incisor tooth had a necrotic pulp. (f) Root canal treatment was completed for this tooth. (g) Three months following root canal treatment, the sinus tract had healed, and there was some evidence of osseous healing of the (a) associated periapical lesion also (images courtesy of Dr. Ronald Corber). (b) (c) (d) (e) (f) (g) 66
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 67 convergent mesial and distal roots should be con- shown in Figure 6.17. Notice that this “extra” root sidered suspicious for having a C-shaped canal appears less radiodense than the other two roots. configuration. Inadequate cleaning and shaping of A first molar tooth having radix entomolaris and this C-shaped lower second molar tooth necessi- associated, but unrelated, bony exostosis is shown tates endodontic retreatment. in Figure 6.18A. Note that both the lingual position of this third root, and the extent and location of this During canal instrumentation, it may appear exostosis, would make apical surgery difficult. that one has perforated into the furcation region, but the apex locator should not fire as if the file is Taurodontism in the periodontal ligament space (Figure 6.14A). Clinical views of the access cavity show the joining The term taurodontism was introduced by Keith of discrete canals via an isthmus, hence the term to describe an anomaly where the body of the “C-shaped canals.” Cone beam computed tomog- tooth was enlarged and elongated, leaving short raphy (CBCT) images showing sagittal and axial roots (Keith, 1913). Taurodontism means “bull-like views of a C-shaped mandibular second molar teeth.” It is a morphological change occurring in tooth are shown in Figure 6.14B. Notice the multirooted teeth characterized by an elongated C-shaped root form throughout the axial slicing of pulp chamber in the apico-occlusal dimension the root. Using CBCT imaging systems will help to resulting in bifurcation or trifurcation of the roots visualize three-dimensionally such anomalous root in the apical root third. The challenge for endodon- and root canal forms. Obturation of a C-shaped tic treatment of such teeth is locating the canal orifi, lower second molar tooth is shown in Figure 6.14C as they are found in the apical region of the root (Cooke and Cox, 1979; Melton et al., 1991). (Figure 6.18B) (Bernick, 1970; Sert and Bayrili, 2004; Shifman and Buchner, 1976). Radicular groove Dilaceration Lingual radicular groove is most commonly seen on maxillary lateral incisors. This condition is not Dilaceration refers to an abrupt change in the root readily seen on conventional two-dimensional angulation, or a sharp curve or bend in the root radiographic images. When it does appear, it can of a formed tooth. Usually, abrupt changes in be mistaken for a vertical root fracture. However, root angulation are also inseparable from abrupt vertical root fracture can usually be ruled out as changes in the root canal angulation. One possible this is unusual to occur in non-root canal-treated etiology is trauma to the developing permanent teeth. Figure 6.15 shows a clinical view of such a tooth. Pre- and postoperative endodontic treat- lingual groove on tooth #1-2 and the lingual surface ment films of a lower left molar tooth are shown in of the same extracted tooth (Everett and Kramer, Figure 6.19A. Canal negation to the apical foramen 1972; Greenfeld and Cambruzzi, 1986; Kerezoudis is difficult in severely dilacerated teeth. et al., 2003; Lee et al., 1968; Pecora and da Cruz Filho, 1992; Peikoff and Trott, 1977; Peikoff et al., Figure 6.19B shows another dilacerated man- 1985). dibular first molar tooth. Root canal treatment of this tooth is made difficult because of the second Radix entomolaris and third curvatures in the root, as well as the abrupt change in root canal curvature. Mandibular first molars may have an additional distal root that can be discerned radiographically. Microdontia When such a root is oriented toward the lingual, it is called the radix entomolaris. This condition can This anomaly describes teeth that are smaller affect both the primary and secondary dentitions than normal. There are two types of microdontia: as shown in Figure 6.16. Endodontic treatment (1) generalized microdontia and (2) specific images of a calcified radix entomolaris tooth are
