Stress Distribution Analysis on Mandibular Implant Supported Overdentures

Cicciù et al Figure 21: Possible positions of dental implant placement for Toronto restorations. Figure 22: A mandibular 3D model of 4 dental implants Figure 23: 3D Model of dental implant positioned in the positioned in interforamina position. mandible. The Journal of Implant & Advanced Clinical Dentistry • 49

Cicciù et al Figure 24: 3D model of the mandible with the prosthesis Figure 25: Axial direction of the chewing forces. structure placed over the implants. acterized by dental implant wide diameter on posi- Figure 26: Mesh of the mandible. tion n°5-6. The bone area around dental implants placed in position n°1-6 is not soliciting like for about 66% in the second trial; implant n°3 load the trial 1 and 2 (central position). Comparing increases by 104%. Comparing trial 1 and 2, trial 3 and 4 with trial 1, there is an 83% decrease there is a general strength changing over the bone on bone soliciting of central implants; load (Von Mises) of 2MPa more in the trial 2. (Table 4). decreasing on bone area under dental implants Trial 2 shows more negative conditions; Table 5 n°2-3 is 76%. Comparing trial 4 with 1, there is underlines how the safe coefficient of lateral can- a 22% decrease of the strength distribution on tilevers (CA and CB) decreases by 22% in trial 2. the bone (Von Mises) (Table 4). The safe coeffi- cient of lateral cantilever is higher in the trial 4 and Trials 3 and 4 show particular different results. this is related to the wide diameter of the dental Both present 6 dental implants but trial 4 is char- implants placed in the lateral position, (Table 5). Two highest negative load stress values of the implants (392 N and 448 N), are analysed by FEM dynamic investigation as well. FEM static analysis shows that there is no static load is able to break the material. Fatigue – dynamic analysis was per- formed by COSMOS 2007®. International refer- ences underline that the number of masticatory cycles is about 500/2000 occlusion contacts per day. In that study we decided to consider the fatigue analysis over 10 years; 3,65E+6 cycles 50 • Vol. 2, No. 9 • November 2010

Cicciù et al Trial 1 Table 2: Static Axial Load Over Each Screw F6 Trial 2 - Trial 3 F1 F2 F3 F4 F5 - Trial 4 269 111 111 392 392 74 448 227 219 392 392 74 74 53 46 392 392 74 53 46 392 392 Table 3: Speci c Geometrical Size and Fundamental Values of Geometrical Characteristics of the Screws for Each Trial 1 2 3 LA(mm) LB(mm) LI(mm) L2(mm) L3(mm) Trial 1 - 45 45 9 9 9.39 11.1 11.1 Trial 2 - 51 50 11.48 11.48 9.41 11.98 11.98 Trial 3 25 66 69 9.58 9.58 11.56 14.52 16.43 Trial 4 25 66 69 9.58 9.58 11.56 14.52 16.43 are investigated here. FEM demonstrate how evaluate the biomechanical load on implants. In the 392 N dynamic loads are not dangerous for the past 2 decades, finite element analysis (FEA) the “life” of the dental implant. Otherwise 448 N has become an increasingly useful tool for the dynamic loads emphasise how dynamic-fatigue prediction of the effects of stress on the implant solicitation could be decisive for a break of dental and its surrounding bone. Vertical and transverse implant screw components after 6 year over loads. loads from mastication induce axial forces and bending moments and result in stress gradients DISCUSSION in the implant as well as in the bone. A key fac- tor for the success or failure of a dental implant The engineering applications in the field of den- is the manner in which stresses are transferred tistry have helped the understanding of bio- to the surrounding bone.14-16 Load transfer from mechanics aspects related to osseointegrated implants to surrounding bone depends on the implants. Several techniques have been used to The Journal of Implant & Advanced Clinical Dentistry • 51

Cicciù et al Figure 27: Von Mises analyses on the mandible. Figure 28: Von Mises analyses of the stress on the mandible and on the bar. Figure 29: Von Mises analyses on the dental implants. or failure of an implant. It has long been rec- type of loading, the bone–implant interface, the ognized that both implant and bone should be length and diameter of the implants, the shape stressed within a certain range for physiologic and characteristics of the implant surface, the homeostasis. Overload can cause bone resorp- prosthesis type, and the quantity and quality of tion or fatigue failure of the implant, whereas the surrounding bone. FEA allows researchers underloading of the bone may lead to dis- to predict stress distribution in the contact area use atrophy and subsequent bone loss.17,18 of the implants with cortical bone and around the apex of the implants in trabecular bone.16 . The topic of the stress distribution is very debated in the international literature and several Analyzing force transfer at the bone–implant animal studies are carried out. With the use of interface is an essential step in the overall analy- load cells in rabbit calvaria, Hassler et al19 showed sis of loading, which determines the success that the target compressive stress level for maxi- mum bone growth occurs at 1.8 MPa, levelling off to a control level at 2.8 MPa. Skalak20 stated that close apposition of bone to the titanium implant surface means that under loading, the interface moves as a unit without any relative motion; this is essential for the transmission of stress from the implant to the bone at all parts of the interface. Analyzing the center of loading, several FEA studies21,22 of osseointegrated implants demon- strate that when maximum stress concentration is located in cortical bone it is in the contact area 52 • Vol. 2, No. 9 • November 2010

