Advancement genioplasty with and without soft tissue pedicle: An experimental investigation

To determine whether maintaining a soft tissue pedicle to the genial segment decreases the amount of bone resorption following an advancement genioplasty, 12 rhesus monkeys (Macaca mulatta) underwent advancement genioplasty of 5–6 mm. The insertion of the digastric musculature and lingual soft tissues on the genial segment was maintained in six of the animals, and six had all soft tissues stripped. Cephalometric analysis of remodeling in the anterior part of the mandible indicated that the pedicled genial segments underwent significantly less resorption than the free graft segments (P < 0.05). The results of this study indicate that soft tissue pedicles to the genial segments should be maintained during advancement genioplasty to minimize the amount of bone resorption in the post-operative period.     

An analysis of 2,067 cases of zygomatico-orbital fracture

A ten-year review of 2,067 cases of zygomatico-orbital fractures is presented. The age and sex distribution, anatomical types of fractures, associated maxillofacial and nonmaxillofacial trauma, and causes of the injuries are described. The majority of fractures were sustained by males and resulted from trauma inflicted in altercations. The most common associated facial fractures were mandibular; the most common associated nonmaxillofacial trauma was extremity fractures. Motorcycle accidents caused the most significant amount of associated trauma, followed by motor vehicle accidents in which no seat restraint was used by the victim. Treatment, when indicated, consisted of elevation via a temporal approach followed by fixation where necessary. The fixation methods used are presented and discussed.     

The frequency and distribution of skeletal and dental components in Class II orthognathic surgery patients

In an effort to identify the skeletal and dental relationships of Class II malocclusion, lateral cephalograms of 253 adult orthognathic surgery patients (76 male, 177 female) who had a Class II molar and cuspid relationship were traced. One hundred and four of the subjects had had presurgical orthodontic treatment and 148 had not. The most common combination of variables found in this study population was a retrusive maxilla, protrusive maxillary incisors, protrusive mandibular incisors, a retrusive mandible, and a long lower facial height.     

The role of suprahyoid myotomy in surgical advancement of the mandible via sagittal split ramus osteotomies

The suprahyoid muscles have been implicated as primary effectors of relapse following surgical advancement of the deficient mandible. Accordingly, suprahyoid myotomy and/or the use of cervical collars have been recommended as adjunctive procedures to minimize postoperative relapse. This computerized morphometric evaluation of 16 patients revealed that suprahyoid myotomy is not essential to skeletal stability following surgical advancement of the mandible.     

Facial injuries in automobile crashes

In automobile accidents, the facial area is the most frequently injured body region in passenger car occupants. Laboratory studies have indicated that the tolerance of facial bones to impact is relatively low. Most of these facial injuries are rated as minor. The windshield, steering wheel, and instrument panel are the major points of contact. Restraints, lap belts, and lap-shoulder belts reduce the frequency of facial injuries at all levels of severity and also reduce the more severe and serious injuries to other body regions.     

Healing of interpositional allogeneic lyophilized bone grafts following total maxillary osteotomy

Healing of allogeneic lyophilized bone grafted to total maxillary osteotomy sites was studied in Macaca fasciularis monkeys using histologic, microangiographic, and autoradiographic methods. Results of the study indicate that allogeneic lyophilized grafts are slowly replaced by host bone. Revascularization around the margins of the graft becomes evident at two weeks and increases until eight weeks; a hypervascular response is still present at six months. The palatal mucosa and facial gingiva provide an adequate nutrient pedicle for interpositional allogeneic grafts.     

Changes in the gonial region induced by alterations of muscle length

Thirty-eight adult rhesus monkeys were used in the study of osseous remodeling of the gonial region following various types of experimental intervention. This study indicated the following: (1) When the length of the masseter muscle is increased by increasing the vertical dimension, resorption in the gonial region takes place. (2) When the original length of the masseter muscle is increased by an appliance and a sham operation is performed, increased resorption, greater than that observed when only an appliance is used, is observed. (3) When a muscle is detached following an increase in vertical dimension and allowed to reattach spontaneously, the largest amount of gonial remodeling is observed. These observations indicate that both blood supply and function influence the shape of the gonial region.     

The nature of vertical maxillary deformities: implications for surgical intervention

A study was performed to identify the area within the maxilla where vertical maxillary deformities are expressed. Analysis of the maxillas of individuals who displayed 4 mm or more of the central incisors at rest were compared with those who displayed less than 1 mm. Similarly, individuals who had greater than or equal to 2 mm negative incisor overbite (open-bite) were compared with those who had greater than or equal to 2 mm positive overbite. The results showed that the vertical position of the maxillary skeleton (palate) was similar in all groups. The vertical excess was found to lie within the dentoalveolus. The clinical implications of these results are discussed.     

