Introduction

The prevention or healing of endodontic pathology depends on a thorough chemo-mechanical cleansing and shaping of the root canals before a dense root canal filling with a hermetic seal. An awareness and understanding of the presence of unusual root canal morphology can thus contribute to the successful outcome of root canal treatment.

In a mandibular first molar, an additional third root, mentioned is called the Radix Entomolaris (RE). This supernumerary root is located distolingually in mandibular molars, mainly the first molars. The presence of a separate RE in the first mandibular molar is associated with certain ethnic groups. Mandibular first molar which has three roots has a frequency of <5% in white Caucasian (UK, Dutch, Finnish, German), African (Bantu Bushmen), Eurasian and Indian populations. In those with Mongoloid traits, such as the Chinese, Eskimos, and Native American populations, it occurs with a frequency of five to more than 30%. RE has an occurrence of <5% in the Indian population and such cases are not routinely observed during dental procedures. Knowledge of such anatomic variation of root and root canals is essential during the treatment of patients presenting with morphological diversities in their root canal anatomy. A case report on morphology, clinical approach to diagnosis and management of Radix Entomolaris or Paramolaris has been presented here.

Case Report

A 24-year-old female visited us for endodontic treatment of the mandibular left first molar. On clinical examination, the tooth was deeply carious and was diagnosed with irreversible pulpitis. Preoperative radiograph shows a deep carious lesion with periapical changes, without any extra root (Fig. 1).

After anesthetizing the tooth, access preparation was done with a medium size round bur and four canal orifices, mesio buccal, mesio lingual, disto buccal and disto lingual were located with DG 16 endodontic explorer. Initial negotiation of the root canals was confirmed with 10 no. K-file. The canal lengths were determined with an electronic apex locator. All the canals were cleaned with 5% sodium hypochlorite along with 17% EDTA and shaped and the patient was recalled after 3 days for obturation.

Master cone gauging was done and an X-ray was taken, in which you can see an extra root that was missed during biomechanical preparation (Fig. 2).

Two radiographs exposed at two different horizontal angles (Buccal object rule) are needed to identify this additional root. Moreover, a primary interpretation of radiological marks, such as an unclear view or outline of the distal or mesial root, may indicate the presence of a Radix Entomolaris or Paramolaris.

In this case, extra root and canal were searched and cleaning and shaping were done with repeat master cone X-ray (Fig. 3).

Discussion

The 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 the penetrance of an atavistic gene or polygenetic system (atavism is the reappearance of a trait after several generations of absence).

The RE is located distolingually, 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 pulp extension is radiographically visible. In general, the RE is smaller than the distobuccal.

Clinical Implications

The presence of RE has clinical implications in root canal treatment. Accurate clinical and radiographic diagnosis can avoid failure of root canal treatment because of a missed canal in the distolingual root. The most important basic principle for successful root canal treatment is the principle of “straight-line access”. The ultimate objective is to provide access to the apical foramen. As the orifice of RE is located distolingually, the shape of the access cavity should be modified from classical triangular form to trapezoidal or rectangular form to better locate the orifice of the distolingual root.

The root canal orifices follow the laws of symmetry which help in locating the RE. Canal orifices are equidistant from a line drawn in a mesiodistal direction through the pulpal floor and lie perpendicular to this mesiodistal line across the center. Straight-line access is essential as most radices entomolaris are curved. Care must be taken to avoid excessive removal of dentin or gauging during access cavity preparation, as this may weaken the tooth structure.

A thorough inspection of the pre-operative radiograph and interpretation of particular marks or characteristics, such as an unclear view or outline of the distal root contour or the root canal, can indicate the presence of a “hidden RE”. To reveal the RE, a second radiograph should be taken from a more mesial or distal angle.

Clinical inspection of the tooth crown and analysis of the cervical morphology of the roots through periodontal probing can facilitate the identification of an additional root. Various instruments such as an endodontic explorer, pathfinder, DG 16 probe and micro-opener can be used. The champagne bubble effect produced by remaining pulp tissue in the canal while using sodium hypochlorite in the pulp chamber can also help. An extra cusp (tuberculum paramolare) or more prominent distal occlusal or distolingual lobe, in combination with a cervical prominence or convexity, may indicate an additional root.

An extension of the triangular opening cavity to the distolingual results in a more rectangular or trapezoidal outline form. Visual aids such as a loupe, intraoral camera or dental microscope can be useful. A dark line on the pulp chamber floor can indicate the precise location of the RE canal orifice.

A severe root inclination or canal curvature, particularly in the apical third of the root, can cause shaping aberrations such as straightening of the root canal or a ledge, with root canal transportation and loss of working length. The use of flexible nickel-titanium rotary files allows a more centered preparation shape with restricted enlargement of the coronal third and orifice relocation. 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 creation of a glide path before preparation, are step-by-step actions that should be taken to avoid procedural errors.

Conclusion

Oral healthcare professionals should be aware of this variation in the anatomy of mandibular permanent first molars. The initial diagnosis is of utmost importance to facilitate the endodontic procedure and to avoid treatment failures. Proper interpretation of radiographs taken at different horizontal angulations may help to identify several roots and their morphology. Once diagnosed, the conventional triangular cavity should be modified to a trapezoidal form distolingually to locate the orifice of the additional root.

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