Cicciù et al Table 4: Physical Alteration and Movement on Bone Shape Analyzed with Van Mises Strength, Maximum Movement and Deformation for Each Trial max (mpA) max ( m max (*E10-4) Trial 1 29 Pos 5 3.15 Pos 4 6,60 Pos 4 Trial 2 Trial 3 31 Pos 1 3.89 Pos 1 8.41 Pos 1 Trial 4 28 Pos 5 3.93 Pos 5 6.21 Pos 5 22 Pos 5 4.22 Pos 5 5.15 Pos 4 = MP Strength • = Load Displacement • = Deformation Table 5: Screws (C1, C2, C3, C4, C5, C6) and Cantilever (CA, CB) C8 Safety Coe cient For Each Trial 2.243 1.759 C1 C2 C3 C4 C5 C6 C7 2.107 2.107 Trial 1 5 12.125 12.125 3.425 3.425 - 2.243 Trial 2 Trial 3 3.001 5.93 6.128 3.425 3.425 - 1.759 Trial 4 18.23 25.289 28.97 3.425 3.425 18.232 2.107 18.23 25.289 28.97 4.247 4.247 18.232 2.107 with the implant, and when the maximum stress the bone–implant interface on the loading side concentration is in trabecular bone, it occurs than the use of a rigid alloy for a superstructure around the apex of the implant. In cortical bone, with the same geometry.(23) Stegariou et al24 used stress distribution is related to the immediate 3-dimensional FEA to assess stress distribu- area surrounding the implant; in trabecular bone, tion in bone, implant, and abutment when a gold a fairly broader distant stress distribution occurs. alloy, porcelain, or resin (acrylic or composite) was High-rigidity prostheses are recommended used for a 3-unit prosthesis. In almost all situa- because the use of low elastic moduli alloys for tions, stress in the bone–implant interface with the the superstructure predicts larger stresses at resin prostheses was similar to or higher than that The Journal of Implant & Advanced Clinical Dentistry • 53

Cicciù et al Figure 30: Von Mises analyses of the passant screws. Figure 31: Von Mises analyses of the mandible after implant placment. Figure 32: Von Mises analyses on the arch bar. diameters provide for more favorable stress dis- in the models with the other 2 prosthetic materi- tributions.27-29 FEA has been used to show that als. However, in his classical mechanical analysis, stresses in cortical bone decrease in inverse pro- Skalak20 stated that the presence of a resilient portion to an increase in implant diameter with element in an implant prosthesis superstruc- both vertical and lateral loads. However, Hol- ture would reduce the high load rates that occur mgren et al.30 showed that using the widest diam- when occluding unexpectedly on a hard object. eter implant is not necessarily the best choice For this reason, he suggested the use of acrylic when considering stress distribution to surround- resin teeth. Nevertheless, several other studies25,26 ing bone; within certain morphologic limits, an could not demonstrate any significant differ- optimum dental implant size exists for decreas- ences in the force absorption quotient of gold, ing the stress magnitudes at the bone–implant porcelain, or resin prostheses. Large implant interface. From the other hand the results of our study clearly demonstrate that a wide diameter implant is able to better distribute the stress. Wiskott and Belser31 studied the relationship between the stresses applied and bone homeo- stasis of different implant neck designs. It has been observed that the polished neck of dental implants does not osseointegrate as do textured surfaces. Lack of osseointegration was postulated to be due to increased pressure on the osseous bed during implant placement, establishment of a physiologic “biologic width,” stress shielding, 54 • Vol. 2, No. 9 • November 2010

Cicciù et al Figure 33: Static load on a single implant. Figure 34: Dynamic load on single implant. Figure 35: Dynamic load on single implant. Ten year and lack of adequate biomechanical coupling masticatory cycle. between the load-bearing implant surface and the surrounding bone. Any viable osseous structure (including the tissue that surrounds the polished implant neck) is subjected to periodic phases of resorption and formation. Hansson32 compared implants with smooth necks to implants with retention elements all the way up to the crest. His FEA study found that retention elements at the implant neck resulted in a major decrease in peak interfacial shear stresses. He suggests that these retention elements at the implant neck will counteract marginal bone resorption. Clinical studies have reported a significant inci- dence of component failure. These include gold screw and abutment screw failures as well as gold cylinder, framework, and implant fractures. The cause of these failures is complex and involves cyclic fatigue, oral fluids, and varied chewing pat- The Journal of Implant & Advanced Clinical Dentistry • 55

Cicciù et al terns and loads. Biomechanically, the following between the surfaces. Because the prosthesis component interfaces can be found in a standard framework splints multiple implants, stress dis- dental implant: fixture–abutment interface, abut- tribution is more complex than with the single- ment screw– abutment interface, cylinder–abut- tooth implant situation. Loading at one point of ment interface, retaining screw cylinder interface, the prosthesis causes stress concentrations in and retaining screw–abutment screw interface. all supporting implants to varying degrees. The prosthesis can be loaded not by a single load but Long-term screw joint integrity at the implant– by multiple loads and in varying directions.37 In abutment screw joint and abutment cylinder screw addition, the flexure of the jaw bones, particularly joint is essential for prosthetic success. Today all the mandible, under functional loading conditions this component as usually titanium grade 4 made. can cause stress in the bone around the implants and may lead to bone resorption. Stress around An increasing number of FEA studies focus the implant can be caused not only by local defor- on biomechanical problems involving the screw mation of the bone because of movement of the joint and on screw loosening phenomena.33,34 The implant and interface relative to the surrounding screw loosening problem frequently affects den- bone, but also by the complex deformation pat- tal implants and implant-supported prostheses. terns of the mandibl Since the preliminary studies When a screw is fastened to fix the prosthesis, a on osseointegration, dental implants have been tensile force (preload) is built up in the shank of widely used for the rehabilitation of completely the screw. This preload acts on the screw shank and partially edentulous patients.38-42 Despite from the head of the screw to the threads. The the high success rates reported by a vast num- preload should be as high as possible because ber of clinical studies, early or late implant fail- it creates a clamping force between the abut- ures are still unavoidable and several papers have ment and implant. The screw elongates when not focused the difference between clinical suc- subjected to tensile forces during tightening. cess and dental implant survival rate.43 Mechani- The more elongation there is, the better the sta- cal complications and failures have frequently bility of the screw in place. Thus, screw design been reported during prosthetic treatment.44,45 is of significance and should allow maximum Therefore, mechanical and biomechanical aspects torque to be introduced into the shank of the are generally agreed to be significant particu- screw. Several authors35, 36 have drawn attention larly during the planning of restorative treat- to the fact that repeated loading and unloading ments and the design of prosthetic appliances. cycles result in alternating contact and separa- tion of components. Clinical findings of screw The intraoral environment is a complex biome- loosening and failure probably result from these chanical system. Therefore, most of the research separation events and from elevated strains in the conducted on the mechanical behavior of pros- screw. The other mechanism of screw loosen- thetic devices for removable, fixed, and implant ing is related to the fact that no surface is com- treatment has been performed in vitro.46 The pletely smooth. Because of the microroughness application of engineering knowledge in dentistry of components, when the screw interface is sub- has helped the understanding of biomechan- jected to external loads, micromovements occur 56 • Vol. 2, No. 9 • November 2010

