The relationship between morphological changes and oral function before and after slow palate expansion

Purpose: Recent reports indicate that Japanese children have narrow dental arches with weakening oral functions. Therefore, this study investigated the relationship between palatal morphology and oral function after expansion treatment with a slow, removable expansion appliance. Materials and Methods: We evaluated changes in the deep, middle, and shallow palatal widths of 22 children with narrow dental arches who visited our hospital. We also assessed the tongue raising force, maximum occlusal force, lip closure force, and masticatory movement patterns, representing the oral function. Changes in the hyoid and resting tongue position before and after treatment were also evaluated using lateral cephalometric radiographs. Finally, the patients were divided into two groups based on the expansion frequency (once every two weeks or once per week) for measurement comparisons. Results: We found that the amount of expansion at the deep width of the palate was half that at the shallow width. Furthermore, the maximum occlusal force and tongue raising forces improved after the treatment. Additionally, multiple regression analysis indicated that the resting tongue position and maximum occlusal force before the expansion treatment were significantly associated with the amount of palate expansion. Conclusions: Slow plate expand can expansion the basal palate. Moreover, oral function improves after expansion therapy.