Effects of Occlusal Appliance on the Mandibular Position and the Mandibular Rotational Torque Movement during Speech

교합장치가 발음시 하악위 및 하악의 비틀림 회전운동에 미치는 영향

This study was performed to investigate the effects of occlusal appliance on the mandibular position and the mandibular rotational torque movement during speech. For this study, 20 patients with temporomandibular disorders(TMDs) and 20 normal subjects without any signs and symptoms in the masticatory system were selected as the patient group and as the normal group, respectively. Biopak $system^{(R)}$(Bioresearch Inc., Milwaukee, USA) and a sentence of 'Sue is missing her house' were used for recording and for observing of speech pattern. There were five mandibular positions observed in this study, that is, mandibular rest position, 'ssi', 'her', 'ha', and 's' speech position. In each position, slant and A-P distance in sagittal plane, vertical distance and lateral distance in frontal plane were measured. Amount of the mandibular rotational torque movement were measured at 'her', 'ha' speech position and for all through speech movement. Centric relation splint(CRS) was placed in both groups, but anterior or posterior bite plane were placed in normal subjects only. Data collected were processed and analysed by SPSS windows program. The results of this study were as follows : 1. Mandibular positions in both groups were not different before adaptation, with CRS, and after removal, but total amount of the mandibular rotational torque movement was greater in patients. 2. Mandible was slightly placed anteriorly with CRS at 'her' and 'ha' speech position in patients, but was placed anteriorly at all the five positions in normal subjects. 3. Difference with type of occlusal appliance in normal subjects were noted only for vertical distance at 'ssi' and 'ha' speech position, and the distance with CRS were more than that with posterior bite plane. 4. Mandibular rotational torque movement at 'her' and 'ha' speech position was greater in patients, but the difference was disappeared after appliance removal. And the torque movement was greater at 'ha' speech position than that at 'her' speech position in frontal plane. It could be concluded that the adaptation of occlusal appliance showed a tendency to locate the mandible anteriorly during speech in both groups, but did not affect total mandibular rotational torque movement which was greater in patients.