Human Root Canals Research Articles

Antibacterial Effects of Silica Nanoparticles Loading Nano-silver and Chlorhexidine in Root Canals Infected by Enterococcus faecalis

IntroductionThe persistence of microbial infection can lead to endodontic failure. Enterococcus faecalis (E. faecalis) is acknowledged to be a closely associated bacterium. This study investigated the antimicrobial effects of mesoporous silica nanoparticles (nMS) carrying nano-silver and chlorhexidine (nMS-nAg-Chx) on E. faecalis. MethodsAnalyses were conducted to assess the antimicrobial efficacy of nMS-nAg-Chx toward planktonic E. faecalis, including the zone of inhibition, minimal inhibitory concentration, and growth curves. The measurement of lactic acid, scanning electron microscopy, live-dead bacteria staining, and quantitative real-time PCR were done to further investigate its anti-biofilm effect. Colony forming unit and scanning electron microscopy were used to assess its efficacy in infected root canals. ResultsThe growth of planktonic E. faecalis was suppressed with a minimal inhibitory concentration value of 25 μg/mL (P＜.05). nMS-nAg-Chx concentration-dependently inhibited biofilm formation of E. faecalis with the reduction of lactic acid (P < .05), sparse biofilm structure, reduced percentage of viable bacteria (P < .05), and suppressed expression of ebpR, gelE, ace, and efa genes (P < .05). The 7-day sealing of nMS-nAg-Chx resulted in a notable reduction in bacterial counts compared to the saline control group in the E. faecalis infected root canals (P < .05). ConclusionsnMS-nAg-Chx effectively inhibits E. faecalis and removes its biofilm from infected human root canals. It may be used for endodontic treatments in the control of E. faecalis bacteria as an intracanal medication.

Lipoteichoic Acid from Lacticaseibacillus rhamnosus GG as a Novel Intracanal Medicament Targeting Enterococcus faecalis Biofilm Formation

The demand for safe and effective endodontic medicaments to control Enterococcus faecalis biofilms, a contributor to apical periodontitis, is increasing. Recently, lipoteichoic acid (LTA) of family Lactobacillaceae has been shown to have anti-biofilm effects against various oral pathogens. Preliminary experiments showed that LTA purified from Lacticaseibacillus rhamnosus GG (Lgg.LTA) was the most effective against E. faecalis biofilms among LTAs from three Lactobacillaceae including L. rhamnosus GG, Lacticaseibacillus casei, and Lactobacillus acidophilus. Therefore, in this study, we investigated the potential of Lgg.LTA as an intracanal medicament in human root canals infected with E. faecalis. Twenty eight dentinal cylinders were prepared from extracted human teeth, where two-week-old E. faecalis biofilms were formed followed by intracanal treatment with sterile distilled water (SDW), N-2 methyl pyrrolidone (NMP), calcium hydroxide (CH), or Lgg.LTA. Bacteria and biofilms that formed in the root canals were analyzed by scanning electron microscopy and confocal laser scanning microscopy. The remaining E. faecalis cells in the root canals after intracanal medicament treatment were enumerated by culturing and counting. When applied to intracanal biofilms, Lgg.LTA effectively inhibited E. faecalis biofilm formation as much as CH, while SDW and NMP had little effect. Furthermore, Lgg.LTA reduced both live and dead bacteria within the dentinal tubules, indicating the possibility of minimal re-infection in the root canals. Collectively, intracanal application of Lgg.LTA effectively inhibited E. faecalis biofilm formation, implying that Lgg.LTA can be used as a novel endodontic medicament.

Calcium silicate-based intracanal medication: Physicochemical properties and effectiveness of techniques for removing medication from the human root canal.

