抄録
‹Objective› The objective of this study was to examine how denture wearings after tooth loss would have an influence on oral transit in oropharyngeal swallowing.
‹Methods› Data were analyzed in nine young dentates (24.9± 1.7ys) and nine denture wearers (66.4±6.5ys) . Subjects were instructed to masticate ten grams of steamed rice, then swallow in one time when food was cut into smaller pieces and softened by saliva. Tongue movement, up and down tongue dorsal movement at the region of first molar, was examined by ultrasonography (TOSHIBA, SSA-250A) . Recordings of mandibular movement using Mandibular Kinesiograph (Myotronics, K6- I ) and muscular activity of infrahyoid muscles on both sides using surface electromyography were performed simultaneously. Measurement points were decided as the onset of oropharyngeal swallowing, the onset of bracing activity by the teeth and the onset of muscle activity. Timing of events was calculated. A statistical analysis was performed with use of Mann-Whitney test in comparison between two groups. ‹ Results and discussion › The typical records were as follows: one or two times peaks of tongue movement record were observed (down and up movement of tongue), then tongue movement stopped (press tongue against the palate) . The last peak is considered the onset of propelling bolus posteriorly, or the initiation of oropharyngeal swallowing. Mandibular movement tracks became a state near to intercuspal position (bracing activity by the teeth) . Two or more continuous muscle activities were observed. Finally, tongue and mandibular movement stopped at the rest position. Muscle action potential on both sides returned to the base line.
When time 0 was defined as the onset of muscle activity. The onset of tongue movement propelling posteriorly in denture wearers was earlier than in young dentates (p<0.05) .
‹Conclusions›
1. Noninvasive examination of oral transit during oropharyngeal swallowing was performed.
2. The onset of oral transit followed the onset of bracing activity by the teeth in all subjects.
3 . It was suggested that denture wearings after tooth loss would have an influence on the initiation of oropharyngeal swallowing.
