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The effect of combining photoinitiator systems on the color and curing profile of resin-based composites
Dayane Carvalho Ramos Salles de Oliveira1, Mateus Garcia Rocha1, Ivo Carlos Correa2
1Department of Biomaterials, School of Dentistry, Oregon Health & Science University, 2730 SW Moody Avenue, 27201 Portland, OR, USA; Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 900, 13414-903 Piracicaba, SP, Brazil.
Objective:
To evaluate the effect of combining camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) on the color and curing profile of resin-based composites.
Methods:
Experimental composites were produced with different CQ and TPO molar concentrations: CQ-only, 3CQ:1TPO, 1CQ:1TPO, 1CQ:3TPO, and TPO-only. Polywave LED was characterized using a beam profiler. Block-shaped samples (5mm×5mm×3mm depth) were cured in a custom-designed mold with a polywave LED positioned to compare the regions exposed to the 420-495nm and 380-420nm LED emittances. To map the cure profile, degree of conversion (DC) of longitudinal cross-sections from each block were evaluated by FT-NIR. Color, light-transmittance and light-absorption during curing were evaluated on specimens 1-3mm thick. Data were analyzed using ANOVA/Tukey's test (α=0.05; β=0.2).
Results:
Though the polywave LED beam profile was non-uniform, up to a depth of 2mm no differences in DC were found among the composites containing CQ with TPO added up to 50%, regardless of the position under the curing tip. Composites with higher TPO concentration showed a decrease in DC beginning with a depth of 1mm, while composites with higher or similar CQ concentrations did not show decreased DC until a depth of 3mm. Higher TPO concentration reduced initial yellowness and color change after curing; and lower CQ concentration decreased light-absorption at greater depths.
Significance:
The combination of CQ with TPO added up to 50% reduced the yellowness and color change of composites after curing without affecting cure efficiency up to a depth of 2mm.
