Cone-beam computed tomography as advanced diagnostic aid in endodontic treatment of molars with multiple canals: Two case reports.

The purpose of these case reports is to emphasize the importance of knowledge regarding the root canal morphology and current diagnostic aids one should have as both of these important factors going to affect the prognosis of the endodontic treatment. These two case reports describe the maxillary and mandibular first molars with multiple canals. After clinical and radiographic diagnosis, additional help of cone-beam computed tomography (CBCT) of mandibular molar has been taken to evaluate the morphology and canal pattern; while maxillary molar was evaluated using CBCT scan to evaluate the canal configuration and obturation. In CBCT evaluation, the mandibular molar was diagnosed with six separated canals with three mesial and three distal canals and with radix paramolaris and radix entomolaris. The maxillary molar had five canals with three mesiobuccal (MB) canals. Both molars were instrumented with conventional hand and rotary file systems and obturated by conventional lateral compaction method. The axial images from CBCT show Vertucci Type VIII canal pattern in both roots of first mandibular molars and in MB root of maxillary first molar Sert and Bayirli Type XVIII canal configuration and no accessory canal in distobuccal and palatal root. With the recent innovations in diagnostic and operating aids, we can come across many variations in the root canal morphology of both mandibular and maxillary teeth, especially multi-rooted one (i.e., molars), and the knowledge of which leads to successful endodontic treatment with an excellent prognosis.

INTRODUCTION

Schilder in 1967 suggested that the main goal of endodontic therapy is to diagnose, prevent, or heal apical periodontitis. For this purpose, cleaning and shaping and thorough disinfection of the root canals that would allow three-dimensional obturation of the root canal system are mandatory.[12] This primary goal of endodontic treatment often got vulnerable because of the complexity of the root canal anatomy and lack of its knowledge and clinical challenges raised because of it.[34] Thus, for any endodontic therapy, one must precede with a thorough knowledge of pulp chamber and root canal configuration and number of canals as the success of the therapy is directly related to the elimination, prevention of microbial contamination, and complete disinfection by the proper endodontic procedure.[5]

The mandibular first molar is the first posterior tooth that erupts in the oral cavity and frequently requires root canal treatment. This tooth has two roots, but occasionally, it has three roots with two or three canals in the mesial root and one, two, or three canals in the distal root.[6] Over the years, there have been numerous reports that described the morphology of teeth including mandibular first molar. The major variant in this group is mandibular molar with five, six, and seven canals.[7] According to Martinez-Berna and Badanellis, who reported a mandibular molar with six canals, three in the mesial root that were independent throughout the root and three canals in distal root with independent orifices in the pulpal floor but join immediately to form two canals.[8] Ghoddusi et al. also reported a mandibular molar with four distal canals.[9] The intracanal communication frequency is higher in mesial root of mandibular molars which make the variant morphology and so the disinfection more difficult to achieve. The middle mesial (MM) canal shows a quite higher incidence of 1%–15% compared to three independent canals in distal root which makes it a rare anatomic configuration with the incidence of 1.3%.[710]

The morphology of the maxillary first molar had been extensively reviewed in the literature, revealing that this tooth may present a great variety of anatomical configurations, mainly in the mesiobuccal (MB) canal.[11] Cohen and Burns described maxillary first molar as “The most treated, but least understood posterior tooth with the highest endodontic failure rate.” It reported that many treatment failures in the maxillary permanent first molar were related to the inability to locate and clean the MB canal.

The significance of advanced diagnostic tools such as dental operating microscope (DOM) and cone-beam computed tomography (CBCT) over the traditional diagnostic tools has been proven by various researchers till now. CBCT assists the practitioner to identify canal morphology, numbers of canals, and relative positioning even in the presence of calcific metamorphosis and dystrophic calcifications. Identification and treatment of lateral canals are supported by viewing their specific location with the use of narrow field of view CBCT before or during endodontic therapy.[12]

The present study reports the successful management of an unusual mandibular first molar with four roots (radix para- and ento-molaris) and six canals with three canals in mesial root and three canals in distal roots and uncommon maxillary first molar with five canals, in which the MB root has three canals, in which CBCT used as a diagnostic aid efficiently to achieve excellent hermetic seal and disinfection as with CBCT, it was possible to judge exact number of canals, location and pattern of canal morphology in both cases.

