The Radix Entomolaris : Non-surgical Approach in Endodontics

Anatomical variations, Non-surgical endodontic treatment, Mandibular molar, Radix entomolaris. Abstract : Mandibular molars often have an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). If present, an awareness and understanding of this unusual root and its root canal morphology can contribute to the successful outcome of root canal treatment. This report discusses endodontic treatment of a mandibular molar with a radix entomolaris, which is a rare macrostructure. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris are described. Avoiding procedural errors during endodontic therapy demand an adapted clinical approach to diagnosis and successful non-surgical endodontic treatment.


Introduction:
The prevention or healing of endodontic pathology depends on a thorough chemo mechanical preparation of the root canals before a dense three-dimentional obturation of the canals.An awareness and understanding of the presence of unusual root canal morphology can thus contribute to the successful outcome of root canal treatment.
It is known that the mandibular first molar can display several anatomical variations.The majority of first molars are two-rooted with two mesial and one distal canal. 1,2In most cases the mesial root has two root canals, ending in two distinct apical foramina.Or, sometimes, these merge together at the root tip to end in one foramen.The distal root typically has one kidney-shaped root canal, although if the orifice is particularly narrow and round, a second distal canal may be present. 3A number of anatomical variations have been described in the mandibular first molar reported the presence of three mesial canals [4][5][6] and the presence of three distal canals. 7ike the number of root canals, the number of roots may also vary.An additional third root, may found either lingually or buccally of the main distal root.When it lies lingually is called the radix entomolaris(RE). 8,9An additional root at the mesiobuccal side is called the radix paramolaris.The identification and external morphology of these root complexes, containing a lingual or buccal supernumerary root, often create problem in non-surgical management resulting an uncertain treatment outcome. 10,11 though both macrostructures are rare in our population, knowledge of their occurrence and location are important.In this report such a case is presented.The prevalence, external morphological variations and internal anatomy of the radix entomolaris are described.The clinical approach to diagnosis and endodontic treatment are also discussed and illustrated.

Case Report
A 24-year-old -male was referred for endodontic treatment of the mandibular right first molar before the replacement of a large amalgam restoration with a ceramic crown.The tooth was free of symptoms and but radiographical examination revealed a signs of chronic apical periodontitis.The pulp chamber was opened, and one distal and two mesial canal orifices were located using an endodontic explorer.The root canals were explored with a K-file ISO 15 (Dentsply Maillefer, Ballaigues, Switzerland) and radiographical length measurement was performed with no.20 reamers {Fig.2(b)}.Upon visual inspection a dark line was observed between the distal canal orifice and the distolingual corner of the pulp chamber floor and the distal canal orifice was also not at the middle but a little bit buccal side of the chamber.At this corner overlying dentin was removed with a diamond bur with a noncutting tip (MANI,INC.Tochigi,Japan) and a second distal canal orifice was detected .The root canals were shaped with ProTaper hand instruments (Dentsply Maillefer ,Ballaigues, Switzerland).During preparation, Glyde (Densply Maillefer ,Ballaigues, Switzerland)) was used as a lubricant and the root canals were disinfected with a sodium hypochlorite solution (2.5%).

Figure 1. Clinical images of extracted mandibular molars with a radix entomolaris or paramolaris. (A) first molar with a radix entomolaris [distolingual view (left), lingual view (right)]. (B) radix entomolaris on a third molar (lingual view). (C) first molar with a separate radix paramolaris (buccal view). (D) first molar with a fused radix paramolaris (buccal view).
Initially, the distolingual root canal was thought to be a second canal in one distal root.Radiographically the outlines of the distal root(s) were unclear; however, the unusual location of the orifice far to the disto-lingual indicated a supernumerary root, and the presence of an Radix Entomolaris was confirmed on the postoperative radiograph (Fig. 2d).The root canals were filled with standardized gutta-percha and Zinc-oxide-eugenol sealer by lateral condensation technique.The cavity was sealed with Silver-Tin-Amalgam cement (ANA 2000, Sweden)and the patient was referred to the Prosthodontist for restoration by permanent restoration as full veneer crown.

Discussion
The presence of a separate RE in the first mandibular molar is associated with certain ethnic groups.In African populations a maximum frequency of 3% is found 12 ), while in Eurasian and Indian populations the frequency is less than 5%. 13In populations with Mongoloid traits (such as the Chinese, Eskimo and American Indians) reports have noted that the RE occurs with a frequency that ranges from 5% to more than 30% . 14 -20Because of its high frequency in these populations, the RE is considered to be a normal morphological variant (eumorphic root morphology).In Caucasians the RE is not very common and, with a maximum frequency of 3.4 to 4.2% 21,22 , is considered to be an unusual or dysmorphic root morphology.
In average, frequency of additional root is about 10.1%, where an extra distal root is on ligual aspect. 23The etiology behind the formation of the RE is still unclear.In dysmorphic, supernumerary roots, its formation could be related to external factors during odontogenesis, or to penetrance of an atavistic gene or polygenetic system (atavism is the reappearance of a trait after several generations of absence. 19,24 A RE can be found on the first, second and third mandibular molar, occurring least frequently on the second molar . 25Some studies report a bilateral occurrence of the RE from 50 to 67% . 18,26The RE is located disto-lingually, with its coronal third completely or partially fixed to the distal root.The dimensions of the RE can vary from a short conical extension to a 'mature' root with normal length and root canal. In most cases the pulpal extension is radiographically visible.However, to avoid perforation or stripping in the coronal third of a severe curved root, care should be taken not to remove an excessive amount of dentin on the lingual side of the cavity and orifice of the RE.The use of flexible nickel-titanium rotary files allows a more centered preparation without unexpected complications as instrument separation.Therefore, after relocation and enlargement of the orifice of the RE, initial root canal exploration with small files (size 10 or less) together with radiographical root canal length and curvature determination, and the creation of a glide path before preparation, are step-by-step actions that should be taken to avoid procedural errors.

Conclusion
Clinicians should be aware of these unusual root morphologies in the mandibular first molars.The initial diagnosis of a radix entomolaris before root canal treatment is important to facilitate the endodontic procedure, and to avoid 'missed' canals.Preoperative periapical radiographs exposed at two different horizontal angles are required to identify these additional roots.Knowledge of the location of the additional root and its root canal orifice will result in a modified opening cavity with extension to the disto-lingual.The morphological variations of the RE in terms of root inclination and root canal curvature demand a careful and adapted clinical approach to avoid or overcome procedural errors during endodontic therapy as well as in prevention of post operative complications.

Figure 2 .
Figure 2. (A) Preoperative radiograph (b) Length determination radiograph, where the RE is visualized (Demarked).(c) Postoperative radiograph.(d) Postoperative radiograph after 6 months with the entomolaris(demarked) in the misio-distal side can be distinguished when a radiograph is exposed 30 degrees from the mesial plane.