Herbal Metabolites as Potential Carbonic Anhydrase Inhibitors: Promising Compounds for Cancer and Metabolic Disorders.

Background: Human carbonic anhydrases (CAs) play a role in various pathological mechanisms by controlling intracellular and extracellular pH balance. Irregular expression and function of CAs have been associated with multiple human diseases, such as obesity, cancer, glaucoma, and epilepsy. In this work, we identify herbal compounds that are potential inhibitors of CA VI. Methods: We used the AutoDock tool to evaluate binding affinity between the CA VI active site and 79 metabolites derived from flavonoids, anthraquinones, or cinnamic acids. Compounds ranked at the top were chosen for molecular dynamics (MD) simulations. Interactions between the best CA VI inhibitors and residues within the CA VI active site were examined before and after MD analysis. Additionally, the effects of the most potent CA VI inhibitor on cell viability were ascertained in vitro through the 2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Results: Kaempferol 3-rutinoside-4-glucoside, orientin, kaempferol 3-rutinoside-7-sophoroside, cynarin, and chlorogenic acid were estimated to establish binding with the CA VI catalytic domain at the picomolar scale. The range of root mean square deviations for CA VI complexes with kaempferol 3-rutinoside-4-glucoside, aloe-emodin 8-glucoside, and cynarin was 1.37 to 2.05, 1.25 to 1.85, and 1.07 to 1.54 Å, respectively. The MTT assay results demonstrated that cynarin had a substantial effect on HCT-116 cell viability. Conclusion: This study identified several herbal compounds that could be potential drug candidates for inhibiting CA VI.

Synthesis and characterization of nano bioactive glass for improving enamel remineralization ability of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP).

OBJECTIVE: Nanomaterials with superior properties such as high surface area over volume ratio are widely used in dentistry and medicine. This in vitro study was performed to synthesize and characterize nano bioactive glass (nBG) and to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) containing nBG (CPP-ACP@nBG) on enamel remineralization by its application to pH-cycled, synthetically demineralized enamel surfaces. MATERIALS AND METHODS: nBG particles were prepared by sol-gel method. X-ray diffraction pattern (XRD), Fourier-transform infrared spectroscopy (FTIR) and transmittance electron microscopy (TEM) were used for nBG characterization. Synthetic CPP-ACP paste was prepared and nBG particles were added to it. To evaluate the degree of remineralization, 32 healthy human premolars were selected. The samples were randomly divided into 4 groups as: Group 1: Commercial CPP-ACFP (MI paste plus), Group 2: Synthetic casein phosphopeptide-amorphous calcium phosphate containing fluoride (CPP-ACP@F), Group 3: Synthetic CPP/ACP containing nBG (CPP-ACP@nBG), and Group 4: Control (received no treatment). The pastes were then applied on the tooth surfaces for 28 days. The Vickers microhardness of enamel surfaces was evaluated, and enamel surface morphology was assessed using scanning electron microscopy (SEM). RESULTS: X-Ray diffraction pattern (XRD) of the synthesized nBG show its crystalline nature with the Larnite crystalline mode. Transmittance electron microscope (TEM) microimage of the synthesized nBG shows its formation as less that 100 nm spherical nanoparticle with partial agglomeration. Fourier transform infrared spectroscopy (FTIR) confirm the success formation of nBG with high purity. The results of this study showed that microhardness of the experimental groups was significantly higher than the control group (p ≥ 0.05). SEM images showed a layer of hydroxyapatite in the CPP-ACP@nBG, synthetic and commercial CPP-ACP@F remineralized groups. CONCLUSION: The results of this study demonstrated that CPP-ACP@F and CPP-ACP@nBG remineralize the surface of the demineralized enamel. Microhardness of the remineralized enamel in the CPP-ACP@nBG group was higher than synthetic and commercial CPP-ACP@F groups.

