Effects of curing time and intensity and polishing technique on color stability of bleach‑shade composite resins

Abstract

Background: Despite the improvements in optical properties of composite resins, their color
stability is still a matter of concern. This study aimed to assess the curing time and intensity and
polishing technique on color stability of bleach‑shade composite resins.
Materials and Methods: In this in vitro, experimental study, 128 discs (1 mm × 8 mm) were
fabricated from two composite resins. The specimens fabricated from each composite were
assigned to 8 subgroups (n = 8) based on the curing time and intensity and polishing with polishing
points or discs. After polishing, the color parameters of specimens were measured by EasyShade
spectrophotometer according to the CIEL* a*b* color system. The specimens were then immersed
in tea solution, and their color parameters were measured again. Color change (ΔE) was calculated
and analyzed at 0.05 level of significance. SPSS 25 was used for data analysis. Univariate four‑way
ANOVA was applied to assess the effects of composite type, curing time, curing intensity, and
technique of polishing on ΔE of composite resins. Since the interaction effects were significant,
subgroup analysis was performed by t‑test. The level of significance for this test was set at 0.05.
Results: The effects of curing intensity and polishing technique were significant on ΔE (P < 0.05).
Filtek Z350 XBW composite specimens polished by polishing points experienced lower color
change than those polished with discs. The minimum ΔE of Gradia XBW composite was recorded
in specimens that underwent high‑intensity curing for 20 s and were polished with polishing points
while the maximum ΔE was recorded in specimens that underwent high‑intensity curing for 20 s
and were polished with discs.
Conclusion: In all groups except on (Filtek, polishing with Disk, curing time = 20 s), high‑intensity
curing and polishing with polishing points were more effective and caused lower color change
compared with low‑intensity curing and polishing with discs.
Key Words: Bleach‑shade composite resins, color stability, light intensity, polishing systems

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Sedighe Sadat HashemiKamangar: Pubmed,Google Scholar