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PubMed1993

Effect of enamel bleaching on the bonding strength of orthodontic brackets.

Various whitening/bleaching systems have been introduced on the market, including an over-the-counter external bleaching material, containing carbamide peroxide. It has been suggested that the process might alter the enamel surface structure in a manner similar to acid etching. Orthodontists are interested in determining whether the process will alter the adhesive characteristics of orthodontic bonding systems. The results of this study indicate that the use of 10% carbamide peroxide did not result in significant changes in the shear debonding strength of orthodontic brackets.

Carbamide Peroxide↗

PubMed1997

Effect of peroxide bleaches on fluoride release of dental materials.

PURPOSE: To investigate the effect of two bleaching agents, 35% hydrogen peroxide (Superoxal) and 10% carbamide peroxide (Opalescence), on the release of fluoride from Ketac-Fil, a glass ionomer cement, Photac-Fil, a glass ionomer/resin hybrid; and Tetric, a resin composite with fluoride. MATERIALS AND METHODS: Seven disks (9 x 3 mm) of each material were immersed in Superoxal for 1 hour to simulate an in-office application; seven other disks of each material were immersed in Opalescence 1 hour daily for 7 days to simulate a week of home bleaching regimen; and seven additional disks of each material without bleach served as a control. The disks were kept in deionized water and the water was tested for fluoride released every 24 hours for 14, 21, 28, and 35 days, respectively. RESULTS: Repeated measures ANOVA showed that the mean daily release of fluoride did not differ significantly (P > 0.05) between the bleaching agents or the control: Superoxal 6.17 ppm, Opalescence 6.45 ppm, and control 6.50 ppm. Statistically significant differences (P < 0.05) occurred for mean daily fluoride (+/- standard error) released from the three materials over the 35-day period: Photac-Fil 12.31 +/- 0.48 ppm > Ketac-Fil 7.07 +/- 0.66 ppm > Tetric 0.12 +/- 0.01 ppm, respectively.

Analysis of Variance↗

PubMed1993

Cytotoxicity and dentin permeability of carbamide peroxide and hydrogen peroxide vital bleaching materials, in vitro.

There has been recent concern about the inadvertent exposure of dentin with patent tubules as well as gingiva to bleaching systems containing 10-15% carbamide peroxide or 2-10% hydrogen peroxide for more than a few minutes. The aims of the present study were: (1) to determine the cytotoxicity of dilutions of hydrogen peroxide in cell culture; (2) to measure hydrogen peroxide diffusion from bleaching agents through dentin in vitro; and (3) to determine the risk of hydrogen peroxide-induced cytotoxicity from exposure of dentin to these vital bleaching agents. The 50% inhibitory dose (ID50) of hydrogen peroxide to succinyl dehydrogenase activity in cultured cells was found to be 0.58 mmol/L after 1 h. All bleaching materials demonstrated diffusion of hydrogen peroxide through dentin in an "in vitro pulp chamber" device. The one- and six-hour diffusates of all bleaching agents through 0.5-mm dentin exceeded the ID50 in monolayer cultures. Inhibition of succinyl dehydrogenase activity corresponded to the amount of hydrogen peroxide that can rapidly diffuse through dentin in vitro and reach concentrations which are toxic to cultured cells in less than 1 h.

3T3 Cells↗

PubMed1992

Effects of home bleaching products on composite resins.

A number of home bleaching products have recently been introduced. This in vitro study evaluated the effect of three representative bleaching products on the microhardness and surface texture of hybrid and microfilled composite resins. Scanning electron microscopic examination revealed cracking of the microfilled specimens treated with carbamide peroxide gels (Proxigel and White & Brite). White & Brite also caused slight roughening of the hybrid composite resin. Microhardness tests indicated that the treated composite resins became somewhat softer. However, the only statistically significant softening was associated with White & Brite.

Carbamide Peroxide↗

PubMed1993

Clinical changes in the gingiva as a result of at-home bleaching.

An investigative study was performed to evaluate changes in gingival health with the application of a 10% carbamide peroxide bleaching gel using exposure times of 2 and 7 hours (overnight). The presence or absence of gingival inflammation was recorded using the Loe and Silness Gingival Index at intervals over a 28-day period. The results showed no statistical significance between the preoperative gingival index scores and those recorded at any point during the study, regardless of exposure time.

