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1 CLINICAL COMPLETE ARTIFICIAL DENTITION SUPPORTED BY ENDOSSEOUS IMPLANTS:ACASE REPORT OF TOTAL IN-OFFICE TREATMENT Dennis Flanagan, DDS KEY WORDS Dental implant Implant occlusion Occlusal scheme Occlusal force This case report demonstrates the construction of a complete restoration of the dentition by the surgical placement of endosseous titanium implants that support a fixed prosthesis in each jaw. The positioning of the implants and teeth in the prostheses are important factors for a successful long-term result. Distribution of the occlusal biting forces over as many implants as possible is important. Off-axial occlusal biting forces should be diverted to the anterior prostheses, where the forces are not as great and the posterior teeth are designed with flat occlusal surfaces that separate during excursionary chewing movements. Medial mandibular flexure caused by the contraction of the medial pterygoid muscle can be addressed by constructing the prosthesis in segments. This is so as not to have a rigid entity encased in flexing bone that may induce stress to the bone, leading to loss of implant integration and failure. Segmenting also insures an appropriate fit of the prosthesis with respect to casting and porcelain firing distortion. Lip support by means of a flange in the prosthesis may be necessary when there has been a large amount of bone loss from edentulous resorption. Cleaning and maintenance of the prostheses every 3 to 6 months is essential. Dennis Flanagan, DDS, is in private practice. Address correspondence to Dr Flanagan at 1671 West Main Street, Willimantic, CT ( dffdds@charter.net). INTRODUCTION Tooth loss occurs by dental caries, periodontal disease, and trauma. In the past, the treatment for completely edentulous patients was complete denture removable prostheses. With time, dentures can allow or even contribute to bone resorption. Removing the osseous denture support can render a patient unable to comfortably wear any prosthesis in their later years. Missing teeth have been replaced using endosseous dental implants to support fixed or removable prostheses. Replacing a complete dentition with endosseous implant-supported fixed prostheses is possible. However, there are certain parameters of treatment that have become important. These parameters of treatment are mostly directed at control of occlusal force Journal of Oral Implantology 91

2 COMPLETE ARTIFICIAL DENTITION distribution to the supporting implants. 1 The implants are made of titanium that reacts in nanoseconds with ambient oxygen to form a biocompatible oxide surface 600 to 1000 nm. Titanium oxide is very biocompatible. The surface of the implants are treated by sandblasting and acid etching or dual thermo-acid etching to create a range of surface roughness of 50 to 120 lm that allows direct bone apposition against the titanium oxide surface to provide bone-toimplant surface contact in a range of 20% to 70%. The surface roughness also engages the bone and provides mechanical retention. These 2 properties give the implant great stability and resistance to dislodging forces even though there can be less than 40% bone-toimplant contact. Cortical bone provides the most implant support. The forces applied to the prosthesis causes the most bone stress at the area where the implant emerges from the cortex. CASE REPORT A 39-year-old female presented for dental treatment. She was examined and evaluated. Her diagnosis was dental caries and chronic periodontitis. All of her remaining teeth were in hopeless condition and were in need of removal. Her medical history was not significant for dental treatment. A treatment plan was designed, explained, and accepted by the patient. Treatment plan The treatment plan was as follows: Construction of immediate complete dentures Extraction of remaining teeth, establishment of appropriate centric relation, and vertical dimension of occlusion and delivery of removable complete dentures Computerized tomography of edentulous jaws Establishment of dental implant positions and grouping for occlusal support and force distribution Construction of surgical guides for implant positioning and surgical installation Surgical implant installation. Healing phase for implant osseointegration Abutment installation and provisional prosthetic construction Substructure construction and fitting Porcelain application, esthetic evaluation, and refinement of occlusion in centric and excursive movements and provisional cementation for evaluation of function Final cementation Maintenance of prosthesis and supporting peri-implant tissue All surgical and prosthetic treatment was performed in office, with the patient sedated with sublingually incrementally administered 0.5 mg triazolam (Halcion). The teeth were extracted and, immediately, complete dentures were placed. An osseous healing period of 6 months was allowed for remodeling and development of supportive bone. The vertical dimension of occlusion in the dentures was established for function and patient comfort. This dimension, although not an exact dimension, was to be transferred to and maintained in the implant-supported prosthesis. 