Objective The effect of different photoinitiators on mechanical properties of experimental composites was evaluated. Materials and Methods Resin composites were formulated by using a blend of bisphenol A-glycidyl and triethylene glycol (50/50 wt%) dimethacrylate monomers, and 65 wt% of barium aluminium silicate and silica filler particles. Photoinitiators used were 0.2% camphorquinone (CQ) and 0.8% co-initiator (DMAEMA); 0.2% phenyl-propanedione and 0.8% DMAEMA; 0.1% CQ + 0.1% phenyl propanedione and 0.8% DMAEMA; 0.42% mono(acyl)phosphine oxide (MAPO); and 0.5% bis(acyl)phosphine oxide (BAPO). Specimens (n = 10) were light cured by using a multiple-emission peak light-emitting diode for 20 seconds at 1,200 mW/cm2 of irradiance and Knoop hardness and plasticization, depth of cure, flexural strength, and elastic modulus were evaluated. Data were statiscally analyzed at significance level of α = 5%. Results Experimental composites containing MAPO and BAPO photoinitiators showed the highest values of flexural strength, elastic modulus, top surface hardness, and lower hardness reduction caused by alcohol compared with CQ. Composites containing CQ and PPD showed similar results, except for depth of cure and hardness of bottom surface. Conclusion BAPO and MAPO showed higher flexural strength, elastic modulus, hardness on top surface, and lower polymer plasticization to CQ.

Objective: To evaluate the color stability and degree of conversion of light-cured resin cement with different activator-initiator systems using LED lights with different wavelengths (polywave x monowave). Materials and Methods: Sixteen resin cement samples were made using a circular silicone matrix (7 mm diameter, 0.5 mm thickness) for each of the following tested materials: Variolink Esthetic LC (Ivoclar, color Light+); RelyX Veneer (3M ESPE, color A1); Filtek Z350XT flow resin (3M ESPE, color A1); Allcem Veneer APS (FGM, color A1); NX3 Light cure (Kerr, color A1). Half of the samples were photocured with a monowave LED light (Elipar Deep Cure), and the other half with a polywave LED light (Valo Grand). The initial color of each cement was measured using a high translucency ceramic sample simulating ceramic venner. Color measurements were performed with a reflectance colorimetric spectrophotometer and the data was collected according to the CIE L* a* b* system in two steps. The degree of conversion was measured using an infrared spectrometer by Fourier transform (FTIR / ATR) using the absorbance method. Statistical analysis was performed using ANOVA repeated measures and Tukey’s post hoc tests (p <0.05). Results: For the color analysis, there were no significant differences between the cement related to time versus light curing (p = 0.084) and also related to time versus cement versus light curing (p = 0.142). Among the factors, there was only a statistically significant difference for the type of cement (p <0.01). In contrast, for the photocuring device (p = 0.504) and the interaction between them (p = 0.738), there was no significant difference. For the degree of conversion analysis (DC), it showed a statistically significant difference for both factors, resin cements (p <0.01) and light curing units (p <0.01). Conclusion: The color stability of RelyX cement is low compared to other cements, while Variolink cement presented the best degree of the conversion value.