Comparison of Setting Time of White Mineral Trioxide Aggregate with and without Disodium Hydrogen Phosphate at Different Liquid-to-powder Ratios.

AIM: The present study was conducted with the objective of evaluating the effect of different liquid-to-powder ratios on setting time of white mineral trioxide aggregate (WMTA) and the effect of adding disodium hydrogen phosphate (Na2HPO4) to white MTA (NAMTA). MATERIALS AND METHODS: Sixty samples were prepared in plastic annular molds with a diameter of 10 mm and a height of 2 mm in order to record setting time where white MTA was placed in 30 samples and 2.5 wt% mixture of Na2HPO4 with white MTA was placed in other 30 samples. Setting times in different ratios of liquid to powder (50, 60, and 70%) and at different times including 5, 10, 15, 20, 25, 30, 40, and 50 minutes as well as 1, 1.5, 2.5, 3, 3.5, and 4 hours were measured with Vicat. Statistical Package for the Social Sciences version 16 software was used to examine the differences between groups. The values of p < 0.05 were considered to be statistically significant in this study. RESULTS: The average setting time of samples in two WMTA and NAMTA was 182.17 ± 57.86 and 67.00 ± 14.42 respectively, and this difference was statistically significant (p < 0.001). Also, the average setting time of samples in ratio groups of 50, 60, and 70% were 146.00 ± 75.90, 85.00 ± 31.71, and 142.5 ± 64.47 respectively, and results showed that there was no significant difference between groups. CONCLUSION: Adding 2.5 wt% of Na2HPO4 mixture to white MTA reduces the setting time, which is lower than the WMTA in 50, 60, and 70% liquid-to-powder ratios. CLINICAL SIGNIFICANCE: According to the findings of this study, it can be seen that adding Na2HPO4 to white MTA is a good way to reduce setting timing in clinical dentistry, especially in one-visit treatments.

Effect of containing silica fume on cytotoxicity of white mineral trioxide aggregate.

BACKGROUND: Mineral trioxide aggregate (MTA) has a high biocompatibility and its physical properties could be improved by adding the containing silica fume an amorphous silicon dioxide (condensed silica fume [CSF]). The aim of this study was to evaluate the cytotoxicity of MTA mixed with CSF on the viability of L929 mouse fibroblast cell using 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide reduction assay (MTT assay). MATERIALS AND METHODS: In this in vitro study white MTA was mixed with distilled water according to the manufacturer's instructions. Mixtures of White MTA with 10%, 15%, and 20% CSF by weight were prepared and mixed with distilled water. Cytotoxicity of mixtures was compared with MTT assay on L929 mouse fibroblast cell line after 24, 48, and 72 h. Differences in cytotoxicity were assessed by one-way analysis of variance (ANOVA). RESULTS: Mean ± SD of vital cell counts cultured in MTA, MTA + 10% CSF, MTA + 15% CSF, and MTA + 20% CSF were 98% ± 6%, 97% ± 6%, 94% ± 4%, and 98% ± 4%, respectively. One-way ANOVA did not reveal any statistically significant difference between the groups (P > 0.05). CONCLUSION: It may be concluded that addition of CSF to MTA may not influence its cytotoxicity.

Compressive Strength of Mineral Trioxide Aggregate with and without Disodium Hydrogen Phosphate at Different Mixing Ratios.

Introduction: Mineral Trioxide Aggregate (MTA) is a substance with favorable physical-mechanical properties. Disodium hydrogen phosphate (DHP) is sometimes added to MTA to reduce its setting time. Therefore, this study was conducted to evaluate the effect of various ratios of liquid to powder of white MTA (WMTA) and addition of DHP on its compressive strength. Methods and Materials: One hundred and twenty samples were prepared with a two-piece stainless steel mold with a height of 6 mm and a diameter of 4 mm in order to evaluate the compressive strength where WMTA was used in 60 samples and DHP in white MTA composition (DHPWMTA) was used in other 60 samples. The compressive strength of WMTA and DHPWMTA was measured in various ratios of liquid to powder including 50, 60 and 70% and at 24 h and 21 days (n=10). Univariate Analysis of Variance test with SPSS 16 software were used to determine the difference between groups. The level of significance was set at 0.05. Results: The maximum and minimum compressive strength of WMTA groups were 63.25±1.96 (50% ratio and 21 days) and 37.79±1.28 (70% ratio and 24 h), respectively. The maximum and minimum compressive strength of DHPWMTA groups were 63.96±1.40 (60% ratio and 21 days) and 37.37±1.62 (70% ratio and 24 h), respectively. The effect of each of factors (type of material, powder to liquid ratio and time) alone were significant on the compressive strength (P<0.05). However, the interactive effect of three factors (type of material, powder to liquid ratio and time) were not statistically significant on compressive strength (P>0.05). Conclusion: Adding 2.5 wt% of DHP to white MTA increased samples compressive strength. Compressive strength in liquid to powder ratios of 50 and 60% compare to 70% and at 21 days compared to 24 h was high.