Cicciù et al ics aspects related to osseointegrated implants. type, geometry, boundary conditions, element However, the mechanisms responsible for bio- selection, and so on.52 The finite element seems mechanical implant failures are not fully under- to be the close physical resemblance between stood, and the literature concerning the influences the actual structure and its finite element model. of several biomechanical factors is inconclu- The model is not simply an abstraction; there- sive.47 The stress occurring around the implants fore, experience and good engineering judgment is so important that in dentistry, many studies are needed to define a good model.53 Stress have reported methods to minimize this stress.48 distribution depends on several parameters like assumptions made in modelling geometry, mate- The finite element method is a numerical pro- rial properties, boundary conditions, and the bone cedure for analyzing structures. Usually, the prob- implant interface. To obtain more accurate stress lem addressed is too complicated to be solved predictions, advanced digital imaging techniques satisfactorily by classic analytical methods. can be applied to model the bone geometry more realistically; the anisotropic and non homo- The problem may concern stress analysis, heat geneous nature of the material must be consid- conduction, or any of several other areas. The ered; and boundary conditions must be carefully finite element analysis (FEA) produces many treated with the use of computational modelling simultaneous algebraic equations, which are gen- techniques. In addition, modelling of the bone- erated and solved on a digital computer.49 The implant interface should incorporate the actual FEA is a technique for obtaining a solution to a osseointegration contact area in cortical bone complex mechanical problem by dividing the prob- as well as the detailed trabecular bone contact lem domain into a collection of much smaller and pattern through the use of contact algorithms in simpler domains in which the field variables can be FEA.53 Finite element analysis can simulate stress interpolated with the use of shape functions.50 An using a computer-created model to calculate overall approximated solution to the original prob- stress, strain, and displacement. Such analysis lem is determining based on the variational prin- has the advantage of allowing several conditions ciples. In other words, FEA is a method whereby to be changed easily and allows measurement instead of seeking a solution function for the entire of stress distribution around implants at optional domain, one formulates the solution functions for points that are difficult to examine clinically.54 its finite element and combines them properly to obtain the solution to the whole structure.50 FEA has been used extensively in the pre- diction of biomechanical performance of dental The power of the finite element method implant systems. Load transmission and resultant resides principally in its versatility. The method stress distribution at the bone–implant interface can be applied to various physical problems. has been the subject of FEA studies. Factors The structure analyzed can have arbitrary shape, that influence load transfer at the bone–implant loads, and supporting conditions. The mesh can interface include the type of loading, implant and mix elements of different types, shapes, and physi- prosthesis material properties, implant length and cal properties.50 This great versatility is contained diameter, implant shape, structure of the implant within a single computer program.51 User-pre- pared input data control the selection of program The Journal of Implant & Advanced Clinical Dentistry • 57

