In vitro effect of light-emitting diode light polymerization on the color stability of three resin-based restorative materials

Abstract

Objective. To investigate the color stability of resin-based restorative materials when polymerized with light-emitting diode (LED) curing light in the constant or exponential mode. Material and methods. Eight specimens of Admira (AD), Compoglass F (CO), and Tetric EvoCeram (TE) constantly cured or exponentially cured with a high-powered LED curing light for 10, 20, or 60 s. The CIE-Lab values (L*, a*, b*) were measured prior to and after performing the water storage or color stability test according to EN ISO 7491 (Suntest). Results. Statistical analysis showed significant changes in the color values after each of the aging processes, as well as between ΔL, Δa, Δb, and ΔE of the materials, which were dependent on curing time, mode, and aging condition (p<0.05). CO performed very well during water storage, but AD and TE exceeded the clinically relevant limit ΔE=1. After the Suntest and 180 d additional water storage, TE showed the highest mean (SD) ΔE=4.4 (1.1) to 5.4 (1.9). Although AD and CO performed best in the constant mode, they exceeded ΔE=1. All materials shifted to more red. Conclusions. The extent of discoloration depended on (a) the curing mode, (b) the curing time, and (c) the aging condition. Not all materials performed clinically acceptably in all tests; TE even showed unacceptable ΔE>3.3. The optimal curing time was 20 s for both curing modes and all tested materials.