Effect of Two Different Bleaching Concentrations on Enamel Color Stability and Surface Roughness: an in Vitro Study, Mostafa, Amr Khaled, Farid Mohamed Riad, ElBaz Maha A., and Basheer Rasha Ramadan , Adv Dent & Oral Health, Volume 5, Issue 1, (2017) Abstract

Introduction: This in-vitro study was designed to investigate bleaching with two different concentrations of hydrogen peroxide on
human enamel surfaces concerning surface roughness and color stability.
Materials and methods: A total number of 60 specimens that were prepared from extracted human anterior teeth were used in this
study. The specimens were randomly divided to two equal groups according to the bleaching agent; 30% hydrogen peroxide (GI) and 38%
hydrogen peroxide (GII) then evaluated for surface roughness and color measurements immediately. They were then subdivided into three
groups according to the solution where it will be immersed as a referred to Cola, B referred to black tea and C referred to artificial saliva.
Specimens were kept in an incubator at 37 degrees celcius and their color was evaluated at 24 and 48 hours.
Results: The results showed a significant increase in surface roughness of the bleached samples compared to the baseline measurements.
However, there was no significant difference between the samples of the two bleached groups concerning surface roughness. Color evaluation
both bleaching agents showed a significant whitening effect compared to the baseline where the 30% hydrogen peroxide was more significant
on immediate measurement. After immersion in cola, black tea and saliva, there was no significant difference between the two groups anymore
while there was a significant relapse in color in both the black tea and cola immersions with the effect of black tea being more pronounced.
Conclusion: Bleaching agents can cause surface alterations and should therefore be used with caution.

Effect of 15% carbamide peroxide bleaching gel on color stability of giomer and microfilled composite resin: an in vitro comparison., Mohammadi, Narmin, Kimyai Soodabeh, Abed-Kahnamoii Mehdi, Ebrahimi-Chaharom Mohammad-Esmaeel, Sadr Alireza, and Daneshi Mehdi , Medicina oral, patologia oral y cirugia bucal, 2012 Nov 01, Volume 17, Issue 6, p.e1082-8, (2012) Abstract

OBJECTIVES: The effect of 15% carbamide peroxide bleaching gel on color stability and surface topography of a giomer and a microfilled composite resin was evaluated in the present in vitro study.

STUDY DESIGN: Forty discs measuring 10 mm in diameter and 1 mm in thickness were prepared from a giomer and a microfilled composite resin. Each material yielded 20 discs with completely smooth surfaces. Then a spectrophotometer was used to measure L* (lightness), a* (redness, greenness) and b* (blueness, yellowness) color coordinates of all the discs. Subsequently, the specimens were subjected to 15% carbamide peroxide bleaching gel. After measuring the color coordinates once again, color changes (ΔE*) were calculated by the CIELAB system. Four specimens from each material (two specimens before bleaching agent application and two specimens thereafter) were viewed under an atomic force microscope (AFM) for surface topography evaluation. Data were analyzed by Mann-Whitney U and Kruskal-Wallis tests at α=0.05.

RESULTS: There were no statistically significant differences in color changes (ΔE*) between the two materials (P>0.05). In addition, no significant differences were detected in surface roughness between composite resin and giomer discs before and after bleaching (P>0.05 for both). However, in both materials the differences in surface roughness were significant before and after bleaching procedures (P<0.001).

CONCLUSIONS: Based on the results of the present study it was concluded that 15% carbamide peroxide does not induce clinically detectable color changes in composite resin and giomer despite an increase in surface roughness.

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