Molecular Docking and Dynamics Simulation of Natural Phenolic Compounds with GSK-3ß: A Putative Target to Combat Mortality in Patients with COVID-19.

OBJECTIVE: In this study, molecular docking analysis was performed to evaluate the binding affinity of 52 plant-based phenolics with the GSK-3ß active sites. Moreover, Molecular Dynamics (MD) simulation was conducted to investigate the stability of interactions between the topranked phenolics and residues within the GSK-3ß active sites. METHODS: Molecular docking and MD simulations were performed using AutoDock and Discovery Studio Client software, respectively. Thereafter, pharmacokinetic and toxicological properties of top inhibitors were predicted using bioinformatics web tools. This study aimed to identify the most effective amino acids involved in the inhibition of GSK-3ß based on the most stabilizing interactions between the residues and compounds, and also by considering the degree centrality in the ligand- amino acid interaction network for GSK-3ß. RESULTS: It was observed that procyanidin and amentoflavone could bind to the GSK-3ß active sites at the picomolar (pM) scale as well as the binding affinity of ΔG binding < -13 kcal/mol, while the inhibition constant for theaflavin 3'-gallate, procyanidin B4, and rutin was calculated at the nanomolar (nM) scale, suggesting that these phenolic compounds can be considered as potential effective GSK-3ß inhibitors. Furthermore, Val70, Ala83, Val135, and Tyr134 were found to be the most important amino acids involved in the inhibition of GSK-3ß. CONCLUSION: The results of the current study may be useful in the prevention of several human disorders, including COVID-19, cancers, Alzheimer's disease, diabetes mellitus, and cardiovascular diseases. However, wet-lab experiments need to be performed in the future.

Effects of C-Factor on Bond Strength of Universal Adhesives to Floor and Wall Dentin in Class-I Composite Restorations.

PURPOSE: To evaluate the effects of C-factor on the bond strength of universal adhesives to floor and wall dentin in class-I composite restorations using a bulk-fill composite. MATERIALS AND METHODS: 108 non-carious humans third molars were randomly divided into four groups as follows: flat wall, flat floor, cavity wall, and cavity floor (n = 36). Then, each group was subdivided into three subgroups according to the type of adhesive used: Single Bond Universal, G-premio Bond (both universal adhesives), or Adper Single Bond 2 (an etch-and-rinse adhesive). After the bonding procedure, X-tra fill resin composite was applied in bulk to build up the flat surfaces or fill the cavities.Then the teeth were sectioned into 1-mm2 sticks and microtensile bond strength (µTBS) was measured using a universal testing machine. µTBS (MPa) was analyzed by one-way, two-way, and three-way ANOVA using SPSS Version 23 (a = 0.05). RESULTS: Interactions between adhesives and bonding surfaces, as well as C-factor and bonding surfaces showed statistically significant differences, but the interaction between the C-factor and type of adhesive was not statistically significant. The comparison of bonded surfaces including the flat wall and the flat floor in Adper Single Bond 2 was statistically significant (p < 0.05), except for the cavity wall and cavity floor. CONCLUSION: Regardless of the type of adhesives, the C-factor reduced the µTBS of the composite resin to dentin. Adper Single Bond 2 mediated higher µTBS than did the universal adhesives G-premio Bond and Single Bond Universal.

Effect of Contamination with Hemostatic Agent on Shear Bond Strength of Composite to Dentin Using G-Premio and Single Bond Universal Adhesives.

