Association of incisal overlaps with /s/ sound and mandibular speech movement characteristics

Modern anterior restorations are intended to achieve esthetic and functional reconstruction and coordination. The positioning of the anterior teeth can affect pronunciation, but the effect of anatomic factors on pronunciation after anterior restoration has not been critically tested. The purpose of this study was to provide possible references for the design of the anterior overlaps in future anterior restorations.

Thirty-nine subjects with normal occlusion (NO) participated. They completed questionnaires, were examined clinically, and were recorded pronouncing the /s/ sound. Links between overlaps with spectral features of the /s/ sound and mandibular movements during speech were investigated.

When NO subjects pronounced the /s/ sound, the average fricative length was 202.54 ± 44.57 ms; the average noise peak was 4052.89 ± 445.80 Hz, which was in the high-frequency region; the center of gravity was 2452.85 ± 623.50 Hz; and the mean intensity was 40.61 ± 4.99 dB. The mandibular speech movements showed a slightly long and narrow backward and downward oblique path. Overbite positively correlated with the /s/ sound's noise peak frequency and negatively correlated with the maximum closing speed. Overjet negatively correlated with the maximum distance in the sagittal plane.

This is the first attempt to correlate the spectral features of the /s/ sound and speaking movements with incisal overlaps. The results suggest that significant associations exist and that these associations can offer some references for esthetic anterior restoration.