Introduction:The success of root canal therapy depends on the locations of all the canals, thourough debridement and proper sealing. At times the clinicians are challenged with variations in morphology of root canal. This review article attempts to list out all the variations of permanent mandibular first molar published so for in the literature.Materials and Methods:An exhaustive search was undertaken using PUBMED database to identify published literature from 1900 to 2010 relating to the root canal morphology of permanent first molar by using key words. The selected artcles were obtained and reviewed.Results:Total ninty seven articles were selected out of which 50 were original article and forty seven were case reports. The incidence of third canal in mesial root was 0.95% to 15%. The incidence of three rooted mandibular first molar was 3% to 33%. Only ninety cases reported with c-shape canal configuration. Incidence of Taurodintism without congenital disorder was very rare.Conclusion:The root canal treatment requires proper knowlegde of variations in root canal morphology in order to recognise, disinfect and seal all portal of exit. This can be accomplished with proper diagnosis using newer modes, modification in access preparation, use of operating microscope, enhanced methods of disinfecting and sealing of all canals.

INTRODUCTIONThe endodontic therapy consists of elimination of bacterial load in the pulpal canal and filling of the entire root canal system three dimensionally. The gutta-percha with the sealer should provide seal both apically and laterally, thus preventing contamination of the root canal [1,2].Incomplete obturation of the root canal accounts for 58% of endodontic failures [3,4]. The incomplete obturation may be because of incomplete instrumentation or improper obturation technique [5]. The sealers used should fill the discrepancies between the canal wall and the gutta-percha; act as a lubricant and aid in seating the gutta-percha cones. The sealers should also fill the patent accessory and lateral canals, entomb the bacteria present within the dentinal tubule and allow for the repair of the periapical tissue [6,7].Recently, there has been improvement in the formulation of root canal sealers. The traditional zinc oxide eugenol sealers have been replaced with resin-based, silicone based, MTA based and bioceramic based sealers. In particular, bioceramic-based sealers are gaining popularity because of their alkaline pH, chemical stability within the biological environment, lack of shrinkage and are more biocompatible [8,9].Calcium hydroxide based sealers have been introduced to have both antibacterial action and to stimulate a sterile biological closure of apical region [10]. The limitation of these sealers is that on contact with moisture the setting time is decreased which would result in poor adaptation to canal walls [6].MTA fillapex, MTA Obtura, Endo-CPM sealer and ProRoot Endo sealer are the most commonly available MTA based sealers. These sealers are reported to have good biocompatibility and sealing properties equivalent to epoxy-based root canal sealer or the pulp canal sealer. When in contact with simulated body fluids, MTA based sealers release calcium and encourage the deposition of apatite crystals [10,11].EndoREZ (Ultradent Products Inc, South Jordan, UT) is a dualcured radiopaque urethane dimethacrylate based sealer that is used with resin coated gutta-percha. This system does not employ dentin adhesives and relies on penetration of hydrophilic resins into the dentin tubules after removal of smear layer. Recently, the bond strength and apical seal of the endorez sealer was improved using dual cured self-etching primer/adhesives [12]. The Endorez system has been shown to have satisfactory sealing ability and an easy delivery system [13].Endosequence BC sealer and iRootSP root canal sealer are bioceramic based root canal sealers which are available as a premixed white hydraulic cement paste and usually contain calcium silicate and/or calcium phosphate [14].The most common technique for evaluating the sealing ability of the root canal sealer is the dye penetration technique which is based on the linear measurement of the dye penetration between the root filling and the canal wall. The study aimed at evaluating the sealing ability of zinc-oxide eugenol, Sealapex, AH plus, EndoRez, MTA Plus and Endosequ...

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Aim: This study is aimed to evaluate the effect of staining solutions on the color stability of bulk fill and conventional nanohybrid resin composites (RCs) when subjected to various immersion periods. Materials and methods:A total of 120 cylindrical Teflon molds (4 × 4 mm) were obtained and divided into four groups of 30 each. Molds of groups I and II were filled with Tetric N Ceram Bulk Fill (Ivoclar Vivadent, Schaan, Liechtenstein) and Filtek Bulk Fill (3M ESPE, St. Paul, MN, USA). Molds of groups III and IV were filled with Tetric N Ceram (Ivoclar Vivadent) and Filtek Z250 XTE (3M ESPE) incremental fill RC. Photo-activation was performed and specimens were incubated. Spectrophotometer analysis was done according to Commission Internationale d'Eclairage Lab color scale. After taking the baseline measurements, 10 samples from each group were immersed in distilled water (control, subgroup a), tea (subgroup b), and coffee (subgroup c) respectively, for 1, 7, and 30 days. The color values of each specimen were remeasured and color change value (E*ab) was calculated after 1, 7, and 30 days. Data were analyzed by Friedman's test and Mann-Whitney U-test; p < 0.05 is considered to be statistically significant. Results:Group III specimens showed perceptible color changes at 30-day immersion period in coffee and tea. In group I specimens, color changes were perceptible at 7-and 30-day immersion periods in coffee and only 30-day immersion period in tea. Groups II and IV specimens showed perceptible color changes after all immersion periods in coffee and after 30 days in tea. Conclusion:It can be concluded that Tetric N Ceram has less color change than the other nanohybrid RCs investigated when immersed in coffee and tea after various immersion periods.