Our purpose was to investigate the physicochemical properties of Bio-C Temp, a bioceramic intracanal medication, and whether its residues remain adhered to the dentine walls after conventional manual irrigation (CMI) or passive ultrasonic irrigation (PUI) in comparison to Calen. The pH after 12 hours, 1 day, 3 days, 7 days, 14 days, 21 days and 28 days, and the flow, radiopacity, and the solubility of the medications after immersion for 7 and 30 days in distilled water (dH2O) or phosphate-buffered saline (PBS) solution were evaluated. Filling capacity, and volumetric changes after 14 days were assessed by micro-computed tomography (micro-CT). The residues of medications after CMI or PUI were analysed with scanning electron microscopy. Statistical analysis was performed using ANOVA and Tukey's post-hoc test, Student's t test or the Kruskal-Wallis and Dunn post-hoc test (α = 0.05). Bio-C Temp presented a lower pH, flow, volumetric change, and weight loss after immersion in PBS on the 7th and 14th days (p < 0.05) and greater radiopacity and filling capacity (p < 0.05) than Calen. Both medications showed lower solubility in PBS than in dH2O (p < 0.05). There was no difference in the residue content of the two medications between two irrigation methods in three-thirds of the roots (p > 0.05). Although Bio-C Temp had less volumetric loss and satisfactory filling capacity, this medication provided lower alkalinity than did Calen. Furthermore, neither CMI nor PUI completely removed the medicament residues within the human root canal.

Comparative Evaluation of Cutting Efficiency of Three File Systems-Kedo-SH Manual, Pedoflex Rotary, and Manual K File: An In Vitro Study.

The purpose of this study was to comparatively evaluate the cutting efficiency of Pedoflex rotary, Kedo SH manual file, and manual K file systems used in root canal instrumentation while performing pulp therapy of deciduous teeth with a stereomicroscope. Forty-five extracted primary human root canals were chosen, and following the removal of pulp tissue, the canals were dyed with Indian ink and left to dry for 2 h. The samples were randomly divided into three groups, Group A: Kedo SH manual file system (n = 15), Group B: Pedoflex rotary file system (n = 15), and Group C: Manual K files (n = 15). After root canal instrumentation, all the root canals were cleared to make them transparent. The teeth after clearing were observed under stereomicroscope and scored according to the amount of dye present in the root canals. The data were tabulated and statistically analyzed with SPSS version 16 using Chi-square, Kruskal-Wallis, and Dunn's test (post-hoc). With regards to cutting efficiency, there was a statistically noteworthy difference among groups A and C [P = 0.000] and groups B and C [P = 0.000]. Furthermore, groups A and B did not differ statistically significantly [P = 0.950]. Cutting efficacy of the Pedoflex rotary files was seen to be superior to that of Kedo SH and manual K files. Rotary files in deciduous teeth have various benefits over manual files, resulting in a noticeable reduction in working time, which has aided in maintaining patient participation by reducing the risk for fatigue. We conclude that NiTi rotary devices result in a superior cutting efficiency and, as a result, greater clinical success.

Photodynamic Suppression of Enterococcus Faecalis in Infected Root Canals with Indocyanine Green, TroloxTM and Near-Infrared Light.

Recently, our group showed that additional supplementation of Trolox™ (vitamin E analogue) can significantly enhance the antimicrobial photodynamic effect of the photosensitizer Indocyanine green (ICG). Up to now, the combined effect has not yet been investigated on Enterococcus faecalis in dental root canals. In the present in vitro study, eighty human root canals were inoculated with E. faecalis and subsequently subjected to antimicrobial Photodynamic Therapy (aPDT) using ICG (250, 500, 1000 µg/mL) and near-infrared laser light (NIR, 808 nm, 100 Jcm-2). Trolox™ at concentrations of 6 mM was additionally applied. As a positive control, irrigation with 3% NaOCl was used. After aPDT, root canals were manually enlarged and the collected dentin debris was subjected to microbial culture analysis. Bacterial invasion into the dentinal tubules was verified for a distance of 300 µm. aPDT caused significant suppression of E. faecalis up to a maximum of 2.9 log counts (ICG 250 µg/mL). Additional application of TroloxTM resulted in increased antibacterial activity for aPDT with ICG 500 µg/mL. The efficiency of aPDT was comparable to NaOCl-irrigation inside the dentinal tubules. In conclusion, ICG significantly suppressed E. faecalis. Additional application of TroloxTM showed only minor enhancement. Future studies should also address the effects of TroloxTM on other photodynamic systems.

Efficacy of Smear Layer Removal of Human Teeth Root Canals Using Herbal and Chemical Irrigants: An In Vitro Study.

