1. Introduction

The understanding of complex root canal system and the acquaintance of uncommon anatomical variations in teeth is vital and foremost for a successful root canal treatment. In spite of efficient chemo-mechanical preparation and proper obturation of root canal system, failure can result unless the clinician has a better cognition of the intricate root canal system and its frequent variations.

Majority of the maxillary first molars normally has three roots with independent canals. The mesiobuccal root is broad buccolingually and flatter mesiodistally. This root usually contains two canals and is associated with highest degree of anatomical variability. The frequency of MB2 canals in the mesiobuccal root was reported to be 92.85% (based on ex vivo results), 95.63% (based on clinical results), and 95.45% (CBCT results) ^{[1, 2]}. The distobuccal root is generally rounded or ovoid in cross section and usually contains a single canal. Variations of two or more canals do also exist ^{[1, 3, 4, 5, 6]}. The palatal root is more broad mesiodistally than buccolingually and ovoidal in shape but normally contains only a single canal. More rarely the palatal root exhibits anatomical diversification of root canal system with two or more canals ^{[4, 5, 6, 7]}. Among the three roots, the least to show unusual morphology is the palatal root ^{[8, 9, 10]}. Extensive studies and case reports regarding the unusual anatomical variation and configuration of the root canal system in maxillary first molars have been illustrated. These include a single root canal in a single root ^{[11, 12]}, two root canals ^[13], five root canals ^{[14, 15, 16, 17, 18]}, six root canals ^{[19, 20, 21]}, seven root canals ^[22], eight root canals ^[1], C-shaped canals ^{[23, 24]}, fusion of two buccal roots ^[25], fusion of two buccal roots with two palatal roots ^[26], four roots including an additional palatal root [27-33]^[27] and also five roots ^[31]. There are innumerable case reports and clinical studies of maxillary first molar on varied root canal morphology. Since this article is on extra palatal root, (Table 1) encapsulates all the case reports done so far in maxillary first molar with palatal root aberrations. Information pertaining to additional palatal root, total number of canals and root canal system classification are also summarized. A close inspection of this table reveals that the frequency of additional palatal root is quite less.

This article presents a case report of a maxillary first molar having two palatal roots with distinct canals and foramena at the apical level and also illustrates a detailed study of one such extracted tooth with cone-beam computed tomography.

2. Case Report

A 41 year old female patient complained of spontaneous pain in the decayed right maxillary first molar. On clinical examination, the tooth had a deep carious lesion on the distoocclusal surface. Pain on probing was present but the tooth was not tender to percussion. Periodontal probing was within physiological limits. Thermal and EPT vitality test was conducted and a response suggestive of irreversible pulpitis was elicited and endodontic treatment was planned. Assessment of preoperative radiograph revealed radiolucency of distal crown portion involving pulp chamber. Lamina dura remained intact. The information regarding number of roots and types of the root canals was inconclusive suggesting some type of morphological variations. Additional off-angle radiographs delineated an extra root.

Table 1. Summary of previous clinical cases with palatal root aberrations in maxillary first molar

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The tooth was isolated with a rubber dam under local anesthesia. Conventional coronal access was performed and pulp tissue removed. Four separate root canal orifices were found at the corners of a quadrangular shaped chamber floor. After scouting the canals with no. 10 and 15 Kfiles, coronal flaring with Gates glidden drill no.3 and no.2 was done. Working length was estimated with an apex locater (Propex Pixi, Dentsply Maillefer). A radiograph with the estimated working length was taken, this confirmed the real root length and the four independent roots, two buccal and two palatal classified as type I according to Christie et al ^[10].

The canals were instrumented initially with no.15 and no.20 K files followed by chemomechanical preparation with rotary Niti files (Protaper, Dentsply Maillefer, Switerland) in a crown down technique. The working solution was 3% sodium hypochlorite (Novo, dental products), changed with each file. 17% EDTA (Desmear, Anabond Stedman, Pharma) solution was used to remove the smear layer. Final rinse was done with 2% Chlorhexidine (RC-Chlor, Azure). The canals were dried with absorbent points and obturation was performed with gutta-percha and Zinc oxide eugenol sealer. Access cavity was sealed with composite material (ValuX plus, 3M ESPE) and an appropriate definitive coronal restoration was planned. After a 12 month period, the patient was reviewed and was found clinically asymptomatic. An orthopantogram (OPG) was taken as an evaluative radiograph. (Figure 1 A-C).

