The knowledge of biofilm and its eradication from the root canal system are of utmost importance in the clinical practice of an endodontist. Various treatment strategies and protocols have been demonstrated and discussed by numerous clinicians and researchers, on these models, that play an important role in the treatment outcome. Once a biofilm model is developed by considering various factors, several methods can be used to assess the biofilms formed on these models. This review discusses the importance of biofilm models in endodontics, types of biofilm models and factors associated with developing and the methods to evaluate these models.

Linear system analysis has been dominating medical and dental research, and most of the research achievements in these fields have come from applying a reductionist view of nature. However, biologic systems are fundamentally nonlinear with highly composite dynamics made up of numerous interacting elements and feedback loops, therefore studying them as linear models may not result in an accurate representation of their true features. The authors reviewed and utilized some of the principles of chaos and nonlinearity and extended them to clinical dentistry, from cracked tooth and flare-up after root canal procedures to the outcome of clinical treatments. Utilization of the concepts of chaos and sensitive dependence on initial conditions, and the concepts of self-organization, stigmergy, and fractals may help us to understand some of the puzzles that have not been solved by conventional linear models. The goal of this paper is to present some areas within nonclinical research that we believe will have important roles in the development of future clinical examination methods and therapies.

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.

Context: Postoperative pain control has been a common challenge to clinicians in endodontics. Aims: This double-blind randomized clinical trial assessed the efficacy of clonidine added to lidocaine for postoperative pain following endodontic treatment of mandibular molars with symptomatic irreversible pulpitis (SIP). Methods: One hundred participants with lower molars experiencing SIP were recruited and randomly assigned to two groups. 1.8 mL of 2% lidocaine with either epinephrine (1:80,000) or clonidine (15 μg/mL) was administered to each group via an inferior alveolar nerve block. A Heft–Parker Visual Analog Scale was used to rate preoperative pain and at 6, 12, 24, 36, 48, and 72 h following endodontic treatment. Their postoperative analgesic consumption was recorded. Statistical Analysis Used: The analgesic efficacy was analyzed by Chi-square test, paired t-test, and repeated measures ANOVA (P < 0.05). Results: Early postoperative pain was significantly lower in the lidocaine/clonidine group than the lidocaine/epinephrine group (6 h: P = 0.038; 12 h: P = 0.031). The lidocaine/clonidine group consumed a significantly lower amount of analgesics (P = 0.048). Conclusions: The administration of clonidine added to lidocaine may reduce early postoperative pain and consumption of analgesics following endodontic treatment in lower molars with SIP.

Objectives: The present study aimed in assessing the coronal defects after access cavity finishing and refinement by micro. Methods: Access cavities on thirty molars were prepared using a diamond bur. To finish and refine the access cavity, the Endo-Z was used in group 1 (n=15) and Start X 1 in group 2. Preparation time was recorded. A micro-CT scan was done before and after access preparation. Formation and location of the new defects were registered, the extension of defects calculated and the direction of the extension registered, preparation time and surface roughness determined (P < 0.05). Results: Preparation time was significantly higher with ultrasonics (P <0.001). Internal walls showed smoother surfaces for Endo-Z group. Newly counts and extension length of defects weren't significantly different between groups (P > .05). Conclusion: Ultrasonic tips induced new cracks. Both instruments caused the extension of cracks. Ultrasonic tips requires more time and results in significantly rougher surfaces.

Objectives: This in vitro study evaluated the effect of toothbrush-dentifrice abrasion on the surface roughness of two restorative posterior resin composites, Filtek Z250 and Z350 after simulated toothbrushing twice daily for a period of 3 months. Methods: All the specimens were polished and cleaned and surface topography was evaluated by Veeco di CP-II Atomic Force Microscope (AFM) at six different points; similarly, these specimens were again subjected to evaluation after simulated toothbrushing using dentifrice. The surface roughness evaluation was done for AFM images using software made available and the factor measured were average roughness (Ra) and maximum peak to valley distance R(p v). Data were normally distributed as tested using the Shapiro–Wilk W-test (P > 0.05). Therefore, analysis was performed using the parametric tests, i.e., independent “t”-test (for comparing two groups). The level of statistical significance was set at P < 0.05. Results: The mean change in Ra and the mean change in Rp-v for Z350 were less as compared to Z250, and this difference was statistically significant. Conclusions: Within the limitation of the present study, it can be concluded that toothbrushing increased the roughness in Z250 in comparison to Z350.

