Influence of photoactivation method and mold for restoration on the Knoop hardness of resin composite restorations

Depth-Related Curing Potential of Ormocer- and Dimethacrylate-Based Bulk-Fill Composites

The aim of this in vitro study was to investigate the degree of C=C double bond conversion of high-viscosity dimethacrylate- or ormocer-based bulk-fill composites as a function of measurement depth. Four bulk-fill composites (Tetric EvoCeram Bulk Fill, x-tra fil, SonicFill, and Bulk Ormocer) and the conventional nanohybrid composite Tetric EvoCeram were applied in standardized Class II cavities (n = 6 per group) and photoactivated for 20 s at 1350 mW/cm². The degree of conversion of the composites was assessed using Fourier-transform infrared spectroscopy at seven measurement depths (0.15, 1, 2, 3, 4, 5, 6 mm). Data were analyzed using repeated measures ANOVA and one-way ANOVA with Bonferroni post-hoc tests (α = 0.05). The investigated bulk-fill composites showed at least 80% of their maximum degree of conversion (80% DC_max) up to a measuring depth of at least 4 mm. Tetric EvoCeram Bulk Fill and Bulk Ormocer achieved more than 80% DC_max up to a measuring depth of 5 mm, x-tra fil up to 6 mm. The conventional nanohybrid composite Tetric EvoCeram achieved more than 80% DC_max up to 3 mm. In contrast to the conventional composite, the investigated ormocer- and dimethacrylate-based bulk-fill composites can be photo-polymerized in thick layers of up to at least 4 mm with regard to their degree of C=C double bond conversion.

Curing Depth and Degree of Conversion of Five Bulk-Fill Composite Resins Compared to a Conventional Composite

Background:

Limited curing depth and its effect on the degree of conversion are among the challenges of working with light-cure composite resins. The use of bulk-fill composites is one strategy to overcome these limitations.

Methods:

Ever X Posterior (EXP), Filtek Bulk-Fill Posterior (FBP), Sonic Fill 2 (SF2), Tetric N-Ceram Bulk-Fill (TNB), and X-tra Fil (XF) bulk-fill and Filtek Z250 conventional composite were evaluated in this in vitro experimental study. Six samples for the assessment of microhardness and three samples for the evaluation of DC were fabricated of each composite. After light curing and polishing, the samples were incubated at 37°C for 24 hours. Microhardness was measured by a Vickers hardness tester three times and the mean value was calculated. DC of the top and bottom surfaces was determined using Fourier-Transform Infrared Spectroscopy (FTIR). Data were analyzed using one-way ANOVA and Tukey’s test.

Results:

Microhardness and DC were significantly different among the groups (P<0.001). XF and Z250 equally showed the highest bottom-to-top surface microhardness ratio (0.97 ± 0.01) and significantly higher DC in the top (P<0.001) and bottom (P<0.005) surfaces compared to other groups. TNB showed the lowest microhardness ratio (0.88 ± 0.04) and DC (68.66 ± 1.52 and 61.00 ± 2.00); the difference in DC of the bottom surface was statistically significant (P<0.003).

Conclusion:

It appears that bulk-fill composites evaluated in this study are adequately polymerized at 4 mm depth. Their DC was optimal and within the range of conventional composites.

The influence of three photoactivation techniques on the sorption and solubility of different composite resins

Abstract Introduction There is a growing demand for aesthetic restorations and the polymerized composite resins are the most used material in these procedures. In order to achieve greater resistance to solubilization proper polymerization is required. Objective Evaluate the influence of three photoactivation techniques, on sorption and solubility of three composite resins. Materials and methods 90 test samples measuring 8 mm diameter and 1 mm thick were made and divided into 9 groups (n=10) of resins -Filtek Z350 XT, Tetric N-Ceram and IPS Empress Direct, each of them was polymerized with LED Bluephase, using the techniques: Conventional, Soft-Start (SS) and Pulse Delay (PD). Afterwards they were placed in desiccator with silica gel at 98.6 F and weighed daily until obtaining a constant mass (m1). Then they were immersed in deionized water for seven days and weighed again (m2). The test sample reconditioning was performed using the m1 procedure, until a constant mass (m3 ) was obtained. The sorption and solubility values were calculated and subjected to ANOVA test (two-way), followed by Tukey post hoc, p<0.05. Result There were no statistically significant differences in sorption and solubility among the studied resins when photoactivation techniques were compared. For solubility analysis, statistically significant differences were observed among the materials. The results for composite resin Filtek Z350 XT presented higher statistical hybridization values than those of the other evaluated resins. Conclusion The different forms of photoactivation had no influence on the sorption and solubility of the tested composite resins.