Radix Mesiolingualis and Radix Distolingualis – A Rare Tooth Radicular Morphological Trait

Human dentition in modern man consists of crown and root structure which has been undergone evolution these years. Normally, in the maxillary teeth with respect to molars three roots are seen such as a mesiobuccal, mesiolingual and a palatal root. When extra roots are seen along with these normal roots, then they are referred as a ‘supernumerary root’. Therefore, the aim of this research paper is to briefly enlighten about an occurrence of a rare ‘root morphological structure’ or ‘trait’ occurring in human maxillary molar teeth.

Keywords: Dental Anthropology; Maxillary palatal root; Radix mesiolingualis; Radix distolingualis; Supernumerary root.

Variations in root numbers have been studied in human dentitions and published in the dental literature [1-7]. Human permanent maxillary molars normally consist of a single palatal root. Rarely an additional, extra root is encountered along with a normal component and that extra root is called as a supernumerary root. This rare palatal radicular structure is termed as ‘Radix mesiolingualis’ (RML) and ‘Radix distolingualis’ (RDL) [8]. When the additional root is placed mesiolingual to the main palatal root then it is termed as Radix Mesiolingualis and Radix distolingualis refers to that extra root which is seen distolingually to the main palatal root. The occurrence of this macromorphological root variation in permanent maxillary molars is not well studied as there are hardly few prevalence studies undertaken in this context among different population across the globe [8]. A recent non-metric analysis of radix mesiolingualis and radix distolingualis in maxillary molars exhibited that these structures were found very rarely on the first molar and with increased frequency in the second and third molars [9]. Hence, the purpose of this short communication is to shed light on the literature pertaining to a rare human dental root aberration and thereby to alert all academicians, clinicians’ evolutionist and dental anthropologist to perform more research about this evolutionary structure.

The two terms coined by Carlsen and Alexandersen [8] to depict occurrence of an additional palatal root in the permanent maxillary molars based on its location are ‘Radix distolingualis’ and ‘Radix mesiolingualis’. There are very few prevalence studies undertaken and hardly countable number of case reports have been published till date [9-15]. Table 1 represents few anatomical studies carried by various investigators to establish the prevalence of two palatal roots in the maxillary first molars.  There is no well-established hypothesis explained behind the formation of these morphotypes in the endodontic literature. The reason for its development is related to the splitting of the Hertiwig’s epithelial root sheath by exogenic or endogenic factors during the root development which results in formation of two similar roots.  For detection of this extra root, multiple radiographs taken in different angles is required. Recently using advanced imaging technology like cone beam computed tomography (CBCT) imaging, morphometric assessment of additional palatal root has been studied.

Table 1: Anatomical studies undertaken to depict prevalence of additional palatal root in the permanent maxillary first molars [10-15].

Regarding morphology of RDL and RML various authors have proposed a classification system based on degree of divergence and separation level from the main palatal root. Carlsen and Alexandersen [8] examined 145 extracted permanent maxillary molars with two palatal roots. Versiani et al [16] in Brazilian population studied anatomy of 25 extracted maxillary molars with additional palatal root using microcomputed tomography and proposed a new classification system based only on the divergence of roots (Table 2). Therefore, radiographic survey is very important in identifying such anatomic root variations as missing of these additional root structures results in failure of the dental treatment.

Table 2: Versiani et al [16] classification on maxillary molars with two palatal roots based only on the root divergence

Presence of additional root like Radix mesiolingualis and Radix distolingualis in human permanent maxillary molars is not only important for dental professionals but also for anthropologist and evolutionist to acquire more scientific evidence-based information. The added literature helps in formulating new guidelines, protocols, classification, diagnostic and therapeutic parameters about dental root variations.