CASE REPORT
A 31-year-old male patient was referred to the Department of Conservative Dentistry and Endodontics with the chief complaint of pain in right upper posterior region of mouth in the past two weeks. The pain was spontaneous and aggravated at night and after taking cold or hot liquids, however, it lingered after a few minutes. The patient’s medical history was non-contributory and unremarkable. Clinical examination revealed a carious maxillary right first molar.The preoperative diagnostic radiograph showed deep carious lesion approximating the pulp, the periodontal line and lamina dura showed no change (Figure 1). According to the symptoms and clinical signs the diagnosis of symptomatic irreversible pulpitis was made and endodontic treatment was initiated.
(Figure 1) Preoperative radiogram
Radiographic evaluation of involved tooth did not indicate any variation in the canal anatomy (Figure 1). After administering local anaesthesia followed by the rubber dam isolation an endodontic access cavity was prepared. After exploring the pulp chamber floor using DG-16 endodontic explorer (Hu-Friedy, Chicago, IL) under 2.5x- 420 magnifying loupes (Galilean loupes, Lifecare Medical Equipments Co., Ltd., Zhejiang, China), two canal openings in mesiobuccal and distobuccal roots and one canal in palatal root were detected (Figure 2). Conventional triangular access was modified into trapezoidal shape to improve access to the additional canals (Figure 2). Even though initial visualization revealed additional canals present, further removal of dentinal shelves from the orifice of mesiobuccal and distobuccal canals using ultrasonic micro-endodontic tip (ET 18D tip; Satelec, Acteon, France), made clearly visible MB2 and DB2 canals. Both distobuccal orifices were located very close with thin dentinal isthmus between them. Coronal enlargement was done with a nickel-titanium (NiTi) ProTaper SX rotary file (Maillefer, Dentsply, Ballaigues, Switzerland) to improve the straight-line access. The working length was determined using apex locator (Raypex5; VDW, Munich, Germany) and confirmed radiographicaly (Figure 3). The pulp tissue was extirpated using barbed broaches (Maillefer, Dentsply, Tulsa, OK). Due to the close approximation of distobuccal canals and the superimposition of anatomical structures on the distobuccal root conventional radiography was useless. To confirm this unusual morphology, SCT (Sensation 64, Siemens, Germany) imaging of the tooth was performed. An informed consent was obtained from the patient, and a multislice SCT scan of the maxilla was performed with a tube voltage 120 kV and a tube current of 390 mA. The involved tooth was focused, and the morphology was obtained in transverse, axial, and sagittal sections of 1-mm thickness. Horizontal slices of the molar were studied at different levels (coronal, middle and apical third of the roots) to determine the canal morphology.SCT scan images confirmed the presence of three roots and five root canals, MB1, MB2, DB1, DB2 and palatal. SCT scan slices revealed second mesiobuccal canal extending up to the middle third of the root, while being absent in the apical third, indicating that it joined to the MB1. Two distinct distobuccal canals were seen extending from the coronal third up to the apical third of the root .At the second appointment, the patient was asymptomatic and cleaning and shaping was performed under rubber dam isolation using ProTaper NiTi rotary instruments (Maillefer, Dentsply, Ballaigues, Switzerland) and the crown-down technique. Irrigation was performed using 3% sodium hypochlorite solution (Cmident; Cmident, New Delhi, India) and EDTA (Glyde File Prep; Maillefer, Dentsply, Tulsa, OK). Master gutta-percha cones were selected by placing the cone that corresponded to the size of finishing file (used to the working length) in the root canal and verifying its size radiographically (Figure 4). The canals were dried using absorbent points (ProTaper; Maillefer, Dentsply, Ballaigues, Switzerland).
(Figure 2) Access opening showing five root canal orifices
(Figure 3) Working length radiogram
(Figure 4) Master cone radiogram
Single cone obturation was performed using ProTaper gutta-percha points (Maillefer, Dentsply, Ballaigues, Switzerland) and AH Plus sealer (Maillefer, Dentsply, Konstanz, Germany). The tooth was restored with a posterior composite resin core (P60; 3M Dental Products, St Paul, MN) (Figure 5). The patient remained asymptomatic during follow up and was referred to a specialist for a full-coverage porcelain crown.