Objectives Over many years, many intracanal irrigants have removed smear layers during routine root canal therapy. The efficacies of conventional endodontic chemical irrigants are documented, but limited research is available on herbal irrigants' role in the endodontic therapy irrigation protocol. This study aimed to evaluate endodontic irrigants' smear layer removal efficacy, namely, 3% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA), green tea extract, and Triphala extract, using scanning electron microscopy (SEM) analysis. Methods Fifty freshly extracted human permanent maxillary and mandibular single-rooted teeth were collected from the Oral Surgery Department of Regional Dental College (RDC), Guwahati, India. The samples were divided into five groups with 10 teeth each: Group A: sterile distilled water (negative control), Group B: 3% NaOCl, Group C: 17% EDTA, Group D: green tea, and Group E: Triphala (citric acid). Each tooth was then longitudinally splitand prepared for SEM inspection under 1000X magnification. The comparison of smear layer removal scores between the groups was done by the Kruskal-Wallis test and Mann-Whitney test, with the significance level set at p<0.01. Results The comparison of the overall mean smear scores and those at different root portions shows that Group C has the lowest mean score, followed by Group E. The pairwise comparison shows that the difference in the mean smear scores between Group C and the other four groups is statistically significant (p-value<0.05). Moreover, the difference in the overall, coronal, middle, and apical mean smear scores between Group A and Group E was highly significant (p-value<0.001). Conclusions The highest smear layer removal efficacy was observed in the samples treated with 17% EDTA. Moreover, the clearing efficacy of Triphala is significantly better than that of distilled water in smear layer removal.

The Roughening Effects of Er:YAG, Nd:YAG and KTP Laser Systems on Root Dentin Surface

Objectives: Present study aimed to evaluate the roughening ability of different laser systems on the middle and apical third of roots. Materials and Methods: Sixty extracted human single-rooted single canal mandibular premolar teeth were randomly assigned to 3 groups (n=20). Standardized preparation and sterilization procedures were performed. The samples were irradiated with Er:YAG, Nd:YAG, and KTP laser systems. The laser irradiations (1.5 Watt) were applied with a spiral motion, starting 1 mm short of the apex and then moving coronally for 10 sec, interleaved with 15-sec recovery intervals for each irradiation. This process was repeated twelve times. The roots that were standardized in the same length and thicknesses were divided parallel to the longitudinal axis. Then, the middle and apical 1/3 surface roughness values of each root section were measured using a profilometer and SEM analysis was performed. The data obtained were analyzed using the two-way analysis of variance (ANOVA) and Tukey post-hoc tests. Results: According to measurements obtained from middle and apical 1/3 surfaces; Although, the statistically highest roughness value was determined after Nd:YAG laser (P &amp;lt; 0.05), the statistically lowest value was detected following the Er:YAG laser irradiation (P &amp;lt; 0.05). Conclusions: In light of the present study, all laser systems caused significant roughness surface. Therefore, laser systems should be carefully applied in human root canals.

Effect of an enamel matrix derivative (Emdogain) on the microhardness and chemical composition of human root dentin: an in vitro study

The advantage of using an Enamel matrix derivative EMD Emdogain as an intracanal medication could be a manner to strength the tooth structure, improving the physical and chemical properties of dentin. We tested, in vitro, the effect of Emdogain on the surface microhardness and chemical composition of root dentin. Ten human teeth were used to produce dentin specimens originated from the canal walls (n = 30) that remained in contact to Emdogain gel for 90 days. Baseline and 90-days after Emdogain treatment measurements were performed using Fourier Transform Infrared Spectroscopy (ATR/FTIR), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Knoop indenters. The use of EMD (Emdogain) for 90 days in contact with human root canal dentin specimens did not alter the microhardness and morphology of dentin. The elemental structure of dentin was altered because there was a reduction in carbonate content.

A critical analysis of research methods and experimental models to study irrigants and irrigation systems.

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro‐computed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Quantification of Bacterial DNA from Infected Human Root Canals Using qPCR and DAPI after Disinfection with Established and Novel Irrigation Protocols.

