Effects of maxillary protraction with an orthopedic facemask on fricatives.

Introduction: This prospective cohort study aimed to investigate the effect of rapid maxillary expansion (RME) and orthopedic facemask (FM) treatment on the acoustic properties of fricative sounds (/s/ and /ʃ/) through objective and subjective (perceptual) assessments.

Methods: Twenty-two patients (7 females and 15 males; mean age: 11.27 ± 1.38 years) underwent speech recordings at 4 time points: immediately before RME (T0), 2 weeks later (immediately before FM application, T1), 3 months later (T2), and 1 week after treatment (T3). Speech therapists recorded the data and conducted acoustic analyses using Praat software. Acoustic parameters-duration, spectral peak, center of gravity, and second formant transition-were analyzed for /s/ and /ʃ/ in monosyllabic words with /a/, /u/, and /ı/ vowels in both word-initial and word-final positions. Data were statistically analyzed using repeated measures analysis of variance and the Friedman test. Cephalometric radiographs were taken at T0 and T3.

Results: After RME and FM therapy, duration decreased significantly in the word-initial positions of /s/ and /ʃ/ (P = 0.002). Spectral peaks decreased significantly in the word-initial and word-final positions during treatment for both /s/ (P <0.001) and /ʃ/ (P = 0.007), returning to baseline by T3. However, a significant overall decrease persisted (P <0.001). Center of gravity also decreased significantly during treatment (P <0.05), whereas second formant transition values did not change. A perceptual evaluation revealed high articulation accuracy (2.00) at T0 for all evaluations, a significant decrease at T2 with increased scores (3.65 for /s/ and /ʃ/ total, 4.00 for overall intelligibility, P <0.001), and a subsequent improvement at T3 (1.33 for all evaluations, P <0.001), with scores significantly lower than at T0 (P <0.001).

Conclusions: RME and FM therapy led to favorable structural and phonetic changes. Improvements in acoustic properties and perceptual scores suggest effective adaptation and enhanced articulation after treatment.