A rare finding of a radix entomolaris and radix paramolaris in a lower first mandibular molar requiring endodontic treatment: a case report

Case report

A 14-year-old male attended complaining of persistent severe pain from the LLQ present for 3 days, with increasing severity. The pain was disturbing sleep and required analgesia relieve symptoms.

The patient was medically fit and well, with no regular medications or allergies. The patient reported a diet that was highly cariogenic with low acidogenic potential. Reported oral hygiene methods described included brushing twice daily with a manual toothbrush and adult strength fluoride toothpaste. There was no reported use of other oral hygiene aids.

Clinical examination identified an extensive occlusal cavity associated with the lower left first molar. The remaining enamel exhibited signs of hypoplasia. Sensibility testing elicited an exaggerated response to Endo-Frost (Coltene/Whaldent Inc, OH, USA) with no tenderness to percussion. Radiographic examination identified a coronal radiolucency extending up to the pulp, without involvement of the mesial and distal marginal ridges, and with no clear indication of peri-apical radiolucency, widening of the periodontal ligament (PDL) or loss of lamina dura. The radiographic outline indicated the existence of two supernumerary roots, found mesially and lingually, indicating that the molar had four separate roots. A diagnosis of occlusal caries with symptomatic irreversible pulpitis and normal apical tissues of the lower left first molar was made. After a thorough discussion of potential treatment options for this tooth, informed consent was gained to initiate endodontic treatment.

After anaesthetizing the tooth and rubber dam placement, complete caries removal was carried out, with carious exposure of the mesial pulp horn. The access cavity was refined, modifying the conventional triangular shape to trapezoidal in order to locate the additional disto-lingual canal. Four canals were initially identified (two mesial and two distal), and they were negotiated with size 10 and 15 K files. All canals were coronally flared and irrigated with 2% sodium hypochlorite. Working length was confirmed using an electronic apex locator and radiographs (Figure 1), although a consistent reading nor radiographic image was able to confirm the distolingual canal to be to full working length.

The distal access was widened and troughed to allow further coronal flaring and improve straight line access for improved negotiation past the mid-root isthmus between the distobuccal and distolingual canals. A fifth canal was identified as the ‘mid-distal’ canal which was patent and negotiable. Its working length was confirmed using the electronic apex locator. The canals were shaped using the ProTaper Universal (Dentsply Sirona, Charlotte, NC, USA) file system. Patency was maintained throughout in all canals except the disto-lingual canal, which still had a firm stop short of its estimated working length. A master cone radiograph was taken (Figure 2) using a parallax technique to increase visualization of the RE. This demonstrated GP short of the apex at the point of the 45-degree curve. Manual dynamic irrigation was carried out using small nickel–titanium pre-curved K files in order to negotiate the blockage and curve, which facilitated patency of this canal. The disto-lingual canal was then prepared to the correct working length using a step-back hand filing technique. Penultimate irrigation with ethylenediaminetetra-acetic acid (EDTA) and a final sodium hypochlorite rinse, followed by drying of all canals and obturation were the final stages. Cold lateral condensation was used for obturation of all canals, with corresponding ProTaper F2 gutta perch (GP) master cones in four canals and an ISO size 25 master GP cones with size B finger spreaders and corresponding accessory cones in the disto-lingual canal. All cones were lightly coated with Tubli-Seal (Kerr Dental, CA, USA). Figure 3 shows clinical photographs of the canal orifices.

An immediate post-operative radiograph was taken, and another 9 months post-operatively (Figure 4). There had been no inter-appointment flare ups, and the tooth was asymptomatic with a satisfactory obturation, therefore 2 weeks post completion of root canal treatment the tooth was restored with a composite core and a lithium disilicate onlay (IPS e.max, Ivoclar Vivadent, Liechtenstein).

Discussion

Anticipating the difficulty of an endodontic procedure prior to commencement of treatment is critical to appropriate case planning, consent, and onward referral where appropriate. The wide range of anatomic variants seen with all teeth can present significant clinical challenges to the operator and may result in an unsuccessful outcome if managed incorrectly.

While, in some cases, clinical findings and patient symptoms alone can be an indication that endodontic treatment is required, radiographic examination is a fundamental component of comprehensive assessment. Peri-apical radiographs are the most common modality for this. Peri-apical radiographs present many advantages including a low radiation dosage and, being quick and accessible in most dental practices. Nonetheless, the limitations of a two-dimensional image may further complicate the diagnosis and treatment of accessory roots. To overcome this, the parallax technique can be used taking a supplemental radiograph 20–30 degrees mesial or distal from the conventional angulation, as seen in this case and well documented in others.⁶ While the parallax method is evident on peri-apicals throughout treatment in this case, it may have been useful for two pre-operative radiographs to have been taken from the offset using this technique, to yield additional information. In more recent times, it may be more appropriate to consider a CBCT as a further diagnostic aid to elucidate anatomic form and pathologies.⁷ This would have been valuable in the case above, in order to allow increased visualization of the supplemental root findings and to exclude other, less likely explanations such as superimposition of PDL spaces; however, due to the patient's age and parental wishes it was not undertaken.

