Effect of Carbamide Peroxide Bleaching Gel on Composite Resin Flexural Strength and Microhardness

Abstract

This study investigated the effect of 16% carbamide peroxide (Whiteness Perfect/FGM) on the Vickers microhardness and flexural strength of the restorative composites Filtek Z100 (hybrid), Filtek Z350 (nanofill), Brilliant (micro-hybrid) and Opallis (micro-hybrid). Discshaped (4x2 mm; n=5) and bar-shaped (12x2x1 mm; n=10) specimens of each restorative material were randomly divided into 2 groups: (G1) 16 weeks stored in distilled water; (G2) 16 weeks stored in distilled water, with 16% carbamide peroxide application during 6 h per day for the last 4 weeks. The mechanical properties were evaluated using a Vickers microhardness tester and a mechanical testing machine. Data were analyzed by twoway ANOVA and Tukey's (HSD) post-hoc test (α=0.05). Filtek Z100 presented the highest microhardness value, followed by Filtek Z350 and finally by Brilliant and Opallis (p=0.00). Filtek Z100 and Brilliant exhibited the highest flexural strength value, followed by Filtek Z350 and Opallis (p=0.00). Bleaching treatment decreased significantly microhardness of Brilliant and Opallis (p=0.00).

Comparison of Different Bleaching Treatments Effect on Micro Hardness of Four Different Aged Composites

“…The results of composite microhardness are consistent with results of Hatanaka's study, who suggested the highest hardness is for Z100, followed by Z350 a (34). The difference between composite groups can also be justified based on the amount of their filler.…”

“…The greatest hardness of composites is related to Z350, followed by Z250, Z100 and P90, respectively. Of course, the type and distribution of composite fillers and the degree of matrix polymerization can also be effective (34).…”

Hydrogen peroxide bleaching induces changes in the physical properties of dental restorative materials: Effects of study protocols

“…Notwithstanding the relative safety of the treatment, the fact that HP or CP is kept in close contact with the teeth and any associated restorations raises the question of whether the bleaching agent causes undesirable and adverse alterations to the teeth and restorative materials, such as softening and degradation . For this reason, numerous investigations have been conducted to evaluate the effects of bleaching on the properties of restorative materials, such as surface microhardness, surface roughness, color, and flexural strength …”

Effect of different bleaching strategies on microhardness of a silorane-based composite resin

“…Microhardness has drawn much attention in the literature because it is an important physical characteristic of dental materials. 15-18 Hardness of a material has been defined as its resistance against permanent surface indentation or penetration; it depends on a material’s strength, ductility, elastic stiffness, plasticity, strain, toughness, viscoelasticity and viscosity. A material’s ability to abrade or its susceptibility to abrasion by opposing teeth, materials, or being softened by chemical agents has a role in the clinical durability of dental restorations.…”