The effects of bleaching products on the colour stability of ion-releasing restoratives / Lee Jian Sheng

Lee , Jian Sheng (2024) The effects of bleaching products on the colour stability of ion-releasing restoratives / Lee Jian Sheng. Masters thesis, Universiti Malaya.

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Abstract

The aim of this study is to evaluate the effects of bleaching products on the colour stability of ion-releasing restorative materials (IRMs). The evaluated IRMs included bioactive composite Activa (AB), giomer Beautifil II LS (BI), bulk-fill alkasite Cention-N (CN), encapsulated Riva light-cured resin-reinforced high viscosity glass ionomer cement (RV) and a conventional nanohybrid composite resin Luna (LN). Customised cylindrical acrylic mould was used to fabricate 45 disc-shaped specimens of each material. The samples were then finished and polished, and immersed in artificial saliva for two weeks. The baseline colour of all samples was measured with a spectrophotometer using the CIEL*a*b* colour space. The specimens were then randomly distributed into three groups of 15. Group A specimens were immersed in artificial saliva (AS) for seven days, Group B specimens were bleached with the take-home bleaching product Pola Night (PN) daily for seven days, and Group C specimens were bleached with the in-office bleaching product Pola Rapid (PR) on day seven, according to manufacturer’s instructions. The colour of the specimens was measured again at 24 hours (T1), two weeks (T2) and one month (T3) after bleaching. The normality of data was first determined using the Shapiro-Wilk test. Then, the colour differences between IRMs and bleaching products were analysed using one-way ANOVA. Their interaction was analysed using two-way ANOVA. Repeated measures ANOVA was done to determine the differences between T1, T2 and T3. All statistical analyses were done with a significance level of p<0.05. The data of all parameters were as follows: ΔL* ranged from (-0.02 ± 1.23) to (4.94 ± 1.37); Δa* varied from (-0.31 ± 0.12) to (0.65 ± 0.13); Δb* differed from (-3.08± 1.24) to (0.31 ± 0.86); ΔE* ranged from (0.94 ± 0.48) to (5.99 ± 1.33). Colour change was mainly ascribed to the increase in L* and decrease in b* values. Results of statistical analysis showed that the colour change in RV was significantly affected by PN (3.34 ± 0.72) and PR (3.55 ± 0.78), compared to the unbleached samples (1.38 ± 0.68). PN and PR produced similar colour changes. At T1, the highest colour change was seen in RV bleached with PN and PR. At T3, AB showed the greatest colour change in AS (5.99 ± 1.33), PN (3.80 ± 1.41) and PR (4.02 ± 1.31). The colour of BI and LN were the least affected by bleaching. Between time intervals, there were no differences in the colour change for all IRMs, except for AB which significantly increased from T1 to T3. In conclusion, the effects of bleaching products on the colour stability of IRMs were material dependent in which RV was significantly affected. There were no differences in the colour change produced by PR and PN. The post-bleaching colour of most IRMs remained stable over time, except for AB. This implied that bleaching product should be cautiously applied to avoid undesirable effects on restorative materials.

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