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PubMed2006

Tooth bleaching by different concentrations of carbamide peroxide and hydrogen peroxide whitening strips: an in vitro study.

OBJECTIVE: To investigate the tooth whitening effects of various concentrations of carbamide peroxide (CP) gels and 6% hydrogen peroxide (HP) whitening strips used on an intrinsic, in vitro stain model in a simulated home-applied bleaching protocol. METHOD: Extracted third molars were sectioned and stained to Vita shade C4 using a standardized tea solution. Stained specimens were then bleached with 10, 15, 20, 22, and 30% CP gels applied in custom-made trays for 8-hour sessions for 14 days. A 6% HP whitening strip product was also tested in a regimen of twice-daily 30-minute treatments for 14 days. Shades were assessed at baseline and at 2, 5, 7, 10, and 14 days of treatment using a shade guide (SG) and a shade vision system (SVS), recorded as shade guide unit (SGU) changes from baseline, and CIE L*a*b* recordings using a chromometer. RESULTS: By day 14, all CP treatments resulted in at least 12 SGU improvements by SG and SVS methods: the HP treatment mean was just less than 12 SGU. With the chromometer, the CP improvements ranged from approximately 19 to 28 units and 16 units for the HP whitening strips. Observationally, by SG and SVS, CP treatments achieved the maximum improvement (12-13 SGU) at different time points: day 5 for 30% CP, day 10 for 22% CP, and day 14 for the other three treatments. SG and SVS data were virtually binary, switching from 0 to scores of 9 or above as bleaching progressed. The differences between the six treatments in the mean day to achieve a positive SG or SVS score (9 or more units) approached significance. For each of the SG, SVS, and L*a*b* scores, the dose-response correlation with CP concentration was significant at one or more assessment times. SG and SVS showed extremely strong agreement in detecting change and substantial agreement with L*a*b*. CONCLUSION: This in vitro study supports the limited data available from the very few available randomized controlled clinical trials indicating that CP and HP home-use bleaching systems can achieve considerable tooth whitening outcomes, albeit at different rates, which appear to be concentration dependent. CLINICAL SIGNIFICANCE: There is a clear significant relationship for both concentration and duration of exposure for CP bleaching agents. The final shade change is independent of the concentration of bleaching agent, with time as the dominant variable. Higher concentrations of CP that have not been investigated previously may be a treatment option for esthetic improvement of shade where time is at a premium, but caution must be exercised in view of the possible increased incidence of sensitivity.

Carbamide Peroxide↗
PubMed1999

The safety-in-use of 10% carbamide peroxide (Opalescence) for bleaching teeth under the supervision of a dentist.

Fears that the dentist-supervised use of a product that contains carbamide peroxide and that emits hydrogen peroxide may not be safe from the viewpoints of toxicity and cancer risk were engendered by unrealistic animal tests. These fears prompted the UK Government Departments of Trade and Industry (DTI) and of Health (DOH) to try to prohibit the marketing of Opalescence (manufactured by Ultradent Inc.). Faced with the fact that Opalescence had already been awarded a CE mark under the EC Medical Devices Directive, the DTI and DOH attempted to bring about its prohibition by reclassifying Opalescence as falling under the EC Cosmetics Directive, according to which the marketing of products containing more than 0.1% hydrogen peroxide is not permitted.

Animals↗
PubMed1997

Effect of 10 percent carbamide peroxide on color of provisional restoration materials.

To improve esthetic results, nightguard vital bleaching of teeth using 10 percent carbamide peroxide, or CP, may be indicated when an anterior tooth is restored with a provisional crown. This study evaluated the effect of NGVB solutions containing 10 percent CP on the color stability of provisional restoration materials. Disks were fabricated from six representative provisional restoration materials and were tested in five different 10 percent CP bleaching agents. An orange discoloration occurred with provisional materials that contained methacrylate when they were exposed to 10 percent CP bleaching solutions.

Carbamide Peroxide↗
PubMed1994

A liquid chromatographic assay for urea in over-the-counter carbamide peroxide products.

A liquid chromatographic assay has been developed and validated for determining the amount of urea present in carbamide peroxide formulations. The method employs an interaction CHO-620 carbohydrate column loaded in the Ca+2 form, a flow rate of 0.6 ml min-1, a column temperature of 85 degrees C, and UV detection at 200 nm. The mobile and stationary phase variables that may have an effect on the urea separation were studied and are discussed. The method was found to be linear over a range of 20 micrograms/g to 340 micrograms/g of urea, with a limit of detection of 1 microgram/g and a quantitation limit of 15 micrograms/g. System precision was found to have a %RSD of less than 1.0% while the method precision was typically less than 5.0%. Recoveries of 97.4% (1.0% RSD) and 98.3% (1.1% RSD) of the theoretical amount of urea (6.6% on a weight to weight basis) contained in two different formulations were obtained.

