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Purpose In February 2011, the Food and Drug Administration issued a postmarket surveillance order to all manufacturers of temporomandibular joint (TMJ) implants in the United States. The objective of the present study was to measure implant subsequent surgical intervention (SSI) among patients who had undergone TMJ reconstruction with the Biomet TMJ replacement system (Zimmer Biomet, Warsaw, IN). Materials and Methods A prospective observational study was conducted by sending a questionnaire to patients who had received a Biomet TMJ replacement system from 1995 to 2010 in the United States. The questionnaire was sent annually from 2012 to 2015. The primary endpoint was the SSIs. SSIs included both device removal and reoperations. Kaplan-Meier survival analysis was used to determine the survivorship, and Cox proportional hazard regression analysis was performed to evaluate the preoperative diagnosis and SSI. Results The mean age at implantation was 46.6 ± 12.5 years, with a gender distribution of 86.1% female. Data from 499 joints in 319 subjects were collected as a part of the survey. The mean follow-up time was 8.6 ± 3.9 years (range, 2-20 years). The first SSI frequency was 11.2% (4.2% removal rate and 7.0% reoperation rate). The survivorship rate (Kaplan-Meier) was 96% at 3 years, 94% at 5 years, and 86% at 10 years. The mean interval to failure using a survival function to determine the time to SSI (Greenwood's formula) was 13.5 ± 0.193 years. The most common causes of SSI included adhesion removal (2.6%; 13 of 498), heterotopic bone/ankylosis (2.0%; 10 of 498), and infection (1.6%; 8 of 498). Conclusions The results from the present study are consistent with the reported survivorship rates for other orthopedic devices (5-year survival for total hip or knee arthroplasty, 95.9 and 97.2%, respectively). The etiology of SSIs in the Biomet TMJ replacement system was primarily secondary to biologic failure (ie, adhesions, heterotopic bone, and infection).

Introduction Although primarily reserved for adult patients, temporomandibular joint (TMJ) total joint reconstructive (TJR) surgery is rarely used in the pediatric population due to its many challenges; it is only performed after all other non-invasive or invasive procedures have been exhausted. Although autogenous grafting has been discussed in the literature, there is very little regarding synthetic or alloplastic materials. In this study, we performed alloplastic TMJ reconstruction on 5 patients with severe ankylosis due to various craniofacial deformities and prior traumatic injuries. Materials and Methods This is a retrospective case series analysis of skeletally immature patients who received alloplastic TMJ reconstruction for recurrent and advanced ankylosis. Our inclusion criteria were as follows: less than 16 years of age, diagnosis of TMJ ankylosis, skeletally immature patients, and unilateral/bilateral total alloplastic TMJ reconstruction. We used the maximum incisal opening (MIO) changes as 1 component to assess for functional improvement. Results Since many of these cases involved gross discrepancies from the normal variants, it was difficult to quantitatively compare the patients with one another. Nevertheless, we used cephalometric analysis to compare pre- and postoperative results on each patient. For this study, we used MIO as our primary assessment: the preoperative average for MIO was 7.4 mm, and the postoperative average 24 mm. Conclusion It is our experience that the use of alloplastic material will not result in harm to either the growth of the mandible or patient's ability to achieve an improved MIO based on our long- and short-term results. These results demonstrate that for even complex craniofacial deformities and traumatic injuries, our patients experienced a significant improvement in MIO, 1 of the main indicators for TMJ function. We conclude that the alloplastic joint can provide a predictable pathway to restore patient's MIO and obviate the need for repeated surgeries, which can be a more challenging alternative with poorer outcomes.

Purpose To assess the safety and efficacy of a stock alloplastic total temporomandibular joint (TMJ) implant system, the Biomet Microfixation TMJ Replacement System. Materials and Methods During a 10-year multicenter clinical trial from 1995 to 2005, 442 Biomet Microfixation TMJ Replacement Systems were implanted in 288 patients (154 bilaterally and 134 unilaterally). Patients were followed at landmark times, including the date of surgery and at 1 month, 3 months, 1 year, 1 year 6 months, and 3 years. The 3 major metrics that were evaluated were preoperative and postoperative pain, interference with eating, and maximal incisal opening. Paired t tests and comparison analyses were used to assess outcomes. Results There was statistically significant improvement in pain level (P = .0001), jaw function (P = .0001), and incisal opening (P = .0001). Although there were complications necessitating the removal of 14 of 442 implants (3.2%), there were no device-related mechanical failures. Conclusions The clinical study presented supports the conclusion that a stock TMJ alloplastic replacement, based on sound orthopedic and biomedical principles, is a safe and efficacious option when alloplastic reconstruction of the TMJ is indicated.