2 Preimplant surgery panoramic and computerized tomographic (CT) scan radiography of the edentulous jaws were performed (Figure 1). A plan for implant positioning and sizing was made from the prepared imaging on compact disk made from the CT scan 3 (Figure 2) (Materialise, Glen Burnie, Md). A clear plastic form simulating tooth position demonstrated that there was good lip support created by the proposed tooth arrangement without a prosthetic flange (Figure 3). Exact implant positions were determined using casts made from the patient s edentulous ridges and dimensional data gleaned from the CT scan. A surgical guide was constructed on the casts of the edentulous jaw arches. The guides used the hard palate for a landmark and support during the procedures, thus providing a stable guide base for the placement of the implants. The surgery was rehearsed with the staff to minimize operative time. Twelve maxillary implants (Implant Innovations Inc., Palm Beach Gardens, Fla) were installed in a 2-hour appointment. At a later appointment, 12 mandibular implants were installed in 2 1/2 hours. An apically positioned gingival flap was made in the mandible to increase the zone of attached gingiva, which protects and supports the epithelial peri-implant tissue. The zone of attached gingiva was adequate in the maxilla and did not need augmentation. The implants were placed so as to maximize osseous support and to insure delivery of axial forces to the implants. Osteotomes were used to compress osteotomy sites with less dense bone to increase the bone-toimplant contact. A panoramic radiograph was taken (Figure 4). The patient was prophylactically medicated with amoxicillin 875 mg bid and a 0.12% chlorhexidine oral rinse. Postoperative pain was 92 Vol. XXXI/No. Two/2005

3 Dennis Flanagan FIGURE 1. Panoramic radiograph of edentulous condition. FIGURE 2. Computerized tomographic section of edentulous maxilla. FIGURE 3. Vacu-form demonstrating lip support without a flange. FIGURE 4. Panoramic radiograph of placed implants. controlled with hydrocodone and acetaminophen (Vicodin ES). Healing on each surgical occasion was uneventful. An osseous healing time of 4 months was allowed to develop integration of supporting bone to the implants. At 1 postoperative month, the distal-most maxillary right implant failed to integrate and was replaced with a larger diameter rescue implant, which successfully integrated (Innova, Toronto, Ontario). At the next phase, abutments were placed and secured with screws into each implant. Each implant abutment was placed at 32 N cm of torque, according to the manufacturers instructions. Working casts of the prepared abutments were made from maxillary and mandibular full-arch polyvinyl siloxane impressions (Imprint, Dentsply, Philadelphia, Pa). The working casts were related to the temporomandibular joint and mounted on a nonarcon, semiadjustable articulator (Hanau). Noble alloy (Pd-Au) substructures for porcelain fused to metal maxillary and mandibular fixed prostheses were to be constructed using a lost-wax technique (Figure 5). The centric relation and vertical dimension of occlusion parameters were transferred to the articulator from the patient using sectioned segments of the complete dentures (Figure 6). Records of the patient s protrusive and excursive mandibular movements were recorded and transferred to the articulator (Figure 7). Provisional acrylic fixed prostheses were constructed to confirm the function and patient comfort of the vertical dimension as well as the esthetics (Figures 8 and 9). Maxillary and mandibular substructures were waxed, cast, fitted, and remounted to confirm the parameters of occlusion (Figure 10). Porcelain was formed and fired to the substructure to give an anterior guidance-type occlusion, where the anterior teeth bear the jaw forces and remove the posterior teeth from contact during chewing or grinding jaw movements (Figures 11 and 12). The following is the occlusal scheme: Class II Anterior guidance Splinting of posterior units Mandibular flexure concerns No cusps, rounded posterior mandibular teeth Short lingual maxillary cusps The final prostheses were fitted and the occlusion adjusted and cemented with zinc oxide and eugenol (Temerex, Dentsply) to provide an esthetic functional dentition (Figures 13 through 18). The patient returns for routine cleaning and maintenance every 6 months. Journal of Oral Implantology 93

