Position and Variability of Minimum Opening Position during Gum-chewing

Abstract

Purpose : Determining the minimum opening position during chewing when food particles are being fractured and the variability of this minimum opening, which also affects the efficiency of the motion, are crucial for dentistry. This paper investigated estimates of the minimum opening position during gum-chewing movements and compared the variability of different mandibular reference points (i.e., lower incisal point, right and left molars). The variability between the maximum intercuspal position and the minimum opening position was also compared.Materials and Methods : Twenty-eight young female subjects participated in this study. The gum-chewing motion of each subject was recorded using an optoelectronic analysis system with six degree-of-freedom. Minimum opening position was defined as the position where the lower incisal point reached its uppermost position between two maximum opening positions.Results : The three reference points at the minimum opening position were located more posteriorly compared with their position at the maximum intercuspal position. The minimum opening position of the molars was more stable than that of the lower incisal point, and the molar had less variability on the working side than on the balancing side. In the lateral direction, the mandibular position at the maximum intercuspal position was less stable than at the minimum opening position during chewing.Conclusion : The minimum opening position was not coincident with the maximum intercuspal position. In addition, its reproducibility was relatively higher than the maximum intercuspal position, especially in the lateral direction, suggesting that closer attention must be paid to lateral deviation of bite registration at the maximum intercuspal position.