Evaluation of factors predictive of lingual nerve injury in third molar surgery

The aim of this study was to investigate risk factors for temporary and permanent lingual nerve injury after extraction of mandibular third molars. It was based on a 4-year prospective study of 2134 consecutive mandibular third molar operations in 1384 consecutive day case patients. During the study period (1994-1998) data were collected prospectively on patient, dental and surgical factors and correlated with lingual nerve injury using Student's t test, xi(2) and multiple logistic regression analysis. The incidence of temporary and permanent lingual nerve injury was 1 and 0.3%, respectively, per tooth. Factors that predicted temporary and permanent lingual nerve injury by univariate analysis were age, depth of application, difficulty of operation, surgeon and surgical technique used. Independent risk factors identified by multivariate analysis for temporary lingual nerve injury were perforation of the lingual plate, exposure of the nerve and increased difficulty of operation. The predictors for permanent lingual nerve injury in order of importance were perforation of the lingual plate, surgeon, increased difficulty of operation, exposure of the nerve and increased age of the patient. Surgical factors are the main contributors to lingual nerve injury during third molar extraction, but patient and dental factors are also involved.