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 experienc ed 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 e lectromagnetic method of jaw tracking was employed to record mandibular spe ech movements for 60 subjects whose teeth exhibited no tooth wear and 30 su bjects with incisal dental attrition. The test speech exercise contained al l of the word sounds that occur in the English language. The test was recor ded 3 times, and mean values for parameters were reported. Results: The spe ech 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 too th wear group speech envelope was also located closer to the intercuspal po sition in the vertical dimension (P < 0.01) and was not as anteriorly place d (P < 0.01). In the normal group, correlations were found between the vert ical incisor overlap and the most superior speech position (r = 0.48, P < 0 .0001), and between the horizontal incisor overlap and the most anterior ma ndibular speaking position (r = 0.63, P < 0.0001). Conclusion: The envelope of mandibular movement during speech differed in dimension and position be tween the 2 groups investigated.