Influence of tongue movements on masticatory efficiency

Introduction: The purpose of this study is to test relationships between tongue movements and electromyographic activity (EMA) of suprahyoid muscles. Methods: The subjects were 6 adults with a normal stomatognathic system. Experiment 1: Each subject performed six types of tongue movement: 1. extrusive, 2. right-and-left lateral, 3. upward, 4. downward, 5. touching the palate with the tongue tip, 6. touching the palatal aspects of the maxillary second molars, while EMAs were recorded with a wireless electrode-type system in the suprahyoid, digastric and masseter muscles. Experiment 2: Tongue movement was restricted with a device fitted into the floor of the mouth. Then compared were masticatory efficiency and EMA when tongue movements were (a) restricted, (b) not restricted, and (c) when free mastication was allowed without use of the tongue movement restriction. Masticatory efficiency was measured as by Manly RS, et al., [1]. Results: In Experiment 1, EMAs of all tongue movements were significantly higher than resting EMAs. In Experiment 2, masticatory efficiencies and EMAs of (a) were significantly lower than those of (c). Comparing (a) and (c), 3 test subjects in (a) had significantly longer masticatory cycles. Comparing (b) and (c), no significant difference was found in either masticatory efficiency or EMA. In (c), a significant positive correlation was found between masticatory efficiency and the EMA of the suprahyoid muscles. Conclusion: EMA of the suprahyoid muscles reflected the tongue movements and the tongue movements significantly influence masticatory efficiency. Correspondence to: Shigeru Watanabe, Department of Human Development and Fostering, Meikai University School of Dentistry, 1-1 Keyakidai, Sakado, Saitama 350-0283, Japan, Tel: (+81) 49-279-2743, Fax: (+81) 49-279-2743, E-mail: shigeru@dent.meikai.ac.jp