Resin Treatment for Enamel Discolorations: Color Changes Due to Aging

Objectives: The objective of this study included evaluation of color change of enamel following acid demineralization and after application of resin infiltrant, Icon™. Also, color difference (ΔE), lightness (ΔL), and metamerism indexes (MI) were examined following exposure to three different artificial accelerated aging (AAA) protocols (thermocycling, UV light, beverage).
Methods: Sixty extracted bovine incisors and/or canines of similar size were cleaned, and baseline refectance spectra measurements of the enamel surfaces were obtained using a CM-5 spectrophotometer. Teeth were demineralized in lactic acid (0.1M lactic acid, 6wt% hydroxyethylcellulose-adjusted to pH 5.1 with 1.0M NaOH) for three weeks followed by color spectrophotometer readings. Icon™ resin infiltration system, which included demineralization of enamel surfaces using 15% hydrochloric acid gel for 60 seconds; rinsing thoroughly with water; immersion in 100%EtOH; and desiccation with air for 30 seconds, was performed. Resin was placed on the entire labial surface with any excess removed and light-cured using an LED light source for 60 seconds. Color meaasurements were again recorded. Specimens were equally divided into three subgroups with exposure to different AAA protocols, followed by final color measurements. Reflectance measurements were made under daylight (D65), fluorescent (F2) and incandescent (A) illuminants. ΔL, ΔE, and MI were determined using the CIEL*a*b* color formula for total and incremental changes. Three-way ANOVA (p < 0.05) tests were performed to determine statistical differences in ΔL, ΔE, and MI between treatments. A threshold of ΔE>2.7 indicated a visible clinical disparity for color comparisons.
Results: In general, for all samples, ΔL and ΔE parameters increased significantly from baseline to demineralization and were subsequently decreased following Icon treatment. Beverage and UV treatments caused a significant change in ΔL and ΔE. MI revealed significant changes for all illuminant combinations following beverage treatment.
Conclusions: Resin infiltration restored the ΔL and ΔE due to the demineralization process while maintaining the ΔL and ΔE with respect to thermocycling. Beverage and UV exposure regimens caused noticeable color differences in the teeth enamel. Resin infiltrants can help to mitigate demineralization.