Purpose Using finite element (FE) computer model simulation, we compared the mechanical characteristics of the mandible after bilateral sagittal split ramus osteotomy (BSSRO) through the use of 2 different techniques to stabilize the osteotomy. Materials and methods Based on the reconstructed geometry from computed tomography scans of dry adult skull with a mandibular deformity requiring surgical correction, we developed 3-dimensional FE models that simulate BSSRO with 2 different techniques to stabilize the osteotomy. Technique 1 uses 3 bicortical titanium screws. Technique 2 uses a curved titanium plate with 4 monocortical screws. Five different load cases were applied to the mandible after the simulated BSSRO with the mandible being constrained at both temporomandibular joints. To evaluate the efficacy of these 2 stabilization techniques, we compared 1) the resulting deflections at the central incisor, 2) the mechanical stresses developed in the bone in the vicinity of the stabilizing implants, and 3) the mechanical stresses developed within the screw/plating system themselves. Results Technique 1, using 3 bicortical titanium screws, leads to smaller deflections at the central incisor for all 5 load cases, suggesting higher mechanical stability. Technique 1 also leads to lower mechanical stresses in the bone and in the implanted screws, whereas technique 2 is associated with higher values in each of these quantities. Conclusions To stabilize osteotomies after a 3-dimensional simulated BSSRO, 3 bicortical screws forming an inverted-L configuration are shown to offer more effective load transmission in the mandibular construct. This technique, when examined in an FE model, leads to higher stability with lower mechanical stresses in the bone near the bicortical screws.

Complications associated with LeFort III osteotomies have led to modifications of the procedure. Attempts to decrease morbidity include performing incomplete osteotomies or eliminating pterygomaxillary dysjunction. The purpose of this study was to determine the amount of tension required for separation of the midface from the pterygoid plates and to observe the fracture patterns. An Instron machine (Instron Corporation, Canton, MA) was used to measure the tension forces in 16 cadaver skulls divided into five groups. The groups varied as to whether the osteotomies were complete and whether pterygomaxillary separation was performed. Specimens with incomplete osteotomies and without pterygomaxillary separation required greater tension forces for separation and exhibited a high percentage (47%) of unfavorable fractures. Because high amounts of tension are required leading to unpredictable separations, we recommend complete osteotomies with pterygomaxillary dysjunction when performing LeFort III osteotomies.

Purpose: The purposes of this investigation were 1) to compare the morphology and function of patients with combined vertical maxillary excess (VME) and mandibular retrognathia with that of controls, and 2) to examine how these parameters change after combined maxillary intrusion and mandibular advancement surgery. Patients and Methods: Fifteen female VME/retrognathic patients were compared with 26 female controls before and for up to 3 years after orthognathic surgery. Facial skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyographic activity (EMG) in selected muscles of mastication were measured on all subjects. Where appropriate, one-way analysis of variance (ANOVA) or t-tests were used to compare the patients with controls. Univariate repeated-measures ANOVA was used to study longitudinal changes. Results: Preoperatively, patients' morphologic measurements were characteristic of VME compounded by mandibular retrognathia. At surgery, the maxilla was elevated an average of 2.8 mm, and the mandible was lengthened by an average of 7.1 mm. All of the postoperative morphologic measurements were closer to normal values. The patients' masseter mechanical advantage was significantly lower than that of controls both before and after surgery. Surgically induced changes in mechanical advantage were very small. The patients' maximum range of motion and excursion during mastication were all lower than those of controls before surgery. All measurements of mobility decreased immediately after surgery, with a gradual return to preoperative values. However, even 3 years after surgery, all of the motion measurements remained smaller than those of the controls. Before surgery, the patients had maximum isometric bite forces significantly lower than those of controls. Bite forces increased significantly after surgery, approaching normal values within 2 years. The activity levels in the muscles of mastication during isometric bites were not significantlyaltered by surgery. Conclusions: This study confirms that VME/retrognathia patients suffer from substantial deficiencies in their oromotor function. Surgical correction of this particular type of dentofacial deformity improves both the morphologic and functional deficits. Although some changes were not statistically significant, all were toward normalization of the presurgical values.

Purpose: This study evaluated mandibular motion and bite force in patients with temporomandibular joint disorders after joint surgery. Patients and Methods: Maximum voluntary mandibular motion, maximum excursion during mastication, and maximum bite force were examined in 25 female patients before temporomandibular joint surgery. Their pretreatment performance was compared with that at 6 weeks, 6 months, and 1 year after surgery, and with performance of 26 normal female volunteers. Results: Before surgery, all of the patients' movements and bite forces were smaller than those of controls. One year after surgery, maximum interincisal opening increased significantly, but lateral excursion and protrusion remained unchanged. Maximum bite forces increased significantly and nearly reached control levels. Conclusions: Patients with severe restriction in temporomandibular joint function exhibit general improvements in some mandibular movements and in maximum bite force after surgical treatment.

