Factors predictive of difficulty of mandibular third molar surgery.

Historically the difficulty of third molar surgery has been judged using radiologically assessed dental factors specifically tooth morphology and position. This study investigated additional factors that have a bearing on the difficulty of extraction. A prospective study undertaken by three clinical assistant grade surgeons who removed 354 single mandibular third molar teeth under day case anaesthesia over the 4-year period (1994-1998). Data relating to patient, dental and surgical variables were collected contemporaneously as the patients were treated. The difficulty of extraction was estimated by the surgeons pre-operatively using dental radiographic features and compared by the same surgeon within the actual surgical difficulty encountered at surgery. Operation time strongly related to both pre and post treatment assessments of difficulty and proved to be the best measure of surgical difficulty. Univariate analysis identified increased patient age, ethnic background, male gender, increased weight, bone impaction, horizontal angulation, depth of application, unfavourable root formation, proximity to inferior alveolar canal and surgeon as factors increasing operative time. Multivariate analysis showed that increasing age (P = 0.014), patient weight (P = 0.024), ethnicity (P = 0.019), application depth (P = 0.001), bone impaction (p=0.008) and unfavourable root formation (P = 0.009) were independent predictors for difficulty of extraction. Half of the six independent factors that predicted surgical difficulty of third molar extraction were patient variables.