Prevalence of Second Mesiobuccal Canals in Maxillary First Molars Detected Using Cone-beam Computed Tomography, Direct Occlusal Access, and Coronal Plane Grinding.

INTRODUCTION: The purpose of this study was to determine the prevalence of the second mesiobuccal canal (MB2) in 100 maxillary first molars using 3 independent methods and a combination method.

METHODS: One hundred extracted human maxillary first molars were collected. The teeth were mounted in the maxillary first molar extraction sockets of a human cadaver head. A cone-beam computed tomographic (CBCT) scan was taken of each tooth. Two radiology faculty independently evaluated the CBCT volume for the presence of an MB2 canal. Additionally, teeth were accessed. If a canal was not found, a preoperative CBCT scan was viewed followed by a second attempt to locate an MB2 canal. Lastly, the mesiobuccal root was dissected by grinding in a coronal plane.

RESULTS: A review of CBCT volumes found the presence of an MB2 canal 69% of the time. Accessing the tooth led to an MB2 detection of 78%. When a CBCT scan was viewed, this brought the access detection rate up to 87%. Coronal plane root grinding had an MB2 canal detection rate of 92%. Differences between each method were statistically significant.

CONCLUSIONS: The results of this study show that an MB2 canal is present up to 92% of the time. Direct access of teeth found statistically significant more MB2 canals than viewing CBCT volumes alone (P = .032). Therefore, exposing every patient to a preoperative CBCT scan may not be appropriate. However, taking a CBCT scan when an MB2 canal is not found clinically can significantly increase the chances of finding an MB2 canal (P < .001).