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Journal of the Korean Association of Oral and Maxillofacial Surgeons

A STUDY ON BONE-CONTACT TO INTER-SEGMENTAL LENGTH RATIO OF RIGID FIXATION SCREWS USED IN BSSRO FOR MANDIBULAR SETBACK

Journal of the Korean Association of Oral and Maxillofacial Surgeons / Journal of the Korean Association of Oral and Maxillofacial Surgeons, (P)2234-7550; (E)2234-5930
2009, v.35 no.5, pp.329-334



Abstract

Objective: To evaluate the ratio between bone-contact length and inter-segmental length of the rigid fixation screw used in bilateral sagittal split ramus osteotomy (BSSRO) for mandibular setback. Material and Methods: Records of 40 patients with Class III malocclusion were selected. 20 of them had BSSRO, while the other 20 had BSSRO with maxillary LeFort I osteotomy. All of the patients had three noncompressive bicortical screws inserted at the gonial angle through transcutaneous approach. Two screws were inserted antero-posteriorly above inferior alveolar nerve and one screw was inserted below. The lengths of bone-contact and that of inter-segmental part were measured using cone-beam computed tomography. Ratio between these two measured lengths was calculated. Results: Both bone-contact and inter-segmental lengths were longer in BSSRO group than in BSSRO with maxillary LeFort I osteotomy group. Ratio of bone-contact to inter-segmental length was lower in BSSRO group than in BSSRO with Lefort I group. Both bone-contact and inter-segmental lengths were longer at the antero-superior position than at the inferior position. However, their ratio showed little difference. Conclusion: This study suggest that stability of screws in BSSRO group was greater than in BSSRO with Lefort I group. Stability of screws at the antero-superior position was greater than at the inferior position. Ratio of bone-contact to inter- segmental lengths was 0.2 in average.

keywords
Screw length and ratios, Rigid fixation, Bilateral sagittal split ramus osteotomy

Journal of the Korean Association of Oral and Maxillofacial Surgeons