A Figure 6.14 A. C-shaped canal. Radiographic images and access cavity photos. (Images courtesy of Dr. James Lin.) 68
B Figure 6.14 (Continued) B. Cone beam computed tomograhpy (CBCT) images showing sagittal and coronal views of the C-shaped mandibular molar seen in Figure 6.14A. Note the C-shaped root configuration of the (yellow) and (blue) axial slicing seen in the coronal, middle, and apical root thirds. (Images courtesy of Dr. James Lin.) 69
C (a) C (b) Figure 6.14 (Continued) C. Obturation of a C-shaped lower second molar tooth. (a) View of the floor of the pulp chamber shows the canal orifi are joined by a C-shaped isthmus. (b) Final film following root canal retreatment of this lower second molar tooth. It appears that root filling is present in the furcation region in this two-dimensional film. (Images courtesy of Dr. James Lin.) (a) (b) Figure 6.15 Clinical photos of palatal groove on this upper lateral incisor tooth (a) pre-extraction and (b) postextraction. Note that his palatal groove extends to the apical root third of this tooth. (Images courtesy of Dr. Raymond Greenfeld.) Figure 6.16 Radix entomolaris: Note this condition for both the lower left primary first molar tooth and also for the lower left permanent first molar tooth. (Image courtesy of Dr. Les Campbell.) 70
(a) (b) (c) Figure 6.17 Radix entomolaris: (a) Patient was referred because the calcified canals could not be negotiated in this lower left first molar tooth. (b) Film of gutta percha placed in the trough created in the region of the disto-lingual root helps orientate the direction of progression during uncovering the orifice to this calcified disto-lingual canal. (c) Postretreatment film showing obturation of all three roots. (a) (b) Figure 6.18 (a) Radix entomolaris with bony exostosis; associated but unrelated finding. (b) Taurodontism occurring in this lower molar tooth. Note the elongation of the pulp chamber toward the apical region. (Image courtesy of Visual Endodontics, 2011.) 71
72 General Principles and Techniques A (a) A (b) B Figure 6.19 A. (a) Pre-endodontic and (b) postendodontic treatment films of this dilacerated lower left first molar tooth. The root canals were instrumented with rotary NiTi files to the beginning of these abrupt curvatures, but then canal shaping was completed using .02 tapered files. B. Dilaceration of this mandibular first molar tooth. Note the abrupt double curvatures of the root canal system in the distal root. (Image courtesy of Dr. Les Campbell.) microdontia. In generalized microdontia, all the for the size of the adjacent teeth. Apical periodon- teeth are smaller than normal. This could happen titis is also associated with this tooth. in cases of dwarfism. Specific microdontia involv- ing a single tooth typically affects the third molar Amelogenesis imperfecta tooth and the maxillary lateral incisor. Figure 6.20A shows an unrestored tooth #1-8 adjacent to tooth Amelogenesis imperfecta is a hereditary defect of #1-6, and this tooth appears even smaller than the enamel involving a disturbance in the ectodermal maxillary first premolar tooth. A “peg lateral” layer. Three types of defect have been classified tooth is shown in Figure 6.20B. In both the panorex according to the stage of development in which and periapical films, one can see that tooth #1-2 has they occur (Witkop and Sauk, 1976): hypoplastic, a a shorter and narrower root than one would expect
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 73 A B (a) B (b) Figure 6.20 A. Microdontia. A microdont is shown in the posterior region of this film of the upper right sextant. B. Microdontia. (a) Panorex and (b) periapical films of this maxillary right lateral incisor tooth. Due to the patient presenting with symptomatic apical periodontitis, and having a large post in this small tooth with a well fitting crown, the treatment decision was to perform periapical surgery. (Courtesy of Dr. Sigrid Coil.) disruption of the deposition of organic matrix ning of the enamel both radiographically and during the formative stage, hypocalcifed, a disrup- clinically, toward the incisal edges of the mandi tion during the calcification stage, and hypo bular incisor teeth. Note that the pulp canal space maturation, where the enamel crystals