Patients with skeletal class III malocclusion can present with complex dentoalveolar problems, including anterior end-to-end or anterior and/or posterior cross-bite, resulting from maxillary retrognathism and mandibular prognathism.1,2 These problems may predispose patients to dental caries, periodontal disease, and edentulism,3,4 as well as adverse psychosocial effects.5 Prosthodontic treatments for this group of patients are challenged by the skeletal discrepancies of the maxilla and the mandible.6 A comprehensive multidisciplinary approach to treatment planning that involved prosthodontists, orthodontists, periodontists, and oral and maxillofacial surgeons is often necessary to ensure accurate diagnoses and appropriate treatments.6–10
The case report describes a patient who had skeletal class III malocclusion with erosion and attrition of his maxillary teeth, several missing mandibular molars, and compromised periodontal support of remaining mandibular teeth. The patient underwent (1) orthodontic treatment and orthognathic surgeries to correct the skeletal discrepancy, (2) implant therapy to replace missing teeth and teeth with compromised periodontal support, and (3) full mouth rehabilitation to restore missing tooth structure and occlusion.
linical R eport
Preoperative information and treatment planning
A 42-year-old Caucasian male was referred from a local general dentist for evaluation and treatment. His chief complaint was, “I need my bite fixed and I cannot chew food properly.” The patient's medical and dental histories were reviewed. No contraindication for dental treatment was identified. However, a few years ago, the patient was given the diagnosis of gastroesophageal reflux disease (GERD) and was treated with antacids and an H2 blocker (Prilosec). The patient's dental problems include maxillary deficiency and mandibular prognathism (Figure 1). He presented with moderate erosion and attrition of the occlusal and lingual surfaces of the maxillary dentition secondary to class III malocclusion and GERD. All mandibular molars were missing except tooth #30 as the result of periodontal disease. Remaining mandibular premolars migrated distally and showed moderate bone loss with class II mobility.
Treatment plan options were discussed with the patient. The option of orthodontic treatment in conjunction with surgical repositioning of the maxilla and mandible, followed by implant therapy to replace teeth that were unrestorable or had a guarded prognosis, and prosthodontic full mouth rehabilitation with maxillary crowns and mandibular implant-supported fixed partial dentures and crowns, was chosen. The patient rejected any treatment plan requiring him to wear a definitive removable prosthesis.
Correcting skeletal class III malocclusion with orthodontic therapy and orthognathic surgeries
Presurgical orthodontic therapy was initiated to reposition the teeth ready to be in ideal class I occlusion after surgery (Figure 2). After the initial phase of orthodontic therapy, Le Fort I osteotomy was performed under general anesthesia. The maxillary arch was anteriorly positioned. At this first orthognathic surgery, we had tried to be conservative, limiting the surgery to 1 jaw. The occlusal plane, dictated by the mandible, was too flat, and we could not inferiorly position the posterior maxilla enough in the first surgery. Therefore, from a prosthetic standpoint, changing the occlusal plane with mandibular surgery became necessary. After postoperative clinical evaluation (Figure 3), the patient's facial profile was significantly improved; however, he had only anterior end-to-end contact, and no posterior occlusal contact was present. In maximum intercuspal position (MIP), 5–8 mm of interdental space was seen. Interocclusal distance in the anterior was insufficient to enable us to increase the vertical dimension of occlusion (VDO) needed for full mouth rehabilitation. Increasing VDO would leave an excessively large interarch space in the posterior (Figure 3). Therefore, mandibular orthognathic surgery was then performed using a sagittal split osteotomy technique. The mandible was rotated superiorly and was repositioned posteriorly using an occlusal surgical stent as a guide (Figure 4).
Implant and prosthodontic treatments
After surgical correction of the maxillary-mandibular relationship, the esthetics of the facial profile improved significantly and occlusion was reasonably improved. The patient had occlusal contacts in most teeth except the most posterior teeth. After the orthodontic appliances had been removed, it was determined that most of the mandibular posterior teeth would not be able to support fixed prostheses because of their compromised periodontal support (Figure 4). In addition, because of a long period of missing several mandibular posterior teeth, the residual ridges between the remaining teeth showed severe to moderate facial resorption. Therefore it was not an option to place implants in these edentulous areas. We chose the implant sites based on the diagnostic wax-up in areas that would be #19, 21, 22, 24, 27, 28, and 30 (note that the mandibular premolars had migrated distally in the area of previous first molars) and on cone-beam computerized tomography scans (Figure 4). The implant sites and the diameter and length of the implant fixture were selected on the basis of available alveolar bone.
