Abstract
OBJECTIVES: The purpose of this paper is to systematically review the various studies and case reports on the morphology and prevalence of middle canals in the mandibular molars. METHODOLOGY: Electronic databases such as MEDLINE, PubMed, EBSCOhost, ScienceDirect and various journals were screened to identify published literature till March 2017 and earlier for articles related to middle canals in the human permanent mandibular molars. Obtained articles were categorized as original researches, case reports and review articles. Well-defined review questions were developed using the patient population, intervention, comparison and outcome framework to summarize the objectives: "Does middle canal vary in morphology and anatomic location? What is the prevalence of middle canals in mandibular molars? Does ethnicity affect the prevalence of middle canals in mandibular molars?" Morphology was studied and prevalence rates were determined from the evaluation of data extracted from the articles. RESULTS: The search strategy resulted in 87 articles, of which 36 were original research papers and 51 were case reports. The prevalence of middle canals in the various populations ranged from 0.26% to 53.8%. Middle canals were reported in Europeans, Asians, Africans and South and North American populations. The prevalence of middle mesial canal and middle distal canal in various races was reported as up to 53.8% and 10%, respectively. The orifice of middle canal exists below a dentinal projection in the groove between the two main canals. They were observed in fin, confluent and independent configuration. Out of these, confluent configuration was more prevalent. CONCLUSION: Middle canal varies in morphology and anatomic location. Ethnicity affects the prevalence of middle canals in the mandibular molars.