Aim: The aim of this study was to evaluate the effect of nonthermal atmospheric plasma (NTAP) on the bond strength of epoxy resin-based and bioceramic root canal sealers. Materials and Methods: Freshly extracted forty (n = 40) single-rooted mandibular premolar teeth were divided into four groups (n = 10) based on the sealer used and NTAP application – Group 1: Epoxy resin-based sealer (AH Plus) without NTAP application, Group 2: Epoxy resin-based sealer (AH Plus) with NTAP application for 30 s, Group 3: Bioceramic sealer (BioRoot RCS) without NTAP application, and Group 4: Bioceramic sealer (BioRoot RCS) with NTAP application for 30 s. After NTAP application in Groups 2 and 4, all the samples were obturated using sealers according to their grouping protocols. Two-millimeter slices were obtained from each sample using hard tissue microtome, which were subjected to push-out bond strength (PBS) under the universal testing machine. Data were subjected to statistical analysis using one-way analysis of variance followed by the Post hoc tukey test. The level of statistical significance was set at P < 0.05. Results: The PBS values were observed to be significantly higher in bioceramic sealer with NTAP application (Group 4) followed by epoxy resin-based sealer with NTAP application (Group 2). Conclusion: NTAP application enhanced the PBS of bioceramic (BioRoot RCS) and epoxy resin-based (AH Plus) sealers compared to their control groups.

Aim: This study was conducted to evaluate the effect of preflaring and file size on the accuracy of the Root ZX and E-PEX Pro electronic apex locators (EALs). Materials and Methods: The actual working length was set 1 mm short of the apical foramen in the forty extracted mandibular premolars. The teeth were embedded in an alginate mold, and two examiners performed the electronic measurements using #10, #15, and #20 K-files. The files were inserted into the root canals until the “0.0” or “APEX” signals were observed on the light-emitting diode or display screens for the E-PEX Pro and Root ZX, respectively, retracting to the 1.0 mark. The measurements were repeated after the preflaring using the S1 and SX Pro-Taper instruments. The mean differences between the actual length and electronic length values were analyzed by the Wilcoxon signed-ranked test with a significance level of P < 0.05. The factors evaluated were “Accuracy of EALs,” “size of file,” and “presence of preflaring. Results: No significant differences were observed in the accuracy of both EALs when compared with the actual lengths. On the size of the file, significant difference noticed with #20 K-file. The preflaring procedure significantly (P < 0.05) increased the accuracy of the measurements for the Root ZX and Epex Pro. Conclusions: The tested EALs showed acceptable accuracy, whereas the preflaring procedure revealed a more significant effect than the used file size.

Context (Background): The color stability of an esthetic material like composite resin may be hampered, due to the constant presence of oral microflora, saliva, and the frequent intake of food. However, as the oral cavity has a dynamic environment, the color stability of these restorative materials has been a challenge to dentistry. Aim: The aim of this study was to evaluate the effect of a saliva substitute (SS) on the color stability of three different nanocomposite restorative materials. Materials and Methods: A total of 66 disc-shaped samples of test materials were prepared using a polycarbonate mold measuring 15 mm diameter and 2 mm height and were randomly assigned to three groups of 22 samples each based on the test material used: Group I – Estelite Sigma Quick, Group II – Solare sculpt, and Group III – Beautifil II LS. They were further divided into two subgroups A and B with 11 samples each based on the immersion solutions, namely distilled water (DW) and saliva substitute (SS), respectively. The samples were immersed for 30 days. Baseline and post immersion color analysis were done with a spectrophotometer. The CIE L*a*b* values were measured and CIE ΔE values obtained were tabulated. Data were analyzed using the two-way-ANOVA test and Tukey's multiple post hoc test. Results: The mean color difference (ΔE) among the three different nanocomposite restorative materials ranged from 4.0 ± 0.26 to 10.62 ± 1.92. Group I showed the lowest color change (7.80 ± 0.55 and 4.00 ± 0.26), followed by Group III (8.59 ± 0.29 and 6.24 ± 0.66) and Group II (10.62 ± 1.92 and 6.85 ± 0.46) when immersed in SS and DW, respectively. Conclusion: All the specimens when immersed in SS showed greater discoloration than compared to the specimens immersed in DW. Group I showed greater resistance to color change compared to other groups.

