J Oral Maxillofac 49222-226.
Surg
1991
Mandibular Anatomy as it Relates to Rigid Fixation of the Sagittal Ramus Split Osteo tomy BRIAN R. SMITH, DDS, MS,* JEFFREY L. RAJCHEL, DDS, MS,t DANIEL E. WAITE, DDS, MS,+ AND LANCE READ, DDS§ Rigid fixation of osteotomy segments is frequently used to reduce relapse and allow for early mobilization of the mandible following the sagittal ramus split osteotomy. This study evaluated cortical bone thickness in the retromolar area of 49 human mandibles to determine if there is an advantage (in terms of cortical thickness) to placement of screws for rigid fixation at the external oblique ridge versus placement at the inferior border. The mandibles were sectioned vertically at three sites in the retromolar area, corresponding to the bone available for rigid fixation of the sagittal osteotomy. Cortical bone thickness was measured, at the external oblique ridge and 5 mm above the inferior border. The buccal and lingual cortices were found to be significantly (P < .OOl) thicker at the external oblique ridge than at the inferior border. This suggests that there may be an advantage in terms of stability to placement of internal fixation screws at the superior border.
the thickness of cortical bone at the external oblique ridge and inferior border have been measured. This study quantifies the cortical bone thickness in the retromolar area of the mandible to determine if there is an advantage to placement of bone screws for rigid fixation at the external oblique ridge or at the inferior border. An additional objective was to determine the vertical position of the mandibular canal in the retromolar region so that its location, relative to completion of the osteotomy and placement of rigid fixation screws, can be known.
Most studies that have examined skeletal stability of mandibular advancement using nonrigid fixation have shown that many patients have significant relapse. I-5 Rigid fixation has shown great promise in reduction of relapse as well as having the advantages of greater patient comfort, earlier jaw mobilization, and quicker return to function.6-1’ However, there is a difference of opinion about whether fixation should be placed at the superior or inferior mandibular border. r2,r3 To date, no studies have been published in which
Materials and Methods * Assistant Professor, Department of Oral and Maxillofacial Surgery, University of Texas Dental Branch at Houston. t In private practice of oral and maxillofacial surgery, Asheville, NC. $ Emeritus Professor and Chairman, Department of Oral and Maxillofacial Surgery, Baylor College of Dentistry, Dallas. $ Resident, Department of Oral and Maxillofacial Surgery, Baylor College of Dentistry, Dallas. Presented at the 71st Annual AAOMS Meeting, Oral Abstract Session, San Francisco, September 1989. Address correspondence and reprint requests to Dr Smith: Department of Oral and Maxillofacial Surgery, UTHSCH, Dental Branch, 6516 John Freeman Ave, Houston, TX 77030. 0 1991 American Association of Oral and Maxillofacial
This study was conducted on 49 dried, intact, adult Asian mandibles of unknown sex. All of the specimens had a complete or nearly complete dentition. Each mandible was cut cross-sectionally in three specific locations perpendicular to the sagittal plane of the body and ramus and the occlusal plane. The sections were made with a 4-in-diameter, Imm-thick, carborundum disk on a high-speed dental lathe. The position of the sections is shown in Figure 1. The three sections roughly divided the overlapping bone available for screw fixation of the sagittal
Sur-
geons 027f3-2391/91/4903-0002$3.00/0
222
Surg
1991
Mandibular Anatomy as it Relates to Rigid Fixation of the Sagittal Ramus Split Osteo tomy BRIAN R. SMITH, DDS, MS,* JEFFREY L. RAJCHEL, DDS, MS,t DANIEL E. WAITE, DDS, MS,+ AND LANCE READ, DDS§ Rigid fixation of osteotomy segments is frequently used to reduce relapse and allow for early mobilization of the mandible following the sagittal ramus split osteotomy. This study evaluated cortical bone thickness in the retromolar area of 49 human mandibles to determine if there is an advantage (in terms of cortical thickness) to placement of screws for rigid fixation at the external oblique ridge versus placement at the inferior border. The mandibles were sectioned vertically at three sites in the retromolar area, corresponding to the bone available for rigid fixation of the sagittal osteotomy. Cortical bone thickness was measured, at the external oblique ridge and 5 mm above the inferior border. The buccal and lingual cortices were found to be significantly (P < .OOl) thicker at the external oblique ridge than at the inferior border. This suggests that there may be an advantage in terms of stability to placement of internal fixation screws at the superior border.
the thickness of cortical bone at the external oblique ridge and inferior border have been measured. This study quantifies the cortical bone thickness in the retromolar area of the mandible to determine if there is an advantage to placement of bone screws for rigid fixation at the external oblique ridge or at the inferior border. An additional objective was to determine the vertical position of the mandibular canal in the retromolar region so that its location, relative to completion of the osteotomy and placement of rigid fixation screws, can be known.
Most studies that have examined skeletal stability of mandibular advancement using nonrigid fixation have shown that many patients have significant relapse. I-5 Rigid fixation has shown great promise in reduction of relapse as well as having the advantages of greater patient comfort, earlier jaw mobilization, and quicker return to function.6-1’ However, there is a difference of opinion about whether fixation should be placed at the superior or inferior mandibular border. r2,r3 To date, no studies have been published in which
Materials and Methods * Assistant Professor, Department of Oral and Maxillofacial Surgery, University of Texas Dental Branch at Houston. t In private practice of oral and maxillofacial surgery, Asheville, NC. $ Emeritus Professor and Chairman, Department of Oral and Maxillofacial Surgery, Baylor College of Dentistry, Dallas. $ Resident, Department of Oral and Maxillofacial Surgery, Baylor College of Dentistry, Dallas. Presented at the 71st Annual AAOMS Meeting, Oral Abstract Session, San Francisco, September 1989. Address correspondence and reprint requests to Dr Smith: Department of Oral and Maxillofacial Surgery, UTHSCH, Dental Branch, 6516 John Freeman Ave, Houston, TX 77030. 0 1991 American Association of Oral and Maxillofacial
This study was conducted on 49 dried, intact, adult Asian mandibles of unknown sex. All of the specimens had a complete or nearly complete dentition. Each mandible was cut cross-sectionally in three specific locations perpendicular to the sagittal plane of the body and ramus and the occlusal plane. The sections were made with a 4-in-diameter, Imm-thick, carborundum disk on a high-speed dental lathe. The position of the sections is shown in Figure 1. The three sections roughly divided the overlapping bone available for screw fixation of the sagittal
Sur-
geons 027f3-2391/91/4903-0002$3.00/0
222