SUMMARY It is well recognized that the proper correction of many dentofacial deformities produces significant soft-tissue changes that can be predicted with relative accuracy. The orthognathic procedure may improve or rarely worsen a pre-existing soft-tissue relationship. In this article, we have shown that orthognathic surgery and rhinoplasty can be successfully combined, in either a concomitant or delayed fashion, when certain guidelines are followed. As our specialty strives to achieve the best possible outcome for patients, one would have to agree that, although not all nasal changes are predicatable preop- eratively, more refined postoperative results are achieved by the inclusion of adjunctive aesthetic procedures.

Purpose: The purpose of this investigation was to compare morphologic parameters and functional performance between controls and a sample of patients with mandibular retrognathia prior to surgical correction, and to examine how oral motor function adapts after treatment. Patients and Methods: Twenty-four retrognathic female patients were compared with 26 female controls before and up to 3 years after mandibular advancement surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyographic activity in the anterior and posterior temporalis and masseter muscles during isometric bites were made on all subjects over time. One-way analysis of variance was used to compare the controls, the patients before surgery, and the patients after surgery. Results: Surgical lengthening of the mandible averaged 7.3 mm, bringing most skeletal measures into the normal range. There were no significant differences in jaw muscle mechanical advantage between patients and controls before surgery, but surgery significantly reduced mechanical advantage of the anterior temporalis and masseter muscles. Jaw hypomobility was apparent at 6 weeks after surgery, but returned to normal values within 12 to 24 months. Before surgery the patients had maximum isometric bite forces less than half those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite force were equivalent to those of controls or somewhat higher. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. Conclusion: The results of this study suggest that correction of mandibular retrognathia by mandibular advancement surgery produces some significant functional benefits.

Individuals with developmental deformities of the jaws may be less efficient at chewing food. Previous studies have reported masticatory deficiency in patients with such deformities. This study was designed to detect any changes in masticatory performance that accompany orthognathic surgery.Masticatory performance was tested in 18 patients with various jaw deformities before application of orthodontic appliances and 2 to 3 years after surgical correction of their malocclusion. A control group was tested at three 6-month intervals. The subjects chewed carrots and masticatory performance was measured using a standard sieve technique. The Rosin-Rammler equation was used to calculate the median particle size and broadness index of each set of carrots. The number of chewing cycles required for each subject to swallow one piece of carrot was also recorded.A statistically significant difference in median particle size between patients and controls was found both preoperatively and postoperatively (P.05), but no difference in median particle size or broadness index was seen between trials for controls or patients (P.05).It was concluded that before surgery patients have a lower level of performance than controls and surgical correction of the malocclusion does not significantly enhance performance.

Extraoral cranial implant-retained prosthetic reconstructions have been proved to be highly successful. Replacement of the eyes, ears, nose, and larger areas including combined midface defects, which frequently have no other option available, has been done successfully. Burn patients and those with congenital defects are good candidates for this type of reconstruction, especially after autogenous attempts have failed. Cranial implant prosthetic reconstruction should be considered as a viable option for difficult craniofacial defects.

Homologous bone grafts were used in 135 maxillofacial surgical procedures, including acute midfacial fracture repair (n = 77), elective osteotomies of the facial bones (n = 35), secondary correction of traumatic deformities (n = 6), mandibular reconstruction (n = 10), facial bone augmentation (n = 5), and reconstruction of maxillary tumor defects (n = 2). Postsurgical complications occurred in five of the patients. This article reviews the rationale for using homologous bone grafts, their immune response, how they heal, and the risk of transmission of disease.

SUMMARY The objective of this article is to provide the reader with information on the different imaging modalities available for the diagnosis of specific bony orbital injuries. After the history and clinical evaluation, initial radiographic examination should include plain radiographs, and if orbital injuries are suspected, CT scanning is of the most diagnostic value. By combining axial and coronal CT scanning of the orbit and midfacial structures, the full extent of involvement can be appreciated to provide goals for surgical repair. In matching the clinical examination with the imaging findings, a management plan in terms of timing, operative approach, and surgical technique can best be prepared prior to surgery.