4 COMPLETE ARTIFICIAL DENTITION FIGURE 5. Working casts were mounted on a nonarcon semiadjustable articulator. FIGURE 6. Centric registration using the provisional complete denture as a guide. FIGURE 7. Protrusive wax registration. FIGURE 8. Appearance of provisional fixed partial denture. FIGURE 9. Close-up of provisional prosthesis. FIGURE 10. Remount registration of cast substructure. DISCUSSION Dental implants will bear axial forces well but may not tolerate off-axial loads. A tolerance of a maximum of 150 lm of micromovement of dental implants has been mentioned in the literature but has not been well studied and has not yet been correlated to a specific amount of force. 4 Design of a tooth arrangement and shape for the purpose of load transfer to the implants in a specific direction and location is desirable (Figures 17 and 18). The axial loads may be delivered to the posterior implants, but the offaxial excursive forces should be delivered to the anterior implants, where the forces are not as great. 5 Up to 500 N of force can be delivered by human jaws. The amount of off-axial forces tolerated by a particular implant in a particular density of bone has not been studied. An appropriate occlusal scheme to minimize offaxial forces to the prosthesis and the supporting implants is necessary. 6 This can be accomplished by keeping the off-axial forces in the anterior segment. Here they are minimal. The forces should be distributed over as many supporting implants as possible. The forces of occlusion are lower where the tooth contact is the farthest away from the temporomandibular joint fulcrum. An occlusal design that allows direct axial forces and minimizes offaxial forces is appropriate. The shape of the mandibular tooth coronas should be flat and rounded convexly toward the gingival. The facial-lingual tooth dimension should be kept to a minimum. The lingual cusps of the maxillary prosthetic teeth should be relatively flat to occlude with the mandibular teeth. 7 A porcelain, pointed tooth cusp that occludes with an opposing flat dentition may be prone to fracture. The facial maxillary cusps can be present but short and rounded to fulfill an esthetic requirement. However, it may be better for these facial cusps not to have contact with opposing teeth during excursive mandibular movements. A disclusion occurs by the contact of the anterior lateral and cuspid teeth with their antagonist lateral and cuspid. Patients may have differing angles of disclusion and may require the first premolar and cuspid to enact the disclusion, depending on the relation of the jaws and jaw-arch shape. Bone loss may preclude the appropriate construction of a prosthesis. Bone augmentation for implant support or prosthetic flanges for support of the lips may be necessary. 8 If the time between tooth loss and implant placement is reduced to minutes or days, there may be reduced bone loss, making prosthesis construction less complex. Traumatic injury may result in bone loss 94 Vol. XXXI/No. Two/2005

5 Dennis Flanagan FIGURE 11. Implant splint groupings. Numbers pertain to particular teeth. Numbers 3 through 5 are the maxillary right first molar and second and first premolars, respectively. Numbers 6 through 8 are the maxillary right canine and the lateral and central incisors, respectively. Numbers 9 through 11 are the maxillary left central and lateral incisors and canine, respectively. Numbers 12 through 14 are the maxillary left first and second premolars and first molar, respectively. Numbers 19 through 22 are the mandibular left first molar, second and first premolar, and canine, respectively. Numbers 23 and 24 are the mandibular left lateral and central incisors, respectively. Numbers 25 and 26 are the right central and lateral incisors respectively. Numbers 27 through 30 are the mandibular right canine, first and second premolars, and first molar, respectively. FIGURE 12. Schematic of posterior occlusal table. or irreversible damage that precludes easy prosthetic construction. Various corrective surgical procedures have been in use to augment or correct available bone to accept dental implants for support of a fixed or removable prosthesis. If there has been much bone loss over time, the support of the lips may have been compromised. A prosthesis that restores this lip support may be necessary. If the time of tooth extraction has been less than 1 year, there may not be sufficient bone loss to create an esthetic or functional problem. There can be as much as 30% alveolar bone loss 3 months after tooth extraction. A flanged prosthesis may be necessary to provide adequate lip support if this occurs. These prostheses may be fixed or removable, depending on its design or the ability of the patient to adequately keep it plaque free. A preoperative construction of a FIGURE 13. Left working occlusion. FIGURE 14. Protrusive occlusion. FIGURE 15. Centric occlusion. FIGURE 16. Profile of lip support. FIGURE 17. Preoperative edentulous profile. FIGURE 18. Panoramic radiograph of final restoration. Journal of Oral Implantology 95

