Prevalence of retromolar foramen in nineteenth century Spanish population

Among the non-metrical variants of the mandible that have been proven to be a key issue for dental practitioners, the retromolar foramen constitutes one of the most controversial details regarding its prevalence and associated variables. Thus, this study evaluated the prevalence of the retromolar foramen and the variables associated with its presence in a large Spanish collection of human dry mandibles from the nineteenth century. Six hundred Spanish human dry mandibles (1200 sides) belonging to an osteology collection were examined. The presence of teeth, the presence or absence of retromolar foramen, as well as its side, diameter, number, and location were evaluated. Descriptive analysis and analysis of the associations between the variables were performed. The retromolar foramen was observed in 184 mandibles (31%) and was predominantly present unilaterally (60.8%). Most mandibles (54.9%) had a single foramen. The most common location was the retromolar trigone region (84%). On analysis of the association of variables, it was observed a strong association (p < 0.001) between the presence or absence of the foramen and the presence of teeth. Moreover, a significant association was also found between sex vs. presence of teeth (p = 0.033), sex vs. presentation side of the foramen (p = 0.028), sex vs. number of foramina found (p = 0.004), and diameter vs. number of foramina found (p < 0.001). This study reveals that the retromolar foramen showed a high prevalence of 31% in nineteenth century Spaniards and was located primarily in the retromolar trigone, suggesting that dentists should be aware of and consider the relevant findings of this study.