The Mandibular Speech Envelope in Subjects with and without Incisal Tooth Wear

Purpose: The purpose of this study was to describe a mandibular envelope of motion during speech for 2 subject groups. One subject group had experienced no tooth wear and the other had incisal tooth wear. The speech envelope was to be described with regard to its maximal dimensions in the vertical, anteroposterior, and lateral directions, and its most superior and anterior positions in relation to intercuspal position. Materials and Methods: An electromagnetic method of jaw tracking was employed to record mandibular speech movements for 60 subjects whose teeth exhibited no tooth wear and 30 subjects with incisal dental attrition. The test speech exercise contained all of the word sounds that occur in the English language. The test was recorded 3 times, and mean values for parameters were reported. Results: The speech envelope of the tooth wear group was significantly smaller (Student's t test, P 0.01) in all 3 dimensions than that of the normal group. The tooth wear group speech envelope was also located closer to the intercuspal position in the vertical dimension (P 0.01) and was not as anteriorly placed (P 0.01). In the normal group, correlations were found between the vertical incisor overlap and the most superior speech position (r = 0.48, P 0.0001), and between the horizontal incisor overlap and the most anterior mandibular speaking position (r = 0.63, P 0.0001). Conclusion: The envelope of mandibular movement during speech differed in dimension and position between the 2 groups investigated