This retrospective study analyzed the relationship between complications and substance abuse following mandibular fracture. Over a 2-year period, the records of 352 patients with 589 mandibular fractures were reviewed for methods of treatment and other variables, including chronic abuse of drugs. An overall complication rate of 18.5% was found. Positive associations between complications and chronic abuse of alcohol and nonintravenous and intravenous drugs were found. Intravenous drug abusers had a 30%, nonintravenous drug abusers had a 19%, and chronic alcohol abusers had a 15.5% incidence of complications. Those individuals who did not use any drug chronically had a 6.2% complication rate. The results of this study show that chronic substance abuse can significantly affect treatment outcomes for management of mandibular fractures.

SUMMARY Orthognathic surgery produces relatively few intraoperative complications when the procedure is well planned and precisely executed. The majority of problems that occur intraoper- atively result, either directly or indirectly, from inadequate or careless preoperative planning or from technical errors during surgery.

Advances in computer technology have aided in the diagnostic and clinical management of complex congenital craniofacial deformities. The use of stereolithographic models has begun to replace traditional milled models in the treatment of craniofacial deformities. Research has shown that stereolithography models are highly accurate and provide added information in treatment planning for the correction of craniofacial deformities. These include the added visualization of the complex craniofacial anatomy and preoperative surgical planning with a highly accurate three-dimensional model. While the stereolithographic process has had a beneficial impact on the field of craniofacial surgery, the added cost of the procedure continues to be a hindrance to its widespread acceptance in clinical practice. With improved technology and accessibility the utilization of stereolithography in craniofacial surgery is expected to increase. This review will highlight the development and current usage of stereolithography in craniofacial surgery and provide illustration of it use.

Purpose: Ten years ago, the American Association of Oral and Maxillofacial Surgeons membership was surveyed to evaluate the influence that integration of a medical degree might have on oral and maxillofacial training. The intent of the current survey was to reassess the influence a medical degree has had on the specialty over the past 10 years. Patients and Methods: The effects of a medical degree on privileges, referral patterns, and its role in the office, hospital, and academic settings were studied. Biographical data was collected and responses were evaluated for the following groups: 1) the nation as a whole, 2) MD versus non-MD oral and maxillofacial surgeons (OMS), 3) geographic regions of practice, 4) population, 5) number of years in practice, and 6) involvement in academic programs. Results: The results of this survey were similar to the previous one. Substantially different responses were seen between the dual-degree and single-degree OMS as well as differences between geographic locations, years in practice, and academic involvement. MD-DDS and academic OMS again possessed a broader spectrum of privileges than their colleagues. Recently trained OMS again possessed a greater number of privileges than more experienced surgeons. Conclusion: Overall there has been a trend toward increasing surgical privileges over the past 10 years for both single- and dual-degree OMS. The results presented emphasize the need to continually assess the influence that a medical degree has on the specialty. © 2001 American Association of Oral and Maxillafacial Surgeons

Distraction osteogenesis has gained acceptance as a viable modality for lengthening hypoplastic skeletal structures in the maxillofacial region. A case of the application of this technique to advance the maxilla in an unrepaired bilateral alveolar cleft via a transoral approach is presented. The distraction devices were applied bilaterally to the zygomatic buttress region with the activating arms protruding from the oral cavity. A high Le Fort I osteotomy was performed under general anesthesia and, prior to distraction, the three maxillary segments were unified with an occlusal acrylic splint. Activation was begun 6 days after placement, at a rate of 1 mm per day, until the planned maxillary advancement had been achieved. An 8-week period of consolidation was allowed prior to removal of the devices.

Purpose: The purpose of this investigation was to study the long-term effects of orthognathic surgery on mastication in patients before and after four surgical procedures: mandibular advancement, maxillary intrusion, maxillary intrusion with mandibular advancement, and maxillary inferior repositioning. Materials and Methods: The components and timing of mandibular motion, electromyography (EMG), and estimated biting forces during mastication were studied in 61 patients who underwent orthognathic surgery for correction of four different deformities. The data were statistically compared with 38 control subjects using ANOVA. Results: Preoperatively, there were no significant differences in the duration of the chewing cycles and mandibular excursions among the groups, nor did surgery have any affect on these variables. Before surgery, estimated occlusal forces in the patient groups were smaller than controls. Although these appeared to increase after surgery, the increases did not exceed changes in our untreated controls. Conclusions: The results of this study suggest that, with the exception of EMG and occlusal forces, mastication in orthognathic surgery patients is not significantly different from controls either before or after surgery. EMG during mastication, although significantly lower than in controls before surgery, showed significant increases after surgery, but these increases did not bring estimated occlusal forces up to control levels.

