Effect of Different Resin Cements on the Bond Strength of Custom-made Reinforced Glass Fiber Posts-A Push-out Study.

AIM AND OBJECTIVE: This study aims to evaluate the effect of different resin cements on the bond strength (BS) of custom-made glass fiber posts (GFPs) using the push-out test. MATERIALS AND METHODS: Twenty-four uniradicular bovine teeth were selected. The crowns were sectioned at the cementoenamel junction, and the root canals were treated. The post spaces of the teeth were prepared to a length of 12 mm to receive a GFP. The specimens were randomly assigned to three experimental groups (n = 8), according to the resin cement used to fix the GFPs: RelyX U200 (U200), Allcem Core (ACC), and Allcem Dual (ACD). Each specimen was sectioned into six slices per root third (cervical, middle, and apical), which were subjected to the push-out test. BS values were calculated and compared using the Kruskal-Wallis and Friedman tests. RESULTS: There were significant differences in the middle third, according to the resin cement type used (p < 0.05). ACD showed lower BS values (p < 0.05). Significant differences were observed for ACD among the thirds of the slices, with the lowest values also observed for the middle third (p < 0.05). CONCLUSION: The present study shows that ACC and U200 showed higher BS values compared with ACD, and were also less influenced by the depth of the root dentin. CLINICAL SIGNIFICANCE: The restoration of endodontically treated teeth is a challenge in dentistry, and, in most cases, will require installation of fiberglass pins. In this respect, several types of resin cements are indicated for cementation of these pins; for this reason, their adhesiveness must be adequately investigated. Conventional cements and self-adhesive cements have shown satisfactory performance in cementing the custom-made GFPs, thereby making these cements satisfactory clinical choices. The present study suggests that ACD had lower performance than the other two cements evaluated.

Esthetic planning with a digital tool: A clinical report.

This clinical report describes digital planning and execution using a novel software tool to enhance digital workflow. The proposed treatment, integrated with the face of the patient, was presented before clinical treatment. The patient was rehabilitated with ceramic veneers. The virtual design contributed to a satisfactory and predictable esthetic outcome.

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 surface area and geometry of specimens on bond strength in a microtensile test: an analysis by the three-dimensional finite element method.

PURPOSE: This study employed three-dimensional (3D) finite element analysis to investigate the stress distribution patterns in a microtensile test with the goal of evaluating the effects of the bond surface area and geometry on bond strength. MATERIALS AND METHODS: Finite element models of six specimens were generated: three stick models and three hourglass models. All models simulated the bond strength between dentin and ceramic. The mechanical properties of the materials-the modulus of elasticity and Poisson's coefficient-were defined according to a literature review. The base of each specimen was considered inserted (constrained area) and possessed nodes with displacements restricted in all directions. A traction load, which was calculated to generate a uniformly distributed stress of 20 N/mm(2) at the bond interface, was applied to the top of the specimen. The distribution pattern of the generated stress was qualitatively and quantitatively measured based on color scales ranging from blue to red, according to the von Mises equivalent stress. RESULTS: Specimens with similar shapes demonstrated similar stress distributions. Ceramic specimens had a higher stress value (30.35 MPa) compared to specimens consisting of resinous cement (23.59 MPa) and dentin (19.77 MPa). At the bond interface, the specimens with square sections demonstrated stress values ranging from 22.00 to 24.20 MPa. For the circular section, the stress values ranged from 23.40 to 27.00 MPa. CONCLUSION: The maximum stress values determined for the circular and square sections were similar among specimens with the same interface area. At the bond interface, the highest stress values were observed in hourglass-shaped specimens.

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.