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The effect of fixed orthodontic treatment with first premolar extraction on mandibular third molars angulation and retromolar space
Sedigheh Sheikhzadeh, Allahyar Geramy, Manouchehr Rahmati Kamel, Tania Ghasemi, Hemmat Gholinia,
Volume 7, Issue 1 (3-2018)
Abstract
Introduction: In most orthodontic patients, mandibular 3rd molars are in early stages of calcification, and prediction of eruption status would be difficult during the course of orthodontic treatment. The aim of this study was to evaluate the effect of first premolar extraction with moderate anchorage on angular changes of third mandibular molar after orthodontic treatment.
Materials & Methods: Panoramic radiographs of 50 skeletal class I patients with normal facial height were selected. The patients were divided into two groups of extraction and non-extraction treatments. The angle between 2nd and 3rd molars and 3rd molar angle to mandibular plane were evaluated. Space for eruption of 3rd molar and 3rd molar position relative to ramus were evaluated with regard to Pell and Gregory classification. Paired T-test was used to compare the changes after treatments.
Results: In both groups, 3rd molar angle relative to mandibular plane was increased after the treatment but the difference was not significant. M2-M3 angle changed during the treatments but it was not significant (P>0.05). The retromolar space had significantly higher amounts in extraction groups after the treatment (P<0.001). In non-extraction group, there was significant increase in stage I of Pell and Gregory classification (P<0.001). In extraction group, counts of patients with no space for eruption of M3M were decreased and the difference was significant (P<0.001).
Conclusion: Extraction of premolars did not have any significant positive effect on mandibular 3rd molar angulation but it can increase the posterior space for eruption of wisdom teeth.

Changes of occlusal plane inclination after orthodontic treatment with and without extraction in Class II patients
Masumeh Darabi, Samaneh Sadeghi,
Volume 9, Issue 1 (3-2020)
Abstract
Introduction: 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.
Materials & Methods: 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.
Results: 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.
Conclusion: 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.

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