Unfavourable fracture patterns resulting from different lower border depth cuts in sagittal split ramus osteotomy Y. Chantravekin, W. Tharanon
J Dent Assoc Thai 2007: 57(2): 82–89 The objective of this study was to determine the split pattern of sagittal split ramus osteotomy (SSRO) with different inferior border depth cuts. Fifteen cadaver mandibles, six males and nine females, with mean age of 68.3 (SD = 10.4), were fixed in plaster of Paris. The inferior border of each mandible was flipped upward and aligned parallel to horizontal plane. The thickness of the inferior border was measured by digital caliper. Standard SSRO was performed in each specimen, but the inferior border osteotomy varied in different depths. In group 1 (five specimens), the depth of osteotomy was 1/3 of bucco-lingual thickness of mandible, whereas the depth in group 2 (five specimens) was 2/3 and group 3 (five specimens) was full thickness. In group 1, four mandibles had favourable splits, whereas one mandible had unfavourable split. In group 2, all mandibles had favourable splits. However, in group 3, only two of five mandibles had favourable splits. The unfavourable splits included factures of lingual plate of molar area, fracture of buccal plate, fracture of posterior ramus, and fracture of condylar neck. From this study, favourable SSRO fragments were more reliably obtained after 1/3 to 2/3 cut of inferior border of mandible, whereas unfavourable fragments occur frequently after complete cortical cut. However, from Fisher’s Exact test, depth of inferior border cut osteotomy was not found to affect the split pattern of SSRO ( p = .077).