Does maxillary advancement alter vocal acoustic parameters in class III skeletal patients?

Any change in the maxillary position can affect the length of the vocal tract. This cross-sectional study aimed to assess the vocal acoustic parameters in 24 class III skeletal patients who underwent Le Fort I osteotomy for maxillary advancement. The vocal acoustic parameters (fundamental frequency, and jitter and shimmer perturbation indexes) were studied before, and at three, seven, and 10 months after maxillary advancement. The age and gender of the patients were the variables of the study. The amount of maxillary advancement was the predictive factor, and the changes in vocal acoustic parameters the study outcomes. Repeated-measures ANOVA were used to analyse the vocal acoustic parameters at different time points. Mean (SD) maxillary advancement was 3.5 (0.59) mm (range 3 - 6 mm). Data analysis did not demonstrate any significant correlation between the mean amount of maxillary advancement and changes in vocal acoustic parameters except for frequency of the 'i' sound. The results did not show a substantial change in the vocal acoustic parameters at 10 months after orthognathic surgery compared with baseline. These changed at three and seven months, but had returned to their baseline preoperative state 10 months after surgery.