The Association between the Anatomic Landmarks of the Pulp Chamber Floor and the Prevalence of Middle Mesial Canals in Mandibular First Molars: An In Vivo Analysis.

INTRODUCTION: The present study aimed to determine the incidence and anatomic variation of the middle mesial (MM) canal in mandibular permanent first molars using cone-beam computed tomographic imaging and to evaluate the association between the presence of MM canals and anatomic landmarks of the pulp chamber floor in the mesial root.

METHODS: In this in vivo cross-sectional study, 210 CBCT scans of mandibular fist molars from 210 patients were included. CBCT scans were evaluated in 3 sections, and the following data were collected for further analysis: identification of the MM canal, the distance between the mesiobuccal (MB) and mesiolingual (ML) orifices, the presence of any isthmus between the MB and ML orifices, and the MB and ML root canal system (RCS) configurations. Binary logistic regression was performed to assess the effect of pulp floor anatomic characteristics as an independent variable on the outcome variable (the presence of an MM canal).

RESULTS: The overall prevalence of the identification of an MM canal regardless of age was 14.7%. Mandibular first molars with an isthmus between the MB and ML RCS configurations were almost 5 times more likely to show an MM canal (P < .05, odds ratio [OR] = 4.9). The MB-ML intraorifice distance was inversely associated with the presence of an MM canal (P < .05, OR = 0.73). Patients less than 42 years old were 4 times more likely to have an MM canal in their CBCT scans compared with patients older than 42 years old (P < .05, OR = 3.9).

CONCLUSIONS: The suggested anatomic landmarks of the pulp chamber floor could act as a reliable predictive factor for the presence of an MM canal. This knowledge of anatomic clues may serve to better direct endodontists in locating an MM canal, which could prevent excessive removal of tooth structures.