Root and canal morphology of the maxillary first molar: A micro-computed tomography-focused review of literature with illustrative cases. Part 1: External root morphology

Cleaning and shaping of the root canal are profoundly affected by the complexity of root and canal morphology. Undiscovered roots or canals may lead to a reduced prognosis of a treated tooth as hidden causative organisms and their by-products can cause re-infection. Most maxillary first molars have three roots, namely mesio-buccal (MB), disto-buccal (DB) and palatal (P). They can be separate or fused, with incidences varying between populations. Anomalies have also been documented that include single rooted, double-rooted, four and even five-rooted teeth. Additional roots are mostly in the form of additional palatal roots and are known as either a radix mesiolingualis (RML) or radix distolingualis (RDL). This paper is the first of two giving an overview, focused on micro-CT, of available literature on various aspects of the root and canal morphology of the maxillary first permanent molar. The aim of this paper is to provide an overview of relevant aspects of the external root morphology in different populations. The content is supported by illustrative micro-CT images and case reports of rare morphological findings on maxillary first molars.