Detectability of Middle Mesial Canal in Mandibular Molar After Troughing Using Ultrasonics and Magnification: An Ex Vivo Study

Brazilian Dental Journal (2019) 30(3): 227-231 http://dx.doi.org/10.1590/0103-6440201802152 ISSN 0103-6440 Detectability of Middle Mesial Canal in Mandibular Molar After Troughing Using Ultrasonics and Magnification: An Ex Vivo Study Ana Carla Prade1 , Renata Da Trindade Mostardeiro1 , Camilla dos Santos Tibúrcio-Machado2 , Renata Dornelles Morgental1,2 , Carlos Alexandre Souza Bier1,2 The aim of this study was to evaluate the frequency of the identification of middle mesial (MM) canals in extracted permanent first and second mandibular molars before and after executing a troughing technique with high magnification. Sample consisted of 105 mandibular molars. After gaining access to the pulp chamber and cleaning the chamber floor, root canals were detected in three different stages. The initial location was performed under direct viewing without magnification. In the second stage, a dental operating microscope was employed at 12 magnification. If the MM canal was not observed, a standardized troughing technique was executed with the use of an ultrasonic tip between the mesiobuccal and mesiolingual canals under magnification. Statistical differences in the frequency of MM canals before and after troughing were determined using McNemar’s test, with the significance level set at 5%. No significant increase in the identification of the MM canal was found when comparing observations before (9.52%) and after (12.38%) the troughing technique under high magnification. However, viewing under magnification and the execution of troughing significantly increased the location of the MM canal (12.38%) when compared to viewing without magnification (3.81%) (p<0.01). The troughing technique with the aid of a dental operating microscope significantly improved the identification of MM canals compared to viewing without magnification. Troughing is a safe, minimally invasive procedure that benefits the treatment of mandibular molars. Introduction Knowledge regarding the root canal anatomy is one of the most important aspects of achieving successful endodontic treatment (1). However, understanding all the particularities of the root canal system is a real challenge due to the highly complex internal morphology of human teeth (2–4). Mandibular molars usually have three root canals: one distal and two mesial (mesiobuccal [MB] and mesiolingual [ML]) canals (2,3,5). However, this group of teeth exhibits considerable anatomic diversity and can have two canals in the distal root or, less often, three or four canals (6). A third canal in the mesial root, denominated middle-mesial (MM) canal (5,7,8) or mesio-central canal (9), may also be found. Prevalence of MM canals is associated with ethnicity (8) and age (10,11). Moreover, the method employed to identify a third mesial canal exerts an influence on the detection rate, which ranges from 1 to 46% (2,11). Micro computed tomography (micro-CT) is a useful tool to study root canal morphology and it is an accurate and contemporary method of detecting MM canals (8). Unfortunately, micro-CT is not available in the clinical practice yet (12). 1Department of Stomatology, UFSM – Universidade Federal de Santa Maria, Santa Maria, RS, Brazil 2Graduate Program in Dental Science, UFSM – Universidade Federal de Santa Maria, Santa Maria, RS, Brazil Correspondence: Camilla dos Santos Tibúrcio Machado, Rua Floriano Peixoto, 1184, 97015 372 Santa Maria, RS, Brasil. Tel: +55-55-3220-9210. e-mail: Key Words: accessory canal, middle mesial canal, ultrasound. Notwithstanding this limitation of micro-CT, new technologies have increased the chances of locating MM canals in clinical situations. Nosrat et al. (10) found a high frequency of negotiable MM canals (20%) using a dental operating microscope. Troughing is another strategy commonly used to locate accessory canals (13), which consists of minimal dentin removal between MB and ML canals of mandibular molars to provide better viewing of root canal orifices. The dentin removal can be done safely by using either low-speed burs or ultrasonic tips, (11,13,14) avoiding the furcation area and at the expenses of the mesial wall (11). The troughing approach has been demonstrated to lead to a significant improvement in the detection of MM canals (11). Therefore, the aim of this ex vivo study was to assess the identification of MM canals before and after executing a troughing technique under high magnification. Material and Methods Ethical Issues and Sample Selection This study received approval from the human research ethics committee of the Universidade Federal de Santa Braz Dent J 30(3) 2019 Maria (UFSM) (certificate number: 53739815.3.0000.5346). Sample comprised 105 extracted permanent mandibular first and second molars that had not previously undergone any endodontic intervention. Specimens were donated by the Human Permanent Tooth Bank of the university. Patient’s sex and age were unknown. Teeth were submitted to cleaning for the removal of carious tissue and dental calculus, followed by a 30-minute sterilization cycle at 121° C. Roots were then embedded in silicone impression material (Zhermack, Badia Polesine, RO, Italy) up to the cement-enamel junction. A. C. Prade et al. Access to Pulp Chamber, Shaping, And Cleaning of Chamber Floor Access cavity was prepared with a 1015 spherical diamond tip (KG Sorensen, São Paulo, Brazil), followed by an Endo-Z bur (Microdont, São Paulo, Brazil) coupled to a high-speed handpiece (Kavo, São Paulo, Brazil) with constant irrigation. Pulp chamber floor was cleaned with a G6-S ultrasonic tip (Schuster, Rio Grande do Sul, Brazil) at 50% power, using the Soniclaxis BP ultrasound system (Schuster, Rio Grande do Sul, Brazil). The procedure was performed with a minimal flow of distilled water (Asfer, São Paulo, Brazil). Localization of Root Canals Two independent operators performed the localization of root canals after undergoing a training process for the execution of the clinical procedures. Location of MM canals was performed in three different stages. Stage 1 (direct viewing): Root canals of the mesial root were first located using an endodontic explorer (Golgran, São Paulo, Brazil) with direct viewing and no magnification. A size 10 K-file (Kendo, Munich, Germany) was inserted in each canal orifice to confirm the presence of the MM canal. Stage 2 (viewing with microscope prior to troughing): A dental operating microscope (DM 2003 model, OPTO Eletrônica S/A, São Paulo, Brazil) at ×12 magnification was used at this stage in the teeth that did not show the MM canal at stage 1. Stage 3 (viewing with microscope after troughing): If the MM was still not located, a guided troughing technique was performed between the MB and ML canals. The troughing technique was executed as previously described (11,13), with minor adaptations. Dentin removal was achieved using a TRA15 CD ultrasonic tip (Trinks, São Paulo, SP, Brazil) coupled to the ultrasound device with 80% power under irr (...truncated)