Abstract
BackgroundTooth bleaching is a safe and conservative treatment modality to improve the esthetic appearance of discolored teeth. One of the problems with the use of bleaching agents is their possible effect on surface microhardness of resin-based materials. The present study was carried out to evaluate the effect of in-office and at-home bleaching on surface microhardness of giomer.Material and MethodsSeventy-five disk-shaped giomer samples (Beautifil II) were prepared and cured with a light-curing unit. The samples were randomly assigned to three groups (n=25). In group 1 (control), the samples were stored in distilled water for 14 days. The samples in groups 2 and 3 underwent a bleaching procedure with 15% carbamide peroxide (CP) (8 hours daily) and 45% CP (30 minutes daily), respectively, for 14 days. Finally, the microhardness of samples was measured with Vickers hardness tester using a 100-g force for 20 seconds. One-way ANOVA was used to compare the mean microhardness values among the study groups, followed by post hoc Tukey test for two-by-two comparison of the groups. Statistical significance was set at P<0.05.ResultsOne-way ANOVA showed significant differences in the mean microhardness values among the study groups (P<0.001). Based on the results of Tukey test, microhardness in the bleached groups was significantly less than that in the control group (P<0.0005). In addition, microhardness in the 45% CP group was significantly less than that in the 15% CP group (P<0.0005).ConclusionsUse of both bleaching agents during in-office and at-home bleaching techniques resulted in a decrease in surface microhardness of giomer. The unfavorable effect of in-office bleaching (45% CP) was greater than that of at-home bleaching (15% CP). Key words:Dental restorations, hardness, tooth bleaching.
Highlights
Achieving favorable and esthetic restorations is one of major concerns for dentists [1]
Since surface hardness reflects the compressive strength and wear resistance and is one of the most important physical properties of resin-based materials, the present study evaluated the effect of tooth bleaching with 15% and 45% carbamide peroxide (CP) on surface microhardness of giomer
Kamangar et al evaluated the effects of 15% CP and 40% hydrogen peroxide (HP) bleaching agents and reported a decrease in microhardness of composite resin after application of these materials [14]
Summary
Achieving favorable and esthetic restorations is one of major concerns for dentists [1]. Different studies have yielded contradictory results in relation to the effect of bleaching gel on surface microhardness of composite resins [9,10,11]. Giomers are a new group of direct, adhesive restorative materials that exhibit esthetic, handling and physical characteristics of composite resins in association with advantages such as high radiopacity, an anti-plaque effect, and release and recharge of fluoride. The present study was carried out to evaluate the effect of in-office and at-home bleaching on surface microhardness of giomer. Conclusions: Use of both bleaching agents during in-office and at-home bleaching techniques resulted in a decrease in surface microhardness of giomer. The unfavorable effect of in-office bleaching (45% CP) was greater than that of at-home bleaching (15% CP)
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