Abstract

Thorough understanding of root canal anatomy is a prerequisite for successful endodontic treatment. The failure of root canal treatment of maxillary molars is highly associated with missing the second mesiobuccal (MB2) canals.

Aim: we aim to assess the prevalence and morphology of MB2 canals of first (1^st) and second (2^nd) maxillary molars based on CBCT images. We further compared the treatment rate of MB2 canals to the rate identified from CBCT imaging analysis.

Methodology: Pre-operative CBCT images of 400 maxillary 1^st molars and 264 maxillary 2^nd molars in a cohort of 661 subjects were examined. Parameters studied were:

A. The root morphology.
B. The incidence of MB2 canals.
C. Vertucci classification of the MB root canals.
D. The distance of MB2 orifice to pulpal floor and E. The percentageof MB2 canals being treated.

Result: 99% of maxillary 1^st and 89.77% of 2^nd molars had three separate roots with 2^nd molars showing higher morphological variability. MB2 canals were found in 77% of maxillary 1^st molars and 46.9% of 2^nd molars. In 3-rooted molars, the most common Vertucci classifications for MB canals in 1^st molars were Type II (37.63%) and in 2^nd molars Type I (47.26%). When MB2 orifices were not at the pulpal floor level (~50% of cases), the average distance below the pulp floor was 0.94mm in maxillary 1^st molars and 0.92mm in 2^nd molars. Clinically, the rates of MB2 canals being treated of 1^st and 2^nd molars were 67% and 37.8%, respectively. With MB2 identified in CBCT images, 86.6% were obturated in maxillary 1^st and 80.64% in maxillary 2^nd molars.

Conclusion: Despite the resolution limit, CBCT remains a widely accepted non-destructive tool to study canal morphology and is readily available to many endodontists. When it is beneficial to patients and cost or radiation exposure is not a concern, pre-operative CBCT images should be thoroughly analyzed before treatment to ensure treatment quality and to limit iatrogenic complications.

Keywords: CBCT imaging; MB2 canals; Maxillary molars; Fused roots