Carbamide Peroxide↗
PubMed1993

Toxicity of two carbamide peroxide products used in nightguard vital bleaching.

This study evaluated the effects of two generic classes of 10% carbamide-peroxide (CP) oxygenating agents (currently under clinical assessment for nightguard vital tooth bleaching) for lethality and genetic mutation after oral administration to mice, and for cellular cytotoxicity to mouse fibroblasts in vitro. The single dose LD50 values for a non-carbopol-containing CP (Gly-Oxide) and a carbopol-containing CP (Proxigel) in mice were found to be 143.8 mg/kg and 87.2 mg/kg, respectively. Genotoxicity, as measured by the Mouse Micronucleus test for mutagenicity, was negative for both 10% CP agents in comparison with positive and negative controls. Cytotoxicity as measured in the L929 fibroblast lysis assay resulted in 50% killing of L929 fibroblasts at 0.62 for the non-carbopol-containing CP and 1.88 mmol/L for the carbopol-containing CP. Both 10% CP agents were compared with seven widely-used dental products in the L929 fibroblast lysis assay and found to be no more toxic than these products.

Analysis of Variance↗
PubMed2001

Effect of carbamide peroxide bleaching agents on the physical properties and chemical composition of enamel.

PURPOSE: To evaluate the effect of two commercially available carbamide peroxides bleaching agents, Opalescence and Nite-White, in concentrations of 10, 15 and 16%, on enamel. MATERIALS AND METHODS: Vickers hardness measurements (VH) were made at the surface and 110 microns below the surface on human enamel samples that were treated for 5 or 10 days, 6 hrs/day. Furthermore, infrared spectrophotometry (IR), Fourier transform infrared spectrophotometer (FTIR) and X-ray diffraction (XRD) measurements were performed after the VH measurements were completed. RESULTS: Using a one-way ANOVA, statistically significant differences in VH could be established between surface and subsurface VH values. For all groups, including the control group, the surface VH values were statistically significantly higher than subsurface VH. IR, FTIR and XRD established a change from hydroxyapatite to primary calcium ortho phosphate [Ca(H2PO4)2] for all experimental groups except for 10% Opalescense tested for 5 or 10 days.

Analysis of Variance↗
PubMed1998

The efficacy and safety of a 10% carbamide peroxide bleaching gel.

OBJECTIVE: A 6-month, double-blind study was undertaken to assess the efficacy and safety of a 10% carbamide peroxide gel designed for at-home tooth bleaching. METHOD AND MATERIALS: Sixty patients were randomized into two equal subgroups balanced by age, gender, and oral health status. Shade guide measurements, color transparency photographs, and colorimeter readings were taken and evaluated at baseline and 1, 2, 3, 6, 12, and 24 weeks. The active phase of treatment lasted 14 days. RESULTS: At 22 weeks postbleaching (week 24 of the study), patients receiving the active agent had a 14.1 rank order difference in the shade guide from baseline, and 66% had a clinically observable color change as determined by photographic assessment. They also had a measurable, statistically significant color change from baseline to 6 months of delta E* = 5.0. The tooth color of maxillary incisors stabilized at week 6 and maxillary canines at week 12. The mean color change lost from weeks 2 to 24 was 45% (in delta E*). Transient tissue and tooth sensitivity, noted in some patients, resolved after treatment was completed. CONCLUSION: The product tested is an effective and safe tooth-whitening agent.

Adult↗
PubMed2000

Penetration of the pulp chamber by carbamide peroxide bleaching agents on teeth restored with a composite resin.

This in vitro study was performed to evaluate the effect of various concentrations of carbamide peroxide bleaching agents on the pulp chambers of teeth restored by a composite resin. Forty-nine human extracted anterior teeth were used. All the teeth were sectioned 3 mm apical of the cemento-enamel junction and the intracoronal tissue removed. The teeth were separated into the seven groups each containing seven teeth. Twenty-eight teeth were used as controls (groups I-IV), standardized cavities were prepared with the remaining 21 teeth (groups V, VI, VII), and restored with a hybrid composite resin (XR Herculite). Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. Group I was exposed only to distilled water. Groups II and V were applied with 10% CP (Contrast PM), groups III and VI were applied with 15% CP (Contrast PM), groups IV and VII were applied with 35% CP (Quik Start) and left for 30 min at 37 degrees C. Then, the acetate buffer solution in the pulp chamber of each tooth was removed and the chamber was then rinsed twice with 100 ml of distilled water. The contents then had leucocryctal violet and enzyme horseradish peroxidase added. The optical density of the resulting blue solution was determined spectrophotometrically, and was converted into microgram equivalents of hydrogen peroxide. A higher level of bleaching agent penetrated into the pulp chamber in the restored teeth than in the sound teeth.

