Color stability assessment of light and self-cured composites following accelerated aging/Procjena stabilnosti boje svjetlosno i samopolimerizirajucih kompozita nakon ubrzanog starenja

Objectives: Measure and compare internal color stability of three light-cured composites and one chemically bonded material after their accelerated aging. Materials and Methods: Color stability tests included nano-filled Filtek Supreme XT (3M ESPE), nano-hybrid Tetric Evo Ceram (Ivoclar Vivadent), microhybrid Herculite XRV (Kerr) of light cured and Bisfil II (Bisco) of self cured composites. All samples were immersed in distilled water of 37[degrees]C and kept in a dark chamber during 24 hours. Thereafter they were divided into three groups. Accelerated aging was performed in accordance with the two different protocols, i.e. water bath at 60[degrees]C and ISO 7491. Control group specimens were stored in distilled water at 37[degrees]C for 30 days. Color differences, CE were calculated from CIE L*a*b* coordinates measured with spectrophotometer against white backing before and after aging of samples. The color perceptibility threshold was set at 1.7 and acceptability threshold at 3.5. Statistical tests carried out on the groups included paired t-test and ANOVA (p [less than or equal to] 0.05). Results: All tested materials showed clinically unacceptable color changes after accelerated aging in water bath, whereas photoaging induced perceptible color change in all light-cured composites. Nano- engineered composites significantly changed their color also in the control group. Conclusions: Internal color stability of tested materials depends on aging conditions and type of dental composite. Chemically-cured material showed better color stability by photo aging. Keywords Composite Resins; Aging; Materials Testing; Color Svrha istrazivanja bila je izmjeriti i usporediti unutarnju stabilnost boje triju svjetlosnopolimerizirajucih materijala i jednoga kemijski stvrdnjavajuceg nakon njihova ubrzanog starenja. Materijali i metode: Testovi za stabilnost boja obavljeni su na svjetlosnopolimerizirajucim kompozitima--nanopunjenju Filtek Supreme XT (3M ESPE), nanohibridu Tetric Evo Ceram (Ivoclar Vivadent) i mikrohibridu Herculite XRV (Kerr) te na samopolimerizirajucem kompozitu Bisfil II (Bisco). Svi uzorci bili su uronjeni u destiliranu vodu (37[degrees]C) i drzani u tamnoj posudi 24 sata. Nakon toga podijeljeni su u tri skupine. Postupak ubrzanog starenja proveden je prema dvama protokolima--u vodenoj kupelji na 60[degrees]C i prema ISO-u 7491. Uzorci iz kontrolne skupine drzani su u destiliranoj vodi 30 dana na temperaturi od 37[degrees]C. Razlike u boji--[DELTA]E, r