The removal of bacterial infections within the root canal system is still a challenge. Therefore, the cleansing effect of established and new irrigation-protocols (IP) containing silver diamine fluoride (SDF) 3.8% on the whole root canal system was analyzed using quantitative PCR (qPCR) and 4′,6-diamidino-phenylindole-(DAPI)-staining. Extracted human premolars were instrumented up to F2 (ProTaper Gold) under NaCl 0.9% irrigation and incubated with Enterococcus faecalis for 42 days. Subsequently, different ultrasonically agitated IP were applied to the roots: control (no irrigation), 1. NaOCl 3%, EDTA 20%, CHX 2%, 2. NaOCl 3%, EDTA 20%, 3. NaOCl 3%, EDTA 20%, SDF 3.8%, 4. SDF 3.8%, and 5. NaCl 0.9%. One half of the root was investigated fluorescent-microscopically with DAPI. The other half was grinded in a cryogenic mill and the bacterial DNA was quantified with qPCR. The qPCR results showed a statistically significant reduction of bacteria after the application of IP 1, 2, and 3 compared to the control group. While IP 4 lead to a bacterial reduction which was not significant, IP 5 showed no reduction. These data corresponded with DAPI staining. With qPCR a new molecular-biological method for the investigation of the complete root canal system was implemented. The novel IP 3 had an equally good cleansing effect as the already established IP.

Atomic force microscopy study on the effect of different irrigation regimens on the surface roughness of human root canal dentin.

Endodontic irrigants could alter the mechanical properties of root canal dentin, such as its roughness. To compare the effect of various irrigation protocols on root canal dentin roughness with respect to their application time, concentration, and additional ultrasonic activation. Forty single-rooted, non-endodontically treated upper incisors were decoronated and further sectioned longitudinally in a buccolingual direction. The surfaces of all eighty samples were polished and randomly segregated to eight equal groups (n = 10): Group A: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group B: 2% NaOCl/5 min followed by 17% EDTA/5 min; Group C: 5.25% NaOCl/2 min followed by 17% EDTA/2 min; Group D: 5.25% NaOCl/5 min followed by 17% EDTA/5 min; Group E: 2% NaOCl solution, ultrasonically activated for 2 min; Group F: 5.25% NaOCl, ultrasonically activated for 2 min; Group G: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated; Group H: Control group (distilled water). All irrigation regimens increased root dentin surface roughness in comparison with the control group. The analysis of the values revealed significant differences between the arithmetical average roughness values (Ra) in the groups (p < 0.001). A statistically significant increase in the Ra parameter was observed in groups E, F, G, and D. The irrigation protocol in Group A showed a significantly smoother dentin surface than those with the ultrasonic activation. All tested irrigants increased root canal dentin roughness and the effect was time and concentration-dependent. The ultrasonic activation of the disinfection solutions roughened the root dentin surface significantly.

Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study

Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study

Evaluation of the Root Canal Morphology of Human Teeth by Cone Beam Computed Tomography and Micro-Computed Tomographic - A Systematic Review with Meta-analysis.

Introduction:To thoroughly plan and execute any dental treatment, the anatomy of the dental root canals is of prime significance. Hence, in this systemic review, we intend to evaluate the cone beam computed and micro-computed tomographic presentations of the root canal morphologies of the secondary teeth.Materials and Methods:We conducted the search for the data from the online sources such as the “EMBASE,” “Pubmed,” “Scopus,” and other sources. Only human studies were collected. Terms searched were cone beam computed tomography (CBCT), micro-computed tomography, permanent teeth, and root canal morphology. The data extraction and meta-analysis were based on the PRISMA guidelines.Results:A total of 170 studies were initially considered for the study. After the application of the inclusion and the exclusion criteria, only ten studies were qualified for the study. In 2 studies, the comparison was done between the conical beam and the microtomograhic views for assessing the root canal anatomies. There were, however, three studies that did not conclude any significant relation between the two imaging systems. When the risk of bias was calculated for the ten studies, there were only low and moderate for the ten included studies. The pooled prevalence among the genders were 21.4% (14.0%–24.6% confidence interval [CI] 95%) and 25.3% (20.0%–30.7% CI 95%), respectively, with high heterogeneity values (= 99.30% and 98.50%, respectively), but no statistical significance (P > 0.05).Conclusion:Both the imaging systems CBCT and the microtomography can be used with accuracy in the evaluation of the anatomic variations of the human root canal. However, a definition is dependent on the voxel size.