6 COMPLETE ARTIFICIAL DENTITION provisional appliance or guide can demonstrate the need for lip support of the final prosthesis. A patient with procumbent maxilla or bimaxillary protruding jaws may not require a flanged prosthesis (Figure 17). The final prosthesis in this case was constructed of porcelain fused to metal. Keeping the cast metal-frame substructure of the porcelain prosthesis to as few units as possible keeps the castmetal processing warpage to a minimum. The metal must be thick enough to maintain rigidity for support of the porcelain and the porcelain must be thick enough to provide an esthetic result. 9 Long-span metal castings can change dimension when cooled from the high heat of casting and porcelain bonding. This may alter the accuracy of the fit of the metal substructure. The fit of the metal substructure should be passive, that is, it should not bind or transmit wedging or compressive forces to the implant abutments and therefore to the supporting implants. With a shorter span length of the prosthesis, there is less change of the dimension of the substructure during the casting and the application of porcelain processes. The mandible bends slightly at the inferior ramus toward the medial during wide opening as a result of the contraction of the medial pterygoid muscle. The splinted implant-prosthesis entity is rigid in the flexing mandible. The medial flexure has been measured to range between and mm. 10 This flexure, though small, has been known to cause symptoms in patients with rigid, fixed appliances in the mandible. This can cause a stress area in the bone against the rigidly splinted implants and may lead to a loss of integration and failure of the implants and prosthesis. Some displacement of the implants beyond the mentioned 150 lm tolerance may occur and then cause a loss of integration by separation of the bone from the implant surface, microhemorrhage, and fibrous tissue ingrowth. The splinted implant grouping should be such as to allow mandibular flexure without stressing the bone-implant interface. Usually the separation in the fixed prosthesis can be made at the canine or premolar region to allow for mandibular flexure without detriment to the boneimplant interface. 11 Implants are best placed with 3 mm of separation, to allow blood supply to the gingiva and interimplant bone In the anterior esthetic area, this may present a problem for the patient if there is a 1-for-1 implant-totooth ratio. This esthetic problem is what appears as black triangles formed by the embrasures of porcelain teeth and the gingival base. This may be resolved by omitting an implant at, for example, the lateral incisor site. The lateral incisor can be replaced with an ovate-type pontic, making the appropriate dimensions in the porcelain to allow an esthetic result. Additionally, in patients with a procumbent maxilla or a lip line that exposes the tooth embrasures, salivary bubbles may be produced from the triangles during certain word pronunciations. The size of the triangle created may allow the salivary surface tension to form a bubbleproducing film. This usually cannot be corrected by augmenting the gingival papilla to fill the triangle. Porcelain can be added to the embrasure areas to minimize the size of the triangle, thus preventing the saliva from bubbling through. However, a larger triangle may allow easy cleansing in these areas that are not accessible to flossing but may allow food particles to catch in some areas. The use of water-irrigation devices is usually not recommended because the force of the water stream may tear the epithelial attachment at the implant percutaneous area. Simple tooth brushing is usually appropriate. The patient s tolerance of the surgical placement of multiple implants is another consideration. Typically American Society of Anesthesiologists (ASA) Class I and II rated patients are acceptable candidates for implant placement. Sedation or general anesthesia may be a consideration. Psychological factors may be considered. Some patients may object to the endosseous nature of the implants. Others have objected to the feel of the implants. Teeth have a periodontal ligament that allows the tooth to intrude about 150 to 250 lm. Integrated implants may intrude 2to7lm, which may give them a rigid feeling. 16 Although many dental implant patients claim to have a sensibility of the implants with time, they may be sensing neuronal perception from the gingiva or temporomandibular joint. Once the patient has been deemed a candidate for implant treatment, the available bone should be evaluated. Radiographs that depict the osseous structures can be made. Periapical, panoramic, or CT scans are useful. Avoiding anatomical structures, such as the mandibular neurovascular bundle, is a goal. The maxillary sinus may have expanded by pneumatization due to edentulism, and the remaining alveolar bone may be inadequate for implant placement. This bone deficit may be corrected by an augmenting sinus 96 Vol. XXXI/No. Two/2005

