Effects of Orthognathic Surgery on Voice Characteristics

Abstract

Orthognathic surgery not only corrects dentofacial deformities but also affects some vital structures involving voice production. The primary aim of this study was to analyze the effects of bimaxillary orthognathic surgery on voice characteristics of patients with class II and III skeletal deformities; the second aim was to evaluate possible associations among acoustic parameters, pharyngeal airway, and skeletal changes after surgery. Using a prospective cohort study design, we enrolled a sample of patients who underwent bimaxillary orthognathic surgery in the university hospital between January 2018 and January 2019. Voice records and cone-beam computed tomography (CBCT) scans of the patients were acquired before surgery and 6months after surgery. Pharyngeal airway volume, minimum cross-sectional area, hyoid bone position, and skeletal movements of the maxilla and mandible were assessed with Dolphin Imaging software using CBCT data as predictor variables. Acoustic analysis of voice samples (vowel/a/) were performed with Praat software as outcome variables. The within-group and between-group differences in data were analyzed using paired-sample and independent-sample t tests. The degree of relationship between voice and CBCT parameters was assessed using Pearson correlation and multiple regression analysis. The study sample comprised 33 patients; 14 patients had class II skeletal deformity and 19 patients had class III skeletal deformity. Orthognathic surgery in both patients with class II and III skeletal deformities resulted in significant changes in all the voice parameters (All P<.05). Only patients with class II skeletal deformity showed significant changes in airway parameters (increase; all P<.001) and hyoid bone positions (anterosuperior movement; P=.001 and P=.008, respectively). Multiple regression analysis showed that some specific structural changes significantly affected some specific acoustic parameters. Bimaxillary orthognathic surgery significantly changed the acoustic parameters of voice in patients with class II and III skeletal deformities. Some of the structural changes were significantly associated with some of the acoustic parameters.