Objectives: Bond strength of composite restorations plays an important role in their success. This in vitro study evaluated the effect of a hemostatic agent on shear bond strength of universal adhesives. Materials and Methods: Thirty-six extracted human molars were used in this study. Buccal and lingual surfaces were reduced to obtain flat dentin surfaces and were ground with a silicone paper. The samples were randomly divided into three groups (n=12) based on the application of hemostatic agent: group 1: no contamination (control), group 2: aluminum chloride application, and group 3: ferric sulfate application. Each group was then divided into two subgroups (n=6) for using G-Premio and Single Bond Universal. Resin cylinders (Filtek Z550) were bonded to dentin surfaces according to the manufacturer's instructions. After 1000 thermal cycles, shear load was applied to the specimens using a universal testing machine at a crosshead speed of 1 mm/min until failure. Data were statistically analyzed using two-way ANOVA and Tukey's post-hoc test (α=0.05). Results: There were statistically significant differences in shear bond strength of the three main groups for both G-Premio and Single Bond Universal (P<0.05). When the adhesive systems were compared with each other, G-Premio showed higher shear bond strength than Single Bond Universal (P<0.05). Conclusion: Contamination with hemostatic agents had an adverse effect on the shear bond strength of universal adhesives. Moreover, G-Premio yielded a higher bond strength than Single Bond Universal.

In Vitro Comparison of Marginal and Internal Fit of Zirconia Copings Fabricated by One CAD/CAM System with Two Different Scanners.

Objectives: Marginal and internal fit of restorations are two important clinical factors for assessing the quality and durability of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated monolithic zirconia restorations. The purpose of this study was to evaluate the marginal and internal fit of CAD/CAM zirconia crowns with two different scanners (i3D scanner and 3Shape D700). Materials and Methods: Twelve extracted sound human posterior teeth were prepared for full zirconia crowns. Two different extraoral scanners namely i3D scanner and 3Shape D700 were used to digitize type IV gypsum casts poured from impressions. The crowns were milled from presintered monolithic zirconia blocks by a 5-axis milling machine. The replica technique and MIP4 microscopic image analysis software were utilized to measure the marginal and internal fit by a stereomicroscope at ×40 magnification. The collected data were analyzed by paired t-test. Results: The mean marginal gap was 203.62 µm with 3Shape D700 scanner and 241.07 µm with i3D scanner. The mean internal gap was 192.30 µm with 3Shape D700 scanner and 196.06 µm with i3D scanner. The results of paired t-test indicated that there was a statistically significant difference between the two scanners in marginal fit (P=0.04); while, there was no statistically significant difference in internal fit (P=0.761). Conclusion: Within the limitations of this study, the results showed that type of extraoral scanner affected the marginal fit of CAD/CAM fabricated crowns; however, it did not have a significant effect on their internal fit.

Efficacy of chitosan-based chewing gum on reducing salivary S. mutans counts and salivary pH: a randomised clinical trial.

OBJECTIVE: To determine chitosan-based chewing gum role on reducing salivary S. mutans counts and salivary pH. MATERIALS AND METHODS: The present double-blind randomised clinical trial with the trial registration number of IRCT20190724044319N1 was conducted on 36 dental students. The volunteers were, randomly, divided into two groups (n = 18) including: G1: intervention group (chitosan chewing gum) and G2: control group (placebo chewing gum). Each participant was given eight pieces of the chewing gum, and was asked to chew each gum piece for 5 min and this was repeated for eight times. Their Saliva was collected before and after chewing gums and the number of S. mutans colonies and salivary pH were determined. Data were analysed using SPSS (ver.21) and independent student t test. p Value less than .05 was set as significant. RESULTS: There was significant difference between two groups for the number of salivary S. mutans colonies (3.31*105  in the intervention group compared to 13.94*105 in the Control group) (p < .001). The salivary pH evaluation showed that salivary pH mean value in intervention group was not significant in compared with control group (p = .17). However, the chitosan chewing gum led to an increase in salivary pH by 0.17, which was statistically significant (p = .01). CONCLUSION: Results of this study showed that chitosan chewing gum has a positive effect on the reduction of numbers of salivary S. mutans colonies but had no considerable effect on the increase of salivary pH.

Molecular docking study of flavonoid compounds for possible matrix metalloproteinase-13 inhibition.