Cicciù et al surface, nature of the bone–implant interface, and The stress over the screw is always highest the quality and quantity of the surrounding bone.55 over the central screw; for this reason two dental implants in the central position could Of these biomechanical factors, implant length, parcel out stress better than one screw alone. diameter, and shape can be modified easily in the The breakage of the prosthesis component implant design. Cortical and cancellous bone is always related to dynamic – fatigue quality and quantity need to be assessed clinically stress strength and when it happens it is and should influence implant selection. When related to cantilever or passant screw. applied to multiple-implant prosthesis design, There no fracture for static axial load. FEA has suggested improved biomechanical situ- The results of the study clearly demonstrate ations when factors such as implant inclination, how the long term success of the dental implants implant position, prosthetic material properties, components supporting Toronto prosthesis is superstructure beam design, cantilever length, bar tightly related to the stress distribution during system, bar span length and stiffener height, and masticatory cycles. This study shows a new sys- overdenture attachment type are optimized.56 -59 tem method to recreate the virtual mandibular model. The elaboration of the 3d detailed model FEA is an effective computa- offers to the surgeon the capability to evaluate the tional tool that has been adapted from stress distribution over the prosthesis structure, the engineering arena to dental implant over dental implant components and over bone biomechanics. With FEA, many design feature opti- area as well, related to the implant position. mizations have been predicted and will be applied to potential new implant systems in the future. Correspondence: Dr Marco Cicciù DDS, PhD CONCLUSIONS Department of Oral Surgery Dental Clinic, IRCCS, Milan Data results analysis evidence that: Via Commenda n°10, 20122, Milano, Italy The Toronto prosthesis supported by 6 dental Tel.: 0039-02-55032621 implants is able to parcel out stress better than Fax: 0039-02-666686 Toronto prosthesis supported by 5 dental E-mail: [email protected] implants. Wide diameter of dental implants placed in the premolar zone is helpful for prosthe- sis function and lateral cantilever safety. Disclosure: considerations [Review] [10 refs]. International 6. Zarone F, Apicella A, Nicolais L, Aversa R, The authors report no conflicts of interest with Journal of Oral and Maxillofacial Surgery. 20 Sorrentino R. Mandibular flexure and stress anything mentioned in this paper. (1991), pp. 75–82. build-up in mandibular full-arch fixed prostheses 4. Tallgren A., The continuing reduction of the supported by osseointegrated implants. Clin Oral References: residual alveolar ridges in complete denture Implants Res. 2003;14(1):103-114. 1. von Meyer H 1867 Die Architectur der wearers: a mixed-longitudinal study covering 25 years. Journal of Prosthetic Dentistry. 27 (1972), 7. Burch J. Patterns of change in human mandibular Spongiosa. Archiv fur Anatomie und Physiologie pp. 120–132. arch width during jaw excursions. Arch Oral 47: 615-628. 5. J.I. Cawood and R.A. Howell, A classification Biology 1972;17:623– 631. 2. Wölff J D 1892 Das Gesetz der Transformation of the edentulous jaws. International Journal of der Knochen. Verlag von August Hirschwald, Oral and Maxillofacial Surgery. 17 (1988), pp. 8. Wall, J.C., Chatterji, S.K. & Jeffery, J.W. ( Berlin. 232–236. 1978) The influence that bone density and the 3. J.I. Cawood and R.A. Howell, Reconstructive orientation and particle’s size of the mineral phase preprosthetic surgery. I. Anatomical have on the mechanical properties of bone. J Bioengineering 1978; 2:517– 526. 58 • Vol. 2, No. 9 • November 2010

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The Twin Implant: Wilcko et al A New Subperiosteal Dental Implant Antonio T. Di Giulio1 • Giancarlo Di Giulio1 • Enrico Gallucci2 Abstract Background: When treating patients with a A stereolithographic model for both maxilla/ resorbed mandible and/or maxilla, fitting a con- mandible was constructed, upon which a sub- ventional denture may be challenging. In such periosteal twin implant was then constructed. circumstances, using a subperiosteal dental This was made up of two implants, one fitting implant may allow a dental implant prosthe- the palatal part and the other the vestibular sis to be fitted. This study reports on a modi- part, connected by a metal crown which holds fication to the traditional subperiosteal implant the implant in place and closely fits the bone. to provide those patients unable to fit a con- ventional subperiosteal implant with a modi- Conclusions: This implant is regarded as an fied implant we have called the “twin implant”. evolution of the subperiosteal dental implant and its success has so far from taking advantage Materials and Methods: All patients seen as of the undercuts present on the maxillary/man- potential candidates for the twin implant under- dibular bone, thus acting as the site of anchor- went a computed tomography (CT) scan to age and conferring stability to the implant. reproduce the bone crest in maximum detail. KEY WORDS: Subperiosteal dental implant, dental implant, maxilla, mandible, dentures The Journal of Implant & Advanced Clinical Dentistry • 63

Giulio et al INTRODUCTION osteal twin implants. Informed consent was obtained from each patient once the procedure Although osseointegrated oral implants have had been explained and the risks and benefits achieved perfection in terms of design, instal- evaluated with the patient. Criteria for exclud- lation, aesthetics, comfort and follow-up, ing installation of the implant were: patients suf- in cases where the bone volume is insuffi- fering from chronic systemic conditions such as cient for conventional implants, a subperios- diabetes, cardiovascular disease, severe osteo- teal implant may be the optimum solution. The porosis, or those undergoing chemo/radiation subperiosteal implant dates back to 1940, therapies, while smokers were encouraged to first installed by Dahl1, then by Goldberg and stop smoking for the success of the implant. Gershkoff2, while Linkow3 can take the credit Candidates for subperiosteal implant therapy for making them a widespread phenomenon. received panoramic radiographies and 64-slice computed tomography (CT) scans (General In a previous paper4, a long-term study was Electric Co, USA) to reproduce their osseous conducted over a period of 25 years on sub- structures in maximum detail. This enabled periosteal implants made either from chrome- us to become familiar with the patient’s three- cobalt or titanium. The results clearly indicated dimensional (3D) bony architecture and critical that this type of implant is appropriate for peo- anatomical structures so as to plan the subperi- ple with a severely atrophic mandible or maxilla, osteal twin implant. All patients were totally providing benefits to recipients and satisfac- or partially edentulous with severely resorbed tion to clinicians, owing to its excellent long- maxillas and/ or mandibles. The analysis made term prognosis. The survival rate reported was it possible to build a maxillary and mandibu- 95.5% and 89.1% at 7 and 20 years, respec- lar stereolithographic model, which was then tively, for chrome-cobalt implants; whereas used to construct custom subperiosteal twin titanium subperiosteal dental implants had a implants. The structure of the titanium maxil- survival rate of 81.1% at 7 years. However, lary/mandibular subperiosteal dental implant in some cases, this type of implant could not was formed by two implants, one fitting the be installed due to the specific shape of the palatal and the other the vestibular part of the maxilla, which made a subperiosteal implant maxilla/mandible. The two implants were con- unsuitable. We have carried out a technical nected and locked with a cemented metal- modification to the construction of the implant lic crown. The two subperiosteal twin-implant to help overcome this limitation without affect- frameworks embrace the osseous crest, tak- ing its resistance. This modified subperios- ing advantage of the undercuts on the bone, teal implant is known as a “twin implant” and to give maximum stability to the implant. is made up of two implants whose abutments are connected by a cemented metallic crown All patients were treated under local anaes- on which the prosthesis will be cemented. thesia, sometimes under sedation. An incision was made on the alveolar crest and mucoperi- MATERIALS AND METHODS osteal flaps were elevated; the fixture was then From 2007, 72 patients received 72 subperi- 64 • Vol. 2, No. 9 • November 2010

