Concentrations Of Carbamide Peroxide Research Articles

Shear Bond Strength of Enamel Treated with Seven Carbamide Peroxide Bleaching Agents

Lower average values of bond strength of adhesive systems to enamel bleached with 10% carbamide peroxide agents have been reported, but the effects of higher concentrations of carbamide peroxide bleaching agents are still unknown. The aim of this in vitro study was to evaluate the shear bond strength of enamel treated with different concentrations of carbamide peroxide to an adhesive system after a postbleaching period of storage in artificial saliva for 15 days. Seven carbamide peroxide bleaching agents with concentrations varying from 10 to 22% were analyzed. A placebo agent was used as a control group. The agents were applied on the enamel fragments for 8 h/d for 42 days. During the remaining time, the specimens were stored in artificial saliva. After that time, the fragments were stored individually in artificial saliva for 15 days. An adhesive system was used to bond resin-based composite cylinders on the enamel surface. Shear bond strength tests were performed and the fractured surfaces of the specimens were visually examined with a stereomicroscope at x 30. The analysis of variance did not show differences in shear bond strength among the treatment agents. The fractures for all treatment agents were predominantly adhesive. After 15 days storage in artificial saliva, different concentrations of carbamide peroxide bleaching agents and a placebo agent had the same enamel shear bond strength values. Concentrations varying from 10 to 22% carbamide peroxide agents cause no differences in shear bond strength of enamel to an adhesive system after 15 days of storage in artificial saliva.

High-concentrated carbamide peroxide bleaching agents effects on enamel surface.

Concern has been expressed regarding the adverse effects of peroxide-containing tooth bleaching agents on enamel surface. This study examined enamel average surface roughness before (baseline) and after an in-office bleaching protocol and investigated the influence of high concentrations of carbamide peroxide gels on its surface staining and morphology. Flat enamel surfaces were submitted to 35 and 37% carbamide peroxide or to no bleaching treatment (n = 10) and evaluated with a profilometer. Eight specimens from each group were randomly selected and immersed in a 2% methylene blue solution. Afterwards, specimens were ground into powder and prepared for the spectrophotometric analysis. Two remained specimens of each group were examined using a scanning electron microscope. Data were subjected to analysis of variance and Tukey test (P > 0.05). Baseline roughness average was statistically similar for all groups, however, 35% carbamide peroxide produced the roughest enamel surfaces. Different concentrations of carbamide peroxide produced similar staining means and enamel surface morphological alterations.

Effect of carbamide peroxide bleaching agents on tensile strength of human enamel

Objectives. The aim of this study was to evaluate the effects of low concentrations of carbamide peroxide bleaching agents (CP) on the ultimate tensile strength of enamel (UTS). Methods. Resin composite structure was built-up on the bonded occlusal surface of 12 sound third molars to facilitate specimen preparation for microtensile testing. The bonded teeth were sectioned in a bucco-lingual direction in slices approximately 0.7 mm thick. Each slice was trimmed with a fine diamond bur to reduce the buccal, internal slope enamel of the cusps to a dumb-bell shape with a cross-sectional area at the ‘neck’ of less than 1 mm 2. The sample was randomly divided into six groups of 10 specimens each: Control (C—untreated); Opalescence 10% (O10), Opalescence 15% (O15), Opalescence 20% (O20), Whiteness 10% (W10) and Whiteness 16% (W16). Specimens in each group received the application of the CP for 6 h/day, at 37 °C, during 14 days and were stored in artificial saliva in between each application. After the bleaching regimen, specimens were tested with the microtensile method at 0.5 mm/min. Data were analyzed by ANOVA and Tukey test (5%). Results. Mean tensile strengths were (MPa): C=47.5±6.2 a; O10=37.6±5.8 b; O15=33.2±6.0 b; O20=31.2±3.5 b; W10=32.5±6.1 b; W16=30.6±7.7 b. Specimens subjected to the bleaching regimen presented significantly lower UTS than the control group. No differences were found among the type and concentration of the bleaching agents. Significance. Results suggested that bleaching enamel with CP could significantly reduce its UTS within a 14 days treatment.