OBJECTIVES: Matrix metalloproteinase-13 (MMP-13) has been reported to be involved in different biological processes such as degradation of extracellular matrix proteins, activating or degrading some significant regulatory proteins, wound healing, tissue remodeling, cartilage degradation, bone development, bone mineralization, ossification, cell migration, and tumor cell invasion. Further, MMP-13 participates in many oral diseases such as tooth decay, gingivitis, and degradation of enamel and tissue around the implant. In addition, inhibition of MMP-13 has shown therapeutic properties for Alzheimer's disease (AD). We performed molecular docking to assess the binding affinity of 29 flavonoid compounds with the MMP-13. Additionally, pharmacokinetic and toxicity characteristics of the top-ranked flavonoids were studied. The current study also intended to identify the most important amino acids involved in the inhibition of MMP-13 based on topological feature (degree) in the ligand-amino acid network for MMP-13. METHODS: Molecular docking and network analysis were studied using AutoDock and Cytoscape software, respectively. Pharmacokinetic and toxicity characteristics of compounds were predicted using bioinformatics web tools. RESULTS: The results revealed that nine of the studied flavonoids had considerable estimated free energy of binding and inhibition constant: Rutin, nicotiflorin, orientin, vitexin, apigenin-7-glucoside, quercitrin, isoquercitrin, quercitrin-3-rhamnoside, and vicenin-2. Proline-242 was found to be the most important amino acid inhibiting the enzyme. CONCLUSIONS: The results of the current study may be helpful in the prevention and therapeutic procedures of many disorders such as cancer, tooth caries, and AD. Nevertheless, validation tests are required in the future.

The effect of dentin pre-treatment with activated riboflavin on the bond strength of a two-step self-etch adhesive system.

BACKGROUND: The cross-linking of collagen fibers in the hybrid layer has been suggested as a way to create more durable bonds. OBJECTIVES: This study evaluated the effect of visible light-activated riboflavin (RF) as a cross-linking agent on the durability of the dentin microtensile bond strength (µTBS) in a 2-step self-etch (SE) adhesive system. MATERIAL AND METHODS: The occlusal surfaces of 21 human premolar teeth were ground down to expose the dentin, and were then randomly divided into 3 groups. The Clearfil® SE Bond was used in the control group. In the RF/BL group, a 0.1 wt% aqueous solution of RF was applied to the dentin surface before applying the adhesive and irradiating with blue light (BL) for 2 min. In the 3rd group, the RF-P/BL group, the RF powder was added to the adhesive primer (P) at a concentration of 0.1 wt%. The teeth were built up using composite resin. After thermocycling, 14 resin-dentin beams from each group were prepared and stored in water for 3 months. The µTBS was determined and the data was analyzed using a linear model with a generalized estimating equation (GEE) (p = 0.05). RESULTS: The highest and the lowest µTBS belonged to the control group (41.15 ±3.50 MPa) and the RF-P/BL group (19.84 ±3.80 MPa), respectively. The mean µTBS in the control group was significantly higher than in the RF/BL and RF-P/BL groups (p < 0.001), but no significant difference was found between the RF/BL and RF-P/BL groups (p = 0.598). CONCLUSIONS: Pre-treatment of dentin surfaces with RF activated with BL had a negative impact on the µTBS of the Clearfil SE Bond as a 2-step SE adhesive.

Effect of Three Commonly Consumed Beverages on Surface Roughness of Polished and Glazed Zirconia-Reinforced Lithium Silicate Glass Ceramics.

