New Page 1 Statement of Problem: Due to the growing popularity of vital bleaching by CARBAMIDE PEROXIDE it is imperative to understand the effect of such agents on enamel and dentine. Purpose: The purpose of this study was to evaluate the effect of a 16% CARBAMIDE PEROXIDE bleaching gel; Vivastyle on enamel staining susceptibility. Materials and Methods: Thirty bovine specimens were selected and randomly divided into two groups of fifteen. The experimental group was subjected to Vivastyle gel and then was immersed in coffee, for half an hour daily for three weeks. The control group was only immersed in coffee. The teeth were evaluated by colorimeter readings to measure L*, a*, b* of each tooth. Total color differences between two colors (ΔE) were calculated using the following formula: ΔE= [(ΔL*) 2 + (Δa*) 2+ (Δb*) 2]. ΔE1 represent color difference after bleaching; ΔE2: bleached and immersed in coffee, and ΔE3 immersed in coffee. Results: Mean color difference were: 9.478, 13.808, and 7.230 for ΔE1, ΔE2, and ΔE3 respectively. Paired comparison by Duncan test showed that there was a significant difference between ΔE1 and ΔE2 (P0.000). t-test showed that there was no significant difference between ΔE3 and ΔE1. (P=0.08), however, ΔE3 had significant difference with ΔE2 (P0.000). Conclusion: After vital bleaching, the enamel staining susceptibility is significantly increased.  

Objective: The aim of this study was to determine the effects of 40% hydrogen PEROXIDE and 15% CARBAMIDE PEROXIDE on microhardness and color change of a silorane-based composite resin in comparison with two methacrylate-based composites.Materials and Methods: Fifty-four disc-shaped specimens (A3 shade) were fabricated of Filtek P90 (P90), Filtek Z350XT Enamel (Z350) and Filtek Z250 (Z250) (3M-ESPE) (n=18). The samples of each composite were randomly divided into three subgroups of 6. The control subgroups were immersed in distilled water; the test groups were exposed to Opalescence Boost (OB) once; and Opalescence PF (OP) (Ultradent) for two weeks. Vickers microhardness testing and a spectrophotometric analysis of the color of samples were performed before and after each intervention.Results: The baseline microhardness of P90 was significantly lower than that of the other two composites (P=0.001), but no difference was found between Z250 and Z350 in this respect (P=0.293). Bleaching treatments significantly decreased the microhardness of Z250 and Z350 (P<0.001), but no change was observed in P90 test and con-trol subgroups (P>0.05). No significant difference was detected between the two types of bleaching (P>0.05). After bleaching with OB, DE value was measured to be 3.12 (1.97), 3.31 (1.84) and 3.7 (2.11) for P90, Z250 and Z350, respectively. These values were 5.98 (2.42), 4.66 (2.85) and 4.90 (2.78) after bleaching with OP with no significant difference.Conclusion: Bleaching decreased the microhardness of methacrylate-based but not silorane-based composites. Although no significant differences were found in DE of composites, DE of all groups did not remain in the clinically acceptable range after bleaching except for P90 after bleaching with 40% H2O2 (E<3.3).

Objective: Bleaching agents may not be safe for dental materials. The purpose of this invitro study was to evaluate the effects of Opalescent Quick "in-office bleaching gel" containing 35% CARBAMIDE PEROXIDE on the surface roughness and hardness of micro filled (Heliomolar) and hybride (Spectrum TPH) composite resins.Materials and Methods: Twenty specimens of Spectrum TPH composite resins and twenty Heliomolar composite resins were fabricated using a metallic ring (6.5 mm diameter and 2.5 mm thickness) and light cured, then their surfaces were polished. Specimens of each composite resin were divided into two equal groups. Ten specimens of each type of composite were stored in water at 37oC as the control groups and 35% CARBAMIDE PEROXIDE gel (Opalescence Quick) as the other group for 30 minutes a week for 3 weeks. Then the specimens were subject to roughness and hardness tests.Results: This study revealed that using 35% CARBAMIDE PEROXIDE bleaching gels had no significant effect on the surface roughness of Spectrum TPH "hybrid" and Heliomolar "micro filled" composite resins. The surface hardness of Spectrum TPH composite treated with the subject gel significantly increased compared to heliomolar, which had no significant change after treatment with this bleaching gel.Conclusion: If tooth color matching of the composite had been satisfactory after office bleaching with 35% CARBAMIDE PEROXIDE gel, this material would have been acceptable because it has no adverse effect on Heliomolar and Spectrum TPH composite resins.

The purpose of this in vitro study was to invtestigate the microleakage of a composite following the use of CARBAMIDE PEROXIDE. A total of 80 Sound permolar teeth were selected, with class V cavity preparation, filled with Tetric Flow or Syntac. Specimens were divided into four groups after being subjected to 500 times of thermal cycling. Group A (Control) was kept in humidor for 3 weeks, while groups B, C and D were kept in contact with lOck CARBAMIDE PEROXIDE using a special appliance for 2, 3 and 4 weeks (time of immersion in bleaching agent was 8 hours in each day). The roots and crowns were primarily sealed using a nail varnish. Each tooth was then immersed in 0.5% Basic Fuchsion. Pollowed by sectionning from about 2 mm below the CEl. Dye penetrations were measured by stereomicroscope in gingival and occlusal margins. Pearson"s test and log linear with 95% significancy were employed to evaluate the data. Results showed:1- No relation be~een the type of margin and dye penetration in group A, Band C. However the frequency was greater in group Band C compare to the group A.2-There was a correlation between type of margin and dye penetration in group D,.3-The highest dye penetration was seen in group D at the gingival margin.4-The highest dye penetration was seen in groups Band D at their occlusal margins, respectively.Inconclusion: Microleakage is seen in restorations after two weeks immersion in CARBAMIDE PEROXIDE, this means that any restoration should be replaced if subjected to the bleaching procedure.