Components of adult Class II open-bite malocclusion

In an effort to identify the frequency and distribution of the dental and skeletal components of adult Class II malocclusion with and without open-bite, 124 adults, half of whom had an anterior open-bite, were evaluated. Significant differences (P less than 0.05) between the open-bite and non-open-bite groups were found for the following measurements: the posterior maxilla exhibited vertical excess in the open-bite group; the maxillary occlusal plane was less steep in the open-bite group; the mandibular occlusal plane was more steep in the open-bite group; the gonial angle was higher in the open-bite group; the mandibular plane angle was higher in the open-bite group; the mandibular ramus was positioned in a more downward and backward (clockwise) location in the open-bite group; the total and lower anterior facial height were increased in the open-bite group; and the mandible was less protrusive in the open-bite group. No significant intergroup differences were noted in the cranial base, the anteroposterior position of the maxilla or of the upper and lower incisors, the palatal plane, posterior facial height, mandibular ramus height, or mandibular body length. The results of this analysis indicate that the average Class II open-bite malocclusion is characterized by aberrations in both the maxilla and the mandible. Therapy, therefore, may frequently require surgical intervention in both jaws to successfully correct this deformity.     

Use of the orthognathic surgery simulating instrument in the presurgical evaluation of facial asymmetry

The use of Orthognathic Surgery Simulating Instrument (OSSI) is described. Two cases of facial asymmetry, one with hemifacial microsomia and one with unilateral condylar hyperplasia, are presented to demonstrate the diagnostic capabilities of the articulator. The OSSI has greatly improved our ability to plan the treatment of cases of gross facial asymmetry.     

Components of adult class III malocclusion

To identify the skeletal and dental relationships of adults who have class III malocclusion, lateral cephalograms of 302 adult patients who had a class III molar and cuspid relationship were traced. Ninety-four of the patients had had presurgical orthodontic treatment and 208 had not. The tracings were digitized, and the following sets of measures were analyzed: maxillary skeletal position; maxillary dentoalveolar position; mandibular dentoalveolar position; and mandibular skeletal position. In addition, the mandibular plane angle and lower anterior facial height were measured as an indicator of vertical facial dimensions. None of these values demonstrated significant gender differences except lower anterior facial height; therefore, the subjects were treated as a group. Although there was considerable variation among patients, the most common combination of variables was a retrusive maxilla, protrusive maxillary incisors, retrusive mandibular incisors, a protrusive mandible, and a long lower facial height.     

Computer-graphic representation of mandibular movements in three dimensions. Part I. The horizontal plane.

A computer-graphics simulation was developed to display the effects of mandibular movement patterns of both the maxillary and mandibular teeth in the occlusal plane. The many parameters affecting mandibular movement patterns may be varied selectively. The effects of these parameters on the pathways of movement described by the supporting cusps during occlusion can be graphically observed in the horizontal plane.     

Comparison of the healing and revascularization of onlayed autologous and lyophilized allogeneic rib grafts to the edentulous maxilla

The healing and revascularization of onlayed autologous and lyophilized allogeneic rib grafts to the edentulous maxilla in the Macaca fascicularis monkey were studied using clinical, histologic, and microangiographic methods at varying intervals of up to eight months. Results indicated that healing and revascularization were similar but resorption of the allografts occurred approximately three months later than resorption of the autografts. Both grafting systems appeared to have minimal osteogenic potential. Osteoinduction and the final bony augmentation obtained were less than were seen with comparable autologous and allogeneic interpositional grafts.     

An experimental and clinical study of osseointegrated implants penetrating the nasal cavity and maxillary sinus

Implants were inserted in the upper jaw of three dogs in such a way that they penetrated the bone wall of the nasal cavity. The dogs were killed one year later, and the hard and soft tissues around the penetrating implants were analyzed. Radiographic and histologic examinations did not show any signs of adverse tissue reaction. The implants were all integrated in bone without fibrous tissue formation in the interface. A total of 139 implants, which pierced the bone of the sinus or nasal cavity, were inserted in the upper jaws of 101 patients. Forty-four sinus- and 47 nasal-penetrating implants were observed for five to ten years. The success rates were 70% and 72%, respectively. For 25 sinus- and 23 nasal-penetrating implants that were observed for two to five years, the success rates were 88% and 96%, respectively. The implant losses in nearly all clinical cases occurred during the first two years of function.     

Stability associated with mandibular advancement treated by rigid osseous fixation

Relapse after a mandibular sagittal ramus split osteotomy (SSO) fixed by transosseous wire has been shown to occur. Authors who use rigid screw fixation claim a lesser incidence of such relapse. Nine subjects with horizontal mandibular deficiency treated by an SSO and fixed with bone screws were prospectively studied. Serial cephalometric radiographs were traced and superimposed on the sella-nasion line and anterior cranial base structures. A markedly reduced horizontal movement during the first six weeks at both points B and Pg, followed by a slight advancement at six months, was observed. Concomitantly, the surgically increased facial height was shown to subsequently decrease during both those time intervals. The stability of this procedure warrants further investigation.