OBJECTIVES: This study aimed to assess the effect of three commonly consumed beverages on surface roughness of polished and glazed zirconia-reinforced lithium silicate (ZLS) glass ceramics. MATERIALS AND METHODS: In this experimental study, 104 rectangular specimens were cut from Vita Suprinity blocks with 2 mm thickness. After ultrasonic cleaning and firing of the specimens, they were finished and polished in two groups. Specimens in the first group were polished using a 2-step polishing kit while the second group specimens were glazed and heated in a porcelain firing oven according to the manufacturer's instructions. Baseline surface roughness was measured using a profilometer. Specimens in each group were then randomly divided into 4 subgroups (n=13) for immersion in artificial saliva (control group), cola, orange juice and black tea. Surface roughness was measured again and data were analyzed using two-way ANOVA. RESULTS: The highest and the lowest mean Ra were found in orange juice and saliva subgroups, respectively in both glazed and polished groups. The Ra values of both polished and glazed groups significantly increased after immersion in orange juice and cola (P<0.05). The polished surfaces showed insignificantly higher surface roughness compared with glazed surfaces (P>0.05). CONCLUSION: Orange juice and cola significantly increased the surface roughness of both polished and glazed ZLS ceramics. Type of surface finishing (polishing versus glazing) had no significant effect on the surface roughness of specimens following immersion in different beverages.

Influence of CO2 Laser Irradiation and CPPACP Paste Application on Demineralized Enamel Microhardness.

Introduction: It has been suggested that the application of casein phosphopeptide-amorphous calcium phosphate paste (CPP-ACP) and CO2 laser irradiation on enamel could increase the resistance of enamel to caries and acid attacks. The aim of the current study was to compare the influence of CPP-ACP paste application and irradiation of CO2 laser on microhardness of demineralized enamel. Methods: Thirty sound maxillary extracted premolars were selected. The crowns were cut at the cervical line and were split into facial and palatal halves. Specimens were mounted in selfcure acrylic blocks in such way that the enamel surface was exposed to 4×4 mm. After a pH cycling of the specimens, they were randomly divided into 4 groups (n=15), as follows: CG: Control group, LAS: CO2 laser, CP: CPP-ACP and LASCP: laser combined CPP-ACP treatment. The Vickers microhardness of the specimens was measured (500 g load, 5 seconds, 3 points). Data were analyzed using one-way ANOVA and post hoc Tukey tests (α =0.05). Results: The lowest mean Vickers microhardness value was observed in CG group (192.57±50.87 kg/mm2 ) and the highest in LASCP group (361.86±22.22 kg/mm2 ). There were significant differences between groups (P<0.001). The pairwise comparison of the groups revealed that there were significant differences between these groups: CG versus LAS, CP, LASCP (P<0.05) and LASCP versus LAS and CP (P<0.05). No significant difference between LAS group versus CP group (P>0.05) was observed. Conclusion: The results of the current study revealed that CO2 laser and CCP-ACP were effective for improvement of enamel hardness value after demineralization. Incorporation of CO2 laser irradiation and CCP-ACP paste application provides additional remineralizing potential for demineralized enamel.

Effect of Green Tea Varnish on Depth of Root Caries.

AIM: Root caries is a common, debilitating condition particularly in the elderly population, which can lead to tooth loss. Evidence shows that green tea has cariostatic effects. Considering the gap of information on green tea varnish, this study aimed to assess the efficacy of green tea varnish in the prevention of root caries. MATERIALS AND METHODS: This in vitro experimental study was performed on 42 sound premolars. Two layers of acid-resistant nail varnish were applied on root surfaces except for a window of 1 × 4 mm. The teeth were randomly divided into three groups (n = 14). Group I (control) received no intervention. Group II received green tea varnish applied on the roots every 48 hours for 21 days. Group III received green tea varnish every 24 hours for 21 days. Sections of 40 µ thickness were prepared from the center of the window, and the depth of carious lesion was measured in three points with 500 µ distance from each other using polarized light microscope. Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 16 and non-parametric Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). RESULTS: The mean (and standard deviation) depth of carious lesion was 54.30 ± 28.64 (µm), 0, and 0 in groups I, II, and III respectively. Control group showed the highest depth of caries. Groups II and III were not significantly different in this respect, but significant differences were noted in depth of caries between groups I and II and also groups I and III (p < 0.001). CONCLUSION: Based on the results, the green tea varnish may possess anticariogenic effects on root caries when applied every 24 or 48 hours over a 21-day period. Application of green tea varnish every 24 or 48 hours for 21 days may prevent root caries. CLINICAL SIGNIFICANCE: Application of green tea varnish can prevent root caries.

