Articulation and Acoustic Voice Changes After Orthognathic Surgery in Turkish-Speaking Adults With Angle Class III Malocclusion

Orthognathic surgery repositions the jaws and may alter both articulation and the acoustic characteristics of the voice, yet the 2 are rarely measured in the same cohort, and almost never in a language whose vowel inventory differs from English. In this prospective single-center study, 34 consecutive nonsyndromic Turkish-speaking adults with Angle class III malocclusion (11 men, 23 women; median age 24 y) were assessed 1 day before surgery and at 6 months; 30 underwent bimaxillary and 4 single-jaw surgery. Articulation was scored with the Turkish Articulation-Phonology Test (SST), and 8 Turkish vowels and 5 syllables were analyzed in Praat for fundamental frequency, formants F1 to F3, jitter, and shimmer. Anteroposterior movements were taken from the presurgical orthodontic plan. The median SST error score fell from 18 to 0 ( P <0.001; d z =−1.81), and 26 patients (76.5%) had no detectable error. Second formant frequency decreased for the back vowels /ı/ (−142.5 Hz; 95% CI: −227.4 to −57.5; P =0.002) and /u/ ( P =0.048), third formant frequency for /ı/ and /i/, and first formant frequency for the syllables /si/ and /la/. Jitter and shimmer increased for /o/, whereas fundamental frequency was preserved. Greater planned maxillary advancement was associated with a greater preoperative error burden ( r =0.351 and P =0.042) and with a greater reduction in F2 of /ı/ ( r =−0.458 and P =0.006); no such association was found for mandibular setback. Orthognathic surgery markedly improves articulation and measurably reshapes vocal-tract resonance while preserving laryngeal function.