Giulio et al Figure 1: Presurgical panoramic radiograph. Figure 2: Components of the twin implant (the vestibular and palatal implants, the metallic crown, and the applied both on the vestibular and the pala- lithographic model obtained from a CT data set). tal side and blocked with a metallic cemented crown. Before suturing of the gingival tis- RESULTS sue, the implant was covered with hydroxy- apatite. Postsurgical instructions were given One significant case from a series of twin to the patient and follow-up CT’s and pan- implants is reported. The patient enrolled for oramic radiographies were performed. A tem- maxillary subperiosteal twin implant presenting porary overdenture was applied to the patient. a severely resorbed maxillary bone; two screw- A four-month healing period was allowed prior type implants were present, one still in use while to placing prosthetic restorations for full func- the broken one was left submerged (Fig.1). tion. The fitness of the implant was evaluated by pulling it in all directions and radiography Figure 2 shows all of the components of was taken to observe bone apposition over the the twin implant, i.e. the vestibular and pala- abutment. Annual check-ups were required to tal implants, the metallic crown, and the litho- verify the success of the implant. The param- graphic model obtained from a CT data set. In eters for assessing implant success were Figure 3, all of the components of the implant based on both subjective and objective clini- are assembled on the lithographic model. cal criteria, such as: 1) absence of clinically- After surgery, panoramic radiography was per- detectable implant mobility; 2) absence of formed (Fig. 4). Healed gingival tissue and inflammation and pain; 3) bleeding on prob- prosthetic restoration, 4 months after surgery, ing; 4) pocket-probing depth; 5) comfort of the are reported in Figures 5 and 6, respectively. patient; 6) absence of foreign body sensation. DISCUSSION This report is devoted to a subperiosteal twin implant that can be regarded as an evolution of the conventional subperiosteal implant. Con- The Journal of Implant & Advanced Clinical Dentistry • 65

Giulio et al Figure 4: Postsurgical panoramic radiograph. Figure 3: Components of the twin implant assembled on a lithographic model. Figure 6: Restored twin periosteal dental implants. Figure 5: Healed twin subperiosteal dental implants prior ventional subperiosteal implants which have to restoration. been used until now, have remarkable long sur- vival rates, averaging in excess of 24 years.1 In some patients, however, subperiosteal implants could not be applied due to the specific shape of the maxillary/mandible bone, such as under- cuts that did not allow for precise fitting and were consequently unstable. The new implant described in the report provides greater flex- 66 • Vol. 2, No. 9 • November 2010

Giulio et al ibility as it embraces the whole of the maxilla/ lithography played an important role in enabling mandible, even in the presence of undercuts a model to be created from a CT data set where traditional implants could not be placed. It is worth mentioning that all the cases treated Correspondence: with subperiosteal implants in this report pre- Dr. Enrico Gallucci sented osseous structures with severe inad- Dipartimento Farmaco-Biologico, equacies. This new type of implant not only Università degli Studi di Bari, offers a viable alternative treatment option for via E. Orabona 4, 70126 Bari, Italy all cases that cannot be treated either with Tel/Fax: +39 0805442794, endosseous implant or with the traditional sub- Email: [email protected] periosteal model, but given the manufacturing precision inherent in the implant, which closely Disclosure fits the patient’s osseous profile, could be advo- The authors report no conflicts of interest with anything mentioned in this article. cated as a therapy of choice for all patients. Acknowledgements Though the study does have its limitations The authors would like to thank their colleague Anthony Green for proofreading in terms of the short study period involved, and providing linguistic advice. The following collaborators: Engineer F. Davolio, the twin implants that have been placed so Radiologist A. Zerbi, Technician E. Puntieri are gratefully acknowledged for their far have been well appreciated by patients, collaboration. and all patients wearing their prostheses seen in the follow-up reported high levels of sat- References isfaction with their implant and prosthesis. 1. Dahl G. Dental implants and superplants. Rassegna Trimestrale Odontoiatria CONCLUSIONS 1956; 4: 25-36. 2. Goldberg N, Gershkoff A. The implant lower denture. Dent Dig 1949; 55: It is often difficult for patients with severe resorption of the mandible and/or maxillary 490-494. bone to wear a dental prosthesis. One alterna- 3. Linkow L, Wagner J, Chanavaz M. Tripodal mandibular subperiosteal implant: tive at their disposal is autogenous bone grafts for endosseous implants. However, the use of basic sciences, operational procedures, and clinical data. J Oral Implantol subperiosteal implants may be an alternative 1998; 24:16-36. practicable solution. Indeed, our studies, in 4. Di Giulio A.T., Di Giulio G., Gallucci E. J Implant Adv Clin Dent 2009,1(8):69- line with others, have demonstrated the good 75. long-term survival of subperiosteal implants. The successful delivery of subperiosteal den- tal implants is aided by three-dimensional computed tomography that enables a precise reconstruction of the patient’s osseous details and the profile upon which the subperiosteal implant is to be placed. In this study, stereo- The Journal of Implant & Advanced Clinical Dentistry • 67