Effect of Proanthocyanidin, Fluoride and Casein Phosphopeptide Amorphous Calcium Phosphate Remineralizing Agents on Microhardness of Demineralized Dentin.

OBJECTIVES: The aim of this study was to evaluate the effect of dentin remineralization using proanthocyanidin (PA), fluoride varnish and casein phosphopeptide amorphous calcium phosphate (CPP-ACP) paste and their various combinations on microhardness of demineralized root dentin. MATERIALS AND METHODS: One-hundred and twenty freshly extracted sound human premolars were selected and randomly divided into eight groups for dentin treatment as follows. C: Deionized water (control); PA: 6.5% PA solution; F: fluoride varnish (5% NaF, 22600 ppm fluoride); CP: CCP-ACP; PAF: 6.5% PA + fluoride varnish; PACP: 6.5% PA + CCP-ACP; FCP: fluoride varnish + CCP-ACP and PAFCP: 6.5% PA + fluoride varnish + CCP-ACP. All specimens were subjected to Vickers microhardness test (500 g, 10 seconds, 3 points). Data were analyzed using one-way ANOVA and Tukey's post hoc test. The significance level was set at 0.05. RESULTS: The mean and standard deviation (SD) values of Vickers hardness number (VHN) in groups C, PA, F, CP, PAF, PACP, FCP and PAFCP were 37.39±4.97, 38.68±4.62, 48.28±2.68, 41.91±3.32, 48.59±2.55, 53.34±2.57, 48.413±4.00 and 55.20±1.82, respectively. Pairwise comparisons of the groups revealed that there was no significant difference between groups C and PA, PA and CP, F and PAF, F and FCP, PAF and FCP, and PACP and FPACP (P>0.05); but significant differences were observed between other groups (P<0.05). CONCLUSIONS: The results of this study showed that the tested dentin treatments increased the microhardness of demineralized root dentin except for PA application.

In-Vitro Evaluation of the Effect of Herbal Antioxidants on Shear Bond Strength of Composite Resin to Bleached Enamel.

OBJECTIVES: A reduction in bond strength of composite to bleached enamel has been reported immediately after bleaching treatment. Application of some antioxidant agents may decrease the adverse effects of whitening agents on bond strength and enhance composite bond to enamel. This study aimed to assess the effect of green tea, sodium ascorbate, sage and grape seed extract on bond strength of composite to bleached enamel. MATERIALS AND METHODS: In this in-vitro study, 90 human enamel surfaces were randomly divided into six groups as follows (n=15): G1, no bleaching; G2, bleaching with 40% hydrogen peroxide (HP); G3, HP+1000 µmol epigallocatechin gallate (EGCG) for 10 minutes; G4, HP+10% sodium ascorbate for 10 minutes; G5, HP+10% sage for 10 minutes and G6, HP+5% grape seed extract for 10 minutes. The specimens were bonded to composite in all groups. The shear bond strength of specimens was measured in Megapascals (MPa). Data were analyzed using one-way ANOVA and Tukey's HSD test (α=0.05). RESULTS: The highest and the lowest mean shear bond strength values were observed in group 1 (22.61±3.29MPa) and group 2 (5.87±1.80MPa), respectively. The reduction in bond strength in group 2 was greater than that in other groups (P<0.001). No significant difference was found among groups 1, 3, 4, 5 and 6 (P>0.05). CONCLUSIONS: All the herbal antioxidants used in this study equally compensated for the reduced bond strength of composite to bleached enamel.

The Effect of Epigallocatechin Gallate on the Dentin Bond Durability of Two Self-etch Adhesives.