Aims: This study aimed to evaluate the effect of preheated nanoceramic resin-based composite (RBC) (Ceram-X-Mono) placed in Class I occlusal cavities over a period of 18 months. Settings and Design: This study involves split-mouth design, randomized controlled clinical trial (RCT) Materials and Methods: One operator restored 60 Class I occlusal cavities in 24 patients. Preheating of nanoceramic RBC to 60°C for 10 min was performed before insertion of the material into 30 prepared cavities, whereas 30 restorations in the nonpreheated group were placed according to the manufacturer's instructions. Two observers evaluated the restorations using Federation Dentaire Internationale (FDI) criteria at baseline, 6, 12, and 18 months. Statistical Analysis: Kappa index, Friedman and Wilcoxon matched pair test, and Krushal-Wallis and Mann-Whitney tests were used for statistical analysis. Results: 100% retention rates were seen in both the groups. In nonpreheated group, significant difference was observed for surface staining ( P = 0.0001), color stability ( P = 0.0277), anatomic form ( P = 0.0431), and marginal adaptation ( P = 0.0051), whereas in preheated group, significant increase in surface staining ( P = 0.0051) was recorded. There was a statistically significant difference observed between the preheated and nonpreheated groups at different time periods for the tested clinical parameters. Conclusion: Within the limitations of this RCT of 18 months, preheated nanoceramic RBC restorations showed better clinical performance compared to nonpreheated group.

A BSTRACT Aims and Objectives: The aim of this study was to evaluate the effectiveness of three different caries excavation methods using micro-computed tomography (micro-CT). Materials and Methods: Fifteen freshly extracted human molar teeth with occlusal dentinal caries were selected. The teeth were sectioned longitudinally into two halves and were randomly divided into three groups ( n = 10) depending on the caries removal technique: Group 1: tungsten carbide (TC) bur, Group 2: cerabur (CB), and Group 3: Excavus (EX) tipEX). A preoperative micro-CT scan of all the samples was taken. The caries excavation procedures were carried out followed by postoperative micro-CT scan. The preoperative and postoperative scans of each tooth were analyzed for caries removal effectiveness (CRE), mineral density (MD), and minimal invasiveness potential (MIP) using Avizo 9.4 software (Thermo Fisher Scientific, Germany). Statistical analysis was conducted by applying three-way analysis of variance and independent sample t -test using the Statistical Package for the Social Sciences software, version 20.0 (IBM Corporation, USA). Results: Among the three groups, the TC group had the smallest RC/IC (residual caries/initial caries) ratio, highest mean MD at the cavity floor, and highest MIP. The EX group significantly had the highest RC/IC, lowest mean MD, and lowest MIP. Both the CRE and MIP parameters of CB group were acceptable (RC/IC = 0.08, mean MD = 1.09g/cm 3 , and MIP = 1.09). Conclusion: As compared with the three excavation methods, CBs can be considered as an alternative to TC burs because of its MIP and complete removal of infected carious dentin.

Aim of the Study: The purpose of the study is to evaluate the occlusal relationship of the mesiobuccal cusp of a mandibular first molar with the marginal ridge of maxillary first molar and second premolar and to analyze the effect of the above occlusal relation on different direct and indirect restorations using finite element analysis (FEA). Methodology: Four hundred volunteers studying in a dental college were screened, of which 100 volunteers were selected for studying occlusal relationships based on the inclusion and exclusion criteria. The two most common occlusal relationships were considered for analyzing two direct (amalgam and direct composite restorations) and two indirect restorations (composite and ceramic restorations). Three-dimensional (3D) scanning of the models was performed, and Class II tooth preparations specific for each restorative material were prepared digitally on 3D models. FEA was employed to study von Mises (VM) stress, principal stresses, and cuspal deflection for each restorative material, and failure of the tooth-restoration unit was calculated using the modified Mohr failure criterion. Results: Among all the analyzed materials, cuspal deformation, principal stresses, and VM stresses were high for direct composite restoration and least for ceramic inlay. According to modified Mohr criteria, except for direct composite, all other materials performed better. Conclusion: Silver amalgam and ceramic restorations presented with minimal stress concentration and cuspal deflection, and Type I occlusal relationship presented with higher stress concentration compared to Type II.

Aim:The aim of this study is to evaluate the effectiveness of ultrasonic activation of photosensitizer (PS) drug Foscan in the elimination of endodontic pathogen from root canal system.Materials and Methods:The minimal bactericidal concentration of “Foscan” was determined using disc diffusion and broth dilution method. Forty-eight extracted single-rooted premolars with periapical pathology were used for the study. After access opening, the first microbial sample was taken. The teeth were then randomly divided into four groups: Group 1: Chemomechanical debridement (CMD), Group 2: CMD and passive ultrasonic irrigation (CMD + PUI), Group 3: CMD and antimicrobial photodynamic therapy (aPDT), and Group 4: CMD and aPDT with activation by ultrasonics. After antimicrobial protocols, the second microbiological sample was collected. The samples were analyzed by multiplex polymerase chain reaction for the effectiveness of four antimicrobial protocols on Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, and Treponema denticola.Statistical Analysis Used:Wilcoxon signed-rank test and Mann–Whitney U-test with the significant level P < 0.05, using IBM SPSS statistics 20 version software.Results:Foscan at concentration of 3.125 μg/ml was chosen for antimicrobial analysis. The prevalence of T. denticola, F. nucleatum, P. gingivalis, and P. intermedia was 79.17%, 70.84%, 70.83%, and 58.33%, respectively. Group 4 showed highest bacterial reduction of 99.51%, followed by Group 1 which showed bacterial reduction of 97.35%.Conclusions:Foscan can be used as an effective PS dye at low concentration with minimal tendency for tooth discoloration. Ultrasonic activation of PS dye facilitated better diffusion into dentinal tubules and biofilm obtaining greater bacterial reduction.