Evaluation and prediction of impacted mandibular third molars by panoramic radiography: A retrospective study

Abstract

Aim: The aim of this study was to evaluate the factors associated with impaction of mandibular third molars and to find a method for predicting eruption of the third molars using panoramic radiographs. Materials and Methods: Ninety pretreatment panoramic radiographs of patients with a full complement of teeth were selected. The mandibular third molars were divided into two groups depending on their eruption status: Group 1: erupted and Group 2: impacted molars. Various angular and linear measurements were made on the panoramic radiographs. Results: Shapiro–Wilk test showed that the data were not normally distributed. Mann–Whitney U-test showed that mean rank of angulation between third molar and second molar (M3M2), gonial angle (GoA), and mesiodistal width of third molar (MDW3M) of impacted group was significantly higher than the erupted group. Spearman's correlation coefficient showed positive correlation between angulation of third molar with mandibular plane (M3MP) and retromolar space (RS) with eruption of mandibular third molar. M3M2, GoA, and MDW3M were found to have negative correlation with eruption of mandibular third molar. Conclusions: Increased RS and M3MP were strongly associated with eruption of the mandibular third molar. An increase in the M3M2 and MDW3M predisposed impaction of third molar. GoA was smaller and mandibular length was larger in the erupted group although both had a weak correlation.