Time-lapse submicrometer particle motion reveals residual strain evolution and damaging stress relaxation in clinical resin composites sealing human root canals

Polymer based composites are widely used for treatment, for example as biofilm resistant seals of root canal fillings. Such clinical use, however, fails more frequently than other dental composite restorations, due to stress-related misfits. The reason for this is that the biomaterials used are inserted as viscous masses that may bond to the substrate, yet shrinkage stresses arising during setting of the cross-linking polymer, work against durable adhesion. Here we combine phase contrast enhanced time-lapse radiography (radioscopy), digital image correlation (DIC) and submicrometer resolution phase-contrast enhanced microtomography (PCE-CT), to reveal the spatial and temporal dynamics of composite polymerization and strain evolution. Radioscopy of cavities located in the upper part of human root canals demonstrates how the composite post-gelation “densification” is dominated by viscous flow with quantifiable motion of both particles and entrapped voids. Thereafter, these composites enter a “stress-relaxation” stage and exhibit several structural adaptations, induced by residual shrinkage stresses. Consequently critical alterations to the final biomaterial geometry emerge: (i) entrapped bubbles expand; (ii) microscopic root filling pull-out occurs; (iii) the cavity walls deform inwards, and (iv) occasionally delamination ensues, propagating out from the root canal filling along buried restoration-substrate interfaces. Our findings shed new light on the interactions between confined spaces and biomedical composites that cross-link in situ, highlighting the crucial role of geometry in channeling residual stresses. They further provide new insights into the emergence of structural flaws, calling attention to the need to find new treatment options. Statement of significanceThis work quantifies recurring spatial and temporal material redistribution in composites used clinically to fill internal spaces in teeth. This knowledge is important for both promoting biomaterial resistance against potentially pathologic biofilms and for improving structural capacity to endure years of mechanical function. Our study demonstrates the significant role of geometry and the need for improved control over stress raisers to develop better treatment protocols and new space filling materials. The use of high-brilliance X-rays for time-lapse imaging at submicrometer resolution provides dynamic information about the damaging effects of stress relaxation due to polymerization shrinkage.

The Effect of Photodynamic Therapy on the Smear Layer Removal: a Scanning Electron Microscopic Study.

Statement of the Problem: The efficacy of photodynamic therapy (PDT) in smear layer removal compared to the currently accepted protocol is not well established.Purpose: This study aims to evaluate the effect of PDT on smear layer removal from human root canal compared to combined use of irrigation solutions including sodium hypochlorite (NaOCl) and ethylene diamine tetra acetic acid (EDTA) by scanning electron microscopy (SEM).Materials and Method: In this in vitro study, straight roots from 48 extracted human maxillary incisors and canines were selected and decoronated. Instrumentation was completed with RaCe rotary system and normal saline irrigation between files. Then roots were randomly divided into 3 groups (n=16). Group 1 was the control group to confirm smear layer formation. In the group 2, the canals were irrigated with 2ml of 2.5% NaOCl solution for 10 minutes and 2ml of 17% EDTA solution for 1 minute. In the group 3, PDT with methylene blue and diode laser (625nm, 150mW, for 5minutes) was the final procedure for smear layer removal. All the specimens were sectioned into two halves, gold coated, and analyzed under SEM. The smear layer in the coronal, middle, and apical thirds, were evaluated and scored by two examiners independently. Statistical analysis was done using Chi-square test.Results: It was observed that the NaOCl+EDTA removed the smear layer significantly better than PDT in the coronal and apical thirds (p< 0.05) whereas PDT was unable to remove the smear layer in none of the root areas. At the apical thirds, there was no significant difference between NaOCl+EDTA and PDT (p< 0.05). Both procedures were unable to remove smear layer from radicular dentine of this area.Conclusion: According to the results of this in vitro study, the use of PDT alone is not recommended to remove smear layer. The combined application of NaOCl and EDTA is ineffective in removing smear layer of apical third, despite its efficacy on the coronal and middle regions.

Interface analysis after fatigue loading of adhesively luted bundled fiber posts to human root canal dentin

ObjectivesThe aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-core interface. MethodCrowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (μCT) was used to exemplary compare pre and post TML geometries. ResultsStatic load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids. ConclusionFracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-Ct analyses after TML, lead to the assumption that applied forces result in alterations in the regions of voids.

