Bulk Fill Properties: Influence of Storage Time and Irradiance Source

Objectives: The aim of this study was to evaluate the light irradiance influence at the intensities of 400mW/cm² and 800mW/cm² and the influence of the storage time on polymerization depth and surface roughness of different Bulk Fill resin composites.
Methods: Samples (n=6) were prepared for each material, Filtek Z250XT (3M/ESPE), Filtek Bulk Fill (3M/ESPE) and Tetric N-Ceram Bulk Fill (Ivoclar Vivadent), and for each intensity of measured light. A three-disc-shaped teflon matrix with central spaces (5mm diameter and 2mm thickness), equivalent to 2, 4 and 6mm depth, was used to make the samples. After the resin composite (RC) was inserted in the first disc, a matrix strip was placed, the second disc was overlaid and more RC filled the central space. The same procedure was performed to the third disc and photoactivated. Photoactivation was performed according to each manufacturer instruction. The samples were stored in distilled water at 37°C for a period of 24hr and 6 months. The depth of cure (DC) evaluation was performed by Vickers microhardness test (HV) in HMV G20 Microdurometer (SHIMADZU) at the top surfaces. Each surface underwent 3 indentations with 50gf load and 15s time. The surface roughness test (R) was performed through three readings with Lc 0.25mm and velocity of 0.5mm/s, considering the arithmetic average between peaks and valleys (Ra) as results, by the rugosimeter (Surftest SJ-301-Mitutoyo). HV and R mean values were submitted to analysis of variance (ANOVA) and Tukey test (significance of 5%).
Results: For R, there was a statistical difference between all the groups of materials for the light intensity of 400mW/cm² for the 6 months storage time. For HV, there was no statistical significance between any of the groups.
Conclusions: Although bulk fill composites admit good properties, the proper use of a light source with appropriate intensity is fundamental to ensure successful results.