remain appears to be of normal width. immature. Dentinogenesis imperfecta The clinical appearance can vary greatly among the different forms of amelogenesis imperfecta. Dentinogenesis imperfecta is a hereditary condi- The color of affected regions can vary in color from tion affecting dentin due to a mesodermal defect. yellow to gray, and the texture can be soft or rela- Several forms of this disease exist, and the clinical tively hard. presentation can vary greatly. Clinically, the teeth may appear in color from gray to yellow-brown, Depending on the amount of enamel present on the tooth, the morphology of the crown may appear normal or abnormal. Figure 6.21 shows the thin-
74 General Principles and Techniques (a) (b) Figure 6.21 Amelogenesis imperfecta. Note the decalcified regions below the incisal edges of the mandibular incisor teeth, evident both (a) radiographically and (b) clinically. (Images courtesy of Dr. Ravindra Shah.) (a) (b) Figure 6.22 Dentinogeneis imperfecta. (a) The typical obliteration of the pulp canal space is seen radiographically. (b) Clinical view showing extensive wear of these lower incisor teeth. (Images courtesy of Dr. Ravindra Shah.) but all exhibit an opalescent hue. The most pro- Ballschmiede who reported observed premature found feature is the partial or complete obliteration exfoliation of multiple teeth and called it “root of the pulp chamber and root canal space seen less teeth” (Steidler et al., 1984). The radiographic radiographically. Figure 6.22 shows a radiographic and a clinical view of this condition. Note that features of this condition include roots that are although the root canal space is obliterated, the periodontal membrane space and surrounding short, blunt, and conically shaped. The pulp bone appear normal. chambers and root canal spaces are typically oblit- erated (Figure 6.23). This obliteration occurs pre- eruptively in permanent teeth. Dentine dysplasia Talon cusp Dentin dysplasia is a condition affecting The talon cusp is an anomalous projection of tooth dentin formation. This anomaly was reported by structure, projecting from the cingulum region of
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 75 Figure 6.23 Dentine dysplasia is seen in the apical region permanent incisor teeth. This structure resembling of these anterior teeth. (Image courtesy of Dr. Ravindra an eagle’s talon, may interfere with occlusion and Shah.) can be an esthetic problem. A deep development groove is present where the cusp joins the lingual portion of the tooth. Figure 6.24A shows the radio- graphic appearance of the Talon cusp for a lower incisor teeth, and the clinical view of extracted tooth with a Talon cusp. A rare combination of dens invaginatus exhibiting a talon cusp on the facial aspect of a maxillary incisor tooth is presented in Figure 6.24B. Congenital syphilis (Hutchinson incisor and Mulberry molars) The Hutchinson incisor has a characteristic notch in the incisal edge, particularly evident for the maxillary incisor teeth (Figure 6.25). Radiographi- cally, the undulations of the incisal edges would mimic the clinical view. Morphological variations A common complexity for endodontic treatment is the treatment of multiple canals in a given root. Although there are guidelines as to expected A (a) A (b) Figure 6.24 A. (a) Talon cusp is seen radiographically as a discrete cusp on this lower incisor tooth. The incisal view of this talon cusp is shown in (b) (Images courtesy of Dr. Raymond Greenfeld).
B (a) B (b) B (c) B (d) B (e) B (f) B (g) Figure 6.24 (Continued) B. Dens invaginatus exhibiting a talon cusp on the facial aspect of the upper left maxillary central incisor tooth. (a) Periapical film showing the invagination and the talon cusp. (b) Clinical image showing the talon cusp on the buccal surface of this tooth. (c) Occlusal film showing the maxillary anterior teeth. (d) Working length film with a file placed in the buccal access cavity. (e) Clinical view of instrument in buccal access cavity. (f) Root canal instruments in two separate canals for this working length film. Note the perforation repair material in the coronal root third just apical to the CEJ. (g) Clinical view of two instruments placed in the buccal access cavity. (Images courtesy of Dr. George Bogen.)
