Evaluation of Root Canal Morphology of Maxillary Single Root Premolars with Two Canals using Cone Beam Computed Tomography in an Iranian Population

Original Article Evaluation of Root Canal Morphology of Maxillary Single Root Premolars with Two Canals using Cone Beam Computed Tomography in an Iranian Population Neda Naghavi1, Samareh Mortazavi2, Maryam Peighoun3 1 Associate Professor of Endodontic Department, School of Dentistry, Mashhad University of 2 Medical Science Assistant Professor of Oral and Maxillofacial Radiology, School of dentistry, Mashhad University of Medical Science 3 Postgraduate Student of Endodontic Department, School of dentistry, Mashhad University of Medical Science Received 7 July 2021 and Accepted 24 Jannuary2022 Abstract Introduction: There are many anatomical maxillary premolars variants, which differ in different races. The lack of information on such variants adds to the failure of endodontic treatment. This aim of this study is to evaluate anatomy and morphology of such variants using cone-beam computed tomography (CBCT), and to evaluate dentin thickness of the buccal and lingual canals of maxillary single rooted premolars with two canals. Methods: In this in-vitro study fifty single rooted maxillary premolars with two canals were collected from medical centers in Mashhad, Iran. The number of canals was assessed using periapical radiography. CBCT was utilized to scan teeth and were evaluated within the axial section for the position of root canals with respect to outer root surfaces and canal variants based on Vertucci’s classification in apical, intermediate, and coronal sections. Result: The smallest dentin thickness was 0.40 and 0.83 ± 0.25 mm for the apical third in mesial and distal direction, respectively. Also, the largest result was 3.10 mm for the coronal third buccal direction. The largest relative frequency of Vertucci class types was found to be type IV, while the smallest relative frequency was derived to be type III. The results 28 JDMT, Volume 11, Number 1, December 2022 revealed that seventeen cases had isthmus. Conclusion: Because of the thin dentin related to the mesial aspect, it is required to utilize low-taper files. It is not recommended to make use of orifice shapers. Keywords: Anatomy, Cone-Beam Computed Tomography, Bicuspid. ----------------------------------------------------Naghavi N, Mortazavi S, Peighoun M. Evaluation of root canal morphology of maxillary single root premolars with two canals using cone beam computed tomography in an Iranian Population. J Dent Mater Tech. 2022; 11(1): 28-36. Introduction It is important to understand the root canal system anatomy and different morphological variants throughout endodontic treatment (1-3). Hence, clinicians need to completely realize root canal anatomy so that they can have proper treatment methods and standards to improve success rate(4). In endodontic treatment, anatomical root canal variants are very important. Remaining necrotic tissue and microorganisms in a possible missed canal that has not been treated could cause apical pathosis (5-6). Single-Rooted Maxillary Premolars with Two Canals Different classifications have been introduced to describe root canal systems of human permanent teeth, e.g., the classifications of Vertucci 1 and Weine(7). We used Vertucci classification which is one of the most common classifications. The research has shown that premolar teeth root canal treatment could get very complicated due to anatomical variants in number of roots and and root canal configuration type (3,8-11). Maxillary first premolar is considered one of the most difficult endodontic treatments due to various factors. Among them we can find roots and canals count, longitudinal root depressions, different configurations of the pulp cavity, and limited visualization on periapical radiographs (12). Furthermore, studies have shown the significant root canal morphology variations of the maxillary second premolar (1,13-15). Different in-vivo and in-vitro methods have been utilized to investigate root canal anatomy. The in-vivo techniques include clinical evaluation during root canal treatment, retrospective assessment of patient records, conventional radiographic evaluation, and more advanced radiographic techniques such as conebeam computed radiography (CBCT) (16-18), while the in-vitro methods include root canal staining and tooth clearing1,18 , root sectioning6, microscopic examination, conventional radiographic examination, and using threedimensional modalities such as microcomputed tomography (μ-CT) (19-23). CBCT has the same accuracy level as that of root canal staining and root canal clearing methods in root canal morphology detection. Eventhough root canal staining and root canal clearing used to be believed to outperform conventional methods adopted in evaluation of root canal system due to the capability of presenting 3D views and detailed morphologic information (5). Since a small number of studies were conducted on maxillary premolars, particularly those with single root and two canals, the present study primarily aims to assess dentin thickness around root canals Naghavi et al. by means of nondestructive CBCT technology to avoid possible future root canal treatment errors. Materials and Methods Total of fifty single rooted maxillary firt premolars with two canals that were verified radiographically were selected. Teeth that had fracture, root resorption, prosthetic abutment, and open apex were excluded from the study. The samples underwent a day of immersion in 5.25% sodium hypochlorite to remove periodontal tissues on the root surface and then were washed with filtered water (24). Later, superficial massaging skeletons were utilized for removal in order to avoid the thickening of cement and dentin (25). Next, in order to avoid CBCT image scatters, amalgam fillings were removed from teeth that had restorations. For CBCT tooth preparation, teeth were mounted on sponge arch in ten groups. Teeth were all subjected to CBCT evaluation by using a ProMax 3D MAX device manufactured by Finnish Planmeca OY Company with a resolution of 160 µm and a view field of 5 × 8 × 8 cm3. The Planmeca Romexis Software Pack was utilized to analyze the images. Then, a radiologist and an endodontist reviewed images on the sagittal, coronal, and axial planes (26). In each sample, minimum distance between the outer root surface and root canal walls in four directions (buccal, palatal, mesial and lingual) were measured. Also, the relationship of the root canals with each other and with the outer root surface in the apical, middle, and coronal sections of the root within the axial view was evaluated (Figure 1, 2) Root anatomical variants, intercostal canals, isthmus, at-risk dentin thickness, and canal segmentation were reported based on Vertucci’s classification. Fisher's exact test was employed to analyze data in SPSS v.22. Statistical Significance was set at P ≤ 0.05. Table I provides the statistical indexes of the regions and directions. JDMT, Volume 11, Number 1, March 2022 29 Figure1: Isthmus, canal distance (...truncated)