Abstract
BackgroundHome bleaching agents may exert some negative effects on surface hardness of restorative materials such as glass-ionomer cements (GICs). Since some studies have shown that some components such as hydroxyapatite (HA), as a bioactive glass, can improve the mechanical properties of dental materials, the effect of bleaching agents on surface hardness of GICs containing hydroxyapatite is questionable. This study was designed to evaluate the effect of home bleaching agents on the surface hardness of two different commercially available GICs containing hydroxyapatite.Material and Methods80 disk-shaped specimens were made from two different GICs, including resin modified glass-ionomer and Zirconomer. Each material was divided into four groups (n=10): 1. control, 2. 20 %wt. hydroxyapatite-containing, 3. bleached and 4. bleached 20 %wt. hydroxyapatite-containing. Group 1 and 2 specimens were stored in distilled water for 2 weeks while group 3 and 4 specimens were treated with 15% carbamide peroxide in that period. Surface hardness was tested with Vickers surface hardness tester. Data were analyzed with 3-way ANOVA and mean comparison done by post hoc Tukey tests (p<0.05).ResultsIn general RMGI had a significantly highest Vickers surface hardness value among all groups. 15% carbamide peroxide reduced surface hardness compared to control groups (RMGI and Zr) significantly. In the HA-containing GICs groups, bleaching agent did not significantly changed the surface hardness value.ConclusionsIn this study we concluded that applied treatments (bleaching and adding HA) in implicit percentages reduced surface hardness of GICs. Also we suggest more studies in clinical conditions be done to verify these results. Key words:Home bleaching, Resin Modified Glass-ionomer cement, surface hardness, Zirconia-reinforced glass ionomer, hydroxyapatite.
Highlights
Widespread use of bleaching agents for improving the aesthetic appearance of natural teeth began in 1990 after the introduction of home bleaching technique by Haywood and Heymann [1]
The results of studies on the effects of HA have been conflicting, with some studies showing that insertion of hydroxyapatite ingredients into tooth-colored dental materials lead to the improvement of some mechanical properties such as surface hardness [11,12] but some other studies have reported that adding bioactive HA to glass-ionomer cement compromises its properties [13]
Considering the inconsistency in these outcomes and according to our knowledge; lack of any report on the effect of home bleaching agents on surface hardness of different kind of glass-ionomer cements (GICs) mixed with HA, the aim of this study was to evaluate the effect of 15% carbamide peroxide gel on the surface hardness of two types of commercial GICs containing 20 %wt. of HA
Summary
Widespread use of bleaching agents for improving the aesthetic appearance of natural teeth began in 1990 after the introduction of home bleaching technique by Haywood and Heymann [1]. The results of studies on the effects of HA have been conflicting, with some studies showing that insertion of hydroxyapatite ingredients into tooth-colored dental materials lead to the improvement of some mechanical properties such as surface hardness [11,12] but some other studies have reported that adding bioactive HA to glass-ionomer cement compromises its properties [13]. Home bleaching agents may exert some negative effects on surface hardness of restorative materials such as glass-ionomer cements (GICs). Since some studies have shown that some components such as hydroxyapatite (HA), as a bioactive glass, can improve the mechanical properties of dental materials, the effect of bleaching agents on surface hardness of GICs containing hydroxyapatite is questionable. This study was designed to evaluate the effect of home bleaching agents on the surface hardness of two different commercially available GICs containing hydroxyapatite. We suggest more studies in clinical conditions be done to verify these results
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