Evaluation of Pederson index as an instrument for predicting difficulty of third molar surgical extraction

This study was intended to assess the clinical reliability of the Pederson index as an instrument for preoperative determination of surgical difficulty in third molar surgery.

Pederson index was used to predict the difficulty of 79 cases of impacted mandibular third molar extractions. The predictions were compared with actual surgical difficulty determined by operation time. The reproducibility as well as the reliability of the index was determined.

The index was found to be highly reproducible (P=0.00). The sensitivity and specificity were 94.9% and 45% respectively. The Positive predictive value (PPV) was 67.2% and the negative predictive value was 90% while the accuracy was 69.6%.

The Pederson index though reproducible is not a reliable instrument for predicting surgical difficulty of third molar surgery when compared with actual surgical difficulty as determined by the operation time. There is a definite need to derive an index that could be used for preoperative prediction of difficulty; however it is much more important that any index so employed should provide accurate information as the consequence of wrong judgments could be quite deleterious to the patients and embarrassing to the surgeon. While it is not completely unimportant, the Pederson index should not be employed as a sole instrument for preoperative assessment of difficulty in third molar surgery.