Three-dimensional position of the overlap relations of impacted mandibular third molar and mandibular canal

Objective To study the method in accurately deciding the three-dimensional positional relationship when impacted mandibular third molar was overlapped with mandibular canal on the panoramic X-ray film,so as to use appropriate clinical methods to extract the mandibular third molar.Methods Fifty-seven impacted mandibular third molars were checkedby CBCT,which were overlapped with mandibular canal on the panoramic X-ray film,and then a detailed classification and appropriate surgical plan were made.Results The position relationship types on CBCT were as follows:22 impacted mandibular third molars' roots were inside the mandibular canal;30 impacted mandibular third molars