The Extra Root Story–Radix Entomolaris: A Case Report

Introduction

Eradication of microorganisms from the root canals and prevention of further reinfection is the basic concept of endodontic therapy. This is accomplished by properly cleaning and moulding the root canals, then filling them three-dimensionally. Obtaining adequate access to the instruments and endodontic irrigants for optimal disinfection is thus essential. To achieve these goals, the clinician must be familiar with root canal anatomy, and its anatomic variations, including additional roots, extra canals, webs, and fins that may complicate the treatment procedure.¹ Several authors have reported anatomic variations regarding the mandibular molars.²

As stated by Barrett, "Of all the phases of anatomic study in the human system, one of the most complex is that of pulp cavity morphology."³ The permanent mandibular first molar is the earliest permanent posterior tooth to erupt into the oral cavity. It is responsible for the development of occlusion and physiologic functions. It is the tooth most commonly in need of endodontic treatment.⁴ Most of the mandibular sectorials are tworooted with one mesial and distal root and one distal canal and two mesial canals. Here, the presence of a third root is the most prevalent type; this supplementary root can be located lingually and identified as a distolingual root. Radix entomolaris (RE) is present in the constant mandibular sectorial. Carabelli originally referred to this additional third root in literature in the year 1844. Usually, this extra root is usually smaller than the mesial and distobuccal roots and can be distinct from or somewhat fused with the other roots. Radix paramolaris (RP) is the terminology for the extra root when it is on the mesiobuccal side.⁵

Etiology

The etiology behind the development of the additional third root in a mandibular molar is not definite. The emergence of an atavistic trait or environmental influences during odontogenesis may be responsible for the development of dysmorphic supernumerary roots or a polygenetic system could be responsible. Racial genetic variables in eumorphic roots affect a gene's most deep expression, which in turn affects the gene's more pronounced phenotypic manifestation.^6,7

Morphology

1.Carlsen and Alexanderson classified radix entomolaris (RE) based on the location of its cervical part into four types:^8,9,10 [Figure 1]

• Type A– Distally located cervical part with two normal distal root components
• Type B– Same as Type A; however, only one normal distal root component
• Type C– Mesially located cervical part Type AC– Between the mesial and distal root components

2.De Moor et al. classified RE based on the curvature in buccolingual orientation into three types:¹¹

• Type I– Refers to a straight root/root canal
• Type II– Refers to an initially curved entrance that continues as a straight root/root canal
• Type III– Refers to an first curve in the coronal third of the root canal, followed by second curve which is buccally oriented initiating from the middle to the apical third.

3. Recently, Wang et al. gave another classification for RE depending on its radiographic appearance.¹²

• Type 1– Presents the most identifiable radiographic image
• Type 2– A large beam angulation is necessary mesially or distally for their identification
• Type 3– Merging of the adjacent distobuccal root makes identification extremely difficult.Carlsen and Alexandersoncategorized RP into two types based on the location of its cervical part:13 [Figure 2]
• Type A– Cervical part of an RP is located on the mesial root complex.
• Type B– Cervical part of an RP resides centrally between the mesial and distal root complexes

Incidence and prevalence

Several anatomical studies have discovered a correlation between specific ethnic groups and the prevalence of RE. A frequency of 3% was reported in the African groups, while the prevalence in Indian and Eurasian populations was less than 5%. RE occurs anywhere between 5% and >30% among populations that exhibit Mongoloid features (such as the Chinese, Eskimo, and American Indians). Due to its widespread in these individuals, it is considered as a distinctive morphological variation. (eumorphic root morphology). The RE is unusual in Caucasians because it only occurs at a high frequency of 3.4%–4.2% (dysmorphic root morphology).^13,14 The second mandibular molar has the lowest incidence of RE, which can develop on the first, second, or third molar. According to reports, the bilateral incidence of RE is between 50% and 67%.¹⁵

Case Presentation

A 44-year–old male who had been experiencing right lower back pain in tooth at the back region for a month visited the conservative dentistry department and endodontics.During a clinical examination, , there was caries on mesio- and disto-occlusal surfaces and the lower left mandibular molar was also tender on percussion. A radiographic evaluation revealed coronal radiolucency approximating the pulp along with widening of the periodontal ligament space. The clinical and radiographic examinationrevealed symptomatic apical periodontitis, and root canal therapy was recommended. The radiograph also revealed an additional distal root which was then confirmed with Cone beam computed tomography (CBCT) [Figure 3].

The extra canal was located by redesigning the access cavity, which was originally triangular into a more trapezoidal shape. As recommended by protocol, the root canal procedure was performed [Figure 4].

Discussion

For the root canal treatment to be effective, the clinician must be well aware of the normal and variable anatomy that can be expected in human dentition. The most current access preparation concepts and technology have made it comparatively simple to identify the atypical canals. The majority of mandibular first molars— roughly 97.8%—have two roots and, of those, 64.4% consist of three canals, one of which is in the distal root and the other two are in the mesial root. Compared to the mesial canals, the single distal canal typically has a bigger, more centrally located, and more oval crosssection. Two distal canals have been documented in 28% of cases when the orifices are small and located either buccally or lingually.¹⁴

A sound understanding of the law of symmetry, the law of orifice location, and proper visualization of the dentinal map and canal bleeding points can be of assistance when it comes to locating additional canals. The use of hand tools such as the, Pathfinder, Microopeners DG 16 probe, and Endodontic Explorer, which rely on the tactile sense acquired is also beneficial.When sodium hypochlorite is set within the pulp chamber, the remnant pulpal tissues in the canal generate effervescence, which aids in the location of the orifices. . Advanced imaging techniques can help find and confirm additional canals in multirooted teeth, particularly molars. These modalities include magnetic resonance imaging (MRI), micro-computed tomography (CT), fiber-optic illumination, orascopy and oral endoscopy, dental operating microscope, surgical loupes, and digital radiography.¹⁶

The radix canal orifice has the potential to be blocked by secondary or calcified dentine.With each access preparation in a calcified root, there is the probability of perforating the tooth.. In this regard, the use of magnification with appropriate illumination and straight-line access, because the majority of the radix root is curved, is critical. Access can now be altered to attain a straight line approach due to the invention of rotary instruments, and access burs like Endo Z and SS white access burs which can create a huge difference in identifying, locating, and cleaning such hidden, additional canals.

Conclusion

Every effort should be made to investigate the presence of extra canal orifices and unusual canal morphologies. This is possible through a thorough understanding of root canal anatomies, a proper interpretation of the radiographs, and a careful inspection of the pulp chamber under suitable magnification. All of this would help in avoiding or overcoming any procedural errors during root canal therapy, thus, reducing the incidence of retreatment.

Conflict of interest

None