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PubMed2002

Extended at-home bleaching of tetracycline-stained teeth with different concentrations of carbamide peroxide.

OBJECTIVE: The degree of color change and the dental sensitivity associated with the use of different concentrations (10%, 15%, and 20%) of carbamide peroxide every night for 6 months was evaluated in tetracycline-stained teeth. METHOD AND MATERIALS: Fifty-nine subjects were shown how to place two different concentrations of carbamide peroxide in the custom trays with reservoirs. For a period of 6 months, the patients were to insert the tray every evening before retiring. Patients returned in 1 and 2 weeks and at 1, 2, 3, 4, 5, 6, 7, 8, and 9 months for evaluation of the degree of color change by subjective shade matching and by photographic means. Sensitivity of hard or soft tissues was self-reported. RESULTS: Fifty-two subjects attended more than 90% of the recalls. A colorimeter was used to convert shade guide tabs to Commission Internationale de l'Eclairage color spaces (CIELAB). The most rapid whitening occurred in the first month. At 3 and 9 months, 91% and 85% of the subjects, respectively, were at least "a little pleased" with the results of the bleaching. In the professional evaluation, 90% of the teeth were deemed to have an excellent or satisfactory esthetic result. The higher the concentration of carbamide peroxide, the more rapidly the lightness value and color difference changed. There was no difference among the three concentrations in resulting gingival sensitivity. Patients experienced less tooth sensitivity with 10% gel than they did with 15% and 20% gels. CONCLUSION: Bleaching with 10%, 15%, and 20% carbamide peroxide is effective for removing tooth staining caused by tetracycline. The 10% concentration has the most advantages and the fewest disadvantages.

Adult↗
PubMed1996

Demineralization effects of 10 percent carbamide peroxide.

OBJECTIVES: The purpose of this in vitro study was to measure the amount of calcium lost from enamel exposed to a 10% carbamide peroxide solution. METHODS: Nine teeth (3 incisors, 2 premolars, 4 molars) were sectioned to serve as paired test and control specimens. Each tooth half was coated with wax, leaving a uniform 3 mm x 4 mm window of exposed enamel. Test specimens were placed in culture tubes with 1.00 ml of deionized water and 0.02 ml of 10% carbamide peroxide for 6 h; controls were exposed to water alone. Calcium concentrations in the solutions were measured using a Perkin-Elmer 5100 atomic absorption spectrophotometer. RESULTS: Teeth exposed to carbamide peroxide lost an average of 1.06 micrograms/mm2 of calcium. This amount of loss was significantly greater than controls (p < 0.001), according to ANOVA. For comparison, teeth were exposed to a cola beverage for 2.5 min, the time equivalent of drinking a 16 oz. beverage. The amount of calcium lost from these teeth was also about 1 microgram/mm2. CONCLUSIONS: Teeth exposed to 10% carbamide peroxide lost calcium. However, the amount of loss was small, and may not be clinically significant.

Analysis of Variance↗
PubMed2002

Effects of a 10% carbamide peroxide bleaching agent on rat oral epithelium proliferation.

The purpose of the present study was to evaluate the influence of short course topical application of carbamide peroxide on proliferating cell nuclear antigen (PCNA) immunohistochemical expression in the oral tongue mucosa of rats. Twelve male Wistar rats were submitted to topical application of 10% carbamide peroxide on one side of the dorsal tongue once a week for three consecutive weeks. Only distilled water was applied on the control side. The animals were killed on days 0, 10, and 20 after the last application. The tongue was fixed in buffered formalin for 24 h and embedded in paraffin. Tissue blocks (3 microns) were subjected to the biotin-streptavidin amplified system for identification of PCNA. The percentage of epithelial-positive basal cells in each side of the tongue mucosa was calculated. The results demonstrated that topical application of 10% carbamide peroxide increases PCNA immunohistochemical expression on the basal layer of the oral mucosa epithelium of rats on day 0 after treatment. In conclusion, short-course use of carbamide peroxide induces transient epithelial cell proliferation of the oral mucosa of rats.

