Mesiolingual root rotation for horizontal mandibular third molar extraction: position classification and surgical simulation.

Extracting horizontal mandibular 3rd molars face considerable difficulty due to the large bone and adjacent tooth resistances. This study aims at evaluating the effectiveness of a novel method-mesiolingual root rotation to extract wisdom teeth of this type. In this study, 73 horizontal teeth extracted using piezosurgery were reviewed and classified based on impaction depth: position I, II, III refers to the highest portion of the crown on a level with upper 1/3, middle 1/3, lower 1/3 of the 2rd molar's root. Based on the surgical simulations on their 3D CBCT reconstructions, traditional method(crown distal rotation) and novel method(root mesiolingual rotation) are applied. 79.17% of teeth in position I and 57.89% of teeth in position II were designed using traditional method, 83.33% teeth in position III were designed using the novel method(p < 0.05). The surgeries were performed according to the designs. Two cases in position II using traditional method were found temporary inferior alveolar nerve(IAN) injury; while only one case in position III using novel method got temporary IAN and lingual nerve injury. Our study suggested that root mesiolingual rotation is an effective method to extract the horizontal mandibular 3rd molars, especially the deep impacted ones.