Adult↗

PubMed2004

Shear bond strength of enamel treated with seven carbamide peroxide bleaching agents.

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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. CLINICAL SIGNIFICANCE: 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.

Analysis of Variance↗

PubMed2002

Comparative response of whitening strips to a low peroxide and potassium nitrate bleaching gel.

PURPOSE: To evaluate the clinical response of a low peroxide concentration bleaching system with a desensitizing agent relative to a marketed control. MATERIALS AND METHODS: After balancing for baseline color and age, 34 healthy adult volunteers were randomized to one of two marketed bleaching systems, 5% carbamide peroxide bleaching gel + potassium nitrate in a custom tray (Colgate Platinum Gentle Plus) or 6.0% hydrogen peroxide bleaching strips (Crest Whitestrips). Daily contact time was 6-8 hours for the tray system compared to 1 hour for the strip system, following manufacturers' instructions. Whitening was measured objectively using digital image analysis to assess L*a*b* after 7 days, while tolerability was assessed through interview and examination. RESULTS: The predominantly female (85%) and non-smoking (91%) study population ranged from 20-47 years of age. Both treatments yielded a statistically significant (P < 0.001) whitening benefit with respect to reduction in yellowness (Ab*) and improvements in other color endpoints (deltaL*, deltaE*, and a new parameter, deltaW*) compared to baseline. The strip group experienced greater color improvement on average for all color parameters in the study. After 7 days treatment, the adjusted mean deltab* was -1.24 in the strip group and -0.65 in the tray group, with these groups differing significantly (P = 0.04). Tooth sensitivity was reported by 13% of subjects using the hydrogen peroxide strips, compared to 22% of subjects using the carbamiide peroxide potassium nitrate tray system. No subjects discontinued treatment early due to an adverse event.

Adult↗

PubMed2001

Effects of carbamide peroxide containing bleaching agents on the morphology and subsurface hardness of enamel.

The purpose of this study is to evaluate the effects of nightguard bleaching agents (Karisma and Yotuel) on the enamel surface of forty anterior teeth. Ten teeth of each group were evaluated with SEM and ten teeth of each group were tested with a microhardness tester Morphologic alterations were observed on the enamel surfaces with SEM. Karisma group showed a significant decrease in enamel hardness (p<0.05) and microhardness values of enamel were increased significantly in Yotuel group (p<0.05).

Carbamide Peroxide↗

PubMed2002

Reversal of compromised bonding in bleached enamel.

Oxygen inhibits polymerization of resin-based materials. We hypothesized that compromised bonding to bleached enamel can be reversed with sodium ascorbate, an anti-oxidant. Sandblasted human enamel specimens were treated with distilled water (control) and 10% carbamide peroxide gel with or without further treatment with 10% sodium ascorbate. They were bonded with Single Bond (3M-ESPE) or Prime&Bond NT (Dentsply DeTrey) and restored with a composite. Specimens were prepared for microtensile bond testing and transmission electron microscopy after immersion in ammoniacal silver nitrate for nanoleakage evaluation. Bond strengths of both adhesives were reduced after bleaching but were reversed following sodium ascorbate treatment (P < 0.001). Resin-enamel interfaces in bleached enamel exhibited more extensive nanoleakage in the form of isolated silver grains and bubble-like silver deposits. Reduction of resin-enamel bond strength in bleached etched enamel is likely to be caused by a delayed release of oxygen that affects the polymerization of resin components.

Acid Etching, Dental↗

PubMedDate not supplied

Effect of home-use bleaching gels on fluoride releasing restorative materials.

