The Root and Root Canal Morphology of the Human Mandibular First Premolar: A Literature Review

Abstract

The purpose of this study was to undertake a comprehensive literature review of the root and root canal morphology of the mandibular first premolar. Published studies citing the anatomy and morphology of mandibular premolars report data for over 6,700 teeth. These studies were divided into anatomical studies reporting number of roots, number of canals, and apical morphology. Variations because of sex and ethnic background have also been reported, along with case reports of anomalies. Approximately 98% of the teeth in these studies were single-rooted. The incidence of two roots was 1.8%. Three roots when reported were found in 0.2% of the teeth studied. Four roots were rare and were found in less than 0.1% of the teeth studied. Studies of the internal canal morphology revealed that a single canal was present in 75.8% of the teeth. Two or more canals were found in 24.2% of the teeth studied. A single apical foramen was found in 78.9% of the teeth, whereas 21.1% had two or more apical foramina. The role of genetics and racial variation may result in differences of incidence of root number and canal number in human populations. The dental literature is not unique in studying ethnicity and sex variations. Higher incidences of teeth with additional canals and roots have been reported in Chinese, Australian, and sub-Sahara African populations. Physical anthropology studies seem to show the lowest incidence in Western Eurasian, Japanese and American Arctic populations. The root and root canal morphology of this tooth can be complex and requires careful evaluation prior to root canal therapy.

Micro-CT Evaluation of Root and Canal Morphology of Mandibular First Premolars with Radicular Grooves

“…of the numerous variations in root canal morphology usually associated with the presence of developmental root concavities (9,17,20). In the present study, the incidence of RG in mandibular first premolars (14%) was similar to that reported by Velmurugan and Sandhya (21), but lower in comparison to the Chinese population (24% to 27.8%) (13,18).…”

“…In the present study, the incidence of RG in mandibular first premolars (14%) was similar to that reported by Velmurugan and Sandhya (21), but lower in comparison to the Chinese population (24% to 27.8%) (13,18). This discrepancy has been mostly attributed to racial factors, but also to diversities in sample size, study design, and evaluation method (9). While a common standard has been used for identification of RG, herein, premolar teeth were selected based on the ASUDAS (12), a common standardized tool used in anthropology that allows to set more precisely a threshold between a slight root depression and a typical groove, overcoming the lack of accuracy in sample selection that may have compromised some previous studies.…”

“…Therefore, a thorough knowledge of the morphology of the teeth and an expectation of their likely variations is paramount to minimize endodontic failure caused by incomplete debridement and obturation (1). Previous studies have shown different trends in the shape and number of roots and canals among populations (2)(3)(4)(5)(6), which appear to be genetically determined (7)(8)(9) and are important for tracing the racial origins of populations.…”

“…Overall, RG is widespread in Africans and native Australians and relatively rare in Western Eurasians (9,11,12). The RG is relevant in clinics as its depth may act as a reservoir for dental plaque and calculus, increasing the difficulty for the management of periodontal disease (13)(14)(15).…”

“…In spite of root and canal morphologies of the mandibular first premolar teeth have been described is different ethnic groups (4,(6)(7)(8)(9)11,15,16,18,20,21), literature lacks detailed data on the relationship between RG and root canal morphology in this group of teeth specially in African, Australasian, South East Asian and South American populations. Therefore, the purpose of this study was to evaluate the external and internal morphologies of singlerooted mandibular first premolars with radicular grooves from a Brazilian subpopulation, using micro-CT technology.…”