(Figure 5 ) Postobturation radiogram
DISCUSSION
Conventional radiography is vital component of the management of endodontic problems. The sum of information gained from the conventional radiographs anddigitally captured PA radiographs is limited by the fact that three-dimensional anatomy of the tooth is shown in two-dimensional image [21]. In the present case, SCT scanning was essential in the diagnosis of this unusual root canal system as well as its successful endodontic management. SCT scanning provides great insight to the internal root canal morphology. Using simultaneous patient translation through thex ray source with continuous rotation of source-detector assembly, SCT scans acquire raw projection data with a spiral-sampling locus in a relatively short period. Without additional scanning time, these data can be viewed as conventional transaxial images such as multiplanar reconstructions or as three-dimensional reconstruction. It is possible to reconstruct overlapping structures at arbitrary intervals using SCT, increasing the possibility to reveal small objects [22]. The only disadvantages of the SCT technique are the exposure to high radiation and the cost. The radiation dose for one section was 0.12 mGy and scan time was 0.2 s. Ten sections per tooth provideda dosage of 1.2 mGy, which is similar to the dose of one panoramic radiograph (1.8 mGy) [23]. Reduction in radiation dose can be achieved by reducing the tube current,using 1.5 mm slice thickness instead of 1.0 mm or using a spiral technique with a pitch factor of more than 1.0. The dosage could be significantly reduced by limiting the area of interest, selecting only the upper or lower jaw and excluding all occlusal scans [24]. Anatomical variations are common in permanent maxillary first molars [25]. Caliskan et al. [10] reported 1.64% of cases to have two distobuccal canals of which 98.40% ended as a single canal at the apex. Cleghorn et al. [11] found that the most common canal system morphology of the distobuccal root of maxillary first molar was a single canal (98.3%). Two canals were found only in 1.7% of cases where a single apical foramen was present 98%. Alavi et al. [12] and Thomas et al. [13] reported the incidence of two canals in distobuccal roots as 1.90% and 4.30%, respectively. Sert and Bayiril [14] reported two or more distobuccal canals in about 9.50% of the teeth studied of which 97% ended into a single apex. Other studies have also reported two canals in the distobuccal root of maxillary first molars [15-19]. It can be concluded thatoverall incidence of two distobuccal canals in the maxillary first molar ranges from 1.64% - 9.5%, which is a rare occurrence. Magnifying loupes and surgical operating microscope are great tools in everyday endodontic practice for detection of unusual canal morphology. However, the clinician should have a good knowledge of possiblevariations. Knowing that the success of endodontic treatment depend on complete debridement and disinfection of all canals, an endodontist should constantly search for “occult” morphology.
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Radiographic evaluation of involved tooth did not indicate any variation in the canal anatomy (Figure 1). After administering local anaesthesia followed by the rubber dam isolation an endodontic access cavity was prepared. After exploring the pulp chamber floor using DG-16 endodontic explorer (Hu-Friedy, Chicago, IL) under 2.5x- 420 magnifying loupes (Galilean loupes, Lifecare Medical Equipments Co., Ltd., Zhejiang, China), two canal openings in mesiobuccal and distobuccal roots and one canal in palatal root were detected (Figure 2). Conventional triangular access was modified into trapezoidal shape to improve access to the additional canals (Figure 2). Even though initial visualization revealed additional canals present, further removal of dentinal shelves from the orifice of mesiobuccal and distobuccal canals using ultrasonic micro-endodontic tip (ET 18D tip; Satelec, Acteon, France), made clearly visible MB2 and DB2 canals. Both distobuccal orifices were located very close with thin dentinal isthmus between them. Coronal enlargement was done with a nickel-titanium (NiTi) ProTaper SX rotary file (Maillefer, Dentsply, Ballaigues, Switzerland) to improve the straight-line access. The working length was determined using apex locator (Raypex5; VDW, Munich, Germany) and confirmed radiographicaly (Figure 3). The pulp tissue was extirpated using barbed broaches (Maillefer, Dentsply, Tulsa, OK). Due to the close approximation of distobuccal canals and the superimposition of anatomical structures on the distobuccal root conventional radiography was useless. To confirm this unusual morphology, SCT (Sensation 64, Siemens, Germany) imaging of the tooth was performed. An informed consent was obtained from the patient, and a multislice SCT scan of the maxilla was performed with a tube voltage 120 kV and a tube current of 390 mA. The involved tooth was focused, and the morphology was obtained in transverse, axial, and sagittal sections of 1-mm thickness. Horizontal slices of the molar were studied at different levels (coronal, middle and apical third of the roots) to determine the canal morphology.SCT scan images confirmed the presence of three roots and five root canals, MB1, MB2, DB1, DB2 and palatal. SCT scan slices revealed second mesiobuccal canal extending up to the middle third of the root, while being absent in the apical third, indicating that it joined to the MB1. Two distinct distobuccal canals were seen extending from the coronal third up to the apical third of the root .At the second appointment, the patient was asymptomatic and cleaning and shaping was performed under rubber dam isolation using ProTaper NiTi rotary instruments (Maillefer, Dentsply, Ballaigues, Switzerland) and the crown-down technique. Irrigation was performed using 3% sodium hypochlorite solution (Cmident; Cmident, New Delhi, India) and EDTA (Glyde File Prep; Maillefer, Dentsply, Tulsa, OK). Master gutta-percha cones were selected by placing the cone that corresponded to the size of finishing file (used to the working length) in the root canal and verifying its size radiographically (Figure 4). The canals were dried using absorbent points (ProTaper; Maillefer, Dentsply, Ballaigues, Switzerland).