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Restoration of a Partial-Maxillectomy Patient witHhonda et al a Prosthesis Supported by Dental Implants in Both the Reconstuctive Bone Graft and the Residual Bone: An 8-Year Follow-up Kosuke Honda, DDS, PhD1 • Kazuki Takaoka, DDS, PhD1 Yoko Yasukawa, DDS, PhD1 • Hiromitsu Kishimoto, DDS, PhD1 Masao Kakibuchi, MD, PhD2 • Masahiro Urade, DDS, PhD1 Abstract We used osseointegrated dental latissimus dorsi osteomyocutaneous flap. Four implants to support a maxillary pros- dental implants were installed in the maxilla, thesis after an oroantral fistula had one of which was placed in the grafted bone in been closed by reconstructive surgery. The order to support the upper denture. Eight years patient was a 61-year-old woman diagnosed with have passed since the abovementioned proce- a malignant schwannoma. The tumor mass was dures, but no problems have been found with extirpated by partial resection of the right max- regard to the adaptation or stability of the den- illa, including the right anterior wall, a portion tures, and the patient has not complained of any of the hard palate, and transection of the fron- discomfort. This case report shows that osseo- tal process, the nasal process of the maxilla, the integrated dental implants can have an impor- zygomatic arch, and infraorbital rim. She did not tant role in supporting maxillary prostheses develop recurrence of the tumor during a 2-year installed after maxillectomy. It also shows that postoperative follow-up period. The oroantral one can make use of grafted bone as an implant fistula was closed using a vascularized scapular- site to add greater support to the prosthesis. KEY WORDS: Dental implants, maxilla, maxillectomy, bone graft, prosthesis 1. Department of Dentistry and Oral Surgery, Hyogo College of Medicine, Japan 2. Department of Plastic and Reconstructive Surgery, Hyogo College of Medicine, Japan The Journal of Implant & Advanced Clinical Dentistry • 69

Honda et al INTRODUCTION Figure 1: A computed tomographic view at the initial consultation in August 2000 showing a large mass of tumor In patients undergoing partial maxillectomy in the left maxillary sinus, which dilated the nasal cavity for tumor resection, the defect is frequently and ethmoidal sinus. closed with maxillary prostheses that include a bulbous obturator. However, such pros- sinus, swelling of the right middle nasal concha, theses are often unsuitable for large maxil- and an alveolar bone defect extending from the lary defects extending into the soft palate or right first premolar to the second molar (Fig.1). the pharyngeal wall because of the difficulty The patient was diagnosed with sinusitis, but a with retention and the discomfort caused by malignant maxillary tumor was also suspected. wearing them. Moreover, large, bulky pros- A biopsy of the soft-tissue mass in the right theses are not favored by patients because nasal cavity was performed and microscopic they severely limit mouth opening. For these examination showed a malignant schwannoma. reasons, surgical reconstruction of the oro- In October 2000, the tumor mass was extir- antral fistula is preferred. However, it is often pated by partial resection of the right maxilla, difficult to construct a denture with ade- including the right anterior wall and a portion quate retention on the reconstructed maxilla. of the hard palate, and transection of the fron- tal process, the nasal process of the maxilla, Recently, the role of osseointegrated den- the zygomatic arch, and the infraorbital rim. tal implants for the retention of maxillary pros- theses has been established, and they have The bony defect caused by the partial maxil- been widely applied to various prosthetic cases. lectomy was not surgically reconstructed initially Maxillary prostheses supported by osseointe- because it was necessary to leave the oroan- grated dental implants are suitable for patients who have few teeth to retain the prosthesis, even when there is a lack of supporting bone. This paper reports on the long-term result of using osseointegrated dental implants placed in the residual maxillary bone, as well as in a scapular bone graft used for reconstruction fol- lowing partial maxillectomy, to support a pros- thesis, and avoid use of a bulbous obturator. CASE REPORT A 61-year-old woman with a history of right buccal swelling was referred to our depart- ment in August 2000. Coronal and transaxial computerized tomography (CT) scans showed diffuse effusion extending from the right maxil- lary sinus to the nasal cavity and the ethmoidal 70 • Vol. 2, No. 9 • November 2010

Honda et al Figure 2: The oromaxillary stula was closed by Figure 3: An intraoral view 2 months after a surgical reconstructive surgery using a scapular-latissimus dorsi reconstruction with a scapular-latissimus dorsi osteomyocutaneous ap. osteomyocutaneous ap. tral fistula open for several years in order to port a denture. Therefore, 4 dental implants observe whether the tumor recurred. Therefore, (Calcitek Implant, ø 3.25×8, 10, 13mm, Zimmer a prosthetic obturator, retained by Aker’s clasps Co, USA) were installed in the maxilla, one of placed on the four remaining teeth, was used to which was placed in the grafted bone in order temporally close the defect. A complete den- to support the upper denture. After 5 months, ture was fabricated for the edentulous mandi- the implant heads were exposed and abut- ble. The patient’s velopharyngeal incompetence ments were connected to each implant in order was improved by wearing the maxillary prosthe- to allow magnetic attachments to be installed sis; however, he had difficulty in inserting and (Figs.4, 5). After 3 months, a removable partial removing it because of severely limited mouth denture (overdenture) was put in place (Fig.6). opening as a consequence of the maxillectomy. While wearing the upper and lower dentures the patient was able to generate an occlusal force The patient did not develop recurrence of of 203N (about 22kg) and the conversational the tumor during a 2-year postoperative fol- speech intelligibility score was determined to low-up period. Therefore, in February 2003, be 1; namely, all monosyllables could be accu- the oroantral fistula was closed using a vas- rately understood by five speech therapists. cularized scapular-latissimus dorsi osteomyo- cutaneous flap (Fig.2). Two months later, the Eight years have passed since the above- reconstructed area had largely healed and was mentioned procedures, but no problems covered with normal epithelial tissue (Fig.3). have been found with regard to the adap- However, the residual maxillary alveolar pro- tation or stability of the dentures, and the cess and hard palate were inadequate to sup- patient has not complained of any discomfort. The Journal of Implant & Advanced Clinical Dentistry • 71

