Prevalence of distal caries in the second mandibular molar among the general population in Mexico and its relationship with the position and angulation of the adjacent third molar

Aims: This study aimed to estimate the prevalence of distal caries in the mandibular second molar (M2M) in a general population and to determine the strength of the association of several factors related to the adjacent mandibular third molar (M3M). Subjects and Methods: This retrospective cross-sectional study assessed digital panoramic radiographs of 753 individuals prescribed for screening and/or diagnostic purposes by different specialists. From these radiographs, 1358 M2Ms/M3Ms were included in the analysis. Age, sex, position, and inclination of the M3Ms with respect to the M2Ms and presence of distal caries in the M2Ms were assessed. Continuous variables were dichotomized using optimal cutoff values using receiver operating characteristic curve analysis. Statistical Analysis Used: A multivariate logistic regression model was performed. Results: In total, 8.2% (95% confidence interval 6.7 to 9.6%) of the M2Ms had distal caries. Multivariate logistic regression analysis showed that >22.5 years of age (odds ratio [OR] 3.42), >4.2 mm between the M2M and M3M (OR 2.67), >31.6° inclination of the M3M (OR 2.12) and the right side (OR 1.61) were positively associated with M2M distal caries. Conclusions: The prevalence of M2M distal caries can range from 6.7% to 9.6% in the general population. M3Ms separated more than 4.2 mm and mesioangulated more than 31.6° with respect to their adjacent M2Ms were 2.7- and 2.1-fold more likely to develop distal caries in their adjacent M2Ms.