7 Dennis Flanagan lift from a lateral (Caldwell-Luc) or inferior (ridge crest) approach. A CT scan is very useful for determining available bone and for implant positioning and spacing. These are accurate to a tenth of a millimeter. Some companies can construct bone models, surgical guides, and provisional prostheses from the CT scan, making the surgical placement and prosthetic treatment less stressful and time consuming (Materialise). The surgical placement of the implants can be parallel or diverging or tripodal. There has been discussion as to which arrangement is appropriate. 17 Prosthetic complications may arise in a diverging or tripod arrangement. There has been a dearth of totally artificial fixed-implantsupported dentition reports. Longterm results are not known. Based on the longevity of smaller prostheses, there can be an intuitive extrapolation that would indicate an excellent prognosis. This patient has been postoperative for over 1 year and is functioning well without sequellae. CONCLUSIONS This case report demonstrates that totally artificial, endosseous implant-supported, fixed dentition, in-office treatment is possible with only local anesthesia and mild sedation for pain and anxiety control. Complete maxillary and mandibular fixed dentition supported by endosseous implants is possible, but distribution of occlusal forces is probably an important factor for long-term survival of the prostheses. Axial occlusal forces can be tolerated by the supporting implants, but off-axial forces should be transferred to the anterior region where the forces are not as great. Lateral excursion movements of the mandible should be borne by the implants in the anterior region of the jaws. Splinting of the supporting implants may be necessary to provide long-term resistance to off-axial occlusal forces. Implant positioning should be 3 mm apart, but esthetic demands may necessitate divergence from this dimension. Parallel or diverging implant positioning may be used in various osseous anatomies to provide an optimal or simplified prosthetic construction. Mandibular flexure should be considered in prosthetic design. Prosthetic material properties may require alterations in the design of the prostheses. Bone loss in the anterior maxilla and mandible may necessitate a prosthesis with a flange for esthetic and functional support of the lips. In-office surgical and prosthetic installation is possible with oral sedation techniques. Cleaning and maintenance of the prostheses should be ongoing, every 3 to 6 months, as with a natural dentition. ACKNOWLEDGMENT The author acknowledges the kind redaction of Danielle Green DMD and Martie Flanagan BSRN. REFERENCES 1. Misch CE. Dental evaluation: factors of stress. In: Misch CE. Contemporary Implant Dentistry. 2nd ed. St. Louis, Mo: Mosby; 1999: Geerts GA, Stuhlinger ME, Nel DG. A comparison of the accuracy of two methods used by pre-doctoral students to measure vertical dimension. J Prosth Dent. 2004;91: Rothman SLG. Dental Applications of Computerized Tomography. Chicago, Ill: Quintessence Publishing Co Inc; Szmukler-Moncler S, Salama H, Reingewirtz Y, Dubrille JH. Timing of loading and effect of micromotion on bone-dental implant interface: review of experimental literature. J Biomed Mater Res. 1998;43: Ferrario VF, Sforza C, Serrao G, Dellavia C, Tartaglia M. Single tooth bite forces in healthy young adults. J Oral Rehabil. 2004;31: Weinberg LA. Therapeutic biomechanics concepts and clinical procedures to reduce implant loading. Part I. J Oral Implantol. 2001;27: Weinberg LA. Reduction of implant loading with therapeutic biomechanics. Implant Dent. 1998;7: Sclar A. The importance of site preservation. In: Sclar A. Soft Tissue and Esthetic Considerations in Implant Therapy. Chicago: Quintescence Publishing Co; 2003; Craig RG, Powers JM, Wataha JC. Dental casting alloys and solders. In: Craig RG, Powers JM, Wataha JC. Dental Materials Properties and Manipulation. 7th ed. St. Louis, Mo: Mosby; 2000: Omar R, Wise MD. Mandibular flexure associated with muscle force applied in the retruded axis position. J Oral Rehabil. 1981;8: Zarone F, Apicella A, Nicolais L, Aversa R, Sorrentino R. Mandibular flexure and stress build-up in mandibular full arch fixed prostheses supported by osseointegrated implants. Clin Oral Implants Res. 2003;14: Tarnow D. The effect of interimplant distance on the height of interimplant bone crest. J Periodotol. 2000;71: Tarnow D, Elian N, Fletcher P, et al. Vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants. J Periodontol. 2003;74: Tarnow D, Magne A, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of interproximal dental papilla. J Periodontol. 1992;63: Tarnow D, Nicolas E, Fletcher P, et al. Vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants. J Periodontol. 2003;74: El-Sheikh AM, Hobkirk JA, Howell PGT, Gilthorpe MS. Passive tactile sensitivity in edentulous subjects treated with dental implants: A pilot study. J Prosth Dent. 2004;91: Renouard F, Rangert B. Biomechanical risk factors. In: Renouard F, Rangert B. Risk Factors in Implant Dentistry. Chicago, Ill: Quintessence Books; 1999: Journal of Oral Implantology 97