The effect of ceramic light scattering on an inhomogeneous beam profile

What is it about?

Aim: The study aimed to measure light scattering of a broad spectrum light curing unit (LCU) as influenced by ceramic type, shade and thickness as well as exposure distance and LCU’s position. Methodology: A broad spectrum LED LCU (ASCENT OL5) was mounted above a spectrometer (MARC Resin Calibrator, Blue, Light Analytics) at exposure distances of 1.0, 1.5 or 2.5 mm. The position of the center of the head was aligned with the spectrophotometer’s sensor and then moved in 1 mm increments in the X-Y plane, while concomitantly recording the irradiance. The process was repeated with lithium disilicate and leucite glass ceramic slabs of similar thicknesses. The loss in irradiance related to the value measured at center position was analyzed by means of linear regressions and multiple ANOVA analysis. Results: The regressions showed a good fit (90% – 99%). Moving away from the center showed decreased irradiance. Values of slope obtained were divided by their respective intercept to eliminate the influence of the irradiance measured at the center. Two three-way ANOVA’s were performed. One examined the influence of ceramic slab, direction and translucency/shade. It shows only the direction of measurement exhibited significant influence (p < 0.0001) on the mean normalized slope values. The other one examined the influence of ceramic slab, direction and slab thickness. It shows the mean normalized slope values are significantly influenced by the direction of measurement and the slab thickness (p < 0.0001). Values of the slopes indicated the ceramic scattering effect of the light. Thicker samples showed more scattering. Conclusion: The ceramic types, translucency/ shade had no significant effect on the light scattering. The thicker the ceramic the less irradiance changes were found indicating that the ceramics were scattering the light and thus slightly alleviating the effect of the inhomogeneous beam profile. Keywords: light curing, beam profile, glass ceramics, light scattering.

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