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This study aimed to evaluate the effect of light attenuation through ceramic veneers and resin cement on degree of conversion (DC), cohesive strength (CS), and microshear bond strength (µSBS) of experimental adhesive systems. Experimental etch-and-rinse and self-etch adhesives were combined with different ratios of camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiators: CQ-only; 3CQ:1TPO; 1CQ:1TPO; 1CQ:3TPO and TPO-only. Square-shaped ceramic veneer (IPS Empress Esthetic, Ivoclar Vivadent) (n = 10; 10mm long x 10mm wide x 0.5mm thick) and resin cement specimens (Variolink Esthetic LC, Ivoclar Vivadent) (n = 10; 10 mm long x 10 mm wide and 0.3 mm thick) were prepared. Light transmittance of a multiple-peak LED (Bluephase G2, Ivoclar Vivadent) was measured through restorative materials using a spectrometer (n = 5). Adhesive specimens were analyzed for DC, CS, and µSBS by light-curing the adhesive with or without (control) ceramic veneer, and with resin cement fixed to output region of the light-curing tip (n = 10). Data were submitted to ANOVA and Tukey's test (a = 0.05). Total light transmittance through the restorative materials was attenuated, and this attenuation was more evident for the violet spectrum. The DC for the TPO groups in ratios up to 1CQ:1TPO was similar to the control. 1CQ:3TPO showed lower values for CS. µSBS was reduced for all groups with light attenuation, but lower values were observed for 1CQ:3TPO and TPO-only. In conclusion, light transmission was reduced with interposed restorative materials. Adhesives combined with CQ and TPO up to 1CQ:1TPO showed greater cure efficiency and mechanical properties compared with a higher amount of TPO. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to evaluate how acid-etching of the cavosurface enamel in Class I resin composite restorations influences the bond strength to the pulpal wall and the restoration, Knoop microhardness and nanoleakage after thermomechanical aging. For this research 76 fresh human molars were selected and restored with Silorane or Clearfil SEBond/Z350XT composite divided in 4 groups (Silorane system restored with or without enamel cavosurface acid-etching and Clearfil SEBond/Z350XT with or without enamel cavosurface acid-etching). To induce artificial aging, samples were subjected to thermomechanical cycling through 200,000 and thermal cycling between 5 and 55 °C with 30 second filling and 15-second drainage steps. Microhardness and microtensile bond strength were evaluated in 32 teeth (n=8) each and nanoleakage evaluation was performed in 12 teeth (n=3). Samples restored by Clearfil SEBond/Z350 XT without cavosurface acid-etching showed significantly lower microtensile bond strength results. The resin composite Z350XT presented higher values of Knoop microhardness. It was observed little or no infiltration for Silorane groups and moderate infiltration for Clearfil SE Bond groups. Acid-etching of the cavosurface enamel during restoration procedure with Clearfil Se Bond resulted in a stronger bond after thermomechanical cycling. Silorane groups showed less infiltration than Clearfil SE Bond groups. [ABSTRACT FROM AUTHOR]

Objectives To evaluate the effect of nanofiller loading on cure efficiency and potential color change of experimental composites. Materials and Methods Four different polymeric materials were produced using the same organic matrix blend. To this matrix, different amounts of 0.05 μm fumed silica filler were added: no filler, 13, 52, and 65wt%. Fourier transform infrared spectroscopy was used to evaluate the degree of conversion (DC) for each composite using near-IR analysis, and spectrophotometry according to CIELab chromatic space was used to evaluate the color change.To induce color change, composites were artificially aged with exposure to cycles of UV-B light for 300 hours. Trasmission electron microscopy was used to illustrate nanoffiler aglomeration in the resin matrix. Data were analyzed using correlation analysis (α = 0.05). Results There was an excellent inverse linear correlation between filler wt% and either DC or color change. Greater changes to red (+Δ a) and yellow (+Δ b) were observed as the filler wt% increased. Conclusions A higher percentage of nano-sized filler particles in dental resin composites directly affects their cure efficiency and potential for color change. Clinical Significance The increase in filler particle loading negatively affected monomer conversion and color stability of resin-based composites. As reduced filler loading results in poorer mechanical properties, to enhance color stability, resin-based composites should be formulated by making the refractive index of the polymeric matrix more closely match that of the filler throughout the polymerization process. (J Esthet Restor Dent, 2016) [ABSTRACT FROM AUTHOR]

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Copyright of Revista Dental Press de Estética is the property of Dental Press International and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)