Abstract
The first molars play an important role in grinding food, whereas the frequency of missing first molars is relatively high due to high caries prevalence. Thus, clinical cases with the intermediary missing mandibular first molar are often observed. In this study, masticatory muscle activities from the onset of chewing to the completion of swallowing were evaluated, using splints simulating three different arches, namely, a full lower dental arch and arches with the unilaterally and bilaterally intermediary missing mandibular first molar (s) in order to investigate the impact of intermediary missing molars on the muscle activities. As a result, the total amount of muscle activities and the number of chewing strokes increased as the number of the missing first molars on the splint increased. However, mean muscle activities required for one chewing stroke was almost constant irrespective of the splint type. In conclusion, it was suggested that the intermediary missing first molar caused increase of chewing strokes, and the bilateral first molar missing showed significant impact on the total muscle activities.
