Correlation between the cytotoxicity of self‑etching resin cements and the degree of conversion.

Aim: The aim of this study was to evaluate the correlation between the cytotoxicity and degree of conversion (DC) of self‑etch resin cements with or without photopolymerization. Materials and Methods: Three self‑etching resin cements with or without photopolymerization were evaluated. Six test groups and one control group represented by a standardized L929‑fibroblast cell culture were formed. The DC was measured by Fourier transform infrared spectrometry and was correlated with cell culture survival. Statistical Analysis: The analysis of variance and Bonferroni–Holm tests were applied (P < 0.05). Results: The results show that, the cytotoxicity of self‑etching resin cements is directly related to the DC. With the exception of Unicem, the other cements show some level of cytotoxicity, even with photopolymerization. Conclusion: These results indicate that photopolymerization of dual cure self‑etching resin cements decrease toxic effects on cell culture. Adequate photopolymerization should be considered during cementation when using dual polymerization self‑etching resin cements.

Influence of different light sources on the conversion of composite resins.

Aims: The purpose of this paper was to evaluate the influence of different light curing units on the conversion of four composite resins with different compositions (Durafill VS® - Heraeus-Kulzer, Tetric Ceram® - Ivoclar/Vivadent, Filtek™ Supreme XT - 3M ESPE™ e Aelite™ LS Packable - Bisco), using differential scanning calorimetry. Materials and Methods: A stainless steel matrix was used to prepare 48 cylindrical composite test samples (n=6), measuring 3 mm in diameter and 1 mm in thickness. The samples were photoactivated using a halogen lamp (Optilux™ 500 - Demetron/Kerr) and three different generations of light-emitting diodes (LEDs) (LEC-470 I - MMOptics, Radii Plus - SDI and Ultra-Lume™ LED 5 - Ultradent). After removal of the matrix, each sample was weighed and hermetically sealed in an aluminum pan and analyzed. The amount of heat liberated by thermopolymerisation of residual monomers after photoactivation was measured in Joules/gram (J/g). The data were submitted to Analysis of Variance (ANOVA) test (P ≤ 0.002) and the Tukey test (P < 0.05). Results: The Ultra-Lume™ LED 5 was superior on degree of conversion for all resins. The Radii Plus was equal to the Ultra-Lume™ LED 5, except for the resin Tetric Ceram® , were the Optilux™ 500 was superior. The LEC-470 I was inferior for the conversion of all resins. Conclusion: The study proves the importance of the compatibility of the different photoinitiators in resin composites with the different light sources.

Effect of hydrogen peroxide topical application on the enamel and composite resin surfaces and interface.

OBJECTIVES: The objective of the present study was to analyze the superficial roughness and the interface between enamel and composite resin restorations after dental bleaching procedure. MATERIALS AND METHODS: Black's class V cavities were made and restored with composite resin, and the whole set, enamel-restorative material, was treated with 35% hydrogen peroxide. Seven procedures of 30 min each were performed. A profilometric assessment was carried out before and after the treatment of each sample, and roughness scores were obtained. Treated and untreated samples were analyzed under scanning electronic microscope and images of their surface were obtained. RESULTS AND CONCLUSION: The treatment with 35% hydrogen peroxide caused no alteration in the interface between enamel and composite resin, Tetric Ceram, fillings and the topical application of 35% hydrogen peroxide on enamel and composite resin, Tetric Ceram, caused an alteration of their surface topography, featuring a predominance of depressions after the bleaching treatment.