Analysis of Variance↗
PubMed1996

In vitro action of various carbamide peroxide gel bleaching agents on the microhardness of human enamel.

The authors verified a decrease in human enamel microhardness after application of the following carbamide peroxide gel bleaching agents for 8 hours daily for 1 week: 10% Nite White, 16% Nite White, Opalescence, Karisma Alpha and Perfect Smile. Statistical analysis showed that these agents caused a decrease in enamel microhardness. Nite White (16%) was the most effective in reducing enamel microhardness and Opalescente the least effective. Nite White (10%), Karisma Alpha and Perfect Smile fell into a statistically intermediate position.

Carbamide Peroxide↗
PubMed2004

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 mm2. 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 degrees 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 +/- 6.2a; O10 = 37.6 +/- 5.8b; O15 = 33.2 +/- 6.0b; O20 = 31.2 +/- 3.5b; W10 = 32.5 +/- 6.1b; W16 = 30.6 +/- 7.7b. 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.

Analysis of Variance↗
PubMed2006

Remineralization potential of a fluoridated carbamide peroxide whitening gel.

PURPOSE: Little knowledge exists regarding the potential remineralizing benefits of adding fluoride to carbamide peroxide-based whitening gels. The aim of this project was to evaluate whether a whitening system with fluoride will remineralize previously demineralized enamel. MATERIALS AND METHODS: Twenty-four extracted teeth were sectioned into quadrants labeled A to D. Tooth quadrants in groups A, B, and D were demineralized with a lactic acid, methyl-cellulose gel system to mimic incipient carious lesions. Group C was neither demineralized nor treated. Group D was demineralized, but not treated with a whitening gel. Groups A and B were exposed to one of two commercially prepared 10% carbamide peroxide whitening gels: one that was fluoride free (group A) and one that contained fluoride (0.463%NaF) (group B). Remineralization was evaluated histologically and analyzed statistically using paired t tests accepting p < 0.05 as significant. RESULTS: Shade comparisons showed equal whitening efficacy of both gel A and B. Paired t tests show a significant reduction in lesion depth after treatment with the fluoride containing gel (B: mean lesion depth = 100 microm; p < 0.01), while there was no difference for the gel lacking fluoride (A: mean lesion depth = 110 microm). CONCLUSION: Under the conditions of this study, the addition of fluoride to a tooth whitening system does not affect the gel's whitening efficacy. The addition of fluoride could provide remineralization properties to the gel. As tooth whitening therapies continue to grow and evolve, a strong focus should rest on improving these materials in ways that will provide ever greater patient benefits. Coupling the esthetic benefits of whitening with the preventive benefits of fluoride is a natural step in this direction. CLINICAL SIGNIFICANCE: Therapuetic quantities of fluoride can impact remineralization properties of commercially available tooth whitening gels without altering whitening properties.

Carbamide Peroxide↗
PubMed1996

Assessing tooth color change after repeated bleaching in vitro with a 10 percent carbamide peroxide gel.

The aim of this study was to obtain information about tooth color changes in 25 extracted human incisors resulting from repeated bleaching with a 10 percent carbamide peroxide gel. Using a colorimeter, the author recorded color changes in the L*a*b* color space after each bleaching period. The observed tooth color change was found to be dependent on the bleaching time, the specific bleached section and the initial color. The most significant total tooth color change was observed in the incisal section of the crown, followed by the middle and the cervical sections.

Analysis of Variance↗
PubMed2005

Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness.

This in vitro study evaluated the surface microhardness of human enamel submitted to bleaching with 10% carbamide peroxide (CP) containing calcium or fluoride. Ninety-eight dental blocks (5 x 5 mm2) with polished enamel surfaces were randomly assigned to 7 treatment groups (n=14), as follows: without bleaching and storage in artificial saliva (control); 10% CP; 10% CP + 0.05% calcium; 10% CP + 0.1% calcium; 10% CP + 0.2% calcium; 10% CP + 0.2% fluoride; and 10% CP + 0.5% fluoride. During 14 days, enamel surfaces were daily exposed to a 6-h bleaching regimen followed by storage in artificial saliva. Surface microhardness was measured before (baseline), during (7th day), immediately after bleaching (14th day) and 1 week post bleaching. Data were analyzed by two-way ANOVA and Tukey's test (p<0.05). All treatments reduced SM significantly during the bleaching cycle (7th day), immediately after bleaching (14th day) and 1 week post bleaching, compared to baseline and to the unbleached control group. In conclusion, in spite of the addition of calcium and fluoride, all bleaching treatments affected the enamel surface microhardness.