Honda et al Figure 4: An intraoral view after implant surgery. Figure 5: An orthopantomographic view after implant placement. DISCUSSION of the subsequent prosthesis. Therefore, we Normal oral functions, e.g., mastication, speech used osseointegrated dental implants to sup- and swallowing, are significantly impaired in port the maxillary prosthesis after the oroantral patients who have undergone a partial max- fistula had been closed by reconstructive sur- illectomy. The approaches used to recover gery. The advantages of using osseointegrated such oral functions include reconstructive dental implants to stabilize a maxillary pros- operations, dental prosthetic treatments, thesis after maxillectomy have already been and maxillofacial rehabilitation.1 However, demonstrated in previous papers.5,6 In most although much time and labor are spent per- of these cases, however, the dental implants forming such treatments, many patients find were placed in the remaining bone such as the that their quality of life is still impaired. While zygomatic bone, and were used in combina- a maxillary prosthesis composed of an obtura- tion with an obturator in order to obtain more tor attached to a denture base may be effica- adequate stability and retention of the maxil- cious for patients with small oroantral fistulas; lary prosthesis. However, it is clear that better they are less effective in improving velopharyn- clinical results can be obtained by also plac- geal incompetence in those with large fistulas. ing implants in the transferred bone graft, as was done in this case, rather than only in the A number of reconstructive techniques for residual bone. Although this was not the situ- repairing oroantral fistulas after maxillectomy ation in our patient, in some cases the resid- have been reported.2,3 Currently, large pala- ual bone may be adversely affected by prior tal defects are often sealed with a combina- irradiation and not be an ideal implant site. tion of reconstructive grafts of soft tissue and/ or bone and dental prostheses.4 However, such It is worth noting that the configuration of the reconstruction sometimes affects the retention bone graft block used in this case differed sig- 72 • Vol. 2, No. 9 • November 2010

Honda et al Figure 6: A frontal view of the patient after placement of Correspondence: the nal maxillary prosthesis. Dr. Kosuke Honda Department of Dentistry and Oral Surgery nificantly from the alveolar bone. In particular, the Hyogo College of Medicine bone graft was joined to the remaining zygomatic 1-1, Mukogawa-cho bone so it was indistinctly demarcated from the Nishinomiya, Hyogo 663-8501 surrounding tissue and the primary mucobuccal Japan fold and maxillary tuberosity were lost. There- Tel : +81-798-45-6677 fore, it was very difficult to design the section of Fax: +81-798-45-6679 the maxillary denture frame that was to be placed Email: [email protected] in the graft area. Additionally, our plans for the implant sites were restricted because the bone Disclosure area used to support the implants was not flat The authors report no conflicts of interest with anything mentioned in this article. and the peri-implant bone had formed as irregu- lar bulges. The placement of an overdenture on References such an area often causes inflammation due to 1. Wheeler R, Logemann J, Rosen M. Maxillary reshaping prosthesis: poor plaque control in the peri-implant soft tis- sue.7.8) Therefore, it is important to observe the Effectiveness in improving speech and swallowing of post-surgical oral cancer peri-implant soft tissues for inflammatory thick- patients. J of Prosthet Dent 1980; 43: 313-319. ening while a provisional denture is in place. 2. Futran ND, Haller JR. Considerations for free-flap reconstruction of the hard In conclusion, this case report shows that palate. Arch Otolaryngol Head Neck Surg 1999; 125:665-669. osseointegrated dental implants can have an important role in supporting maxillary prostheses 3. Wells MD, Luce EA. Reconstruction of midfacial defects after surgical installed after maxillectomy. It also shows that resection of malignancies. Clin Plast Surg 2000; 22:79-89. one can make use of grafted bone as an implant site to add greater support to the prosthesis. 4. Kim PD, Blackwell KE. Latissimus-Serratus-Rib Free flap for oromandibular and maxillary reconstruction. Arch Otolaryngol Head Neck Surg 2007; 133:791- 795. 5. Aydin C, Delilbasi E, Yilmaz H, Karakoca S, Bal BT. Reconstruction of total maxilloectomy defect with implant-retained obturator prosthesis. NY State Dent J 2007; 11: 38-41. 6. Weischer T, Schetter D, Mohr C. Titanium implants in the zygoma as retaining elements after hemimaxillectomy. Int J Oral Maxillofac Surg 1997; 12: 211-214. 7. Boronat A, Carrillo C, Penarrocha M, Penarrocha M. Dental implants placed simultaneously with bone grafts in horizontal defects: a clinical restrospective study with 37 patients. Int J Oral Maxillofac Surg, 2010; 25: 189-196. 8. Akca K, Cehreli MC, Uysal S. Marginal bone loss and prosthetic maintenance of bar-retained implant-supported overdentures: a prospective study. Int J Oral Maxillofac Surg 2010; 25: 137-145. The Journal of Implant & Advanced Clinical Dentistry • 73

