A case of diachronic observation of tongue movement before and after removable partial denture treatment using ultrasonography

Patient: The patient was a 68-year-old woman who came to our hospital complaining of a masticating disorder due to loss of a mandibular removable partial denture. The remaining teeth of the maxilla were the right second premolar and second molars on both sides. A maxillary removable partial denture had been set at the site of the defect. The mandibular right second premolar, and first and second molars on both sides were missing. A removable partial denture was manufactured by the traditional method and fitted to the mandible. The tongue movement during mastication was observed using ultrasonography, and was classified into the early, intermediate, and final periods from the M-mode waveform. Then, by tracing the B-mode coronal images at the lowest points of the M-mode for five consecutive waveforms of each period, we measured the distance to the surface of the mandible skin from two points on the surface of the tongue in the left and right sides 15 mm away from the midline. The difference in height between the left and right sides of the tongue was observed before and after treatment. Movements were chewing on one side of the left or right. The test food was 10 g of cooked rice. Tongue movements were observed before treatment, and at 1 and 6 months after treatment. Discussion: The difference in height of the tongue did not change in each period before treatment, but showed a decreasing trend with the progress of mastication at 1 and 6 months after treatment. Furthermore, at 6 months after treatment it was similar to the clinical reference value of dentate elderly. Conclusion: In this case, it was considered that tongue movement during mastication adapted to the environment by chewing denture in about 6 months, and that wearing dentures affects tongue movement during mastication.