Effect of bleaching protocols on surface roughness and biofilm formation on silorane‑based composite resin

Mahmoud Bahari, Mohammad Esmaeel Ebrahimi Chaharom, Mehdi Daneshpooy, Sarah Gholizadeh, Hamed Pashayi


Background: Knowledge about the effect of bleaching on behavior of composite resins is important
to find a suitable composite resin for restoration of teeth undergoing bleaching. This study aimed
to assess the effect of different bleaching protocols on surface roughness and biofilm formation
on a silorane‑based composite resin.
Materials and Methods: In this in vitro experimental study, 60 silorane‑based composite resin
samples measuring 3 mm in thickness and 6 mm in diameter were fabricated and polished. They
were then randomly divided into four groups (n = 15). In Group 1, samples were stored in distilled
water as control. Samples in Groups 2, 3, and 4 were subjected to bleaching with 15% carbamide
peroxide, 35% hydrogen peroxide, and 35% hydrogen peroxide activated by light, respectively. Surface
roughness was measured using a profilometer. Streptococcus mutans cultured in brain‑heart infusion
broth was used for the assessment of biofilm formation on the samples. The bacterial colonies
were counted using the pure‑plate technique. Data were analyzed using one‑way ANOVA and post
hoc Tukey’s tests. Regression model was used to assess the association between surface roughness
and biofilm formation (P < 0.05).
Results: The mean surface roughness of the four groups was not significantly different (P = 0.11);
however, a significant difference was noted in the mean biofilm formation among the groups (P = 0.00).
Conclusion: Bleaching decreased biofilm formation. The lowest biofilm formation was noted in the
group subjected to light‑activated 35% hydrogen peroxide. Increased surface roughness enhanced
biofilm formation to a certain level; excessive roughness did not increase biofilm formation.
Key Words: Biofilm, composite resin, silorane, tooth bleaching

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