Effects Of Second Premolar Extractions In Orthodontic Treatment On Third Molar Eruptions Angle

ObjectiveThe purpose of this study was to determine the relationship between the inclinations of second and third molars in patients treated orthodontically with and without p remolar extractions.Methods16 second premolar extraction patients and 16 nonextraction patients were selected from the School of Stomatology,China Medical University from 2005 to 2009. The pretreatment and posttreatment panoramic radiographswere analyzed. The angleswere measured between the long axis of the third molar andthe occlusal plane and between the long axis of the third molar and the long axis of the second molar. Changes in third molar angulations from pretreatment to posttreatment for two group swere compared by Paired-Samples T test.ResultsStatistical analysis revealed that compared with nonextraction group,the changes of the angles between the long axis of third molar decreased had statistically significant difference (p＜0.05).The angle between the long axis of the second and the third molar decreased.But there is no statistically significant difference in maxillary third molar (p＞0.05). So mandibularthird molars showed an improvement in angulation relative to the occlusal plane in the second premolar extraction group.ConclusionsWith the premolar extractions, the third molareruption will be more vertical angle and the frequency of third molar eruption will increase, which may reduce its impacted possibilities.