Influence of the photoactivation distance on the color and whiteness stability of resin-based composite after bleaching and aging.

Abstract Objectives To evaluate the influence of photoactivation distance on color stability and whiteness changes after bleaching and water storage of a resin-based composite (RBC). Methods Twenty disc-shaped specimens (12 mm x 1 mm; n = 5) from a nanofilled RBC (Filtek Z350 XT) were photoactivated from two distances (0 and 8 mm) and bleached using either an at-home (HB) or an in-office (OB) bleaching protocol. Specimens were stored in distilled water up to 6 months (aged specimens). A spectrophotometer (Vita Easyshade) was used to measure CIE L*a*b* coordinates. Color stability was calculated using CIEDE2000 ( Δ E 00 ) metric, and whiteness variations using the whiteness index for dentistry ( Δ W I D ). The 50:50 % visual thresholds were used to analyzed Δ E 00 values (PT- perceptibility, and AT- acceptability) and ΔWID values (WPT- whiteness perceptibility, and WAT- whiteness acceptability). Color parameters L*, a*, b* and Δ W I D were analyzed using repeated measures two-way ANOVA. Results After bleaching, RBC specimens photoactivated from 0 mm showed Δ E 00 values below AT and the ones from 8 mm had values above AT. After OB, Δ W I D values were below WPT, but all other comparisons were above WAT. Conclusions Bleaching protocol did not influence on color change, but water storage (aging) did influence on color ( Δ E 00 ) and whiteness ( Δ W I D ) changes. However, RBC specimens photoactivated from 8 mm showed color changes above AT after bleaching. Clinical significance Color instability is one of the major causes for replacing esthetic restorations. The whiteness index for dentistry (WID) was able to show the “whiter-darker” effect on RBC after bleaching and aging. Dentists should be aware that RBC may appear darker after HB. Regardless of the photoactivation distance, OB did not show a perceptible difference immediately after bleaching. However, OB and HB showed a darker effect after aging procedure.