Middle mesial canals in mandibular molars: incidence, prevalence, anatomical characterisation and clinical implications

Objective: In recent years attention has been given to the presence of the middle mesial canal (MMC) in mandibular molars. This attention has caused a proliferation of case reports and even some systematic reviews. However, little attention has been paid to the actual presence of a 'separate canal', as opposed to the presence of an anastomosis that is patent or partially calcified that allows the penetration of an instrument. Furthermore, due to the complexity of this anatomical entity, even less has been addressed regarding the thorough management of this challenge and its potential impact on procedural outcomes. The aim of this review was to address the latter issues in an attempt to clarify and provide clinical directives. Materials and methods: Case reports and series published on MMCs were included and relevant data was extracted. They were analysed and interpreted to address the aim of the review. Other pertinent published data regarding true MMCs versus anastomoses were also reviewed. Results: Published case reports and series were majorly on true MMCs. However, evidence showed that the majority of MMCs were anastomoses. The clinical importance of managing anastomoses is emphasised. This paper also identifies areas that require more research and evidence regarding the management of MMCs. Keywords: anatomical irregularities, mandibular molars, middle mesial canals, procedural outcomes