CASE REPORTS

Case 1

An 18-year-old male patient reported to the Department of Conservative Dentistry and Endodontics, School of Dental Sciences, KIMSDU, Karad, M. H., India, with a chief complaint of pain in the right mandibular region. On history taking, there were episodes of intermittent pain for the past 15 days. The pain was moderate in nature, nonradiating, aggravates on taking sweets and chewing foods, and relieves on having medication. On clinical examination, a deep carious lesion was seen with respect to 46. The exaggerated response was observed during pulp testing with electric pulp tester, and lingering pain was observed with cold pulp test compared to contralateral teeth. Intraoral periapical radiograph (IOPAR) revealed radiolucency involving enamel, dentin, and pulp with no periapical changes in relation to 46. It was diagnosed as acute irreversible pulpitis. Root canal treatment was decided and explained to the patient.

The treament was initiated with local anesthesia i.e Inferior Alveolar Nerve Block on the right side of jaw using 2% Lignocain (Lox 2%, Neon Lab Ltd., Mumbai, Maharashtrfa, India), inferior alveolar nerve block on the right side. The rubber dam was applied, and endodontic treatment was initiated. After gaining the proper access, four canals were located, two in the mesial and two in the distal. It was evident under magnification of DOM (Roslane Meditech, Haryana, India) that the MB and mesiolingual (ML) were placed well apart with an isthmus joining two canals and the same was found on the distal part of the pulp chamber. Hence, the possibility of MM and middle distal canal should be anticipated in the isthmus. On exploration with the DG-16 probe (Hu-Friedy, Chicago, IL, USA), one additional canal was found between MB and ML [Figure 1]. IOPAR revealed one MM joining the MB canal and another joining the ML canal in the middle third. To confirm this, we advised a CBCT of the right mandibular molar. CBCT scan transverse sections (Carestream CS 9300, Carestream Dental LLC, Atlanta, GA, USA) [Figure 2] revealed three canals in the mesial root and three canals in distal root. The remaining transverse sections also revealed Vertucci Type VIII canal configuration in both mesial and distal roots of this right mandibular first molar.[6] Access was refined, and orifices were enlarged using Gates Glidden Drill (Prime Dental Products, Thane, India) [Figure 3a]. The working length was determined with radiographic technique and apex locator (Root ZX mini; J Morita, Tokyo, Japan) and later confirmed using a radiograph. Both the mesial and distal canals were enlarged up to the ISO tip 25.04 taper using Revo-S (Micromega, Brasseler, Germany), followed by an intracanal medication with calcium hydroxide (R C Cal, Prime Dental Products, India) was placed for 1 week. In the 3rd appointment, the master cone was selected [Figure 3c], and obturation was performed using cold lateral compaction technique with AH-plus root canal sealer (Dentsply Maillefer) [Figure 3b and c].

Figure 1

(a) Master cone radiograph, (b) postoperative image showing complete sealing of canals and isthmus

Figure 2

Cone-beam computed tomography scan of a transverse section of the mandible showing the presence of six canals bilaterally in both the right and left first molar

Figure 3

(a) Access opening with orifice enlargement using GG drills, (b) master cone radiograph, (c) postoperative image showing complete sealing of canals and isthmus