Purpose: The purpose of this investigation was 1) to compare functional and morphologic measurements between controls and patients scheduled for anterior or inferior repositioning of the maxilla, and 2) to examine how these patients' oral function adapted after surgery. Patients and Methods: Nine male patients undergoing anterior and/or inferior repositioning of the maxilla were compared with 26 male controls preoperatively and up to 3 years after surgery. Measures of skeletal morphology, mandibular range of motion, maximum voluntary bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were made on all subjects over time. One-way ANOVA was used to compare the controls, the patients before surgery, and the patients after surgery. Results: Before surgery, most of the patients had morphologic characteristics of mandibular prognathism and maxillary retrognathism. Surgery made the patients' skeletal morphology similar to controls except for mandibular length, upper facial height, and palatal plane angle, which were significantly greater than those of controls. There were no significant differences in jaw muscle mechanical advantage between controls and patients either before or after surgery. Hypomobility of the jaw was apparent at 6 weeks and 6 months after surgery, but returned to normal values within 1 to 2 years. Before surgery, the patients had maximum voluntary bite forces significantly less than those of controls. Bite forces in patients steadily increased after surgery, approaching significantly higher values than those of controls. Before surgery, patients' muscle activity levels per unit of bite force were not significantly different from those of controls. Most of the patients' muscle activity levels per unit of bite forces at all bite positions showed no significant change after surgery. Conclusions: The results of this study suggest that anterior or inferior repositioning of maxilla produces some significant functional benefits in patients.

Purpose: The purpose of this investigation was 1) to compare morphologic parameters and voluntary bite forces between controls and a sample of patients with mandibular prognathism before surgical correction, and 2) to examine how these patients' bite forces adapt after treatment. Patients and Methods: Twenty-four prognathic patients were compared with 24 controls before and up to 3 years after mandibular setback surgery. Measures of skeletal morphology and maximum isometric bite force were made on all subjects over time. Statistical analysis compared the controls, the patients before surgery, and the patients after surgery. Results: Surgical shortening of the mandible averaged 4.1 mm, bringing most skeletal measures into the normal range. Before surgery, the jaw muscle mechanical advantages for patients were significantly smaller than for controls; surgery did not significantly change this relationship. Before surgery the patients had maximum isometric bite forces that were significantly less than those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 to 3 years. Conclusions: The results of this study suggest that correction of mandibular prognathism by mandibular setback surgery produces some significant functional benefits.

Purpose: The purpose of this investigation was to 1) compare morphological characteristics and functional performance of a sample of patients with vertical maxillary excess (VME) with controls, and to 2) examine how the patients' oral motor function adapts to surgery. Materials and Methods: Fifteen female VME patients were compared with 26 female controls before and up to 3 years after maxillary intrusion surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyogram (EMG) activity in some of the muscles of mastication were made on all subjects over time. One-way analysis of variance (ANOVA) was used to compare the controls with the patients before and after surgery. Univariate repeated measures ANOVA was used to study longitudinal changes in the patients. Results: Preoperatively, the patients possessed morphological measurements characteristic of vertical maxillary excess. Superior repositioning of the maxilla averaged 3.3 mm. Concurrently, most skeletal measures were brought closer to normal values. Masseter muscle mechanical advantage was significantly lower in the patients than in controls both before and after surgery (P < .05). There was no significant difference between patients and controls for other biomechanical measurements. Mandibular hypomobility was apparent at 6 weeks after surgery, but returned to control values within 6 to 12 months. Before surgery, the patients had maximum isometric bite forces significantly less than those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite forces were equivalent to those of controls or somewhat lower. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. Conclusions: The results of this study suggest that correction of vertical maxillary excess with maxillary intrusion surgery improves some characteristic functional deficits.

Purpose: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. Patients and Methods: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. Results: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. Conclusions: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.

Purpose: To quantify the connective tissue forces generated during surgical lengthening of the mandible. Patients and Methods: Sixty-three patients who had mandibular advancements by sagittal ramus osteotomy were used in this study. Prior to sectioning the rami, the overjet was recorded. After sectioning the rami, a spring-gauge was attached to the mandibular orthodontic wire and pulled anteriorly to determine how much force was necessary to bring the mandibular incisors into a Class I relationship with the maxillary incisors. Aggressive stripping of the perimandibular periosteum and connective tissues on the distal segment was then performed. The amount of force was again recorded. Results: The mean preoperative overjet in the 63 patients was 6 mm (range, 3 to 11 mm). The mean amount of force required to advance the mandible prior to stripping the tissues was 1,498 g compared with a mean of 787 g after stripping (P < .001). There were statistically significant correlations between the preoperative overjet and the prestripping and poststripping force levels (P < .001). There was also a significant relationship between prestripping and poststripping values (P < .001). Conclusion: The results of this study indicate that orthopedic forces are generated by the perimandibular connective tissues following advancement by the mandible. The effect of these forces on the temporomandibular joint should be evaluated in future studies.

