Influence of the difference in how to mastication on swallowing movement

Abstract

【Objective】We investigated the location of bolus at the beginning of the swallowing reflex and found that the swallowing movement and bolus coordination depended on three patterns of chewing. The purpose of this study was to know whether different chewing methods influence the swallowing movement.

【Method】Six healthy adults (average age 28.5 ± 2.6) participated in this study. Subjects were instructed to eat 8-g cookies containing barium by three kinds of chewing methods： a） free mastication, b） mastication with a fixed number of times, or c） mastication by anterior teeth. Bolus transportation was imaged with videofluorography from a side view and recorded by digital video. The position of the leading edge of the bolus was classified into oral cavity (OC), upper-oropharynx (UOP), valleculae (VAL), or hypopharynx (HYP). The swallowing movement was divided into three stages： stage 1 ＋ transport, postfausial aggregation time (PFAT), valleculae aggregation time (VAT), and hypopharyngeal transit time (HTT). Swallow onset was defined as the time when movement of the hyoid began its rapid elevation.

【Result】The position of the bolus at the beginning of the swallowing reflex was frequently at the VAT in the free mastication method and mastication with a fixed number of times method. In the mastication by anterior teeth method, the position was frequently at the HYP. Mastication by the anterior teeth method reached HYP earlier. Food transportation time was shorter in the mastication with a fixed number of times method, and longer in the mastication by anterior teeth method at VAT. Longer VAT can be the risk of aspiration.

【Discussion】The mastication with a fixed number of times method was effective to prevent aspiration. On the other hand, mastication by the anterior teeth method made it raise a risk of aspiration. This was because the swallowing reflex started earlier in the mastication with a fixed number of times method, and later in the mastication by anterior teeth method. Thus, the chewing method affected the swallowing movement.