Case 2

A 22-year-old male patient came with the chief complaint of the spontaneous pain in his right upper back region of the jaw for 1 week. Clinical and radiographic examination revealed that the pulp was exposed by caries, and the tooth was tender to percussion. A preoperative radiograph revealed mesio-occlusal radiolucency, approaching the pulp space with periodontal ligament space widening in relation to the MB root. From the clinical and radiographic findings, a diagnosis of chronic irreversible pulpitis with chronic apical periodontitis was made, and endodontic treatment was suggested to the patient. Radiographic evaluation of the involved tooth did not indicate any variation in the canal anatomy. The tooth was anesthetized with 1.8 mL (30 mg) 2% lignocaine (Lox 2%, Neon Lab Ltd, Mumbai, Maharashtra, India). An endodontic access cavity was established using number 2 round bur and excess dentin was removed by Endo Z (Dentsply Maillefer) bur. Clinical examination with a DG16 endodontic explorer (HuFriedy, Chicago, IL, USA) revealed two canal openings in the MB root. During examination with a surgical operating microscope, under ×8 magnification, a third canal was located more mesial to the main MB3 canal. To confirm this rare and unusual morphology in contralateral tooth also, dental imaging of the tooth with the help of CBCT (Carestream CS 9300, Carestream Dental LLC, Atlanta, GA, USA) was planned even after the endodontic treatment. Informed consent was obtained from the patient, and a multi-slice scan of the maxilla was performed with a tube voltage of 90 KV and a tube current of 15 mA. All measures were taken to protect the patient from radiation. The cross-sectional images were obtained in axial, transverse, and sagittal planes [Figures 4 and 5]. All images were analyzed with the help of CS three-dimensional (3D) imaging software (Carestream Dental LLC). Axial images were obtained at 180 μm thickness and were studied at cervical, middle, and apical third of the roots to determine the canal morphology [Figure 5]. The images revealed that the right maxillary first molar had three roots and five root canals (three MB, one distobuccal, and one palatal); the same was found to be true for treated left first maxillary molar. Transverse section CBCT scanned images of the MB and distobuccal root confirmed the canal configurations that were seen in the working length radiographs, which is Sert and Bayirli Type XVIII (i.e.,, MB1, MB2, and MB3 originate separately and terminate as one in the apical third of the root.[13] Furthermore, the contralateral tooth appeared to have a same root canal anatomy [Figure 4]. Coronal enlargement was done with a nickel–titanium ProTaper series orifice shaper (Dentsply Maillefer) to improve the straight-line access. The working length was determined with the help of an apex locator (Root ZX Mini; J Morita, Tokyo, Japan) and later confirmed using a radiograph [Figure 1a]. The biomechanical preparation was done using Revo-S (Micromega, Brasseler, Germany) till ISO tip size 25.06 taper and confirmed by master cone IOPAR [Figure 1b], and canals were obturated [Figure 5] using cold lateral compaction technique and AH-plus root canal sealer (Dentsply Maillefer).

Figure 4

Cone-beam computed tomography scan of a transverse section of the maxilla showing the presence of three mesiobuccal canals bilaterally in both the right and left first molars

Figure 5

Cone-beam computed tomography scan of a coronal section of the maxilla at mesiobuccal root showing complete radiopacity in mesiobuccal 1, mesiobuccal 2, and mesiobuccal 3 canals indicating the complete hermetic seal through canal and isthmus

DISCUSSION

Anatomy of the teeth is a very complex system which consists of a number of foramina which open at different locations - lateral, collateral, accessory, etc., and it need not be a simple root canal. Disinfection in such systems is apparently a challenging task. Various factors responsible for such disinfection such as irrigants and intracanal medicament are impossible to maintain without the thorough knowledge of the respective teeth.

In the maxillary molars, anatomic variations are not uncommon, with the number of canals, from 1 to 8. Vertucci identified eight pulp space configurations.[6] Recently, 14 new additional canal types were reported by Sert and Bayirli, highlighting the complexity of the root canal systems.[13]

Studies have described the presence of aberrant canals in the mandibular first molar with three canals in the mesial as well as distal roots. Many authors have agreed on the presence of three foramina in the mesial root; however, only a few reported the presence of three independent canals, which presents itself as a rare anatomical variant.

Knowledge from laboratory studies is essential to provide insight into the complex root canal anatomy.

These factors also emphasize the importance of the use of magnification for exploring canals and modification of the access cavity to ensure proper endodontic treatment. Diagnostic measures such as multiple angled preoperative radiographs, examination of the pulp floor with a sharp explorer, troughing of grooves with ultrasonic tips, visualizing the hemorrhagic points, staining the chamber floor with 1% methylene blue dye, and hypochlorite champagne bubble test are few important aids in locating root orifices. In the present case, examination of the pulpal floor and exploration of hemorrhagic points with the DG16 hinted at the presence of extra orifices and canals. A hemorrhagic point of both MB2 and MB3 was noted at 1 mm interval from MB1 canal palatally. All these canals joined in the apical third region and terminate as single canal. Digital radiovisiograph at 20° angulation revealed the anatomy, unlike the case reported by Kottoor et al.,[14] wherein the MB root showed a Sert and Bayirli Type XV canal configuration.