Previous studies have indicated that patients scheduled for orthognathic surgery tend to have lower maximum bite forces and exert lower forces during mastication. The effect of these deficits on masticatory performance have not been previously assessed. Masticatory performance was analyzed in four groups: male and female orthognathic surgery patients prior to presurgical orthodontics (n = 12 and 23), and male and female controls (n = 27 and 31). Mastication performance was analyzed by having the subjects chew 5-g pieces of carrot for 20 cycles and measuring the resulting median particle size with a standard sieve method. Masticatory performance showed the same trends as maximum bite force and masticatory forces: male controls had the best and patients the poorest masticatory performance. There was a weak correlation between masticatory performance and maximum bite force at the molar positions. Masticatory performance also weakly correlated to electromyographic signals during mastication of a constant bolus (gummy bears) for all muscles except the left posterior temporalis. Correlations were generally not present or were very weak between masticatory performance, estimated masticatory forces, and muscle efficiency, suggesting that muscle efficiency and forces generated during mastication are not the primary factors that determine masticatory performance. Other factors contributing to a person's ability to chew food might include occlusal relationships and mechanical advantage.

blastoma. A case report and review ofthe literature. Int J Oral Maxillofac Surg 2 1:40, 1992 9. Mintz S, Anavi Y, Sabes W: Peripheral ameloblastoma of the gingiva. A case report. J Periodontol6 1:649, 1990 10. Monson ML, Postgate J, Bowe R, et al: Pedunculated soft-tissue mass on the alveolar gingiva. J Oral Maxillofac Surg 48: 13 11, 1990 11. Baden E. Doyle JL, Petriella V: Malignant transformation of peripheral ameloblastoma. Oral Surg 75214, 1993 12. Simpson HE: Basal cell carcinoma and peripheral ameloblastoma. Oral Surg 38:233, 1974 13. Anneroth Cl, Johansson B: Peripheral ameloblastoma. Int J Oral Surg 14:295, 1985 14. Ueno S. Nakamura S. Mushimoto K. et al: A clinicouatholoeic study of ameloblastoma. J Oral Maxillofac Surg 44i36 1, 1986 15. Frankel KA. Smith JD. Frankel LS: Soft tissue ameloblastoma in a 92 year old woman. Arch Otolaryngol 103:499, 1977 16. Ng KH, Siar CH: Peripheral ameloblastoma with clear cell differentiation. Oral Surg 70:2 10, 1990 17. Lin SC, Lieu CM, Hahn LJ, et al: Peripheral ameloblastoma with metastasis. Int J Oral Maxillofac Surg 16:202, 1987 18. Edmondson HD, Browne RM, Potts AJC: Intraoral basal cell carcinoma. Br J Oral Sung 20~239, 1982 19. McClatchey KD, Sullivan MJ, Paugh DR: Peripheral ameloblastic carcinoma: A case report of a rare neoplasm. J Otolaryngol 18:109, 1989 20. Woo B, Smith-Williams JE, Sciubba JJ, et al: Peripheral ameloblastoma of the buccal mucosa. Oral Surg 63:78, 1987 2 1. Schroeder HE, Listgarten MA: Fine structure of the developing epithelial attachment of human teeth, in Wolsky A (ed): Monographs in Developmental Biology, ~012. Base], Karger, 1971, pp l-134 22. Wysocki GP, Brandon RB, Gardner DG, et al: Histogenesis of the lateral periodontal cyst and gingival cyst of the adult. Oral Surg 501327, 1980 23. Spouge JD: Odontogenic tumors. Oral Surg 24:392, 1967 24. Greer ROJ, Hammond WS: Extraosseous ameloblastoma. Light and ultrastructural observations. J Oral Surg 36:553, 1978 25. Sciubba JJ: Comments on El-Mofty SK, Gerard HO, Farish SE, Rodu B: Peripheral ameloblastoma: A clinical and histologic study of 11 cases. J Oral Maxillofac Surg 49:970, 199 1

There has been relatively little study of masticatory forces in dentofacial deformity patients before orthognathic surgery. This study used a mathematical equation based on electromyographic activity (EMG) during mastication and forces obtained during isometric bites to estimate masticatory forces in 55 control subjects and 48 patients. Subjects chewed on a constant bolus while EMG recordings were made bilaterally from the superficial masseter, anterior temporalis, and posterior temporalis muscles. Unilateral isometric bite forces in the first molar position and simultaneous EMGs were recorded in these same subjects. Superficial masseter muscle activity and isometric bite forces were strongly correlated. The slope of masseter EMG versus isometric force was used to estimate the masticatory forces. Males were found to have significantly higher estimated masticatory forces than females.

