Pernambuco index: predictability of the complexity of surgery for impacted lower third molars.

This study aimed to develop and validate an index of surgical difficulty for the removal of impacted lower third molars. The study was performed in two steps. The first was a cross-sectional analysis of clinical, demographic, and radiographic variables collected from patients undergoing the removal of an impacted lower third molar between 2008 and 2012. The second step was a prospective cohort study involving the same surgical procedures to validate the index; this was performed between 2013 and 2016. Univariate regression analysis was applied, followed by multiple linear regression analysis. A total of 753 surgical procedures were analyzed in the first stage, which led to the identification of the most important variables and their levels of significance. The index was then applied to 280 surgical procedures. The preoperative difficulty was in concordance with the index results in all cases. Among cases with a low level of difficulty, 93.1% had been indexed as low difficulty; likewise, among cases with a high level of difficulty, there was 87.9% concordance with the index. With the use of reference statistics in the development and quality assurance processes, this validated index has proven to be a reliable and easily applicable instrument, with high sensitivity, specificity, and accuracy.