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Ilie, Nicoleta (2017): Impact of light transmittance mode on polymerisation kinetics in bulk-fill resin-based composites. In: Journal of Dentistry, Vol. 63: pp. 51-59
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Objectives: to determine the mode of light transmission and its impact on the polymerisation kinetic in modern bulk-fill resin-based (c)omposites (B-RBC). Materials and methods: Four low-viscosity methacrylate-based and one high-viscosity ormocer-based B-RBCs were considered. One material was available in three different shades that were all analyzed. Polymerization kinetic and light transmittance were assessed in 2 and 4 mm specimen depths. Incident and transmitted irradiance and radiant exposure were measured in real-time on a laboratory-grade spectrometer. Results: A progressive enhanced light transmittance during polymerisation was identified in all materials except for TetricEvoFlow BulkFill, which became progressively opaque in all shades. One-way ANOVA and multivariate analysis (alpha = 0.05) were performed. The parameter material has a significant (p < 0.001) effect on DC (eta(2)(P) = 0.856) and light transmittance parameters (irradiance, eta(2)(P) = 0.965;radiant exposure, eta(2)(P) = 0.956);specimen depth influences only transmittance (eta(2)(P) = 0.978;0.980). DC variation in time was best described by an exponential sum function (R-2 > 0.95), differentiating between the gel-and the glass-phase and revealing a faster initiation of polymerization and a slower transition into the glass-phase by lowering the filler volume. Depth retarded the transition into the glass-phase, but did not alter DC measured 300 s post-irradiation. Moderate inverse correlation was identified among DC and filler volume% (-0.646) or filler weight% (-0.403), while no correlation among DC and light transmittance (p = 0.141;0.125). The maximal rate of carbon-carbon double bond conversion varied within the analyzed materials but was independent from specimen's depths. Conclusions: Light transmission changes during polymerization do not alter polymerization kinetics in modern B-RBCs. DC 300s post-irradiation was maintained with depth, while light was attenuated, the faster the more translucent the material was. DC and quality of curing cannot be related to light transmittance in B-RBCs.