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STATEMENT OF THE PROBLEM: Long-term success of ceramic veneers depends on the color stability of resin cement used for their cementation. Color change of cement may be seen through the ceramic and compromise esthetics. PURPOSE: This study aimed to compare the color change of two resin cements and their visibility through the ceramic veneers after accelerated artificial aging. MATERIALS AND METHODS: In this in vitro study, color change (ΔE) was measured in the following groups (n = 10) before and after accelerated artificial aging: group 1, IPS e.max press high translucent ceramic discs; groups 2, Variolink NLC resin cement discs; group 3, Choice 2 resin cement discs; groups 4, Variolink NLC discs bonded to e.max ceramic discs; group 5, Choice 2 disc bonded to e.max ceramic discs. Color change was measured using a spectrophotometer according to International Commission on Illumination Lab (CIELab). Data were analyzed using one-way ANOVA and Tukey's post-hoc test. RESULTS: Group 2 showed the highest (ΔE = 10.4 ± 0.9) and group 1 the lowest (ΔE = 0.9 ± 0.4) color change. The color change of Variolink was significantly greater than Choice 2 either alone (p < .001) or through the ceramic discs (p < .004). The color change of both cements was lower through the ceramic veneer and this reduction was statistically significant (p < .001). CONCLUSION: Noticeable color change may be expected in areas of cement exposure for both cements studied. Also, in case of using Variolink cement, the color change may be seen through the ceramic veneers.
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STATEMENT OF THE PROBLEM: The progression of incipient carious lesions may be simply prevented by non-invasive remineralization of lesions, eliminating the need for invasive and high-cost restorative procedures. PURPOSE: This study aimed to assess the effect of two commonly used remineralizing agents and resin infiltration on surface micro hardness of incipient enamel lesions at different time points. MATERIALS AND METHOD: In this in vitro study, 45 intact human maxillary central incisors were selected. After disinfection, enamel samples measuring 5x5x2.5 mm were cut out of the labial surface of the teeth. The surface of samples was polished and they were mounted in auto-polymerizing acrylic resin. According to Amaechi's method, samples were immersed in acidified hydroxyethylcellulose system (pH= 4.5) for 96 hours to induce white spot lesions (WSLs). The baseline value of surface micro hardness of samples was measured using a Vickers hardness tester, then the samples were randomly divided into three groups (n=15) based on different remineralization methods: MI-Paste Plus, Remin Pro and ICON-Infiltrant according to the manufacturer's instructions. All samples were stored in anti-dry mouth treatment agent during the experiment and their surface hardness was measured at 15 days (T1) and 20 weeks (T2). RESULTS: The hardness of samples in MI-Paste Plus and Remin Pro groups significantly increased at both T1 and T2 (p< 0.001) but this increase was not significant in ICON group (p> 0.05). CONCLUSION: MI-Paste Plus and Remin Pro can efficiently increase the hardness of incipient enamel lesions.
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Objectives: Inadequate removal of the hemostatic agent can adversely affect the bond strength of restorations to the tooth structure. This study aimed to assess the effect of different cleansing protocols on the shear bond strength (SBS) of an etch-and-rinse adhesive to dentin contaminated with aluminum chloride hemostatic agent. Materials and Methods: In this experimental study, the mid-coronal dentin of 96 premolars was exposed. They were contaminated with a hemostatic agent (ViscoStat Clear) and then randomly divided into 7 groups (n=12). One group served as the control. The groups underwent various cleaning methods as follows: water spray, aluminum oxide particles (27µ diameter), a slurry of pumice with water, GC dentin conditioner (GCDC), sodium hypochlorite 2% (SHC), and chlorhexidine 2% (CHX). Composite cylinders were then fabricated and bonded to the surfaces using Scotchbond Multi-Purpose etch-and-rinse bonding agent. After thermocycling (10,000 cycles), the SBS was measured using a universal testing machine. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey HSD (honestly significant difference) test, and the significance level was set at 0.05. Results: The SBS of the groups was significantly different (P=0.036). The SBS was the highest in the CHX and SHC groups, and the lowest SBS was related to the control group and GCDC groups. The difference between other groups was not significant (P=0.996). Conclusion: CHX and SHC yielded the highest bond strength among the tested modalities for cleansing the ViscoStat Clear from the tooth surface.
