Reliability of Pederson Scale in Surgical Extraction of Impacted Lower Third Molars: Proposal of New Scale

The aim of this study was to evaluate the clinical reliability of the Pederson index in preoperative assessment of the difficulty of surgical removal of impacted mandibular third molars. Pederson index was found to be unreliable predictor of true difficulty with low sensitivity and specificity. A new index (Kharma scale), which takes into consideration the anatomical form of tooth roots, is proposed and evaluated both pre- and postoperatively. The results of the evaluation indicate that the new estimating index is more reliable and accurate measure than Pederson scale.