Effect of electric currents on antibacterial effect of chlorhexidine against Entrococcus faecalis biofilm: An in vitro study.

BACKGROUND: This in vitro study was mainly aimed to evaluate the effect of high-frequency alternating currents (AC) applied by an electronic apex locator (EAL) on the antibacterial properties of chlorhexidine (CHX) on E. faecalis biofilm. MATERIAL AND METHODS: The root canals of 120 extracted human single-rooted teeth were prepared using Gates-Glidden drills and hand K-files. After contaminating the root canals with E. faecalis, they were incubated for 60 days. Then, the teeth were randomly divided into six experimental groups (n=20). Group 1, 2% CHX; group 2, normal saline (NS) with direct current (DC); group 3, normal saline (NS) with high-frequency alternating current (AC); group 4, 2% CHX with DC; group 5, 2% CHX with AC; group 6, control (normal saline). The samples were collected from the root canal walls of 16 teeth in each group and 1:10 serial dilutions were prepared and added to Muller-Hinton agar (MHA) plates and incubated at 37°C for 48 h. The longitudinal sections of the other 4 teeth used to observe under a scanning electron microscope (SEM). A classic colony counting technique was used for counting the vital E. faecalis bacteria in MHA. Two-way ANOVA was used for statistical analysis of the data. The level of significance was set at P<0.05. RESULTS: The electric current significantly changed the colony-forming units (CFU) values (P<0.001). According to pair-wise comparisons, the highest CFU difference was observed between the AC group and the group without electric current (P<0.001); furthermore, the difference between the DC group and the group without electric current was not significant (P=0.823). CONCLUSIONS: The highest bioelectric effect occurred with the use of high-frequency alternating electric current in the form of an apex locator with CHX as a canal irrigant. Key words:Biofilm, Chlorhexidine, Direct current, Electric current, Enterococcus faecalis.

Effect of aluminum chloride hemostatic agent on microleakage of class V composite resin restorations bonded with all-in-one adhesive

Objectives: Since hemostatic agents can induce changes on enamel and dentin surfaces and influence composite resin adhesion, the aim of the present study was to evaluate the effect of the aluminum chloride hemostatic agent on the gingival margin microleakage of class V (Cl V) composite resin restorations bonded with all-in-one adhesive. Study design: Cl V cavities were prepared on the buccal surfaces of 60 sound bovine permanent incisors. Gingival margins of the cavities were placed 1.5 mm apical to the cemento-enamel junction (CEJ). The teeth were randomly divided into two groups of 30. In group 1, the cavities were restored without the application of a hemostatic agent; in group 2, the cavities were restored after the application of the hemostatic agent. In both groups all-in-one adhesive and Z250 composite resin were used to restore the cavities with the incremental technique. After finishing and polishing, the samples underwent a thermocycling procedure, followed by immersion in 2% basic fuschin solution for 24 hours. The samples were sectioned and gingival microleakage was evaluated under a stereomicroscope. The non-parametric Mann-Whitney U test was used to compare microleakage between the two groups. Statistical significance was defined at P<0.05. Results: A statistically significant difference was observed in microleakage between the two groups (P<0.001). Conclusions: Contamination of Cl V composite resin restorations bonded with all-in-one adhesive with aluminum chloride hemostatic agent significantly increases restoration gingival margin microleakage (AU)

Effect of aluminum chloride hemostatic agent on microleakage of class V composite resin restorations bonded with all-in-one adhesive.

OBJECTIVES: Since hemostatic agents can induce changes on enamel and dentin surfaces and influence composite resin adhesion, the aim of the present study was to evaluate the effect of the aluminum chloride hemostatic agent on the gingival margin microleakage of class V (Cl V) composite resin restorations bonded with all-in-one adhesive. STUDY DESIGN: Cl V cavities were prepared on the buccal surfaces of 60 sound bovine permanent incisors. Gingival margins of the cavities were placed 1.5 mm apical to the cemento-enamel junction (CEJ). The teeth were randomly divided into two groups of 30. In group 1, the cavities were restored without the application of a hemostatic agent; in group 2, the cavities were restored after the application of the hemostatic agent. In both groups all-in-one adhesive and Z250 composite resin were used to restore the cavities with the incremental technique. After finishing and polishing, the samples underwent a thermocycling procedure, followed by immersion in 2% basic fuschin solution for 24 hours. The samples were sectioned and gingival microleakage was evaluated under a stereomicroscope. The non-parametric Mann-Whitney U test was used to compare microleakage between the two groups. Statistical significance was defined at P<0.05. RESULTS: A statistically significant difference was observed in microleakage between the two groups (P<0.001). CONCLUSIONS: Contamination of Cl V composite resin restorations bonded with all-in-one adhesive with aluminum chloride hemostatic agent significantly increases restoration gingival margin microleakage.