Precise Extraction Of Complicated Mandibular Third Molar

PURPOSE To introduce a new classification system for adjacent tooth trauma and inferior alveolar nerve injury,as well as computer assisted surgical design.METHODS In this retrospective study,consecutive patients,who underwent piezosurgery extractions of complicated impacted mandibular third molars by the same surgeon were included.Risk degree of adjacent tooth trauma is based on the adjacent teeth resistances(degree I: no adjacent teeth resistance;degree II: got resistance released after mesial-half crown sectioning;degree Ⅲ: still had resistance after mesial-half crown sectioning).Risk classification of inferior alveolar nerve injury is based on the proximity of the root to the inferior alveolar canal(IAC)(grade I: contacting;grade II: compressing;and grade Ⅲ: penetrating),as well as the relation to the IAC(class I: on the lingual side;class II: above the IAC;class Ⅲ: on the buccal side;and class Ⅳ: roots surrounding the IAC).Surgical methods concluded by computer assisted design: mesio-distal and bucco-lingual rotation(with or without tooth sectioning).χ2 test was used to analyze the data.RESULT In this study,136 teeth were included.In 136 teeth in contact with their adjacent teeth,teeth in degree I(37 teeth)were extracted by rotating mesio-distally;teeth in degree II(44 teeth)were extracted by rotating bucco-lingually or mesio-distally after mesio-half crown sectioning;teeth in degree Ⅲ(55 teeth)were extracted by rotating bucco-lingually or mesio-distally after crown-root sectioning.Only one adjacent tooth was subluxated.Of 92 teeth(84 patients)in close proximity to the IAC,36.96%,33.70%,29.35% were in risk degree I,II,Ⅲ,with 5,2,0 cases of IAN injuries in each degree recorded(p<0.05);31.52%,55.43%,11.96%,and 1.09% were in classes I,II,Ⅲ and Ⅳ,with 0,3,4,0 cases of IAN injuries in each class were recorded.CONCLUSIONS The analysis of adjacent tooth resistance could decrease the incidence rate.Teeth with higher adjacent teeth trauma risks should consider lingual rotations.There was a positive correlation between the degree of root proximity to the IAC and IAN injury with the highest incidence being in class Ⅲ.Precise surgical design could aviod permanent damage of IAN.