Evaluating external and internal root and canal morphology of first molars in Black South Africans

Abstract

Introduction The aims and objectives of this project were to: 1) to standardise the determination of the orifice location of root canals using micro-CT and the pulp floor, 2) describe main root canal configurations using the Ahmed et al. classification system criteria, 3) describe a novel classification system for complex root canal configurations and 4) describe the root and canal morphology of mandibular and maxillary first molars in Black South Africans. Methods This is a descriptive, retrospective, observational and cross-sectional study evaluating root and canal morphology of 187 first molars. Firstly, orifice location was determined using Avizo software and stable landmarks. Root canal configurations were determined by using the Ahmed et al. classification system criteria (main canals) and the newly developed method (complex configurations). The new classification system consists of four groups (A to D) and three subtypes (1 to 3). Root and canal morphology were evaluated which included a calculation of the number of roots and canals. The relationships between sex and arch sides on root and canal morphology were recorded. Results The newly developed methodology to determine orifice location could accommodate all molars using minor modifications. According to the Ahmed et al. classification, the most common maxillary configuration was 3MXFM MB1DB1P1 (n=33/93, 35.5%) (three separate roots). Configurations in mandibular molars were more diverse and the most common configuration was 2MDFM M1-2 D1 (n=8/84, 9.5%). According to the new classification system, the most common type of configuration in all teeth was Type 3 (A3, B3, C3, and D3). Maxillary molars more often classified as A3 (n=47/101, 46.53%) and D3 more often in the mandible (n=26/86, 30.23%). In maxillary molars, a relationship was found between configuration type and age groups but not between sides or sex. No relationship was noted between sides, sex and age and configuration types in mandibular teeth. Statistical significance level was set at a 5%. All maxillary molars had three roots (separate or fused). Root fusion was found in 7.9% of maxillary molars (n=8/101). Most mandibular molars had two roots and no fusion was noted. A Radix Entomolaris (RE) was found in 2.3% of teeth (n=2/86). Three and four canals were common in maxillary and mandibular molars: 39.6% (n=40/101), 50.49% (n=51/101) and 55.81% (n=48/86), 24.42% (n=21/86), respectively. In maxillary molars, the second mesiobuccal canal was identified in 60.39% (n=61/101), the third mesiobuccal canal in 5.94% (n=6/101) and fourth mesiobuccal in 0.99% (n=1/101) of teeth. In mandibular molars, the middle-mesial and middle distal canals were found in 18.60% (n=16/86) and 3.49% (n=3/86) of molars, respectively. Conclusions The proposed classification system was repeatable and could 1) accommodate all complex configurations, 2) compare root canal configurations between jaws, 3) determine the degree of complexity of the root canal complex with possible clinical implications, 4) indicate which teeth should be considered for referral for specialist care and 5) be useful in future studies. Root canal anatomy of mandibular molars is more complex than previously thought. Treating clinicians should take note for diagnostic and treatment planning purposes for Black South Africans.