STATEMENT OF THE PROBLEM: Self-etch adhesives can activate matrix metalloproteinase (MMP) which hydrolyzes organic matrix of demineralized dentin. Epigallocatechin gallate (EGCG), especially found in green tea, could inhibit the activation of MMP. PURPOSE: The aim of this study was to evaluate the effect of adding Epigallocatechin gallate (EGCG) into two types of adhesives on dentin bond strength. MATERIALS AND METHOD: In this experimental study, 64 extracted third molars were randomly divided into 16 groups. Clearfil SE Bond and Filtek Silorane System with 0 µM, 25µM, 50µM, and 100µM concentration of 95% EGCG were used for bonding. Following the bonding and fabrication of beams (1±0.1 mm(2)) and storage in distilled water, the specimens were subjected to thermal cycles. Microtensile bond strengths of 8 groups were examined after 24 hours and others were tested after 6 months. The fracture modes of specimens were evaluated by stereomicroscope and SEM. Data were analyzed by three-way ANOVA and t-test (α = 0.05). RESULTS: The results of the three- way ANOVA test showed that types of bonding, storage time and interactive effect of EGCG concentration and bonding influenced the bond strength of specimens significantly (p<0.05). The results of the t-test indicated that storage time only had significant effect on bond strength of Clearfil SE Bond with no EGCG (p= 0.017). The most common failure modes in Filtek Silorane System groups and Clearfil SE Bond groups were adhesive and mixed/cohesive, respectively. The results of SEM at different magnifications showed that most fractures have occurred in the hybrid layer. CONCLUSION: Although adding 100 µM volume of EGCG to Clearfil SE Bond can preserve the dentin bond, incorporation of EGCG in the silorane system, especially in high concentrations, decreases the bond strength after 6 months.

Effect of cyclic loading on bond strength of fiber posts to root canal dentin.

OBJECTIVE: The aim of this study was to evaluate the effect of cyclic loading on the bond strength of quartz fiber posts to root canal dentin after different surface treatments of different regions of root canal dentin. MATERIALS AND METHODS: Forty-eight single-rooted human teeth were selected. Post spaces were prepared and then the teeth were divided into four groups: G1: no treatment (control); G2: irrigation with a chemical solvent; G3: etching with 37% phosphoric acid; G4: treatment with ultrasonic file. The fiber posts were cemented using dual-cured resin cement. Half of the specimens were load-cycled (10000 cycles, 3 cycles/s) and the others did not undergo any load cycling. From each root, two slides measuring 1 mm in thickness were obtained from the apical and cervical regions. The push-out bond strength test was performed for each slice. Data were analyzed by using 3-way ANOVA and Tukey HSD tests. The fracture modes were evaluated under a stereomicroscope at ×20. RESULTS: The effect of load cycling and surface treatment as the main factors and the interaction of main factors were not significant (P=0.734, P=0.180, and P=0.539, respectively). The most frequent failure mode under the stereomicroscope was adhesive. CONCLUSION: It appears that load cycling and surface treatment methods had no effect on the bond strength of fiber posts to root canal dentin, but it depended on the region of the root canal dentin.

Effect of ascorbic acid on bond strength between the hydrogen peroxide-treated fiber posts and composite resin cores.

AIM: This study evaluated the effect of 10% ascorbic acid on the bond strength between fiber post and composite resin core after applying 24% hydrogen peroxide. MATERIALS AND METHODS: Twenty-four hydrogen peroxide-treated fiber posts were divided into 4 groups (n = 6). Group 1 was the control group with no treatment. In groups 2-4, post surfaces were treated with 10% v ascorbic acid solution for 10, 30 and 60 minutes, respectively. Cores were built up using flowable composite resin. Two sticks were prepared from each specimen. Microtensile bond strength test was performed for each stick. Failure modes of sticks were evaluated under a stereomicroscope (×20). Surface morphologies of two fractured sticks from each group were assessed by SEM. STATISTICAL ANALYSIS: Data were analyzed using one-way ANOVA and Tukey HSD tests (α = 0.05). RESULTS: The highest microtensile bond strength was observed in Group 4 (20.55 ± 2.09) and the lowest in Group 1 (10.10 ± 0.55). There were significant differences in microtensile bond strength between all the groups (P < 0.05). CONCLUSION: It is concluded that ascorbic acid application increased the microtensile bond strength between the hydrogen peroxide treated fiber post and composite resin core. The increase is dependent on the duration of exposure to the antioxidant.

