Relationship between impacted lower third molars and the mandibular canal: A new classification for radiographic signs in orthopantomographs

Abstract

Purpose: The aim of the study was to evaluate the increase in nerve damage after surgery of the lower third molar at different stages of rhizogenesis. The association between the existence or absence of a close relationship to the roots of the third molar and the mandibular canal was considered according to sex, age and complicated tooth, as well as the enshrining of a new classification of the types of radiographic signs, which allows to relate the tooth in rhizogenesis with the mandibular canal. Materials and Methods: The sample consisted of 150 lower third molars impacted in stages 6-10 of the Nolla Classification, with all teeth being fully impacted. In orthopantomography, the type of inclusion was evaluated according to the classification of Winter and Pell and Gregory, the degree of rhizogenesis according to Nolla (1960), the relationship between the roots and the mandibular canal and the type of radiographic signal. All cases were obtained by the same radiologist. Results: The most frequently encountered types of radiographic sign were darkening of the roots (46%), rhizogenesis (39%) and interruption of the white lines (17%). The type of radiographic sign most frequently associated with nerve lesions was darkening of the roots. Conclusion: The fact of extracting the impacted lower third molar, in close relationship with the mandibular canal, seems to have an increased risk of nerve damage in the last stages of risogenesis, that is, with fully formed roots. The presence of the closely related radiographic signal found in orthopantomography represents, in most cases, a true relationship, requiring the classification of the type of radiographic signal to avoid nerve damage.