Aging Restorations in the Esthetic Zone: A Visual and Spectrophotometric Outcome

Statement of Problem: The tooth in the esthetic zone can be restored using various direct and indirect restorative materials. While their appearance may be acceptable on the day of delivery, their optical characteristics may change over time, resulting in patient dissatisfaction and the need for replacement. A lack of clinical follow-up monitoring of the color stability of these restorations necessitates the development of methods that may offer insight into raising awareness of this issue. Objective: To assess the color stability of direct and indirect restorative materials following simultaneous aging in coffee and simulated toothbrushing followed by repolishing of the restoration. Methods and Materials: A central incisor ivory tooth was prepared for a veneer and was restored with seven different restorative materials (n = 5). A direct packable composite resin (PC), flowable composite resin (FC), and 5 indirect restorative materials (lithium disilicate [LD], 4% yttria partially stabilized zirconia [4Y-PSZ], zirconia reinforced lithium silicate [LS], additive manufactured nanoceramic [AM], and milled composite resin [MC]). The indirect veneers were cemented with a light-cured adhesive resin cement. All veneers were polished according to manufacturers' instructions. The aging method was defined by immersion in coffee at 37°C for 24 h and then moving to the toothbrush simulator for a 3500-brush cycle, and this cycle was repeated for a total of 28 days between immersion in coffee for a total of 14 days and a total of 50,000 toothbrushing cycles. After this period, the restorations were repolished according to the common clinically recommended method for each material. Spectrophotometric readings and standardized photographs were taken at baseline and following the 14-day aging method. Color difference (ΔE_oo) was calculated for each veneer. A repeated measures two-way analysis of variance (ANOVA) and Tukey's post hoc test (α = 0.05) were used to analyze the data. Results: Both restorative material type and aging method affected ΔE_oo (p < 0.001). Discoloration varied among restorative materials across aging method stages (p < 0.001). AM exhibited the greatest color difference after the aging method (9.1 ± 0.87), while ΔE_oo values decreased following repolishing for all materials. Repolished 4Y-PSZ veneers demonstrated the lowest ΔE_oo values (0.70 ± 0.53). Conclusions: LD veneers maintained the highest degree of color stability during the method of aging. The restorative materials' original color may be restored to a level that is acceptable through repolishing. Not only did AM veneers exhibit a lack of color stability, but there was also visual staining of the margins. Clinical Relevance: A clinician's understanding of the composition of restorative materials and its impact on color stability and appearance over time determines their ability to select the most appropriate restorative material that can support esthetic longevity.