Effect of conventional and experimental silanes on the adhesion of fiberglass posts to root canals: In vitro study

Introduction: Thiourethane addition to methacrylate of resin cements improves properties of flexural strength, toughness modulus, and fracture toughness. The aim of this study was to evaluate the effect of experimental silanes based on thiourethane in the adhesion of fiberglass posts to the root canal submitted to thermal and mechanical cycling. Materials and Methods: Two oligomers were synthesized with catalytic amounts of triethylamine. Multifunctional thiol–pentaerythritol tetra-3-mercaptopropionate was combined with difunctional isocyanates – 1,6-hexanedioldiissocyante (aliphatic) or 1,3-bis (1-isocyanato-1-methylethyl) benzene (aromatic). Human dental root canals were treated with conventional and experimental silanes, establishing six experimental groups (n = 10) endodontically rehabilitated with fiberglass posts. The specimens were submitted to 1.2 x 106 mechanical cycles and 500 thermal cycles (5°C and 55°C). One slice from each root region (cervical, middle, and apical) was submitted to the push-out bond test, and the fracture pattern evaluated. Scanning electron microscopy micrographs were obtained from the marginal gaps occurred in the adhesive interfaces. Data were analyzed with two-way ANOVA followed by Tukey's test at α = 0.05 confidence level. Results: Conventional and experimental silanes improved bond strength (P Conclusions: Conventional and experimental silanes provided greater adhesive strength, reduced dentin-cement failures, and the marginal gaps were similar, except for the control group Angelus, showing greater slit.

Numerical simulation and experimentation of endodontic file using Taguchi DoE

The endodontic file is a tapered, needle shape body used for the preparation of curved human root canals. During the preparation, process files get failed due to the locking action offered by the canal wall. The present study aimed to find the fatigue life of endodontic files at 23°, 33° and 43° root canal curvature angles. Four brands of files were selected for the present study viz. Hyplex CM, Pro-Taper Next, Hero Shaper, Pro-File Vortex. The strain life analysis done using ANSYS showed that the Hyplex CM file gives the highest fatigue life at 23°, 33° and 43° root canal curvature angles. Therefore, Hyplex CM file was selected for DoE Taguchi Optimization study. Each experimental reading was conducted on X Smart Plus experimental setup under purely rotary and combined reciprocating-rotary motion, at 500 rpm, 600 rpm and 700 rpm and 23°, 33° and 43° root canal curvature angles. Hyplex CM file given maximum fatigue life at 23° root canal curvature angle and 500 rpm speed of rotation. But if file motion is combined rotary-reciprocating, life reduces. The ANNOVA study showed that P-value and significance F are very small, which represented that the regression model is effective.

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal

ObjectivesTo evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal. MethodsSixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test. ResultsNo significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months’ time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group. SignificanceConsidering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.

An in-vitro Comparison of the Bleaching Efficacy of 35 Percent Carbamide Peroxide with Established Intracoronal Bleaching Agents

Introduction: Intracoronal bleaching is the simplest, least invasive, and least expensive means available to lighten non-vital discolored teeth. The objective of the study: To evaluate the intra coronal bleaching efficacy of 35% Carbamide peroxide relative to 35% Hydrogen peroxide and Sodium perborate using artificially stained extracted human teeth. Materials and Methods: Eighty extracted human permanent maxillary and mandibular anterior teeth and single-rooted premolars were artificially stained using whole human blood and root canal treatment was completed. They were bleached twice 7 days apart using: Group I (n=20) – 35% Carbamide peroxide gel, Group II (n=20) – 35% Hydrogen peroxide gel, Group III (n=20) – 2 gm Sodium perborate mixed with per ml of distilled water, Group IV (n=20)– Distilled water only (control). Evaluation of shade was performed on day 0,7,14. Results: On day 7, In Groups I and Group II, there was a reduction in the shade by 2 vita tab positions, whereas Group IIIlightened by 1-tab position only. On day 14, CP and HP lightened by overall 3-tab positions and SP by 2-tab positions. There were no statistical differences between the groups on day 7 and day 14. Conclusion: 35% Carbamide peroxide, 35% Hydrogen peroxide and Sodiumperborate were equally effective for Intra coronal bleaching.