Several terminologies have been employed in the dental literature to describe the roots and root canal systems of mandibular molars with no consensus being arrived at, thus far. The anatomical relation of roots and their root canals were identified and a naming system was formulated. The proposed nomenclature attempts to make certain essential modifications to the traditional approach to accommodate the naming of various aberrations presented in mandibular molars. A simple, yet extensive nomenclature system has been proposed that appropriately names the internal and external morphology of mandibular molars.
Nomenclature refers to a set of terms used in communication by persons in the same profession that enables them to better understand one another. The comprehension of these terms aids in diagnosing and treating disease and defects of the teeth [
As with any tooth anatomy, mandibular molars have also been reported with numerous variations with regards to their root and root canal morphology. Variations in their root anatomy have ranged from 2 roots, as described earlier, to as many as 4 distinct roots [
Table summarizing the variations of roots and the canal anatomy of mandibular molars, as reported by various authors, with the numerous terms that have been used to name these aberrancies.
Root nomenclature | Root canal nomenclature | Reference |
---|---|---|
M, DB, | MB, ML, DB, | [ |
M, D | MB, ML, | [ |
M, DB, DL | MB, ML, DB, DL, | [ |
M, D | MB, | [ |
M, D | MB, | [ |
M, D | M, D | [ |
[ | ||
[ | ||
MB, ML, D | [ | |
MB, ML, DB, DL | ML, MB, DL, | [ |
M, DB, DL | [ | |
M, D | [ | |
Mesiocentral canal | [ | |
M, D | MB, ML, | [ |
M, DB, DL | MB, ML, | [ |
To date, no nomenclature system has been presented that simultaneously considers the relationship of the root and the root canal anatomy of mandibular molars. Thus, though there appears to be a general agreement with regards to the presence of internal and external morphological aberrations, no consensus has been arrived at for their nomenclature. The aim of this paper is to propose a new nomenclature to allow for a comprehensive anatomical description of the roots and root canals in mandibular molars.
Identification of the principle canals in two rooted mandibular molars.
Most commonly the mandibular molars present with two principle roots, the mesial and the distal. In the principle mesial root, the principle mesiobuccal (MB) or mesiolingual (ML) canal is the canal whose orifice is located most mesially and buccally or mesially and lingually, respectively (Figure When the principle distal root contains a single canal whose orifice is located centrally, it is identified as the principle distal (D) canal (Figure However, when the distal root presents with its most common variation of two canals, both canals would be considered as the principle canals. They would be identified based on their respective anatomical positions and named as the distobuccal (DB) and distolingual (DL) canals (Figure Also, the path of entrance of the canal at the level of the orifice can be used to identify the principle canals (MB, ML, D, DB, or DL), whereby the name of the canal is opposite to its path of entrance into the canal orifice.
An additional canal in two rooted mandibular molars.
When an additional canal is located between the two principle canals of the same root, the prefix “middle”, denoted as “M”, is added to describe its anatomical position between the two principle canals. The name of the additional canal would also include its mesio-distal position within the tooth, that is, “mesial” or “distal”. Thus, the canal would be named as middle mesial (MM) or middle distal (MD) canal (Figures
Multiple additional canals in two rooted mandibular molars.
If two additional canals are contained within the same principle root(s) (i.e., 4 canals in the same root), the additional canals would be named based on their buccolingual position in relation to the nearest principle canal. The term
Diagrammatic representation of the pulpal floor in mandibular molars, illustrating the names of different canal configurations, according to the proposed nomenclature. The principle canals are named in accordance with the traditional approach in (a), as MB—mesiobuccal, ML—mesiolingual, and D—distal, or in (b) as MB—mesiobuccal, ML—mesiolingual, DB—distobuccal, and DL—distolingual. (c) An additional canal located in the distal root between the two principle canals is named as middle distal, MD. (d), Two additional canals located in the distal root are named as linguo-distobuccal (L-DB) and bucco-distolingual (B-DL).
