Changes in masticatory performance during the retention period following 4-premolar extraction and non-extraction orthodontic treatment

Abstract

Objectives To evaluate changes in masticatory performance (MP) during the retention period after extraction and non-extraction treatment and compare it with MP in individuals with normal occlusion. Materials and methods Adult patients who had completed orthodontic fixed appliance treatment comprised the extraction and non-extraction treatment groups, and those with normal occlusion comprised the control group. Their mixing ability (MA), maximum bite force (MBF), and occlusal contact area (OCA) were recorded immediately after the fixed appliance was removed and at 1 month, 6 months, and 1 year post-treatment. The MA was measured via the two-color chewing gum MA test using ViewGum software, and the MBF and OCA were measured using Dental Prescale II system.Results MA immediately after orthodontic treatment was lower than that in the normal group but showed a time-dependent gradual increase during a 1-year retention period (P < 0.01). The MA at 1 month post-treatment was not significantly dif-ferent between the three groups (P > 0.05). The MA revealed a significant correlation with the MBF and OCA (P < 0.01).Conclusions The MP immediately after orthodontic treatment was lower than that in the normal group but increased gradu-ally, with levels comparable to those of the normal occlusion group at 1 month post-treatment. Further, extraction did not affect the recovery of the MP after orthodontic treatment.Clinical Relevance No other study has evaluated the changes in MP during the retention period after orthodontic treatment. The findings show that compared with MBF and OCA, the patients' MP improved faster to levels found in normal occlusion.