Abstract
Purpose: Treatment policies for shortened dental arch (SDA) with the loss of few posterior teeth are divided into two contrary options: positive prosthetic treatment and no treatment. In this study, the effect of chewing with a simulated SDA on masticatory muscle activity was investigated in order to evaluate functional features of SDA during chewing.
Materials: Eight healthy dentate subjects participated in this study. An acrylic resin occlusal splint covering the lower full dental arch was fabricated for each subject and then the posterior region of the splint was removed consecutively to simulate SDA without bilateral second molars and that without bilateral first and second molars. Activity of the masseter and temporal muscles from the onset of chewing to the completion of swallowing was measured when the subject was instructed to eat rice or beef jerky while wearing one of three types of splint. The muscle activity and number of chewing cycles were compared among the three types of splint.
Results: The total muscle activity and number of chewing cycles increased as the splint was shortened. The effect of simulated SDA on muscle activity was larger when using the splint without bilateral first and second molar regions than that without bilateral second molar regions. However, the mean muscle activity required for one chewing cycle was almost constant irrespective of the type of splint.
Conclusions: It is suggested that positive prosthetic treatment is effective for SDA in cases which have lost all occlusal support in the molar region.