Objective: This study aimed to evaluate the efficacy of passive ultrasonic irrigation (PUI) and the easy clean instrument by micro-computed tomography (CT) for removing remnant filling materials during endodontic retreatment. Materials and Methods: Forty mesial roots of mandibular molars were divided into four groups (n = 10) according to the agitation system and sealer used: Group 1: PUI/AH Plus; Group 2: PUI/TotalFill; Group 3: Easy Clean/AH Plus; and Group 4: Easy Clean/TotalFill. The groups were compared by micro-CT analysis according to the volumes of the obturation and the remaining material before and after the agitation systems were used. Results: There was no difference between the groups for total filling volume and initial and final remaining filling volume (P > 0.05). Conclusions: Both the PUI and easy-clean instrument are effective for removing remnants of filling material with no difference between the groups.

Aims and Objectives: The purpose of this study is to evaluate the surface topography of gutta-percha (GP) after disinfecting with sodium hypochlorite (NaOCl) (5.25%), silver nanoparticles (AgNPs) (70 μg/ml), and chitosan nanoparticles (ChNPs) (1.5 mg/ml) by atomic force microscopy (AFM). Materials and Methods: Forty GP cones were taken in this in vitro study. These samples were divided into four different groups such as Group I – control group (untreated GP Points) and Group II, III, and IV were treated with 5.25% NaOCl, 70 μg/ml AgNPs, and 1.5 mg/ml ChNPs, respectively. The surface topography analysis of the samples was performed using AFM. Statistical Analysis: Root mean square (RMS) and surface roughness parameters were used to compare the structure of GP points with contact mode imaging. These values were tested by IBM SPSS-20.0 version statistical software using one-way ANOVA and post hoc (Tukey's honestly significant difference) tests. They were considered statistically significant when P < 0.05. Results: The RMS and surface roughness values are significantly higher for NaOCl group (5.25% NaOCl) when compared with AgNPs group (70 μg/ml AgNPs) and ChNPs group (1.5 mg/ml ChNPs). Conclusion: This study has shown more surface topography deterioration of GP treated with NaOCl and lesser deterioration with AgNPs and ChNPs which affects postoperative prognosis.

Aim: The aim is to compare the shaping ability, canal straightening, and the preparation time of five different nickel-titanium rotary files in simulated J-shaped canals. Materials and Methods: Ninety J-shaped canals in resin blocks were filled with 2% Methylene Blue solution and pre-instrumentation images were taken using a Leica microscope at a ×10. They were prepared until size 25 taper 0.04 using (n = 18 per group): T-Flex, HyFlex CM, Vortex Blue, S5, and iRace. After instrumentation, images were captured again, and composite images were made using Adobe Photoshop imaging software. The differences in canal width and canal curvature at each respective landmark were measured and compared. The preparation time and canal abbreviations were also recorded. Statistical analyses were performed using one-way ANOVA and post hoc Tukey HSD tests. The level of statistical significance was set to P = 0.05. Results: HyFlex CM demonstrated the least difference in canal width after instrumentation, but no significant difference (P > 0.05) as compared to T-Flex and Vortex Blue. The mean canal straightening ranged between 0.91° and 7.65°. T-Flex created the least canal straightening after instrumentation which was significantly less (P < 0.05) than S5, but there was no significant difference (P > 0.05) when compared to HyFlex CM. Instrumentation with the S5 file was significantly faster (P < 0.05), whereas HyFlex CM was the slowest. Conclusion: T-Flex, HyFlex CM, and Vortex Blue demonstrated better shaping ability, whilst T-Flex and HyFlex CM maintained the original canal curvatures well. S5 tended to straighten the canals and caused the greatest canal transportation, but it required the least amount of time to shape the canal.