Antibacterial properties of composite resins incorporating silver and zinc oxide nanoparticles on Streptococcus mutans and Lactobacillus.

OBJECTIVES: Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. MATERIALS AND METHODS: Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30). The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683) and Lactobacillus (PTCC 1643) were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at 37℃ for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. RESULTS: Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05). The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05). There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. CONCLUSIONS: Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

Effect of Epigallocatechin Gallate on shear bond strength of composite resin to bleached enamel: an in vitro study.

OBJECTIVES: The aim of this study was to determine the effect of epigallocatechin gallate (EGCG) on the shear bond strength of composite resin to bleached enamel. MATERIALS AND METHODS: Ninety enamel surfaces of maxillary incisors were randomly divided into 9 groups as follows: G1: control (no bleaching); G2: bleaching; G3: bleaching and storage for seven days; G4 - 6: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 10 minutes, respectively; G7 - 9: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 20 minutes, respectively. The specimens were bleached with 30% hydrogen peroxide gel and a composite resin cylinder was bonded on each specimen using a bonding agent. Shear bond strength of the samples were measured in MPa. Data was analyzed using the two-way ANOVA and Tukey HSD tests (α = 0.05). RESULTS: The maximum and minimum mean shear bond strength values were observed in G1 and G2, respectively. Time and concentration of EGCG showed no significant effects on bond strength of the groups (p > 0.05). Multiple comparison of groups did not reveal any significant differences between the groups except for G2 and all the other groups (p < 0.05). CONCLUSIONS: There is a significant decrease in bond strength of composite resin to enamel immediately after bleaching. A delay of one week before bonding and the use of EGCG increased bond strength of composite resin to bleached enamel.

Effect of Ethylene diamine tetra acetic acid and sodium hypochlorite solution conditioning on microtensile bond strength of one-step self-etch adhesives.

BACKGROUND: Attempts to improve bond strength of self-etch adhesives can enhance the durability of composite restorations. AIMS: The aim of the present study was to evaluate the effect of collagen and smear layer removal with sodium hypochlorite solution (NaOCl) and EDTA on micro-tensile bond strength (µTBS) of self-etch adhesives to dentin. SETTINGS AND DESIGN: It was an in-vitro study. MATERIALS AND METHODS: Seventy-two teeth were divided into eight groups and their crowns were ground perpendicular to their long axis to expose dentin. The teeth were polished with silicon-carbide papers. The groups were treated as follows: No conditioning, 0.5-M EDTA conditioning, 2.5% NaOCl conditioning, NaOCl + EDTA conditioning. The surfaces were rinsed and blot-dried. Clearfil S3 and I-Bond were applied according to manufacturers' instructions and restored with Z100 composite. After 500 cycles of thermo-cycling between 5°C and 55°C, the samples were sectioned and tested for µTBS. STATISTICAL ANALYSIS: Data were analyzed by two-way ANOVA and Tukey-HSD test. RESULTS: The highest µTBS was recorded with Clearfil S3 + NaOCl + EDTA, and the lowest was recorded with I-Bond without conditioning. µTBS in EDTA-and EDTA + NaOCl-treated groups was significantly higher than the control and NaOCl-conditioned groups. CONCLUSIONS: Application of EDTA or EDTA + NaOCl before one-step self-etch adhesives increased µTBS.