To evaluate the effects of two home-use bleaching gels (Nite-White and Contrast PM) on the surface roughness of one high-viscosity glass ionomer cement (Fuji IX GP), four polyacid-modified resin-based composites (Dyract AP, F2000, Elan and Compoglass F), two resin-modified glass-ionomer cements (Vitremer and Fuji II LC), a microfilled fluoride-releasing resin-based composite (Tetric) and a microfilled non-fluoridated resin-based composite (Valux) were used as controls. The null hypotheses tested were: (1) the use of bleaching gels would not result in surface roughness values different from those obtained at baseline; (2) differences in the amount of carbamide peroxide present in the gels would not influence surface roughness. Thirty specimen disks (the first 10 used for controls and the balance divided randomly into two groups) were made for each material according to the manufacturers' instructions. Finishing and polishing of the test and control specimens was performed after 24 hours using a sequential series of three (medium, fine and superfine) Sof-Lex disks, keeping the restoration surface wet. For every sequence, 10 strokes were made in one direction using a low-speed handpiece. Ultrasonic cleaning of the polished specimens was performed for two minutes in distilled water to remove any surface debris. Prior to bleaching treatment, the specimens were stored in 37 degrees C deionized water for 24 hours. The specimens were exposed to the bleaching gels for a period that simulated the equivalent of 15 days (eight hours/day) under bleaching treatment. The average surface roughness (Ra) of the control and treated specimens was measured. Three separate Ra measurements along the direction of rotation of the finishing and perpendicular to the finishing direction and edge of the mold were made for each specimen surface. After treatment with bleaching gels, there was an increase in surface roughness for F2000, Dyract AP, Elan, Valux and Tetric, while Fuji IX, Fuji II LC, Vitremer and Compoglass F displayed decreased surface roughness values, suggesting that the effects of the gels appear to be material-dependent. Although Contrast PM contains 5% more carbamide peroxide as the active ingredient, the second null hypothesis was rejected for Fuji IX, Vitremer, Dyract AP, Compoglass F, Elan and Valux.

Carbamide Peroxide↗

PubMed1994

In vitro action of various bleaching agents on the microhardness of human dentin.

The authors verified a decrease in human dentin microhardness after application of the following bleaching agents for 72 hours: sodium perborate+water, sodium perborate + 3% hydrogen peroxide, sodium perborate + 30% hydrogen peroxide, Endoperox (crystallized hydrogen peroxide), Proxigel (carbimide peroxide), and 30% hydrogen peroxide. Sodium perborate+water and sodium perborate + 3% hydrogen peroxide caused less of a decrease in dentin microhardness than Endoperox, Proxigel and 30% hydrogen peroxide which caused the greatest decreases in dentin microhardness. Sodium perborate + 30% hydrogen peroxide fell into a statistically intermediate position.

Analysis of Variance↗

PubMed2004

Evaluation of biocompatibility of sodium perborate and 30% hydrogen peroxide using the analysis of the adherence capacity and morphology of macrophages.

OBJECTIVE: The purpose of this study was to evaluate the biocompatibility of the most used bleaching materials for pulpless teeth, sodium perborate and 30% hydrogen peroxide, in an experimental model of macrophages, through analysis of the adherence index and the cellular morphology. METHODS: Inflammatory macrophages were obtained from peritoneal washed of Wistar rats. The evaluation of the adherence capacity of these cells to the plastic surface was conducted in Eppendorf tubes containing RPMI, after treatment with the bleaching agents diluted in 1:10, 1:100 and 1:1000 for 15 and 30 min, and incubation at 37 degrees C and humidified atmosphere of 5% CO(2) in air. The cellular morphology was verified after incubation of the cells treated with the bleaching agents in culture plaques and compared with normal cells in culture medium. RESULTS: Results showed that sodium perborate neither increased the adherence index, nor altered the cellular morphology when compared to the control group. The distribution, cellular morphology, cytoplasmatic and nuclear characteristics, reproduced the aspects observed in normal macrophages. However, the treatment with 30% hydrogen peroxide presented an increase in adherence index when compared to the control group (RPMI), in all dilutions, according to Mann-Whitney test (n=08 and p=0.001 for dilutions 1:10 and 1:100, and n=08 and p=0.004 for dilution 1:1000). The morphology of the cells treated with this product presented structural alterations proportionally greater, depending on the dilution of this bleaching agent, and even in the highest dilution (1:1000) the cells presented very evident alterations. CONCLUSIONS: This irreversible cellular damage as well as the elevation of the adherence index, characterizes the aggressive potential of 30% hydrogen peroxide, regardless of its dilution. Sodium perborate, on the other hand, showed biocompatibitity, since, no morphological nor functional alteration was observed in macrophages.