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BACKGROUND: Application of hemostatic agents can negatively affect the bond strength of adhesive systems to dental substrate. This study aimed to assess the effect of ferric sulfate on microshear bond strength of four total- and self-etch adhesives to dentin after water storage. MATERIALS AND METHODS: In this in vitro study, 192 dentin slices with 2 mm thickness were made of 64 extracted sound human third molars. The samples were divided into 8 groups (n = 24) as follows: G1: Scotchbond Multi-Purpose, G2: hemostatic agent + Scotchbond, G3: Adper Single Bond, G4: hemostatic agent + Adper, G5: Clearfil SE Bond, G6: hemostatic agent + Clearfil, G7: Single Bond Universal, and G8: hemostatic agent + Single Bond Universal. Composite cylinders with 0.7 mm diameter and 1 mm height were bonded to the surfaces. Each group was then divided into two subgroups (n = 12) for water storage for 24 h and 3 months. The microshear bond strength was then measured. Data were analyzed using the Shapiro-Wilk test, three-way ANOVA, one-way ANOVA, and Tukey's test (P < 0.05). RESULTS: Application of ferric sulfate decreased the bond strength of all bonding agents after both 24 h and 3 months of storage; but, this reduction was not statistically significant (P > 0.05). Single Bond Universal at 24 h showed the highest and Adper Single Bond at 3 months showed the lowest bond strength (P < 0.001). CONCLUSION: Dentin contamination with hemostatic agents negatively affects the bond strength of total- and self-etch adhesives.
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OBJECTIVES: This study aimed to assess the effect of wet and dry finishing and polishing on microhardness and roughness of microhybrid and nanohybrid composites. MATERIALS AND METHODS: Thirty samples were fabricated of each of the Polofil Supra and Aelite Aesthetic All-Purpose Body microhybrid and Grandio and Aelite Aesthetic Enamel nanohybrid composite resins. Each group (n=30) was divided into three subgroups of D, W and C (n=10). Finishing and polishing were performed dry in group D and under water coolant in group W. Group C served as the control group and did not receive finishing and polishing. Surface roughness of samples was measured by a profilometer and their hardness was measured by a Vickers hardness tester. Data were analyzed using two-way ANOVA (P<0.05). RESULTS: The smoothest surfaces with the lowest microhardness were obtained under Mylar strip without finishing/polishing for all composites (P<0.0001). The highest surface roughness was recorded for dry finishing/polishing for all composites (P<0.0001). Dry finishing/polishing increased the microhardness of all composites (P<0.0001). CONCLUSIONS: Dry finishing and polishing increases the microhardness and surface roughness of microhybrid and nanohybrid composite resins.
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OBJECTIVES: Mineral trioxide aggregate (MTA) is extensively used in endodontics. However, MTA is difficult to handle because of its granular consistency, low mechanical properties and initial looseness. The objective of this study was to assess the compressive strength (CS), diametral tensile strength (DTS), and pH of set MTA using methyl cellulose as liquid. MATERIALS AND METHODS: White ProRoot MTA was used as the control group; modified MTA cement was prepared by mixing Portland cement, bismuth oxide and calcium sulfate (75%, 20% and 5%, respectively) as the experiment group. Methyl cellulose was used as hydrating liquid and compared with distilled water. The data were analyzed by two-way ANOVA. RESULTS: The pH values of modified MTA cement set using deionized water and methyl cellulose were slightly, but not significantly, different (P>0.05). The DTS and CS tests for modified MTA cement hydrated with methyl cellulose showed a significant difference at one day and one week (P<0.05). CONCLUSIONS: The results suggest that using methyl cellulose as the hydrating liquid enhances some mechanical properties but does not compromise pH of white ProRoot MTA.