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

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 0.05). The MA revealed a significant correlation with the MBF and OCA ( P