Animals↗

PubMed2002

Effect of home bleaching and smoking on marginal gingival epithelium proliferation: a histologic study in women.

BACKGROUND: Animal studies have suggested that home bleaching agents can cause morphological alterations and changes in the proliferative rate of oral epithelium. METHODS: A bleaching agent containing 10% carbamide peroxide with carbopol was used in 11 women (five smokers and six non-smokers) during a 5-week period. Two biopsies were performed, one of them 15 days before the beginning of the home bleaching treatment and the other immediately after the 5-week bleaching treatment. Two analyses were performed in the histological sections obtained from the biopsies: epithelium morphometry and assessment of the epithelium's proliferative activity by proliferating cell nuclear antigen (PCNA) immunohistochemistry. RESULTS: The home bleaching agent increases epithelium thickness and the PCNA index in both smoker and non-smoker patients. CONCLUSION: Carbamide peroxide (10%) caused an augmentation in the proliferative activity within the basal and parabasal layers of the gingival epithelium, resulting in a change in this tissue's morphometry.

Acrylic Resins↗

PubMedDate not supplied

The effect of hydrogel and solution of sodium ascorbate on bond strength in bleached enamel.

Compromised bonding to bleached enamel can be reversed with sodium ascorbate as an antioxidant. This study evaluated the effect of hydrogel and solution of sodium ascorbate on enamel-resin composite shear bond strength after bleaching. Sixty buccal enamel surfaces obtained from human, sound third molars were randomly divided into 4 groups (n=15). Enamel surfaces were subjected to different treatments: 1) bleaching (10% carbamide peroxide gel); 2) bleaching + 10% sodium ascorbate solution; 3) bleaching + 10% sodium ascorbate hydrogel and 4) bleaching + 20% sodium ascorbate hydrogel. The specimens were bonded with Single Bond and restored with a composite. The specimens were prepared for shear bond testing. The data was evaluated using ANOVA and Tukey tests. Bond strengths were significantly increased following hydrogel and solution of sodium ascorbate treatments (p<0.05). Also, there was no significant difference among the different forms of sodium ascorbate preparations.

Acrylates↗

PubMed2005

Nanoindentation study of human premolars subjected to bleaching agent.

Bleaching of teeth is gaining popularity due to cosmetic reasons. However, the effect it has on teeth is still largely unknown. This paper seeks to evaluate the effect of a bleaching agent, 30% hydrogen peroxide, on the nanomechanical properties of dentin and enamel using the nanoindentation technique. The Young's modulus and hardness obtained from nanoindentation before and after bleaching were compared. Five newly extracted human premolars were used. Nanoindentation was first done on the sliced enamel and dentin regions to determine their mechanical properties. One batch of samples was kept in Hank's balanced salt solution as control while the other was bleached in 30% hydrogen peroxide for 24h. The same number of nanoindentations was then done near the previously indented regions for both the control and bleached samples and the results compared. Using paired sample t-tests with alpha=0.05, it was found that there were no significant differences in both the Young's modulus and hardness of dentin and enamel kept in control. However, the mechanical properties of the bleached dentin were significantly decreased. For intertubular dentin, the mean hardness decreased by 29-55% and the mean Young's modulus decreased by 19-43%. For enamel, the mean hardness decreased by 13-32% while the mean Young's modulus decreased by 18-32%. The exact mechanism by which hydrogen peroxide affects the dentin and enamel has yet to be fully elucidated. However, it is observed to have an undermining effect on the nanomechanical properties of teeth.

Bicuspid↗

PubMed2003

Effect of three bleaching agents on the surface properties of three different esthetic restorative materials.

