The impact of volitional chewing on tongue movement, jaw movement, and food transport during the feeding sequence

Abstract

Mastication is usually performed with little conscious effort and is controlled by a central pattern generator (CPG). In elderly individuals with reduced swallowing function, poor bolus formation from inadequate mastication may increase the risk of pharyngeal residue and aspiration. Chewing with a conscious effort may be an effective compensatory strategy for the elderly, but the details are still unclear. This study aimed to clarify the impact of volitional chewing on tongue movement, jaw movement, and food transport.
The subjects were 27 dentulous volunteers (17 men, 10 women; mean age, 27.8±3.1) with normal occlusion. Solid agar jelly containing barium sulfate was used as the test food. Subjects were asked to eat under two feeding conditions: chewing normally in their usual manner and chewing with a conscious effort. The oral cavity and pharynx were classified into four areas: oral cavity (OC), upper oropharynx (UOP), valleculae (VAL), and hypopharynx (HYP). Lateral videofluoroscopy was performed to assess the number of chewing sequences, pushing forward movement of the tongue, bolus transit time, and masticatory cycle time (bolus transit time divided by number of chewing cycles in each area).
Chewing with a conscious effort significantly increased the number of chewing cycles and pushing forward tongue movement. Bolus transit time in the OC, UOP, and VAL was significantly lengthened. Masticatory cycle time was significantly shortened while the bolus was retained in the OC and lengthened in the VAL.
Present results suggested that volitional chewing improved bolus retention and formation in the oral cavity by changing in tongue movement and masticatory jaw movement, resulting in easier swallowing.