Mandibular setback and its effects on speech

Abstract

PurposeTo study effects of mandibular set back by BSSRO on phonetic quality of vowel sounds and compare it with preoperative recording. Patients and methodsTen non syndromic male patients of mandibular skeletal excess between 16 and 24 years of age undergoing pre-surgical Orthodontic treatment were included in the study. Before surgery vowel sounds in Hindi language were recorded by suitable software. The patients were treated by bilateral sagittal split ramus osteotomy for mandibular setback. Postoperatively same sets of sounds were recorded at an interval of 4, 8, 12, 24 and 52 weeks. The acoustic features were divided into two groups: F1 being vowel sounds of posterior region (Oropharyngeal) and F2 being vowel sounds produced in the anterior region. The data analysis was done using Praat software (ver 5404). ResultsA total of 10 male patients were selected with an average age of 17.4 years. Amount of mandibular setback on an average was 6 mm. It was observed that frequency values of F1 reduced after the surgery till 12 weeks following which it improved to its preoperative status. F2 values increased postoperatively and continued to be higher than the preoperative values throughout the follow up period. ConclusionMandibular set back by bilateral sagittal split osteotomy have profound influence on the acoustic qualities of the subjects. In our study it was realised that, such changes are attributable to changes in transverse and vertical changes of the oro-phyarngeal and oral apertures respectively.