Shade reproduction and the ability of lithium disilicate ceramics to mask dark substrates

Objectives@#This study aimed to evaluate the ability of lithium disilicate ceramics to reproduce the A2 shade and to mask A4 substrates. @*Materials and Methods@#Twenty-four discs (8 mm in diameter, shade A2) of high translucency (groups 1–3) and low translucency (groups 4–6) of IPS e.max ceramic with different thicknesses (0.5, 0.75, and 1 mm) were fabricated as monolithic structures. In addition, discs of medium opacity (group 7–8) with different core/veneer combinations (0.3 mm/0.7 mm and 0.5 mm/0.5 mm) were fabricated as bilayer structures. Specimens were superimposed on an A4 substrate (complex). The color changes of the complex were measured using a spectrophotometer on a black background, and the ΔE values of the complex were compared with either the A4 substrate or the A2 shade tab. One-way analysis of variance, the Tukey honest significant difference test, and the Fisher test were used to analyze the data (p < 0.05). @*Results@#Significant between-group differences were found for comparisons to both the A4 substrate and the A2 shade (p < 0.05). When compared with the A4 substrate, the ΔE values in all groups were in the non-acceptable range. When compared with the A2 shade, the ΔE values in all groups, except groups 2 and 3, were in the clinically acceptable range. @*Conclusions@#All translucencies and thicknesses masked the underlying dark substrate.However, the low-translucency IPS e.max Press better reproduced the A2 shade.

Shade reproduction and the ability of lithium disilicate ceramics to mask dark substrates

Objectives@#This study aimed to evaluate the ability of lithium disilicate ceramics to reproduce the A2 shade and to mask A4 substrates. @*Materials and Methods@#Twenty-four discs (8 mm in diameter, shade A2) of high translucency (groups 1–3) and low translucency (groups 4–6) of IPS e.max ceramic with different thicknesses (0.5, 0.75, and 1 mm) were fabricated as monolithic structures. In addition, discs of medium opacity (group 7–8) with different core/veneer combinations (0.3 mm/0.7 mm and 0.5 mm/0.5 mm) were fabricated as bilayer structures. Specimens were superimposed on an A4 substrate (complex). The color changes of the complex were measured using a spectrophotometer on a black background, and the ΔE values of the complex were compared with either the A4 substrate or the A2 shade tab. One-way analysis of variance, the Tukey honest significant difference test, and the Fisher test were used to analyze the data (p < 0.05). @*Results@#Significant between-group differences were found for comparisons to both the A4 substrate and the A2 shade (p < 0.05). When compared with the A4 substrate, the ΔE values in all groups were in the non-acceptable range. When compared with the A2 shade, the ΔE values in all groups, except groups 2 and 3, were in the clinically acceptable range. @*Conclusions@#All translucencies and thicknesses masked the underlying dark substrate.However, the low-translucency IPS e.max Press better reproduced the A2 shade.

Bioactivity of endodontic biomaterials on dental pulp stem cells through dentin

OBJECTIVES@#This study investigated the indirect effect of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA), as 2 calcium silicate-based hydraulic cements, on human dental pulp stem cells (hDPSCs) through different dentin thicknesses.@*MATERIALS AND METHODS@#Two-chamber setups were designed to simulate indirect pulp capping (IPC). Human molars were sectioned to obtain 0.1-, 0.3-, and 0.5-mm-thick dentin discs, which were placed between the 2 chambers to simulate an IPC procedure. Then, MTA and CEM were applied on one side of the discs, while hDPSCs were cultured on the other side. After 2 weeks of incubation, the cells were removed, and cell proliferation, morphology, and attachment to the discs were evaluated under scanning electron microscopy (SEM). Energy-dispersive X-ray (EDXA) spectroscopy was performed for elemental analysis. Alkaline phosphatase (ALP) activity was assessed quantitatively. The data were analyzed using the Kruskal-Wallis and Mann-Whitney tests.@*RESULTS@#SEM micrographs revealed elongated cells, collagen fibers, and calcified nucleations in all samples. EDXA verified that the calcified nucleations consisted of calcium phosphate. The largest calcifications were seen in the 0.1-mm-thick dentin subgroups. There was no significant difference in ALP activity across the CEM subgroups; however, ALP activity was significantly lower in the 0.1-mm-thick dentin subgroup than in the other MTA subgroups (p < 0.05).@*CONCLUSIONS@#The employed capping biomaterials exerted biological activity on hDPSCs, as shown by cell proliferation, morphology, and attachment and calcific precipitations, through 0.1- to 0.5-mm-thick layers of dentin. In IPC, the bioactivity of these endodontic biomaterials is probably beneficial.