All mandibular teeth were extracted. At the same surgical visit, 8 Osseospeed Astra Tech implants (Astra Tech Inc, Waltham, Mass) were immediately placed (4.0 × 9 mm for #19 and 30 sites, 3.5 × 13 mm for #24 and 26 sites, 3.5 × 15 mm for #21 and 28 sites, and 4.0 × 15 mm for #22 and 27 sites) (note that these sites were numbered according to the planned definitive restorations). Six of 8 implants (all except #21 and 28 implants) were placed in the extraction sockets. Healing abutments were placed. A mandibular immediate complete denture was delivered with tissue conditioner relined (Coe-Comfort, GC America, Alsip, Ill). This interim prosthesis was fabricated at the patient's existing VDO.
During the implant healing period, maxillary teeth were prepared for full coverage restorations. Maxillary provisional crowns were fabricated with bis-acryl-methacrylate–based resin (Integrity, Dentsply International, York, Pa) at the centric relation (CR) using previous VDO from the natural dentition. Eight weeks later, 8 prefabricated abutments (4.0 Direct Abutments, Astra Tech Inc) were installed and tighted to 25 N-cm. Three mandibular provisional fixed partial dentures—#18-21, 22-27, and 28-31—were fabricated (Integrity, Dentsply). The CR and VDO were preserved. Provisional prostheses were used to assist in fabrication of the definitive restorations. Maxillary and mandibular final impressions were made with polyvinyl siloxane (Extrude, Kerr Corporation, Orange, Calif). The definitive prostheses were fabricated in the CR position. The CR record was made between the abutment teeth using polyvinyl siloxane (Regisil, Dentsply), while the anterior provisional restorations were kept in place to maintain the VDO. Another CR record was made in a similar manner between the mandibular posterior abutments and the maxillary provisional prostheses. The working casts were mounted and cross-mounted with casts of the provisional prostheses. In addition to CR records, a protrusive record was made to set the condylar inclination of the articulator.
Based on the provisional prostheses, the definitive restorations were fabricated as single porcelain-fused-to-metal crowns for the maxillary arch and 3 implant-supported cement-retained fixed partial dentures for the mandibular arch—#18-21, 22-27, and 28-31. The definitive restorations were fabricated in a canine-guided occlusion similar to the occlusion in the diagnostic wax-up and provisional prostheses. The 4 anterior mandibular implants were splinted together to minimize possible lateral forces generated by canine-guided occlusion.
Palladium-silver alloy (Aureolite 61, Argenco: 60.5% Pd, 28% Ag, and 2.5% Sn) was used to fabricate the metal frameworks. The frameworks were tried in the mouth. The fitting and the maxillary-mandibular relationship were verified. The unglazed porcelain was tried in the mouth for evaluation of esthetic contour and occlusion. Note that the most posterior mandibular molars were slightly off centric occlusion (2 sheets of Shim Stock) to minimize the functional load to the cantilever portion of the terminal fixed partial dentures. The definitive prostheses were cemented with resin modified glass ionomer cement (Fujiplus, GC America) (Figure 5). A week later, a maxillary occlusal splint was delivered. The patient was advised to wear the occlusal splint nightly. Daily tooth brushing and use of topical fluoride were also advised. The patient was seen at 2 weeks, 1 month, 6 months, 1 year, and 2 years after definitive restorations and occlusal splint delivery. The patient maintained excellent oral hygiene and continued nightly wearing of an occlusal splint. No sign of tooth movement was seen. The implants were osseointegrated, and no sign of excessive peri-implant bone loss was noted. The patient demonstrated a favorable prognosis with our treatments.
We learned a few important things from this case. First, it may be difficult to define posterior occlusion in the patient during orthognathic surgeries if several posterior teeth are missing. The surgical stent in our case had helped in the mandibular orthognathic surgery. Second, teeth with compromised periodontal support can be used initially to facilitate orthodontic therapy and orthognathic surgeries. Third, immediate implant placements, after orthodontic/surgical treatments, can be done successfully with careful planning and a multidisciplinary approach. Finally, occlusal stability can be attained with full mouth restorations and an occlusal splint.
This case report presents a comprehensive treatment for a patient with severe skeletal class III malocclusion. The patient also had problems with worn dentition in the maxilla and compromised periodontal support in the mandible. Functional occlusion and esthetics were restored with orthodontic treatment, orthognathic surgery, implants, and complex fixed prosthodontic therapy.