Sixty-five consecutive patients with fractures of the mandibular angle were treated by open reduction and internal fixation using two dynamic compression plates placed through a transoral incision using transbuccal trochar instrumentation and 2.4-mm screws. In the first 20 cases, the screws were inserted without tapping the drill holes. In the remaining 45 cases, the drill holes were tapped. No patient was placed into postsurgical maxillomandibular fixation or training elastics. Overall, 21 fractures (32%) developed infections requiring secondary surgical intervention. The infection rate was higher in those fractures where the holes were not tapped (40%) than those cases when the holes were tapped (29%). Of the 21 fractures that required hardware removal, 9 fractures were healed and required no further treatment; 12 had no firm bony union and required postsurgical maxillomandibular fixation. Only one case resulted in a malunion with resulting malocclusion. The use of two dynamic compression plates was found to be relatively easy, but resulted in an unacceptable rate of infection.

This retrospective study analyzed complications in 96 patients with 99 mandibular angle fractures treated during a 3-year period with either closed reduction or nonrigid means of fixation combined with maxillomandibular fixation. An overall complication rate of 17% occurred. Infection was the most common complication, occurring in 17 fractures. Thirteen fractures had infection as the only complication; in the remaining four patients, infection was combined with malunion/malocclusion. The results of this study show that mandibular angle fractures in an inner-city population are associated with a high incidence of postsurgical complications.

The functional state of dentofacial deformity patients before orthognathic surgery has received relatively little study. In this study, the ability to generate occlusal force was compared between 84 patients before treatment for various dentofacial deformities and 57 controls. Maximal and submaximal bite forces were measured at the incisor and right and left first molar bite positions. Electromyographic activity (EMG) was recorded bilaterally from the anterior temporalis, posterior temporalis, and masseter muscles during each bite. An efficiency ratio was calculated for the jaw muscles by dividing the level of EMG by the occlusal force. There was a reduced ability to generate occlusal forces in the patients before surgery, especially among female patients. The reductions in maximal occlusal force were correlated with reduced efficiency of the jaw muscles.

The purpose of this investigation was to compare our ability to perform the surgery that is planned in the prediction tracing and model surgery when using the mandible as a guide to maxillary repositioning, using internal and external reference points to establish the vertical dimension at the time of surgery. A total of 146 consecutive patients who underwent maxillary repositioning by means of Le Fort I osteotomy were selected. In all patients the unoperated mandible was used to provide anteroposterior and transverse maxillary position. In 100 patients, measurements made on the lateral wall of the maxilla (internal reference points--IRP) were used to determine the maxillary vertical dimension. In 46 patients, the vertical dimension was established by measuring between a Kirschner wire in the nasal bridge and a maxillary incisor (external reference points--ERP). Comparison between the predicted and actual change in the position of the incisor was calculated. Statistical analysis showed that there were significant differences between the predicted and actual change in vertical and horizontal position of the incisor (p less than 0.0001) for both experimental groups. However, there was a significant difference between the 2 experimental groups (p less than 0.001) for the accuracy of vertical repositioning. The use of an external reference point proved to be a more accurate method for vertical maxillary repositioning. The results of this investigation indicate that the ability to determine vertical repositioning of the maxilla with internal reference lines is limited.