Buhrley et al. concluded that when the maxillary first molars were considered separately, the frequencies of MB2 and MB3 canal detection under the microscope, dental loupes, and no magnification groups were 71.1%, 62.5%, and 17.2%, respectively.[15] In the present case, it was very difficult to predict the root canal anatomy on the basis of preoperative radiograph alone. Inadvertent search for extra canals could have led to perforations and excessive removal of tooth structure. Success, in this case, was largely dependent on the use of magnification sources such as operating microscopes, which allowed for the identification of the three distinct root canals in the MB root. Hence, clinicians should familiarize themselves with dental microscopy and new imaging technology.

As the radiographic examination is one of the vital constituent in the diagnosing the endodontic problems and also to predict the canal morphology to some extent, we have followed following protocol for radiographic examination of the respective tooth. Images taken in 20° angulation from mesial and distal side reveal the basic information on the tooth's anatomy and variations in root canal system [Figures 1a, b, and 3b]. They provide a clue to the type of canal configuration in spite of its inherent limitations. Treatment was completed in three appointments using the same diagnostic methods only. However, as the newer diagnostic methods such as CBCT scanning greatly facilitate access to the internal root canal morphology, to rule out the presence of other accessory canals in palatal and distal roots like reported by Baratto Filho et al., seven canals in three roots, the decision was taken to go for CBCT scan.[16] Matherne et al. investigated the use of CBCT and concluded that CBCT images always resulted in the identification of a greater number of root canal systems than digital images.[17] Although conventional CT scans produce a high level of detail in the axial plane, it is essential that the radiation dose is kept as low as reasonably achievable.[18]

The transverse view of the treated 26 clearly shows three radiopaque points of three filled MB canals [Figure 4]. Furthermore, the coronal section of MB root shows the thick triangular opacity of obturating material and sealer [Figure 5].

However, in case of a mandibular molar with six canals, the CBCT scan was carried out before the initiation of treatment only, to eliminate the bias caused because of access opening, instrumental errors, etc.

Computer-assisted tomographic imaging or CBCT, a technology borrowed from medicine, previously focused on the need for better surgical guidance during implant placement.[19] The principle of as low as reasonably achievable as related to radiation exposure and the lack of resolution initially limited CBCT use in endodontics.[12] A new area of research emerged, and old paradigms were shifting. These advances solved many of the listed 2D limitations. Specific applications of this technology developed and the endodontic community embraced them. The current narrow field of view CBCT provides a 3D, low-radiation/high-resolution solution to many endodontic diagnostic and treatment problems.[1220]

The fine details from CBCT revealed the presence of six canals in both right and left mandibular first molars and also evidenced a rare combination of the presence of radix paramolaris and entomolaris in, i.e., one extra root in mesial as well as distal aspects of the molar [Image 1]. Transverse slice from CBCT also provides the exact canal configuration of the right mandibular first molar (i.e., 46). Root canal treatment thus planned accordingly and completed in three appointments with finer perfection in every step.

In the present cases, we used CBCT scanning for a better understanding of canal configuration which must have affected the prognosis of the treatment. CBCT transverse section images show Vertucci Type VIII canal pattern (i.e., three canals and exiting as three orifices) in mesial and distal roots of a mandibular first molar. Whereas MB canal of maxillary first molar showed Sert and Bayirli Type XVIII, which is MB1, MB2, and MB3 originate separately and terminate as one in the apical third of the root. Thus, CBCT scanning again proved to be a pivotal tool in successful endodontic treatment and its utmost prognosis.

CONCLUSION

The present case series again proved the importance of knowledge of root canal system and the most common variations one must keep in his/her mind before starting an endodontic treatment whether it is of maxillary or mandibular multi-rooted tooth. With the recent innovations in diagnostic and operating aids, we can confirm many variations in the root canal morphology of both mandibular and maxillary molars. However, one should not give a second thought for whether to use these aids for diagnosing these teeth variations as this ultimately going to affect the final prognosis of the treated tooth.

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Conflicts of interest

There are no conflicts of interest.