Aim: The aim is to assess and compare the microcrack formation in radicular dentin after obturating the root canals with cold lateral condensation (CLC), warm vertical condensation (WVC), and injectable gutta-percha (IGP) techniques using micro-computed tomography (CT). Materials and Methods: Human extracted mandibular premolar teeth (n = 60) were haphazardly assigned based on the obturation technique into three experimental groups (n = 20 each). Root canals are cleaned and shaped with M Two rotary files and 3% sodium hypochlorite irrigant. Cross-sectional images were taken with Micro-CT to record the baseline defects present on root samples. After root canal obturation either with CLC or WVC or injectable obturation techniques, micro-CT images were captured again to analyze the increase in the number and type of dentinal defects. Statistical analysis of data was performed using the Mann–Whitney U test and the Mcnemar test at 5% significance level. Results: An increase in the number of radicular micro-cracks was identified in samples obturated with lateral condensation technique (1.66%). No change in the percentage of micro-cracks was recorded after obturation with warm vertical or injectable guttapercha (IGP) techniques (P > 0.05). The three obturation techniques were not statistically different in the occurrence of micro-cracks after obturation. Conclusion: The three obturating techniques tested showed no significant increase in radicular dentin defects' occurrence or propagation.

Context: Lower degree of conversion (DC%) of monomer to polymer in a resin composite restoration could be a health hazard for the patient as well as it could affect the longevity of the restoration. Aims: This study is aimed to compare and evaluate the DC% of four different composites polymerized using ultrafast photopolymerization. Settings and Design: In-vitro study. Materials and Methods: A total of 40 disc-shaped composite samples were used in the study. Twenty samples were prepared for each group using 2 mm height and 6 mm diameter Tygon tube as a matrix. All of the composites were cured using the Woodpecker i Led light-curing unit with an intensity of 2300–2500 mW/cm² (TURBO mode). Samples in Group 1 were cured for 1 s and samples in Group 2 were cured for 3 s. Each group had 4 subgroups of five samples of the 4 resin composites tested. After photo-activation, the specimens were stored under dark dry conditions at room temperature for 24 h before testing. The DC% was measured using Fourier-transform infrared spectroscopy. Statistical Analysis Used: The DC% were analyzed using ANOVA, and Tukey HSD post hoc test using IBM SPSS 21 software. Results: Among the experimental groups, Group 2 showed a higher DC% which ranges from 93.7% to 95.4% than Group 1 which ranges from 58.5% to 65.5%. There was a statistically significant difference in the DC% among the materials tested (P < 0.05). Conclusions: Within the limitations of the study, it was concluded that composites cured for 3 s showed a higher DC% which ranges from 93.7% to 95.4% than those cured for 1 s. The DC% also varied among the four different composites tested.

Aim: The aim of this in vitro study was to compare the effects of herbal irrigants with conventional irrigants on microhardness and flexural strength of root dentin. Materials and Methods: Sixty extracted permanent maxillary canines were selected. Decoronated roots were sectioned longitudinally into buccal and lingual segments to get 120 specimens. These were embedded in auto polymerizing acrylic resin and further grounded with fine emery papers under distilled water. Of these, 100 root segments without any defects were selected , further divided into four test groups and a control group according to the irrigants used (n = 20). Group 1: 2.5% Sodium hypochlorite, Group 2: Miswak stick extract, Group 3: Cashew leaves extract. Group 4: Mango leaves extract and Group 5: Normal saline (control). All specimens were treated with 5 ml of each irrigant for 10 minutes and rinsed immediately. Dentin microhardness was measured with a Vickers indenter, and the flexural strength test was done using a universal testing machine. The data were analyzed using one-way ANOVA and the intergroup comparison by student t-test. Results: The experimental groups showed a significant reduction in microhardness values when compared with the control group. Intragroup comparison among experimental groups, herbal irrigants showed the least reduction in microhardness values at cervical, middle, and apical thirds. When compared to the control group, the flexural strength values decreased significantly with experimental groups. Conclusion: Within the limitation of this study, it was concluded that herbal irrigants were least detrimental to root dentin microhardness when compared with conventional irrigant. But the flexural strength was equally reduced by both conventional and herbal irrigants.