Figure 1. Right maxillary first molar with four roots. (A) Preoperative radiograph. (B) Master cone radiograph. (C) OPG after one year follow-up to simultaneously check for bilateral presence

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3. Cone Beam Computer Tomography (CBCT)

CBCT imaging was performed on an extracted maxillary molar with 4 roots to study the internal root canal anatomy. This tooth had been extracted from a patient in surgery department due to poor periodontal prognosis. 3D imaging was done with a CBCT scanner (Planmeca Promax 3D Mid, Chennai, India ) at a tube voltage of 90kvp and tube current of 10mA. Axial slices of molar tooth of 200µm thickness were obtained at different levels to exactly evaluate the root canal pattern in the 4 roots. The axial images were transmitted to a commercially available dental program (Planmeca Romexis Software) to reformat into 3-dimensional images in all three planes.

CT scan slices revealed 4 roots and 4 root canals. All the 4 roots- mesiobuccal, distobuccal , mesiopalatal and distopalatal roots presented with a Vertucci type I and Weine type I canal pattern (Figure 2 A-E). The anatomic laws generally act as a guidance for proper access and exact location of canal orifices ^[41]. All anatomic laws are applicable to maxillary molars except Laws of symmetry 1and 2. The Law of symmetry 1 states that the orifices of the canals are equidistant from a line drawn in a mesial-distal direction through the center of the pulp chamber floor. Law of symmetry 2 states that the orifices of the canals lie on a line perpendicular to a line drawn in a mesial-distal direction through the center of the pulp chamber floor. On examining the pulp chamber floor of a maxillary molar with 4 roots having a Christie et al type I root pattern, both the Laws of symmetry 1 and 2 are appropriate and applicable (Figure 2 B).

CBCT reconstructed images are invaluable for assessing the variations in root canal anatomy In fact the datas obtained can be considered as “Gold standard”. If radiographs are considered to be the “eyes” of the dentist according to Walton, then CBCT can be considered as a “true vision” to endodontist.

Figure 2. CBCT images of an extracted maxillary molar with four roots showing axial sections. (A) Root of pulp chamber; (B) Floor of pulp chamber; (C) Tetrafurcation level (D) Middle 1/3^rd; (E) Apical 1/3^rd

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4. Discussion

Extensive literature ^{[9, 45]}, clinical study ^{[2, 8, 30, 41, 46, 47, 48, 49]} and case reports are presented on maxillary first molars (Table 2). Among the root canal anomalies of maxillary molars, the least frequent appears to be that of palatal root. In reviewing root and canal morphology according to Cleghorn et al ^[9] the frequency of a maxillary first molar with two roots or two palatal canals is very low 3.9 and 1% respectively. The presence of double palatal roots in maxillary molar is quite a rare phenomenon most frequently limited to maxillary second molar. Many reports and clinical studies of second maxillary molar with 4 roots are published. Libfeld and Rostein ^[45] in a survey of 1200 maxillary second molars found 0.4% of the sample having this condition. Peikoff et al ^[50] indicated the frequency of variation to be around 1.4 %.

Table 2. List of reviews and anatomical studies on maxillary first and second molars

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Christie et al ^[10] also speculated that maxillary molars with 2 palatal roots may be encountered once every 3 years in a busy endodontic practice. The frequency of 4 rooted anatomy in maxillary 1^st molars is extremely low. Very few case reports of maxillary 1^st molar with 4 roots are discussed (Table 1).

The dentist should posses thorough knowledge and be aware that any tooth in the dental arch can present with unusual anatomical variations. To treat such cases successfully a schematic representation in access management “Access Success Triad” which includes triple ‘A’- Armamentarium, Acquaintance to extra canals and Advanced diagnostic aids is shown in (Figure 3).The ultimate goal of endodontic treatment is to create a conducive environment for effective healing. To achieve this proper access is of prime importance. Successful access management followed by procedure such as cleaning, shaping, filling and final restoration leads to eventual endodontic success.

Figure 3. A schematic representation of a successful access management in teeth with uncommon morphological variztion

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5. Conclusion

A careful exploration of radiographs and if required additional advanced diagnostic tools like CBCT, Micro CT are essential. Awareness regarding possible variations in internal anatomy of teeth is of paramount significance in treating the challenges of pulp space anatomy and eventually leading to success in root canal treatment.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

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