Evaluation of the effect of home bleaching agents on surface microhardness of different glass-ionomer cements containing hydroxyapatite

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.

How a 16% Carbamide Peroxide Home Bleaching Agent Affects the Surface Properties of Chairside CAD/CAM Materials?

“…The carbamide peroxide breaks down into hydrogen peroxide and urea. Hydrogen peroxide causes oxidation by generating free radicals and might induce the breaking of polymer chains (21). Furthermore, free radicals can affect the resin-filler interface and cause filler-matrix debonding (22,23).…”

“…The surface roughness of all materials used in this study was increased, but the increase in BC and VE was statistically significant. A large particle size can increase the microporosity in the structure (21,32). The increase in the surface roughness of BC can be explained by its larger particle sizes (<1μm) (Table 1).…”

Effect of Hydroxyapatite on Surface Roughness of Zirconomer, and Conventional and Resin-Modified Glass Ionomers

“…These materials were developed by adding resin monomers to GICs, resulting in much better esthetics, higher mechanical and handling properties, and higher bond strength to enamel and dentin. Another shortcoming of the conventional glass ionomer cements (CGICs) is their low mechanical strength [ 8 ]. The main reasons for the application of zirconia as a filler are its good chemical and dimensional stability, high toughness and mechanical strength, and a Young’s modulus similar to that of stainless steel alloys.…”

Evaluation of the effect of micro-hydroxyapatite incorporation on the diametral tensile strength of glass ionomer cements

“…[10] Considering the high biocompatibility of hydroxyapatite, some researchers have made attempts to evaluate the effects of incorporating hydroxyapatite powder into restorative dental materials such as GICs. [811121314] The interaction between GICs and hydroxyapatite takes place through carboxylate groups in the polyacid structure. It has been reported that hydroxyapatite incorporation into GICs may improve the mechanical properties of GICs.…”

“…An increase in the bond strength of GIC to the tooth structure can also occur due to similarity of hydroxyapatite to the structure of enamel and dentin. [1213]…”