Aim: The aim of the study was to evaluate and compare the retreatability of BioRoot RCS and AH Plus sealer with two different retreatment file systems using cone-beam computed tomography (CBCT) for assessing the filling remnants. Materials and Methods: A total of sixty mandibular premolars with single and oval root canals were prepared till size F3 and obturated with GP/AH Plus (Group 1) and GP/BioRoot RCS (Group 2). Canals were then retreated using two different retreatment file systems – ProTaper Universal Retreatment (PTUR) system and NeoEndo Retreatment system. The ability to re-establish working length (WL) and apical patency was recorded, and the percentage volume of residual filling material was evaluated using CBCT at the coronal, middle, and apical thirds. Data from the study were analyzed using one-way analysis of variance with Pearson's Chi-squared analysis and the Kruskal–Wallis test. Results: No statistically significant difference was found in the amount of residual sealer (AH Plus and BioRoot RCS) after retreatment throughout the whole study (P > 0.05) at various root canal levels. Furthermore, the BioRoot RCS group retreated with the PTUR system showed a higher frequency of failure in re-establishing WL and regaining apical patency than the other groups. Conclusion: Complete removal of root canal sealers could not be achieved regardless of the type of sealer used and the retreatment technique employed. Furthermore, in clinical settings, the retreatability of novel BioRoot RCS may be deemed feasible.

Aim: This study aimed to compare the efficiency of continuous and intermittent irrigating methods on the removal of dentin debris from the simulated grooves and to evaluate the dynamics of irrigant using computational fluid dynamics (CFD). Methodology: Seventy-five extracted human permanent maxillary canines were selected. Access cavities were made, working length was determined, and canals were prepared by crown down technique. The teeth were split longitudinally and standard groove 2.0 mm in length was made in split halves and each groove was filled with dentin debris and the images were taken under a microscope (E200). The halves were re-assembled and divided into five groups based on different irrigation methods. Group 1: ultrasonic Irrigation with continuous flow for 3.0 min; Group 2: ultrasonic irrigation with continuous flow for 1.5 min; Group 3: ultrasonic irrigation with intermittent flow for 3.0 min; Group 4: ultrasonic irrigation with the intermittent flow for 1.5 min; and Group 5: syringe irrigation for 1 min. The root halves were again separated and re-evaluated for debris elimination after the irrigation protocol for all the groups separately. The effect of time and method of passive ultrasonic irrigation were compared. For the computational fluid analysis, a GAMBIT 2.2 (Ansys) software was used for mesh construction. FLUENT 6.2 (Ansys) software was used to set the boundary conditions and reconstruction of the canal; flow patterns and turbulence were graphically constructed. Results: The continuous irrigation methods were better at debris removal than intermittent irrigation flow methods. The CFD showed that the turbulence of flow of irrigant was dependent on the inlet velocity and pressure of the irrigant. Conclusion: Debris removal from the simulated grooves was better with continuous irrigation compared with intermittent irrigation. CFD study revealed that the turbulence that was affected by the velocity and pressure of the irrigant introduced and is a variable entity.

Restorative treatment in recent times has seen a paradigm shift due to minimally invasive adhesive dentistry. With advent of material science, bonding mechanisms, and superior isolation techniques, treatments based entirely on adhesion are effectively attainable. The choice between direct and indirect restorative technique, mainly in posterior areas, is still a challenge and involves biomechanical, anatomical, functional, esthetic, and economic considerations. The rationale of this case report is to demonstrate a revised cavity design based on morphological principles in terms of geometry (height of contour and cuspal inclines) and structure (dentinoenamel junction morphology) inspired from conventional preparation techniques.

The present case highlights the endodontic management of a maxillary second molar with three roots and seven canals. Root canal treatment was performed for the maxillary second molar diagnosed with symptomatic irreversible pulpitis. During the procedure under magnification, extra canals were detected in the mesiobuccal root. Cone-beam computed tomography (CBCT) evaluation confirmed four canals in the mesiobuccal root with Vertucci's Type XXI (4-1) pattern. The distobuccal root exhibited two canals with Vertucci's Type III (1-2-1) configuration. The palatal canal was single and large. A 4 year follow-up revealed satisfactory clinical and radiographic findings. Magnification and CBCT allow us to explore possible anatomic variations with insights to tackle such situations clinically.