Radiographic Analysis of Anomalous Tooth Forms and Morphological Variations Related to Endodontics 77 Figure 6.25 Hutchinson’s incisor shown clinically are with anomalous root formation. Oral Surg Oral Med easily identifiable and are easily seen radiographically as Oral Pathol, 62, 82–88. well. (Image courtesy of Dr. Ravindra Shah.) Hulsmann, M. (1997) Dens invaginatus: aetiology, clas- sification, prevalence, diagnosis, and treatment con- frequencies for the number of canals, and configu- siderations. Int Endo J, 30, 79–90. ration of what to expect in a given tooth type, the Keith, A. (1913) Problems relating to the teeth of the true configuration is usually observed following earlier forms of prehistoric man. Proc R Soc Med, treatment. With the increased use of CBCT, three- 6(Odontol Sect), 103–124. dimensional evaluations of teeth and supporting Kerezoudis, N.P., Sisko, G.J., and Tsatsas, V. (2003) Bilat- structures are now possible. However, most initial eral buccal radicular groove in maxillary incisors: a impressions are fettered by careful assessment of case report. Int Endood J, 36(12), 898. two-dimensional periapical radiographs. Lee, K.W., Lee, E.C., and Poon, K.Y. (1968) Palato- gingival grooves in maxillary incisors. Br Dent J, References 124, 14. McCulloch, K.J. et al. (1997) Dens evaginatus from an Bernick, S.M. (1970) Taurodontia. Oral Surg Oral Med Oral orthodontic perspective: report of several clinical Pathol, 29, 549. cases and review of the literature. Am J Orthodont Dentofac Orthopedics, 112(6), 670–675. Canadian Academy of Endodontists. Standards of Prac- Melton, D.C., et al. (1991) Anatomical and histological tice, August 1998, pp. 4–5. features of C-shaped canals in mandibular second molars. J Endod, 17, 384–388. Cooke, H.G., 3rd. and Cox, F.L. (1979) C-shaped canal configurations in mandibular molars. J Am Dent Assoc, Oehlers, F.A.C. (1957) Dens invaginatus (dilated com 99, 836–839. posite ondontoma). I. Variations of the invagination process and associated anterior crown forms. Oral Everett, F.G. and Kramer, G.M. (1972) The disto-lingual Surg Oral Med Oral Pathol, 10, 1204–1218. groove in the maxillary lateral incisor: a periodontal hazard. J Periodontol, 443, 352. Pecora, J.D. and da Cruz Filho, A.M. (1992) Study of the incidence of radicular grooves in maxillary incisors. Greenfeld, R.S. and Cambruzzi, J.V. (1986) Complexities Braz Dent J., 3, 11–16. of endodontic treatment of maxillary lateral incisors Peikoff, M.D. and Trott, J.R. (1977) An endodontic failure caused by an unusual anatomical anomaly. J Endod, 3, 356–359. Peikoff, M.D., et al. (1985) Endodontic failure attributable to a complex radicular lingual groove. J Endod, 11, 573–577. Sert, S. and Bayrili, G. (2004) Taurodontism in six molars: a case report. J Endod, 30, 601–602. Shifman, A. and Buchner, A. (1976) Taurodontism. Report of sixteen cases in Israel. Oral Surg Oral Med Oral Pathol, 41, 400–405. Steidler, N.E. et al. (1984) Dentinal dysplasia: a clinicopathological study of eight cases and review of the literature. Br J Oral Maxillofac Surg, 22, 274– 286. Witkop, C.J., Jr. and Sauk, J.J., Jr. (1976) Heritable defects of enamel. In: R.E. Stewart and G.H. Prescott, eds., Oral Facial Genetics, pp. 151–226. C.V. Mosby Co., St. Louis.
Part 2 Endodontic Disease Chapter 7 Radiographic Expression of Endodontic Disease Chapter 8 Image Interpretation of Periapical Abnormalities Chapter 9 Radiographic Interpretation of Traumatic Injuries Chapter 10 Radiographic Analysis of Acquired Pathological Dental Conditions Chapter 11 Radiographic Analysis of Periodontal and Endodontic Lesions Chapter 12 Radiographic Imaging in Implant Dentistry
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