STATEMENT OF PROBLEM: Information related to the effect of night-guard vital bleaching procedure on the surface properties of esthetic dental restorative materials is incomplete. PURPOSE: The aim of this study was to examine the effects of 3 proprietary carbamide peroxide bleaching agents on the surface properties of 3 dental esthetic restorative materials. MATERIAL AND METHODS: Three bleaching products (Nite White, Opalescence, and Rembrandt Lighten Gel) and 3 restorative materials (Duceram, Fuji II LC, and Silux Plus) were studied. A stainless steel mold and a 6-mm-thick polytetrafluoroethylene plate with a 1-cm-diameter hole were used to prepare 30 standardized specimens for each of the 3 restorative materials tested. Each group was divided into 3 subgroups (n=10). Two specimens from each subgroup were selected to form a control group. Three different carbamide peroxide bleaching agents were applied to each restorative material group for 8 hours per day for 30 days, respectively. Initial roughness measurements (Ra measured in microm) were made by use of a profilometer, at repeated intervals of 24 hours, 48 hours, 1, 2, 3, and 4 weeks (30 days). Surface topography of the specimens was assessed by scanning electron microscopy, and results were compared with the control group graphically. Surface structure and alterations of atomic weight percentages of element were made by use of energy-dispersive x-ray microanalysis. One-way analysis of variance was used to evaluate the surface roughness measurements. Significant results were evaluated with Fisher and Duncan's multiple range test (P<.005) RESULT: Surface roughness values for all restorative materials increased during the bleaching procedure. The only significant increase was found with the effect of Rembrandt bleaching gel on modified glass ionomer cement (mean Ra was 0.48 microm initially, 0.5 microm at 24 hours, 0.75 microm at 2 weeks, and 0.83 microm at 30 days). Surface roughness values increased significantly during the first 2 weeks (P<.005) for all bleaching groups of each restorative material, and no significant changes were seen in the following periods. SEM micrographs of the feldspathic porcelain specimens for each bleaching agent appeared to be similar to the control group. All of the modified glass ionomer specimens revealed serious cracking areas, whereas microfilled composite specimens showed increased surface porosity and cracks in certain areas when compared with control specimens. Surface spectral analyses results indicated a decrease in the SiO(2) content in the feldspathic porcelain and the microfilled composite groups for all bleaching agents. Modified glass ionomer specimens bleached with Nite White and Rembrandt showed an increase in mass percentage of SiO(2), whereas Opalescence specimens showed a decrease. However, there were no significant differences between the groups. CONCLUSION: Within the limitations of this study, no significant difference was found between bleaching agents. Most changes occurred in the first 2 weeks; the products tested were relatively stable in the following test periods. No significant change in the surface roughness of feldspathic porcelain was observed. On the other hand, the microfilled composite tested showed slight changes in the surface roughness. Significant changes were found for the modified glass ionomer cement (P>.005).

Aluminum Silicates↗

PubMed1999

A clinical assessment of the effects of 10% carbamide peroxide gel on human pulp tissue.

Bleaching vital teeth with 10% carbamide peroxide gel is a routine procedure in which there has been no evidence of associated permanent pulpal damage. Synthesis of the enzyme heme oxygenase-1 (HO-1) is increased after exposure of eukaryotic cells to conditions of oxidative stress (including H2O2) as a defense against the damaging effects of free radicals. Dental pulps were evaluated for HO-1 (aka Heat Shock Protein 32) presence in teeth treated with 10% carbamide peroxide. Seventeen intact first premolars scheduled for orthodontic extraction were bleached for 4 h immediately preceding extraction. Fourteen additional premolars from the same individuals were not bleached. All 31 teeth were extracted, fixed, demineralized, frozen, sectioned, and immunostained with anti-HO-1 antibody using a standard ABC protocol. There was no significant difference in the presence of HO-1 between total bleached versus total unbleached teeth using the Fisher's Exact Test (p < or = 0.05). However, the histological findings could be interpreted to suggest that coronal odontoblasts and endothelial cells in the underlying pulp proper may have the potential to respond to oxidative stress by increasing the synthesis of HO-1 (HSP32). This could represent a component of an initial defensive response by specific cells in strategic locations in the pulp that precedes classical inflammatory pathways.

Adolescent↗

PubMed2000

Degradation of gel in tray whitening.

This article will address the breakdown or lowering of active bleaching agent concentration during use in the mouth. A greater than expected degradation occurs during the first 5 minutes followed by an exponential rate loss. Subjects have a large variation in degradation rates. After 2 and 6 hours there was 52% and 24% respectively, of the active agent present in a carbamide peroxide gel. The presence or absence of the pellicle did not affect the rate of degradation. The relationship of gel degradation to the whitening capability of a gel is yet to be determined.

Biodegradation, Environmental↗