Bioactivity of endodontic biomaterials on dental pulp stem cells through dentin

OBJECTIVES: This study investigated the indirect effect of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA), as 2 calcium silicate-based hydraulic cements, on human dental pulp stem cells (hDPSCs) through different dentin thicknesses.MATERIALS AND METHODS: Two-chamber setups were designed to simulate indirect pulp capping (IPC). Human molars were sectioned to obtain 0.1-, 0.3-, and 0.5-mm-thick dentin discs, which were placed between the 2 chambers to simulate an IPC procedure. Then, MTA and CEM were applied on one side of the discs, while hDPSCs were cultured on the other side. After 2 weeks of incubation, the cells were removed, and cell proliferation, morphology, and attachment to the discs were evaluated under scanning electron microscopy (SEM). Energy-dispersive X-ray (EDXA) spectroscopy was performed for elemental analysis. Alkaline phosphatase (ALP) activity was assessed quantitatively. The data were analyzed using the Kruskal-Wallis and Mann-Whitney tests.RESULTS: SEM micrographs revealed elongated cells, collagen fibers, and calcified nucleations in all samples. EDXA verified that the calcified nucleations consisted of calcium phosphate. The largest calcifications were seen in the 0.1-mm-thick dentin subgroups. There was no significant difference in ALP activity across the CEM subgroups; however, ALP activity was significantly lower in the 0.1-mm-thick dentin subgroup than in the other MTA subgroups (p < 0.05).CONCLUSIONS: The employed capping biomaterials exerted biological activity on hDPSCs, as shown by cell proliferation, morphology, and attachment and calcific precipitations, through 0.1- to 0.5-mm-thick layers of dentin. In IPC, the bioactivity of these endodontic biomaterials is probably beneficial.

Effect of water storage on flexural strength of silorane and methacrylate-based composite resins

OBJECTIVES: This study assessed the effect of water storage on the flexural strength (FS) of low shrinkage composites. MATERIALS AND METHODS: A total of 165 bar-shaped specimens (2 × 2 × 25 mm) were fabricated of 2 low shrinkage composites (Filtek P90 [3M ESPE], GC Kalore [GC International]) and a conventional methacrylate-based composite (Filtek Z250 [3M ESPE]). The specimens were subjected to 3-point bending test at 6 time intervals, namely: immediately after curing, at 24 hours, 1 week, 1 month, 6 months, and 1 year following storage in wet and dry conditions. The FS of the specimens were measured by applying compressive load at a crosshead speed of 1.0 mm/min. Data was analyzed using 3-way analysis of variance (ANOVA) and Tukey's test. RESULTS: Three-way ANOVA revealed significant interactions between time, type of composite, and storage condition (p = 0.001). Tukey's multiple comparison test revealed significant reductions in FS of all composites after 6 months and 1 year of storage in distilled water compared to dry condition. CONCLUSIONS: Filtek P90 showed the highest and GC Kalore showed the lowest FS after 1 year storage in distilled water. The immediate high strength of Filtek Z250 significantly decreased at 1 year and its final value was lower than that of Filtek P90.