The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time

Different concentrations of carbamide peroxide (10 to 22 percent) have been used successfully as bleaching agents, but the adverse effects on enamel microhardness at different times are unknown. The authors analyzed seven bleaching agents and a placebo. The agents were applied on the surface of human dental fragments for eight hours per day for 42 days and stored in vials containing artificial saliva. Microhardness measurements were performed at baseline, eight hours and seven, 14, 21, 28, 35 and 42 days, as well as at seven and 14 days after treatment had ended. Enamel treated with different bleaching agents or a placebo experienced a similar decrease in microhardness values over time, with the exception of fragments exposed to Opalescence PF 20 percent (Ultradent Products, South Jordan, Utah), or OPA20. Until the 49th day, the enamel exposed to OPA20 exhibited the lowest differences from baseline values. After 14 posttreatment days, enamel treated with placebo, Nite White 10 percent Excel (Discus Dental, Los Angeles), Nite White 16 percent Excel and Opalescence 10 percent exhibited the greatest differences from baseline values. An increase in enamel microhardness occurred at the end of the posttreatment period, although baseline values were not reached. Different concentrations of carbamide peroxide agents result in decreases in enamel microhardness. A post-bleaching period in artificial saliva resulted in recovery of baseline microhardness values (one agent) or an increase in values, although baseline values were not reached for these products. Clinical Implications. Higher concentrations of carbamide peroxide containing 0.11 percent ion fluoride can bleach teeth in a shorter period, with fewer hazardous effects on the enamel mineral content.

Higher-concentration carbamide peroxide effects on surface roughness of composites.

Ten percent carbamide peroxide has been used extensively within the dental profession for the purpose of bleaching teeth. Although this method has been successful, the use of higher-concentration carbamide peroxides (20-35%) for home bleaching has increased substantially in the past few years. The purpose of this study was to evaluate changes in surface roughness of a hybrid and a microfilled composite after exposure to bleaching agents containing higher concentrations of carbamide peroxide. Sixty-eight circular, resin-based composite specimens (8 mm x 2 mm) were prepared against a Mylar surface. Half of the specimens were fabricated from a hybrid composite material and the other half with a microfilled composite. Specimens were polished with aluminum oxide finishing disks, divided into four groups, and then exposed either to 20% carbamide peroxide for 3 hours per day for 14 days or to 35% carbamide peroxide for 1 hour per day for 14 days. The mean surface roughness (Ra) was determined for each specimen before and after exposure to bleaching agents, using mechanical profilometry. Data were analyzed by two-way analysis of variance (ANOVA) for differences between composite type, carbamide peroxide concentrations, and interaction of the two factors with respect to average surface roughness. All data analysis was performed at alpha = 0.05. Mean change from baseline of surface roughness (Ra) of microfilled composite and 20% carbamide peroxide was -0.03 microm +/- 0.10 microm; microfilled composite and 35% carbamide peroxide: 0.01 microm x 0.02 microm; hybrid composite and 20% carbamide peroxide: -0.43 microm x 0.91 microm; hybrid composite and 35% carbamide peroxide: -0.19 microm x 0.43 microm. Surface roughness of hybrid or microfilled composite did not change significantly from baseline with either concentration of carbamide peroxide (p = .300). Higher-concentration carbamide peroxide bleaching agents, used as intended by the manufacturer, pose no significant risk to resin composite restoration surfaces.

Effects of three concentrations of carbamide peroxide on the structure of enamel.

Carbamide peroxide bleaching agents have raised important questions on their potential adverse effects on the structure of enamel. The purpose of this study was to examine the effects of three carbamide peroxide bleaching agents in different concentrations (10, 16 and 35%) on the structure of enamel. Forty enamel slabs prepared from human third molars were divided equally among four groups. The specimens in the first and second group were subjected to 10% or 16% carbamide peroxide for 8 h per day for 6 weeks. Thirty-five percent carbamide peroxide was applied to the third group for 30 min a day for a 4 day period according to the manufacturers recommendation. The fourth group served as the control and was kept in artificial saliva during the test period. At the completion of the treatment, all the specimens were examined by infrared absorbtion spectroscopy and X-ray diffraction analysis. The results revealed that 10% or 16% carbamide peroxide did not seem to effect the structure of enamel, whereas 35% carbamide did affect the structure. The use of lower concentrations of carbamide peroxide (10-16%) is recommended over higher concentrations (35%) to avoid changes to the enamel.

Oxidative stress aspects of the cytotoxicity of carbamide peroxide: in vitro studies

Carbamide peroxide is the active ingredient in many at-home patient-applied tooth whiteners. The cytotoxicity of carbamide peroxide, as related to oxidative stress, was evaluated in vitro with several human cell lines, including Smulow-Glickman (S-G) gingival epithelial cells. The potency of carbamide peroxide was related to its hydrogen peroxide component rather than to carbamide, was eliminated in the presence of exogenous catalase, and was enhanced in the presence of aminotriazole, an inhibitor of cellular catalase. The intracellular level of glutathione, a scavanger of toxic oxygen metabolites, was decreased in cells exposed to carbamide peroxide; at higher concentrations of carbamide peroxide, leakage of lactic acid dehydrogenase was also evident. Cells pretreated with the glutathione-depleting agents, buthionine sulfoximine, chlorodinitrobenzene, and bis(chloroethyl) nitrosourea, were hypersensitive to subsequent challenge with carbamide peroxide. Conversely, pretreatment with the iron chelator, deferoxamine, protected the cells against subsequent exposure to carbamide peroxide.