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. 1. Introduction Surgical extraction of impacted mandibular third molars is a common practice in the field of oral and maxillofacial surgery. Therefore, establishing objective criteria that can estimate the clinical difficulty of such procedure preoperatively is very important. This would allow oral surgeons to undertake correct management with minimal complications. A search in the literature has shown that only few studies attempted to evaluate elements, which can complicate surgical removal of impacted mandibular third molars [1]. Among these studies, Pederson difficulty index (Table 1) which is mainly based upon anatomical and radiographic features, including angulations, depth, and ramus relationship [2]. Table 1: Spatial relationship (position of the molar). However, Pederson scale was tested by several studies and was claimed to be unreliable predictor of true difficulty [3–7]. Other studies were more comprehensive and took into consideration other variables than Pederson’s ones such as abnormal root curvature, width of root, and number of roots [4, 6, 8]. These studies have suggested new indices and claimed that their suggested criteria are more reliable and accurate than Pederson’s scale. In view of the lack of sufficient data, the current study was undertaken in an attempt to establish scientific standards that can be utilized reliably and accurately to assess preoperatively the level of difficulty of extraction of impacted mandibular third molars. 2. Subjects and Methods A successive surgical extraction of 100 impacted lower third molars from a total of 75 patients (40 men, 35 women) has been studied. The operations were undertaken between September 2010 and July 2012, by the authors, at the Department of Oral and Maxillofacial Surgery of Aleppo University, Syria. 2.1. Operative Technique All extractions were carried out in outpatient department by the same senior surgeons (Dr. Kharma and Dr. Sakka) to remove the operator bias. A standard protocol under local anesthesia was