While the aetiology of RE and RP is unknown, some speculate links with gene expression or external factors. There are, however, no widely accepted aetiologies for these anatomic variants. Numerous epidemiological surveys suggest associations between the number of roots in first mandibular molars and ethnicity. De Pablo et al found the incidence rate of a third root was 13% and strongly correlated with the ethnic origin in the population studied. Other studies found that in populations with Mongoloid traits (American Indians, Chinese, Eskimo) the frequency of RE ranged from 5% to 30% and is considered a normal anatomic variant among these groups.^8,9,10 In European populations, it is considered to be dysmorphic root morphology as the incidence is much lower, varying from 0.7% to 4.2%.¹¹ Much less is known about the epidemiology of RP due to its rarity across all ethnicities, therefore the incidence rates reported vary from 0% to 2% in mandibular first molars; however, it has been discussed in multiple case reports.^12,13,14

When considering the morphology of supernumerary roots, classifications described in the literature help to categorize the type of RE and RP present; however, detailed knowledge anatomy, rather than just the presence of the root itself can further help to aid instrumentation and treatment. Carlsen and Alexandersen¹⁵ and De Moor et al¹⁶ proposed classifications of root morphology. Carlsen and Alexandersen used a classification system consisting of four types of RE (types A, B, C, and AC), which considers cervical location of the RE. Both type A and type B refer to a distal location of the cervical part of the RE with A having two normal distal root components and B having one. Type C refers to a mesial location of the cervical part, and type AC refers to a central location between the distal and mesial root components. De Moor et al described RE based on its curvature in bucco-lingual orientation, type 1 refers to a straight canal, type 2 refers to an initial curved entrance with straight continuation and type 3 refers to an initial curve in the coronal third and a second curve that continues in the middle and apical third. This case report reflects a type 3; however, this was not confirmed until the master GP radiograph was taken where the apical curve can be seen. The final classification described by Carlsen and Alexandersen applies to the morphology of the RP, consisting of only two types. Type A, this is where the location of the cervical part is on the mesial root complex, and the dimensions may be shorter or equal to the mesial root complex, in this case the latter applied. Type B is described as the location of the cervical part being central, between the mesial and distal root complexes.

There is a significant spectrum of instruments and materials available to be used during endodontic preparation. These can be selected based on the type, shape and access of a canal, and may differ between each canal within a single tooth, as can be seen in this case in which one canal was hand-filed due to the limitations of size for variable taper rotary files to negotiate around the narrow 45-degree apical curvature. File system considerations may include the flexibility of files and their cross section, taper, tip and mechanism (manual or rotary). While taken into consideration, it can be difficult for practitioners to use the most appropriate equipment due to the availability of a broad armamentarium, especially in non-specialist practice. The introduction of nickel–titanium (NiTi) files has facilitated instrumentation of more complicated root canal systems due to the influence of material treatments on super elasticity and shape memory.¹⁷ The Pro-taper system used has a non-cutting guiding tip which, when used in curved canals, reduces the risk of both root end and lateral wall perforation.

Other materials that must be considered are those to provide coronal restoration of the tooth. Without a suitable restoration, the tooth will be prone to unrestorable fracture and coronal leakage leading to endodontic failure.¹⁸ It is well documented within the literature that cuspal-coverage restorations significantly improve long-term clinical outcomes of posterior endodontically treated teeth, and this may take the form of partial or full coverage restorations.¹⁹ In this case, a direct composite core was placed in order to provide intra-coronal strength, supplemented by an overlying indirect lithium disilicate onlay. A significant amount of sound tooth structure remained; however, evidence of hypomineralized enamel necessitated an appropriate preparation to allow predictable adhesive bonding to sound tissue, a partial coverage onlay facilitated an appropriate restorative option, with superior aesthetics and strength, while allowing the preservation of tooth structure.

Conclusion

Clinicians performing endodontic treatment should be aware of the ‘conventional’ anatomy expected in each tooth. However, it is also imperative to appreciate the variations that can occur within these teeth and use a thorough pre-operative assessment to identify any potential abnormalities. In lower first molars, certain ethnicities show a high prevalence of RE, and infrequently RP, these findings influence the clinician's adaptation in multiple stages of the endodontic procedure to facilitate a successful outcome. Consideration of the morphological variations of supernumerary roots will further aid clinicians in reducing procedural errors during treatment. Pre-operative assessment and imaging is arguably the most important stage of the procedure as it allows for appropriate planning. In cases such as the one discussed, we have highlighted the important use of parallax in plain radiographs due to superimposition or use of more advanced methods such as CBCT. The use of advanced equipment such as high magnification loupes with lights and microscopes may further aid in location and treatment of supplemental canals.