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Butterhof, Maximilian; Ilie, Nicoleta (2020): Mathematical model for assessing true irradiance received by luting materials while curing through modern CAD/CAM resin composites. In: Dental Materials, Vol. 36, No. 8, E255-E265
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Statement of problem. Measurement of irradiance passing through a dental restoration for properly curing a dual- or light-polymerized luting composite is imprecise due to surface reflection. Objective. To provide a mathematical correction of measured transmitted irradiance for predicting true transmitted light intensity through CAD/CAM restorations. Methods. A total of 432 specimens were fabricated. Seven modern CAD/CAM resin -based composites (RBCs) and one CAD/CAM glass -ceramic (control group) were sectioned and polished into specimens of 0.5-5 mm thickness (in 0.5 mm steps, n = 6). Irradiance of a violetblue LED light curing unit (LCU) (power modes: Standard, High and Plasma) was measured after passing through each specimen with a spectrometer. Data was compared based on 95% confidence intervals and using univariate ANOVA followed by Tukey HSD (a = 0.05). Results. The measured transmitted irradiance passing through the specimens decreased exponentially. Significantly highest values of transmitted irradiance were measured for 0.5 mm thick specimens for all materials (p <0.05). The decadic absorption coefficient for CAD/CAM-RBCs ranged from 0.292 mm 1 to 0.387 mm 1 while the control group (glass ceramic) reached a significantly lower value of 0.283 mm-1. The reflection ratio for all materials ranged from 12.6% to 18.5%. Significance. A correction can be implemented to predict the true transmitted irradiance after passing through a dental restoration as function of initial irradiance, specimen thickness and material specific parameters. For a practitioner, this model may be applied depending on the specific treatment conditions, the individual LCU's radiant emittance and restoration thickness for the tested materials. (C) 2020 The Academy of Dental Materials.