The aim of this prospective study was to define the patterns of recovery of mandibular mobility following three commonly performed orthognathic surgical procedures. Twenty-two consecutive patients undergoing either isolated Le Fort I osteotomy (LE FORT; n = 7), sagittal split ramus osteotomies (SSRO; n = 7), or intraoral vertical ramus osteotomies (IVRO; n = 9) were studied. LE FORT and SSRO patients had no mandibular immobilization, whereas IVRO patients were immobilized by dental fixation for 3 weeks. Mandibular mobility was assessed by measurement of maximal mandibular opening (MMO) and lateral and protrusive excursions. No significant difference in MMO was observed between groups prior to surgery (LE FORT, 47.0 mm; SSRO, 50.7 mm; IVRO, 54.5 mm). A significant reduction in MMO occurred immediately after surgery in the LE FORT and SSRO groups and at release of fixation in the IVRO group. Each group returned to presurgical levels of mandibular mobility at a different rate following surgery. LE FORT patients recovered quickly, regaining 83% (mean, 38.7 mm) of MMO by 1 month and exceeded preoperative levels (mean, 49.6 mm) by 6 months. SSRO patients showed hypomobility (mean, 23.5 mm) after 1 month, with significant improvement in MMO (mean, 38.0 mm) at 2 months, and nearly complete recovery (96.2%; mean, 48.8 mm) at 6 months. IVRO patients recovered rapidly after release of dental fixation, achieving 78% (mean, 39.8 mm) of preoperative MMO at 2 months. This study shows that significant differences in recovery patterns of mandibular mobility exist between surgical procedures. The clinician should be aware of these differences in recovery patterns in defining goals for individual patient rehabilitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Fifty percent of the American Association of Oral and Maxillofacial Surgeons membership in the United States was polled in an effort to evaluate the influence a medical degree might have on privileges and referral patterns, and its role in the office, hospital, and academic settings. Biographical data were collected and responses evaluated for the following groups: 1) the nation as a whole, 2) geographic regions of practice, 3) population, 4) number of years in practice, and 5) involvement in academic programs. Questions concerning the spectrum of privileges as well as referrals and desire to possess a medical degree were asked. Substantially different responses were seen between the MD/non-MD oral and maxillofacial (OMF) surgeons as well as differences between geographic locations, years in practice, and academic involvement. In general, MD and academic OMF surgeons possessed a broader spectrum of privileges than their colleagues. No consistent patterns were seen between the various geographic regions. No significant differences existed in privileges based on the size of a community in which a surgeon practices. A greater or equal percentage of privileges was possessed by more recently trained OMF surgeons than their more experienced colleagues. The results presented may aid future graduates in making a more informed decision when considering obtaining a medical degree.

The purpose of this investigation was to determine the ability to perform the surgery that is planned based on the prediction tracing and model surgery when using the mandible as a guide to maxillary repositioning and internal reference points to establish the vertical dimension at the time of surgery. One hundred consecutive patients who underwent maxillary repositioning by means of Le Fort I osteotomy were selected. In all patients the unoperated mandible was used to provide anteroposterior and transverse maxillary position and measurements made on the lateral wall of the maxilla (internal reference points, IRP) to determine the maxillary vertical dimension. Tracings of all cranial structures were made of the preoperative cephalograms and superimposed on the postoperative cephalogram and on the prediction tracing using cranial base structures. Points were digitized to compare the preoperative, postoperative, and predicted position of the maxillary central incisor and first molar of each patient by computer. Comparison between the predicted and actual change in the position of the incisor and molar was calculated. Statistical analysis showed that there were significant differences between the predicted and actual change in vertical and horizontal position of both the incisor and the molar (P less than .0001). The results of this investigation indicate that the ability to determine vertical repositioning of the maxilla with internal reference lines is limited.

The purpose of this study was to prospectively define the recovery of touch discrimination following four commonly performed surgical procedures in 22 consecutive patients with no previous maxillofacial surgery. The surgical groups studied were Le Fort I osteotomy (LEFORT; n = 13), sagittal split ramus osteotomy (SSRO; n = 6), intraoral vertical ramus osteotomy (IVRO; n = 9), and isolated genioplasty (GENIO; n = 5). Neurosensory function was assessed by three different testing modalities which included static light touch (SLT), moving touch discrimination (MTD), and two-point discrimination (TPD). Cutaneous sensation of the lower lip and chin were examined for the mandibular procedures, whereas the infraorbital and upper lip regions were evaluated following maxillary surgery. Immediately following surgery, each group varied in both the incidence and magnitude of neurosensory deficits (NSD). The SSRO group had the highest percentage of sites with immediate postsurgical NSD to both SLT (72%) and MTD (67%), followed by the LEFORT (SLT = 50%, MDT = 58%), GENIO (SLT = 27%, MTD = 6%), and IVRO groups (SLT = 11%, MTD = 18%), respectively. Each group also varied in the severity of the initial postoperative deficit as measured by SLT, with the SSRO group showing the greatest deficit followed by the LEFORT, GENIO, and IVRO groups. During the 6-month recovery period each group approached preoperative levels of sensation at a different rate. The LEFORT group recovered most rapidly, with few anatomic sites showing NSD (SLT = 20%, MTD = 5%) at the 1-month postoperative examination, and the majority of the group (96%) returned to preoperative sensation by 3 months following surgery. The SSRO group recovered more slowly, with approximately half of the group demonstrating a deficit (SLT = 50%, MTD = 59%) at 1 month, which diminished to about one fourth of the sites (SLT = 25%, MTD = 5%) by 3 months. Most of the SSRO group (90%) exhibited no residual deficit 6 months following surgery. The IVRO group had few sites with immediate NSD (SLT = 11%, MTD = 15%). In none of the surgical groups was a statistically significant correlation found between the severity of the initial NSD and length of time to complete recovery.