Effect of 10% Sodium Ascorbate on Bleached Bovine Enamel Surface Morphology and Microhardness

Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces. The aim of present study was to evaluate the effect of 10% sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics. A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin. Subsequent to polishing, they were randomly divided into 3 groups of 23 specimens each; 3 for Scanning Electron Microscopy (SEM) analysis and 20 for hardness test. In group 1 the specimens were immersed in distilled water as control group; in group 2 the specimens were bleached with 35% carbamide peroxide for 30 min a week for 3 consecutive weeks; and in group 3 the specimens were exposed to 10% sodium ascorbate for 30 min subsequent to bleaching similar to group 1. After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA (P < 0.05). The highest and lowest microhardness values were observed in group 1 and group 2, respectively. However, there were no statistically significant differences in microhardness between the groups (P = 0.12). The use of 35% carbamide peroxide alone or with 10% sodium ascorbate does not affect bovine enamel hardness. SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers.Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n = 19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey post-hoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite.Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups.Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin

Effect of surface treatment with sandblasting and Er,Cr:YSGG laser on bonding of stainless steel orthodontic brackets to silver amalgam

Objectives: Satisfactory bonding of orthodontic attachments to amalgam is a challenge for orthodontists. The aim of this in vitro study was to compare the shear bond strength of stainless steel orthodontic brackets to silver amalgam treated with sandblasting and Er,Cr:YSGG laser. Study Design: Fifty-four amalgam discs were prepared, polished and divided into three groups: In group 1 (the control group) the premolar brackets were bonded using Panavia F resin cement without any surface treatment; in groups 2 and 3, the specimens were subjected to sandblasting and Er,Cr:YSGG laser respectively, before bracket bonding. After immersing in distilled water at 37°C for 24 hours, all the specimens were tested for shear bond strength. Bond failure sites were evaluated under a stereomicroscope. Data was analyzed using one-way ANOVA and a post hoc Tukey test. Results: The highest and lowest shear bond strength values were recorded in the laser and control groups, respectively. There were significant differences in mean shear bond strength values between the laser and the other two groups (p<0.05). However, there were no significant differences between the sandblast and control groups (p=0.5). Conclusions: Amalgam surface treatment with Er,Cr:YSGG laser increased shear bond strength of stainless steel orthodontic brackets. © Medicina Oral

Effect of 10% sodium ascorbate on Streptococcus mutans adherence to bleached bovine enamel surface

Sodium ascorbate has been suggested to modify bleaching agents’ side effects especially on composite resin bonding to dental hard tissues. The aim of the present study was to evaluate the effect of 10% sodium ascorbate on Streptococcus mutans adherence to bleached enamel surfaces. Sixty enamel slabs from bovine incisors were used. After sterilization of the intact enamel surfaces with UV light, the specimens were randomly divided into the following treatment groups: (1) immersion in normal saline containing 2%NaN3; (2) bleaching of enamel surfaces with 10% carbamide peroxide; (3) bleaching of enamel surfaces with 10% carbamide peroxide followed by 10% sodium ascorbate treatment. Adherence of S. mutans to enamel surfaces was determined bacteriologically. Data was analyzed using one-way ANOVA and post hoc Tukey tests (P &lt; 0.05).10% sodium ascorbate after bleaching (Group 3) caused a significant increase in surface adherence of S. mutans compared to groups 1 and 2 (P &lt; 0.001). Because of bacterial adherence subsequent to use of sodium ascorbate to bleached enamel caries risk may be increased.Keywords: Sodium ascorbate, Streptococcus mutans, carbamide peroxideAfrican Journal of Biotechnology Vol. 9(33), pp. 5419-5422, 16 August, 201

Effect of sodium ascorbate on the bond strength of all-in-one adhesive systems to NaOCl-treated dentin

Background: Ascorbic acid and its salts are low-toxicity products, which are routinely used in food industries as antioxidants. The aim of the present study was to evaluate the effect of 10% sodium ascorbate on the bond strength of two all-in-one adhesive systems to NaOCl-treated dentin. Material and Methods: After exposing the dentin on the facial surface of 90 sound human premolars and mounting in an acrylic resin mold, the exposed dentin surfaces were polished with 600-grit SiC paper under running water. Then the samples were randomly divided into 6 groups of 15. Groups 1 and 4 were the controls, in which no surface preparation was carried out. In groups 2 and 5 the dentin surfaces were treated with 5.25% NaOCl alone for 10 minutes and in groups 3 and 6 with 5.25% NaOCl for 10 minutes followed by 10% sodium ascorbate for 10 minutes. Then composite resin cylinders, measuring 2 mm in diameter and 2 mm in height, were bonded on the dentin surfaces in groups 1, 2 and 3 with Clearfil S 3 Bond and in groups 4, 5 and 6 with Adper Easy One adhesive systems according to manufacturers’ instructions. The samples were stored in distilled water for 24 hours at 37°C and then thermocycled. Finally, the samples underwent shear bond strength test in a universal testing machine at a strain rate of 1 mm/min. Data were analyzed with two-way ANOVA and post hoc Tukey tests at α=0.05. Results: The differences between groups 1 and 2 ( P =0.01), 1 and 5 ( P =0.003). 1 and 6 ( P =0.03) and 4 and 5 ( P =0.03) were statistically significant. Two-by-two comparisons did not reveal any significant difference between other groups ( P >0.05). Conclusions: Use of 10% sodium ascorbate for 10 minutes restored the decreased bond strength of the adhesive systems to that of the control groups

