Acoustic analysis of vowel sounds before and after orthognatic surgery

Introduction and Aim: Orthognathic surgery is the surgical correction of anatomic defects in the parts of the maxilla and mandible that contain teeth. Patients in this group are those who cannot ideally be treated with orthodontic methods alone. The aim of orthognathic surgery is to provide an ideal facial aesthetics as well as the correction of the dental alignment. Besides these two main purposes, at least as important as them are the effects on the speech voice. Especially with the development of sound recording devices and sound analysis programs, more objective and detailed evaluations can be made in this area. In the correction of dentofacial deformities, Lefort 1 osteotomy and sagittal split ramus osteotomy are the most frequently used methods. In the double chin operation, which is the combination of these two operations, it provides a great advantage in providing occlusion with minimal movements rather than sobering movements of the soft tissues of a single jaw. Computerized voice analysis is mainly used for monitoring the voice disorder and the effectiveness of the treatment. Acoustic analysis provides objective assessment of sound and is particularly effective in evaluating the situation before and after treatment. In our study, we aimed to investigate the effect of orthognathic double chin surgery treatment on patients with dentofacial deformity with occlusion disorder, follow-up with acoustic analysis and on voice quality. Patients and Method: In this prospective cross-sectional study, a total of 26 patients, 13 men and 13 women, who underwent orthognathic double chin surgery after orthodontic treatment due to developmental malocclusion between the years of 2018- 2020 in the Department of Plastic, Reconstructive and Aesthetic Surgery, Faculty of Medicine, Çukurova University. The vowel recordings of the patients (a, e, i, ı, o, ö, u, ü) were taken in the preoperative period and at the 6th month postoperatively, when there were no additional pathologies that were thought to affect the vocal quality of the patients. Sound recordings taken with the Audacity(Open Resource Software) program and the acoustic analysis of each letter before and after the operation with the Praat acoustic analysis program, and the fundamental frequency, shimmer, jitter and harmony noise ratios (NHR) were examined. For the comparison of continuous measurements before and after the operation, the distributions were checked. Dependent Group T test was used for variables showing parametric distribution, and Wilcoxson test was used for variables that did not show parametric distribution. Statistical significance level was taken as 0.05 in all tests. Results: For all vowel sound recordings used in the study, a numerical decrease in the fundamental frequency (f0), jitter, shimmer and harmony noise values obtained as a result of the acoustic analysis and a statistically significant change in at least two parameters for each letter were found. Conclusion: As a result of our study, it was observed that the acoustic analysis of vowels used in the Turkish alphabet of orthognathic double jaw surgery patients, which we applied after orthodontic treatment, increased the sound quality. Keywords: Acoustic Analysis, Double Jaw surgery, Malocclusion, Orthognatic Surgery