(Figure 2) Access opening showing five root canal orifices
(Figure 3) Working length radiogram
(Figure 4) Master cone radiogram
Single cone obturation was performed using ProTaper gutta-percha points (Maillefer, Dentsply, Ballaigues, Switzerland) and AH Plus sealer (Maillefer, Dentsply, Konstanz, Germany). The tooth was restored with a posterior composite resin core (P60; 3M Dental Products, St Paul, MN) (Figure 5). The patient remained asymptomatic during follow up and was referred to a specialist for a full-coverage porcelain crown.
(Figure 5 ) Postobturation radiogram
DISCUSSION
Conventional radiography is vital component of the management of endodontic problems. The sum of information gained from the conventional radiographs anddigitally captured PA radiographs is limited by the fact that three-dimensional anatomy of the tooth is shown in two-dimensional image [21]. In the present case, SCT scanning was essential in the diagnosis of this unusual root canal system as well as its successful endodontic management. SCT scanning provides great insight to the internal root canal morphology. Using simultaneous patient translation through thex ray source with continuous rotation of source-detector assembly, SCT scans acquire raw projection data with a spiral-sampling locus in a relatively short period. Without additional scanning time, these data can be viewed as conventional transaxial images such as multiplanar reconstructions or as three-dimensional reconstruction. It is possible to reconstruct overlapping structures at arbitrary intervals using SCT, increasing the possibility to reveal small objects [22]. The only disadvantages of the SCT technique are the exposure to high radiation and the cost. The radiation dose for one section was 0.12 mGy and scan time was 0.2 s. Ten sections per tooth provideda dosage of 1.2 mGy, which is similar to the dose of one panoramic radiograph (1.8 mGy) [23]. Reduction in radiation dose can be achieved by reducing the tube current,using 1.5 mm slice thickness instead of 1.0 mm or using a spiral technique with a pitch factor of more than 1.0. The dosage could be significantly reduced by limiting the area of interest, selecting only the upper or lower jaw and excluding all occlusal scans [24]. Anatomical variations are common in permanent maxillary first molars [25]. Caliskan et al. [10] reported 1.64% of cases to have two distobuccal canals of which 98.40% ended as a single canal at the apex. Cleghorn et al. [11] found that the most common canal system morphology of the distobuccal root of maxillary first molar was a single canal (98.3%). Two canals were found only in 1.7% of cases where a single apical foramen was present 98%. Alavi et al. [12] and Thomas et al. [13] reported the incidence of two canals in distobuccal roots as 1.90% and 4.30%, respectively. Sert and Bayiril [14] reported two or more distobuccal canals in about 9.50% of the teeth studied of which 97% ended into a single apex. Other studies have also reported two canals in the distobuccal root of maxillary first molars [15-19]. It can be concluded thatoverall incidence of two distobuccal canals in the maxillary first molar ranges from 1.64% - 9.5%, which is a rare occurrence. Magnifying loupes and surgical operating microscope are great tools in everyday endodontic practice for detection of unusual canal morphology. However, the clinician should have a good knowledge of possiblevariations. Knowing that the success of endodontic treatment depend on complete debridement and disinfection of all canals, an endodontist should constantly search for “occult” morphology.
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