Effect of silane on shear bond strength of two porcelain repair systems

Objectives: ceramics have advantages such as optimal esthetics and biocompatibility. However, in the oral environment, they are subjected to high levels of stress due to masticatory forces, saliva, thermal changes and alterations of pH, which increase their risk of fracture. Since replacement of these restorations is costly and time-consuming, composite resin is often used for intraoral repair of these restorations. This study aimed to assess the shear bond strength of two porcelain repair systems by Pulpdent and Ultradent and evaluate the effect of number of silane layers on the shear bond strength

Methods: this invitro experimental study was conducted on 66 porcelain blocks measuring 3×5×8mm. In each kit, samples were randomly divided into three groups of 11. Silane was not used for group one. Groups two and three received one coat and two coats of silane, respectively. After surface preparation, composite was bonded to ceramic surfaces. Data were analyzed using two-way ANOVA

Results: the LSD test showed that application of Ultradent silane significantly affected the shear bond strength [P<0.05] while Pulpdent silane had no such effect [P=0.89]. Application of one layer and two layers of silane was not significantly different [P=0.94]

Conclusion: ultradent ceramic repair kit yields higher shear bond strength at the ceramic-composite interface compared to Pulp dent ceramic repair kit. Use of one or two layers of silane does not make any significant difference with regard to the shear bond strength of ceramic to composite

Microleakage in class V cavities restored with sandwich technique: self-etch versus total-etch bonding systems

Objective: Microleakage has always been a problem in restorative dentistry. To decrease microleakage, modern bonding systems, different application methods and sandwich technique have been recommended. The purpose of this study was to assess the microleakage in class V cavities restored with open sandwich technique using self-etch and total-etch bonding systems

Methods: In this in vitro study, class V cavities were prepared on the buccal and lingual surfaces of 20 extracted sound human third molars and restored with sandwich technique. Fuji II LC glass ionomer [GI] was applied to the cavity floor. After curing, half the cavities received Single Bond and the other half, Clearfil SE Bond application and were all restored with Z250 composite resin. Specimens were immersed in 2% fuchsin solution for 24 hours. After copious water irrigation, specimens were sectioned and evaluated under a stereomicroscope to determine microleakage. Data were analyzed using the Mann-Whitney U test [p<0.05]

Results: The microleakage at the GI-composite interface was less than that at the occlusal and gingival margins; but this difference was not significant. No significant difference was found in microleakage between the two bonding agents in neither of the two layers

Conclusion: The etch and rinse and self-etch systems are similar in terms of microleakage

In Vitro comparison of the effects of two different acid etchants on the microleakage of composite restorations

Objective: Etching of enamel and dentin is an important step in restoration of teeth with composite resin ensuring the retention of restoration and decreasing microleakage. This in vitro study sought to compare the effects of Kimiya and Etch-Rite acid etchants on the microleakage of composite restorations

Methods: This experimental study was conducted on 30 sound human molar teeth. Class V cavities were prepared on the buccal surface of teeth and the teeth were randomly divided into 2 groups of 15. Iranian acid etchant [Kimiya, Iran] was used in group 1 and Etch-Rite [Pulpdent, Watertown, MA, USA] in group 2. The teeth were restored with Valux Plus [3M, ESPE, St. Paul, MN, USA] composite resin and polished by disc. The canal apices were sealed with sticky wax and the entire tooth surface was coated with 2 layers of nail varnish except for 1 mm around the restoration margins. Specimens were immersed in 2% Fuchsin [Fuchsin Dye, Merck, Germany] for 24h and then buccolingually sectioned. Specimens were evaluated under a stereomicroscope [SF-100B, Lomo, Russia] at 40X magnification and the degree of microleakage was determined using a 0-4 scale. The degree of microleakage was statistically analyzed using Mann Whitney U test

Results: No significant difference was found between the two groups of Kimiya and Etch-Ritein the degree of microleakage at the occlusal wall [p=0.1]. The degree of microleakage at the gingival wall was not significantly different between the two groups either [p=0.68]

Conclusion: Based on the results, Kimiya Iranian acid etchant has an efficacy equal to that of Etchrite