Two-rooted mandibular molars If all canals are located within the two principle roots, no further modification of the nomenclature is required. Thus, when the canals are named without any mention of the roots, it would signify that the canals are located in their respective principle roots. For instance, a two-rooted mandibular molar containing four principle canals would retain their names as MB, ML, DL, and DB (Figure Three-rooted mandibular molars In cases when two roots are located in place of the single principle root of that region, with each such root containing a single canal, the name(s) of the roots and their canals would be as per the anatomically based criteria mentioned above. This root variation is communicated by adding the suffix Thus, a three-rooted mandibular molar with two roots located distally (mesial, distobuccal, and distolingual roots) with four canals, the root, and canal configuration would be denoted as MB, ML, DB Four-rooted mandibular molars In cases when there are three roots in place of the single principle root of that region, with each such root containing a single canal, the canals are named as per their anatomical position as mesiobuccal, middle mesial, and mesiolingual for the mesial or distobuccal, middle distal, and distolingual for the distal. Additionally, to communicate the root variation, the suffix Three- or four-rooted mandibular molars with multiple canals in the additional roots. In cases when any of the additional root(s) contains 2 or more canals, the name of each canal in the additional root would be based on its anatomical position within that root. The prefix bucco- ( However, each of the canals in this additional root would be denoted by the suffix
Diagrammatic representation of various root and canal configurations in mandibular molars named according to the proposed nomenclature. (a) Names of the canals would remain unaltered if the principle roots contain their principle canals; MB—mesiobuccal, ML—mesiolingual, DB—distobuccal, DL—distolingual or distal (D). (b) In mandibular molar with an additional distal root, the names of the canals in the mesial principle root will not be altered when it contains two principle canals. The canals in the two distal roots are named based on their anatomic position, as mentioned previously, and denoted by adding the suffix
For ease of communication, the cited illustrations for description have been purposefully explained with relation to the distal roots and canals. However, the same criteria would also apply when morphological variations are present in the mesial roots and canals. Also, when additional canals and roots are present, they have been described to be in the same buccolingual plane as this is the pattern that mandibular molars most often demonstrate.
In cases when only a single canal is located in the mesial root of a mandibular molar, the canal is named as
In case of a single rooted mandibular molar with a single canal, we propose that it be named as “central” canal, denoted as “Cn” (Figure
In cases of C-shaped canals, the prefix “C” is added to the canal name. The canal name is expanded to include the path of the C-shaped canal. For instance, a C-shaped configuration involving the ML and DB canal, with an independent MB canal, its root and canal configuration would be
When a tooth contains a single canal which is C-shaped, it is termed as C-shaped central canal and denoted as “C-Cn”. The shape, position, and extent of the canal are also included in its name, in the same order. For instance, C-Cn-MB-ML would signify a C-shaped central canal extending from the MB to the ML (Figures
Diagrammatic representation of various root and canal configurations in mandibular molars named according to the proposed nomenclature. (a) A single canal in each principle root is named as mesial (M) and distal (D). (b) A single-rooted mandibular molar with a centrally located single canal is named as central canal, denoted as “Cn”
The proposed formula for naming of a root and root canal of mandibular molars, according to the present nomenclature is XR, where “X” is the anatomical location of the canal and
A name based on an anatomical position provides its most appropriate description. Terms that have over time gained popularity because of their simplicity are often inappropriate and imprecise. Such terms fail to anatomically describe the locations of the canals and have no parallel in scientific terminology. The present nomenclature is based on the use of anatomic terms to name the roots and their canals. This is in line with the traditional approach which employs similar anatomically based terminologies. However, in addition to the traditionally accepted terms, the proposed additional specifications help to precisely name roots and canals, inclusive of rare morphologic variations, based on anatomical considerations. This maintains the simplicity of the terms used and further widens the scope of their application and acceptance. According to Weine [
Reeh [
(a) Diagrammatic illustration of the access cavity of the mandibular first molar showing the locations of the seven canals contained within the principle roots and named using the traditional nomenclature. MB—mesiobuccal, ML—mesiolingual, DB—distobuccal, DL—distolingual, D—distal. (b) Naming of the canals in (a), as per the proposed anatomically based nomenclature, linguo-mesiobuccal (L-MB), bucco-mesiolingual (B-ML), MD—middle distal. (c) Diagrammatic illustration of the access cavity of the mandibular first molar showing the locations of the six canals contained within four roots and named using the traditional nomenclature. (d) Naming of canals, shown in (c), in accordance with the recommended nomenclature which clearly conveys the information of the root and canal morphology of the tooth.
Clinical and radiographic images of anatomic aberrations demonstrating the use of the proposed nomenclature. (a, b) Pulp chamber floor showing an additional distolingual root and canal (DL
The prognosis of an endodontically treated tooth depends mainly on the adequate cleaning and shaping of the various aberrations of the root and canal system. Thus, giving adequate importance to both, the roots and their canal systems, is imperative for long-term success of endodontic treatment. The proposed system enables better communication of the root configuration of the tooth by positively including the information of the additional root(s) in the nomenclature. For instance, a mandibular first molar with four roots (MB, ML, DB, DL) containing six canals were named as MB, ML, DB1, DB2, MD, and DL [
In the proposed nomenclature, no specific mention has been made of the terms radix entomolaris (RE) [
The salient features of the proposed nomenclature are its anatomical basis for location and naming of roots and canals and consideration of the root to canal relationship. It is elaborate to cover various aberrations of the root and root canal anatomy yet is simple, self explanatory, easy to understand and communicate. A certain paradigm shift has been adopted for the proposed nomenclature, but a genuine effort has been made to use the traditional naming system wherever feasible to allow for an accurate anatomical description of roots and their canals. Also, an attempt has been made to include various previously reported root and canal variations in mandibular molars within the purview of the proposed nomenclature [
The proposed naming system is an anatomically based nomenclature which takes into account the root-to-root-canal relationship in mandibular molars.