Mackey

Mackey Dental Practice Marketing for the Next Decade Shannon Mackey As we approach the onset of a new vate the reader to action. How does your web- decade, it seems an appropriate time for site demonstrate to current and potential clients reflection. When it comes to marketing that you are indeed superior to the competition? for the dental practice, turn-of-the-millennium mar- keting strategies may already be sorely outdated. Accessibility is Key So moving forward, how can top-tier dental pro- The overwhelming popularity of search engines viders maintain a measurable presence in a com- such as Google, Bing and Yahoo! is certainly petitive and ever-changing market, and thereby nothing newsworthy. In April, 2010 alone, Ameri- continually attract high-quality new patients? cans conducted an astounding 15.5 billion web searches,² and that number continues to climb as A Living, Breathing Extension of more and more consumers turn to internet search Your Practice engines as a jumping off point for decision mak- More than ever before, consumers are relying ing. Of note is the fact that web pages ranked on information from the internet in all avenues of in the first ten positions, which are displayed on decision-making. One recent study reveals that page one of search engine query results, received 77.3% of Americans are regular internet users, a remarkable 89.71% of all click-through traffic.³ a number that has more than doubled since the year 2000.¹ It stands to reason then, that your Professionals in all markets and around the business must be represented adequately online, globe, including dental providers, have real- with an impactful website that showcases your ized the sheer marketing power behind search premiere dental practice, your advanced training, engine queries, and many have decided to take and your top-notch treatment philosophy. As your the reins. Search engine optimization (SEO) is website is often the first contact many patients a cutting-edge marketing strategy being utilized make with your office, great attention needs to by such clinics as a way to capture that all impor- be paid to the information made available on the tant page one ranking. SEO involves a process site, as well as the way in which it is presented. of ensuring that a gorgeously-crafted, user-friendly website is also receptive to search engines by A professional dental website must stand employing a litany of methods to achieve higher head and shoulders above the crowd, with an page rankings. Designing a useful, beautiful web- appearance that pleases the eye, and usable infor- site and failing to optimize it for search engines mation that answers questions potential dental is something like erecting a billboard advertising patients in your area want to know. It also reflects your practice high in the Himalayan Mountains. your unique personality and style. It should be Though it may be aesthetically pleasing and infor- warm, inviting, professional, and above all, moti- mational, it makes no impact if few will ever see it. The Journal of Implant & Advanced Clinical Dentistry • 75

Mackey Optimization of your website is an endeavor to their computer to find a local dentist before which takes time, patience, and know-how, they pick up the Yellow Pages, can your market- as well as the ability and drive to continu- ing strategy stand up to the changing times? Is ally regroup and utilize a fresh approach. As your practice represented by a website that an ever-increasing number of dental provid- reflects adequately what kind of dentist you ers employ such methods in their marketing are, and is that website easily findable? And scheme, one must wonder: Just who is captur- are you benefiting from increased exposure of ing that essential page-one traffic in your area? your brand through social media marketing? Going Social Refuse to let your marketing strategy stag- Peer endorsement has long been held as one nate! As we enter the next decade, take this of the best ways to capture new clients in any opportunity to vigorously evaluate your market- market. You may feel likewise that many high- ing scheme, and be proactive about making quality new patients are acquired through the changes where necessary to ensure that your referrals of their friends and family. An excit- practice continues to remain competitive. ing new phenomenon is the fact that informa- tion gained through one’s peers online via Shannon Mackey serves as Vice-President of social media sites such as Facebook and Twit- Customer Relations and Co-Founder of Road- ter is regarded with almost as much trust side Multimedia, a dental website design and as such information received in person.4 marketing company. She is also a member of JIACD’s Editorial Advisory Board. Shannon From a marketing standpoint, it is truly rous- has two decades experience in the dental field, ing to think that business such as your excellent both in clinical dentistry, and business man- dental practice may be able to exercise a mea- agement which proves a great asset in assist- sure of control over peer reviews and endorse- ing premiere dental providers nationwide ments online. This can be accomplished using a and internationally find creative ways to effec- bit of creativity to motivate positive reviews, thus tively market their practices. Shannon Mackey reaping the benefits in the form of new patients. can be contacted through Roadside Multime- Major retailers across the globe have thrown dia’s website at www.roadsidemultimedia.com. their hats in the ring, so to speak, running Face- book marketing campaigns and utilizing Twitter SOURCES: and other social media sites to showcase their 1. Internet World Stats, Usage and Population Statistics. Top 20 Countries products and services. Dental practices are quickly following suit, delving into the world of With the Highest Number of Internet Users. Available at: http://www. social media in a way that effectively markets their internetworldstats.com/top20.htm. Accessed September 10, 2010. brand and still maintains a professional image. 2. April 2010 U.S. Core Search Rankings conducted by comScore inc. Available at: http://comscore.com/Press_Events/Press_Releases/2010/5/comScore_ Where Do You Stand? Releases_April_2010_U.S._Search_Engine_Rankings. Accessed September As potential dental patients in your area turn 10, 2010. 3. Seomoz: How People Interact With Search Engines. Available at: http:// guides.seomoz.org/chapter-2-how-people-interact-with-search-engines. Accessed September 10, 2010. 4. Everyday Influence: The New Symbiosis of Professional Networks. Available at: http://everydayinfluence.typepad.com/everyday_influence/2009/11/the- new-symbiosis-of-professional-networks-social-medias-impact-on-business- and-decision-making-.html. Accessed September 12, 2010. 76 • Vol. 2, No. 9 • November 2010