A study on colour stability of self-etching and etch-and-rinse adhesives

The purpose of this study was to investigate the color change in two "self-etch" and one "etch and rinse" adhesive under dark/water and photoaging conditions and to evaluate the influence of these changes on the color stability of resin composite restorative systems.

The adhesives were: One-Up Bond F (OB/Tokuyama), Adper Prompt L-Pop (PL/3M Espe) and Optibond Solo Plus (OS/Kerr). 10 sample disks of each material were prepared (OB(1), LP(1), OS(1)). Additionally, 30 sample discs of TPH Spectrum (Caulk/Dentsply) resin composite were prepared and bonded with the three adhesives tested (OB(2), LP(2), OS(2) groups) to freshly cut dentin discs. 30 days of storage in deionised water (37+/-1 degrees C) in dark conditions was followed by exposure of all samples to UV light photoaging. A colorimetric evaluation (CIEL*a*b* system) was performed immediate after sample photopolymization (baseline), at 7 and 30 days of dark/water storage and after the 360h of UV aging. Color changes (DeltaE*) were calculated between baseline and subsequent measurements. The results were analyzed by independent two-way Anova and Sheffe's statistical tests (a=0.05).

All the adhesives evaluated exhibited significant color changes even after early aging time into water. One-Up Bond F presented the highest color alterations under both experimental conditions and Optibond Solo Plus the lowest. The adhesives were proved able to influence the color stability of a resin composite, which is bonded to a dentin substrate. One-Up Bond F induced the strongest effect on color change of the resin composite while no differences were clarified between Adper Prompt L-Pop and Optibond Solo Plus.

Significant color changes were determined under water and photoaging conditions for the "self-etch" and "etch and rinse" adhesives evaluated and the resin composite combined with these agents.