Effects of bimax and segmental surgeries for correction of bimaxillary dentoalveolar protrusion class I on soft tissue parameters: upper lip thickness and curvature, nasolabial angle and nasal prominence.

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Results of this study can show if bimax surgery for posterior repositioning of maxilla and correction of BPCLI has priority to the currently used segmental orthognathic surgery or not. This study was done on 40 white- skinned Iranian patients with bimaxillary dentoalveolar protrusion class I (BPCLI) who sought treatment for their deformity. In the first group, treatment includes segmental surgery for backward replacement of anterior segment of the upper and lower jaw. In the second group, treatment was bimax surgery, in which whole upper and lower jaw moved backward. Twenty patients were included in each group. For this purpose, we measured upper lip thickness (ULT, distance between LS and IA), nose prominence (NP, distance between nasal tip and the perpendicular line from upper lip vermilion on FHP), subsulcus depth (SSD, distance of SLS from this perpendicular line), SN to H line distance and finally, nasolabial angle (NLA) before and after surgery. In our study, 65% of patients were female and the mean of age was 27 (17-39) years old. The mean of SNA, SNB, ANB and INA in our patients were 81.7 ± 2.9, 78.8 ± 2.8, 4.50 ± 1.4 and 120 ± 8.7, respectively. All variables except SSD were analyzed with t-test to compare the results of two methods of surgery. Differences in the values of NP, NLA, SN to H line distance and ULT before and after segmental and bimax surgeries between before and after surgery were significant. After surgeries, ULT and the SN to H line distance reduced significantly, and NLA became corrected to its normal range (90-110). The results of this study showed that bimax and segmental surgeries can effectively correct BPCLI. Because of possible dental and periodontal complications of segmental surgery, we highly recommend bimax surgery for treatment of BPCLI.