Changes of occlusal plane inclination after orthodontic treatment with and without extraction in Class II patients

The inclination of the occlusal plane (OP) is related to type of dental occlusion. The aim of this study was to evaluate and compare the inclination of occlusal plane in Class II patients treated with the upper first premolars extraction or non-extraction modalities.

Totally, forty 16-25-year-old patients (15 males and 25 females) with class II malocclusion, whose active phase of orthodontic treatment was completed using MBT with 0.022-inch slot size, were selected. Twenty patients were treated with extraction of upper first premolars and the rest were treated without any extraction. Pre- and post-treatment cephalograms were traced and several cephalometric variables were measured. The pre- and post-treatment changes of angles within each group and between two groups were compared via paired t-test and independent t-test, respectively. The statistically significant level was set at p<0.05.

After treatment, functional occlusal plane (FOP) angle to sella-nasion (SN) plane angle increased in both groups (0.5 degree in extraction group and 0.6 degree in non-extraction group), which was not statistically significant in both groups. Bisecting occlusal plane (BOP) angle to SN plane one in the extraction group enhanced by 0.8 degree, which was not statistically significant, but it decreased by 0.8  degree in the non-extraction group, which was not statistically significant.

Although the use of extraction and non-extraction protocols for the treatment of Class II patients did not cause significant changes in the BOP-SN and FOP-SN angles, small changes in these angles can have marked clinical changes in facial harmony and occlusal relationships. Extraction decision depending on factors such as amount of crowding, incisors protrusion, etc.