Three-dimensional mandibular change after sagittal split ramus osteotomy with a semirigid sliding plate system for fixation of a mandibular setback surgery.

OBJECTIVE: This study proposes a new plate system, a sliding plate, after sagittal split ramus osteotomy (SSRO). The sliding plate was designed to adjust the spatial relationship between the proximal and distal segments during the postoperative period. This plate was used for mandibular setback surgery to minimize forward early relapse. STUDY DESIGN: Twenty-six Korean subjects who had undergone mandibular setback surgery by SSRO were included in this study. Skeletal stability was evaluated with lateral cephalograms and 3-dimensional cone-beam computerized tomography. RESULTS: Forward mandibular movement during the postoperative period was ~2 mm. The condyles rotated inward on the axial view after surgery. Postoperatively, the condyle rotated outward on the axial view, inward on the coronal view, and forward on the sagittal view by a statistically significant amount. CONCLUSIONS: The fixation method with sliding plates after SSRO was stable and convenient for the operators during surgery and postoperative care.

Evaluation of stress distribution in resorbable screw fixation system: three-dimensional finite element analysis of mandibular setback surgery with bilateral sagittal split ramus osteotomy.

The purpose of this study was to evaluate the stress distribution of resorbable screw (RS) and cortical/cancellous bone in the mandibular setback surgery with bilateral sagittal split ramus osteotomy (BSSRO) according to fixation geometry and number of RSs using three-dimensional finite element analysis. Three-dimensional virtual models of the mandible and bicortical RS (INION CPS System; diameter, 2.5 mm; length, 12 mm [Inion Ltd, Tampere, Finland]) were constructed by Mimics (Materialise, Ann Arbor, MI) using three-dimensional computed tomography DICOM data with 0.5-mm-thickness cut. After 8-mm setback BSSRO was performed, fixation between the proximal and distal segments of the mandible was done with bicortical RS. Fixation options were classified into 3RL (3 RSs with linear configuration at the retromolar area), 2R1A (2 RSs at the retromolar area and 1 RS at the mandibular angle area), 2R1B (2 RSs at the retromolar area and 1 RS at the mandibular body area), and 3R1A (3 RSs at the retromolar area and 1 RS at the mandibular angle area). After applying the occlusal load of 132 N on the lower first molar, stress distributions of the RSs and cortical/cancellous bone in each option were analyzed by ANSYS program (ANSYS Inc, Canonsburg, PA). Maximum stress concentration was found at the anterior RS fixation in the retromolar area in all options. Although 3R1A fixation showed more even distribution of stress concentration than other fixation options, 2R1A fixation was comparable with 3R1A fixation in view of yield stress in RSs. In terms of fixation geometry and number of RSs, both 2R1A and 3R1A fixation configurations might provide proper stress distribution in BSSRO.

Simultaneous correction of hard- and soft-tissue facial asymmetry: combination of orthognathic surgery and face lift using a resorbable fixation device.

The purpose of this study was to evaluate outcomes of simultaneous correction of the hard- and soft-tissue facial asymmetry with face lift procedure using a resorbable fixation device (Endotine Ribbon; Coapt Systems, Palo Alto, CA) during bimaxillary orthognathic surgery in cases with severe facial asymmetry. The samples consisted of 8 patients (mean age, 23.3 [SD, 4.4] years; 8 skeletal class III and 2 class II malocclusion) who received bimaxillary orthognathic surgery and a face lift procedure using a resorbable fixation device. Preoperative cephalometric evaluation of the maxillary occlusal plane cant and chin point deviation and data on surgical movement, site, time, and difficulty of face lift procedure were collected at 1 week before operation and during operation procedure. The amounts of lip cant between preoperation and postoperation were compared. Pain, stability of fixation, adverse effects, relapse, and patients' and surgeon's satisfaction were evaluated at 6 months after operation. Initial and final amounts of the lip cant were 4.15 (SD, 0.53) and 0.80 (SD, 0.48) mm (correction rate, 76.8%). The face lift procedure took 28.4 (SD, 3.3) minutes without difficulty. There were no severe complications such as hematoma, facial nerve injury, and postoperative scar. By the patients' and surgeon's view, all had satisfactory jowl elevation, lip canting correction, and achievement of the soft-tissue symmetry without evidence of recurrent asymmetry or loss of fixation. If the face lift procedure using a resorbable fixation device is done with proper vector control during orthognathic surgery, the hard- and soft-tissue facial asymmetry can be corrected simultaneously with satisfactory outcomes.

Surgical accuracy of maxillary repositioning according to type of surgical movement in two-jaw surgery.

OBJECTIVE: To compare the surgical accuracy of the maxillary repositioning according to the maxillary surgical movement type (SMT) in two-jaw orthognathic surgery (TJOS). MATERIALS AND METHODS: The samples consisted of 52 Korean young adult patients with skeletal Class III malocclusion treated with TJOS by one surgeon. Lateral cephalograms were taken 1 month before (T0) and 1 day after surgery (T1). The samples were allocated into maxillary advancement (MA), total setback (MS), impaction (MI), and elongation (ME) according to SMT. The distance from the upper incisor tip and the mesiobuccal cusp tip of the upper first molar to the horizontal and vertical reference lines at T0 and T1 were measured. Any discrepancy between the surgical treatment objective (STO) and the surgical result less than 1 mm was regarded as accurate. The accuracy rate (AR [number of the accurate sample/number of the sample] x 1000) and the surgical achievement ratio (SAR [amount of movement in surgical result/amount of movement in STO] x100) were calculated. Analysis variance (ANOVA) and crosstab analyses were used for statistical analysis. RESULTS: Although the MS (69.2%) and MI (69.0%) showed a lower AR than the MA (87.5%) and ME (83.3%), there was no significant difference in the distribution of accurate and inaccurate samples among the groups. The mean discrepancy between the STO and the surgical result was less than 1 mm in all groups. Although the ME (93.54%) showed a tendency of undercorrection and the MS (107.10%) and MI (105.42%) a tendency of overcorrection, there was no significant difference in SAR among the groups. CONCLUSIONS: If the surgical plan and procedure is done with caution, the MS and MI can be regarded as just as accurate a procedure as the MA and ME.