Optimal Distance of the Light-curing Tip for Light Transmission Through the Resin Composite

Objectives: Light transmittance of dental composites varies according brand of composites, irradiation related parameters of the light curing unit, including the shape of the curing tip. Aim of this study was to evaluate the influence of distance of the light curing tip to the transmittance of the curing light through the particulate resin composite.
Methods: Light transmittance of four restorative composites (Supreme XTE A3, Supreme XTE Flow A3, G-aenial Posterior, Grandio Flow) were compared using MARC resin calibrator (Blue Light Analytics) radio-spectrometer. Composite disks of 1 mm thickness (ø 6mm) were fabricated. Light intensity was measured by chahing the distance of the light tip to the composite (0,2,4,6,8,10 mm). Two LED light curing units Elipar S10 (3M-Espe) and Silverlight (GC) was used. Light intensity was measured in parallel through the composite disk and without the disk, and an light transmission intensity ratio was calculated. Statistical analysis was carried using analysis of variance (ANOVA,Tukey´s, α =0.05)
Results: Light transmission intensity ratio varied between 20% to 35% with composites (p<0.05). The highest light transmission intensity ratio with Elipar S10 was noted with 4 mm distance of the light tip, whereas Silverlight had highest intensity ratio with distance of 6 mm. Light transmission intensity with Elipar S10 was higher with tip distance of <5 mm, which was opposite for the Silverlight curing unit.
Conclusions: In general, the increase of the distance of light during tip decreased light transmission intensity through composite. However, light curing tip of tested curing devices seemed to focus the light, and thus the optimal distance of the tip varied between 4-6 mm.