The Influence of Mandibular Third Molar Position on Distal Caries in Mandibular Second Molar

Introduction: Distal caries of mandibular second molars has been documented to be associated almost exclusively with impacted third molars. The level of involvement of second molars in distal caries is influenced by the angulation of the occlusal surface of mandibular third molars and third molars depth. In spite of the importance of these factors on the occurrence of distal caries, their influence on prophylactic extraction decision of asymptomatic impacted molars for Iraqi population did not get enough attention. Aim: of the study: To determine the influence of mandibular third molar impaction, as identified by panoramic radiograph, on distal caries incidence in second molar in Iraqi population. Materials and Methods: Panoramic radiographs of impacted mandibular third molars prior to surgical extraction were retrieved from the database of Al-Karamah Secondary Dental Care Centre in the period 2004-2013. Demographic data were collected for all cases. Each panoramic radiograph was examined for the presence of distal caries of mandibular second molar and for the level of depth and degree of angulation of adjacent impacted mandibular third molar. Results: One hundred forty-eight panoramic radiographs of 214 pre-surgically extracted impacted mandibular third molars were reviewed. Eighty-four (56.8%) of the cases were for males and sixty-four (43.2%) were for females. ChiSquare Test showed significant relationship between age group, impaction angulation, impaction depth and incidence of mandibular second molar distal caries. It also showed highly significant relationship between angulation and depth of impaction. Conclusion: Horizontally impacted mandibular third molars close to the level of occlusion increases the chance of distal caries incidence in adjacent mandibular second molars. Close monitoring for such cases would be a suitable option. Further prospective studies should be conducted to study the influence of other factors on distal caries incidence.