Reparability of giomer using different mechanical surface treatments

In the repair process achieving high bond strength between the new and old resin based materials is necessary for clinical longevity. This study compared the effect of three different mechanical surface treatments (air abrasion, Nd:YAG laser and diamond bur) on the repair bond strength of giomer. In this in vitrostudy, 125 cylindrical giomer samples were used. The giomer samples were randomly assigned to 5 groups (n=25). In group 1, the samples did not undergo any surface treatment. In groups 2 to 4, the samples underwent surface treatments with air abrasion, Nd:YAG laser and a diamond bur. The samples in group 5 were prepared to measure giomer cohesive strength. Subsequently, the new giomer was bonded to the existing giomer in groups 1 to 4. Then the repair bond strength of the samples was measured. One-way ANOVA and post hoc Tukey test were used to compare the bond strength. There were significant differences between the different surface treatments (P<0.001); the repair bond strength in the air abrasion group was significantly higher than that in the Nd:YAG laser group, in which it was significantly higher than that in the diamond bur group, which was in turn higher than that in group 1 (no surface treatment) (P<0.001). In addition, the cohesive strength of giomer was significantly higher than the repair bond strength in the 4 other study groups (P<0.001). Of all the surface treatments, air abrasion and Nd:YAG laser, in descending order, yielded the highest repair bond strength values, with the repair bond strength values of 60?70% of the giomer cohesive strength

The effect of pre-heating on monomer elution from bulk-fill resin composites

The present study was aimed to evaluate the effect of pre-heating of bulk -fill resin composites on monomer elution from them. Three different types of resin composites were used including Tetric N-Ceram Bulk Fill, X-tra Fill and X-tra Base. 10 cylindrical samples were prepared from each resin composites. Before light curing, 5 samples were pre-heated until reaching 68?C, then 5 other samples were polymerized at room temperature. After 24 hours, release of UDMA, TEGDMA and BIS-GMA monomers were measured by High-Performance Liquid Chromatography analysis. Data analysis was performed by two-way ANOVA test, Games-Howell and Sidak post hoc tests. Pre-heating did not have any statistically significant effect on the mean values of UDMA, TEGDMA and Bis-GMA elution (p>0.05). The greatest amount of released Bis-GMA and UDMA was obtained from Tetric N-Ceram Bulk-fill composite. The greatest amount of released TEGDMA was obtained from X-tra Fill composite. X-tra Base composite showed the lowest amount of monomer release (P<0.001). Pre-heating did not have any effect on monomer release from bulk-fill resin composites. Moreover, the amount and the type of monomers released from various bulk-fill resin composites were not similar

The effect of repeated preheating of dimethacrylate and silorane-based composite resins on marginal gap of class V restorations

Background. One of the problems with composite resin restorations is gap formation at resin‒tooth interface. The present study evaluated the effect of preheating cycles of silorane- and dimethacrylate-based composite resins on gap formation at the gingival margins of Class V restorations. Methods. In this in vitro study, standard Class V cavities were prepared on the buccal surfaces of 48 bovine incisors. For restorative procedure, the samples were randomly divided into 2 groups based on the type of composite resin (group 1: di-methacrylate composite [Filtek Z250]; group 2: silorane composite [Filtek P90]) and each group was randomly divided into 2 subgroups based on the composite temperature (A: room temperature; B: after 40 preheating cycles up to 55°C). Marginal gaps were measured using a stereomicroscope at ×40 and analyzed with two-way ANOVA. Inter- and intra-group comparisons were analyzed with post-hoc Tukey tests. Significance level was defined at P < 0.05. Results. The maximum and minimum gaps were detected in groups 1-A and 2-B, respectively. The effects of composite resin type, preheating and interactive effect of these variables on gap formation were significant (P<0.001). Post-hoc Tukey tests showed greater gap in dimethacrylate compared to silorane composite resins (P< 0.001). In each group, gap values were greater in composite resins at room temperature compared to composite resins after 40 preheating cycles (P<0.001). Conclusion. Gap formation at the gingival margins of Class V cavities decreased due to preheating of both composite re-sins. Preheating of silorane-based composites can result in the best marginal adaptation