Calcium↗
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↗
PubMed2005

Influence of the duration of treatment using a 10% carbamide peroxide bleaching gel on dentin surface microhardness: an in situ study.

This in situ study evaluated the influence of two home-use tooth bleaching regimes (1 hour/day and 7 hours/day) using 10% carbamide peroxide (Nite White Excel 2Z) on the surface microhardness of dentin over a 21-day period. Nine blocks of dentin derived from the teeth of subjects, each with at least two thirds molar in need of extraction, were obtained from the cervical region and submitted to surface-hardness analysis (Shimadsu HMV/2000), fixed to an intraoral palate device fabricated for each subject, and positioned (3 left side, 3 right side, 3 center) according to experimental group. During the bleaching period, casts bearing the whitening agent were applied to the blocks for 7, 1, and 0 hours, respectively (7 left side, 3 right side, 0 center). After the treatment period, the specimens were once again submitted to microhardness analysis, using the same equipment as before, and then analysis of variance and the Scheffé test were applied to the mean differences between the initial and final evaluations. The results demonstrated that the statistical difference between the 1-hour and 7-hour groups was not significant. However, the 7-hour group, when compared with the control group, demonstrated statistically significant differences with a reduction in microhardness. Despite the occurrence of mineral loss in the 1-hour and 7-hour groups, this difference was only 3.1% and 5.4%, respectively, which allows one to conclude that these values probably have no clinical significance.

Adolescent↗
PubMed2002

Efficacy of a novel, nontray, paint-on 18% carbamide peroxide whitening gel.

A double-blind, 3-week, randomized, placebo-controlled, parallel-group clinical trial was conducted to evaluate the tooth-whitening efficacy of a novel nontray, "paint-on" liquid whitening gel containing 18% carbamide peroxide (Colgate Simply White Clear Whitening Gel). Efficacy was based on measured Vita tooth-shade scores collected at baseline and after 2 and 3 weeks of product use. Eighty healthy volunteers were balanced into 2 groups based on gender, age, and shade scores (A3 or higher). The duration of product usage was 30 minutes, twice daily, for 3 weeks. Results from this clinical study showed that subjects' teeth in the liquid whitening gel-treated group exhibited an overall mean 3.84-shade improvement and a 3.5-shade difference compared with teeth in the placebo gel group (statistically significant, P < .05) after 3 weeks. Furthermore, this improvement exceeds the minimum requirement to claim "clinical efficacy" as established by the "Guidelines for the Acceptance of Peroxide-Containing Oral Hygiene Products," published by the American Dental Association in 1994. Therefore, it can be concluded that Colgate Simply White Clear Whitening Gel significantly whitens teeth.

Adolescent↗
PubMed2002

Clinical comparison of the stain-removal efficacy of a novel liquid whitening gel containing 18% carbamide peroxide and a commercially available whitening dentifrice.

The objective of this examiner-blind clinical study was to compare the extrinsic tooth-stain removal efficacy of a novel, nontray, "paint-on" liquid whitening gel containing 18% carbamide peroxide (Colgate Simply White Clear Whitening Gel) with a commercially available whitening dentifrice. After a baseline examination for extrinsic tooth stain, qualifying adult men and women from Canada were randomized into two treatment groups balanced for age, gender, and level of extrinsic tooth stain. Subjects were instructed to brush their teeth twice daily (morning and evening) for 1 minute with their assigned dentifrice (Group 1: nonwhitening dentifrice; Group 2: whitening dentifrice). The subjects in Group 1 also were instructed to use the paint-on whitening gel for 30 minutes twice daily. Examinations for extrinsic tooth stain were repeated after 2 and 3 weeks. Ninety-seven subjects complied with the protocol and completed the entire study. At both the 2- and 3-week examinations, subjects assigned to the liquid whitening gel-treatment group exhibited statistically significant reductions in extrinsic tooth stain (P < .05) with respect to stain area (22.7% reduction at 3 weeks), stain intensity (26.3% reduction at 3 weeks), and overall stain removal (32% reduction at 3 weeks) compared with the commercially available whitening dentifrice group. Thus, the results of the examiner-blind clinical study support the conclusion that Colgate Simply White Clear Whitening Gel provides a significantly greater level of extrinsic tooth-stain removal efficacy than a commercially available whitening dentifrice.

Adolescent↗
PubMed1999

Carbamide peroxide whitening of nonvital single discolored teeth: case reports.

Patients who present with a single discolored tooth represent a significant restorative challenge. These case reports describe an economic and conservative treatment option for these patients. The situations presented demonstrate techniques for bleaching with carbamide peroxide in a traditional nightguard or with an inside-outside technique to achieve acceptable esthetic results on isolated nonvital discolored teeth. Although these techniques may not be effective in all cases, they do not compromise or eliminate any future treatment options.

Adult↗