Purpose: The purpose of this study was to investigate the effects of prosthetic interventions in patients with Kennedy Class Ⅱ (unilateral missing posterior teeth) on mastication predominance. Methods: The subjects comprised patients with Kennedy Class II and healthy dentate volunteers (HD group). The subjects were asked to freely chew the test foods (chewing gum, beef jerky, and peanuts). Electromyographic activity of the bilateral masseter muscles was recorded twice (before and after prosthetic intervention). The chewing side (right or left) was judged by the level of the root mean square electromyographic amplitude. Mastication predominance was assessed using the mastication predominance index (MPI; range 0–100%). Each patient was restored with a removable partial denture (RPD) or an implant-supported fixed prosthesis (IFP). The effects of prosthetic interventions were statistically evaluated by the differences between MPI before and after prosthetic interventions (pre-MPI and post-MPI, respectively). Results: There was a significant difference between pre-MPI of patients with Kennedy Class II and MPI of the HD group (HD-MPI) for all test foods (P < 0.0001). Statistical analysis also demonstrated a significant difference between pre-MPI and post-MPI measured with each of the three food items in both the RPD and IFP groups (P < 0.0001). Multiple comparisons revealed that post-MPI in the IFP group, but not in the RPD group, was statistically comparable with HD-MPI, although there were no significant differences among the three groups when MPIs were calculated using peanuts. Conclusions: Prosthetic interventions improved mastication predominance in patients with Kennedy Class Ⅱ patients. Depending on the food type, IFP might contribute to better improvement of mastication predominance than RPD depending on food.
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