Animals↗
PubMed1999

Effect of carbamide peroxide bleaching on the shear bond strength of composite to dental bonding agent enhanced enamel.

STATEMENT OF PROBLEM: Carbamide peroxide bleaching has been implicated in adversely affecting the bond strength of composite to enamel. PURPOSE: This in vitro study evaluated the effect of 3 dental bonding agents (OptiBond, All-Bond 2, One-Step) on the shear bond strength of a hybrid composite to enamel which was treated by a 10% carbamide peroxide bleaching system. MATERIAL AND METHODS: Cylinders of composite were bonded to carbamide peroxide-treated enamel on extracted human teeth using 3 dental bonding agents. After thermocycling, shear bond strengths were determined with a universal testing machine. RESULTS: OptiBond aided bond strengths were 23.7 +/- 5.6 MPa to bleached and 19.6 +/- 2.9 MPa to unbleached enamel. For All-Bond 2, bleached enamel exhibited bond strengths of 14.9 +/- 4.0 MPa and unbleached enamel exhibited a bond strength value of 20. 4 +/- 2.3 MPa. The composite bond strength for One-Step was 13.6 +/- 5.9 MPa to bleached and 23.0 +/- 3.9 MPa to unbleached enamel. There was no statistical difference between OptiBond (alcohol base) aided bond strengths for bleached and unbleached enamel; however, the bond strength of composite to bleached enamel with All-Bond 2 or One-Step (acetone base) was significantly lower than unbleached controls. CONCLUSION: The effect of bonding agent usage on composite bond strength to enamel bleached with a particular carbamide peroxide was dependent on the bonding agent used.

Analysis of Variance↗
PubMed2004

In situ effect of 10% carbamide peroxide on resin-dentin bond strengths: a novel pilot study.

PURPOSE: This pilot study used a novel study design to evaluate the effect of a 10% carbamide peroxide bleaching gel on the bond strength of a resin-based composite system to dentin. MATERIALS AND METHODS: Dentin disks were obtained from human third molars, polished to 600 grit, and mounted on the palatal aspect of a removable orthodontic retainer. Two disks were exposed to a 10% carbamide peroxide bleaching gel for 2 h/d for 21 days, whereas two disks were not treated and served as controls. A retainer was worn by the participant regardless of whether bleaching was used, simulating the action of the saliva/oral fluids on the dentin specimens. After the treatment phase, the dentin disks were retrieved and a resin-based composite system was applied to the specimens following manufacturer's instructions. Composite dentin "sticks" were obtained and tested in microtensile mode. Bond strength values were obtained for treated (n = 20) versus nontreated (n = 26) dentin and were analyzed statistically. RESULTS: Mean bond strengths values (SD) were 29.9 MPa (6.2) and 39.2 MPa (5.8) for treated and nontreated dentin specimens, respectively (p < .001). CONCLUSION: The results of this study suggest that nightguard (home) bleaching with 10% carbamide peroxide for 2 h/d for 21 days significantly affects resin-dentin bond strengths when dentin is exposed to bleaching material. CLINICAL SIGNIFICANCE The findings of this novel pilot study imply that dentin bonding, such as to exposed root surfaces and cervical areas of the teeth, should not be performed immediately after bleaching with 10% carbamide peroxide.

Adult↗
PubMed2004

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.

Carbamide Peroxide↗
PubMedDate not supplied

The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ.

This in situ study evaluated the microhardness of sound and demineralized enamel and dentin submitted to treatment with 10% carbamide peroxide for three weeks. A 10% carbamide peroxide bleaching agent--Opalescence/Ultradent (OPA)--was evaluated against a placebo agent (PLA). Two hundred and forty dental fragments--60 sound enamel fragments (SE), 60 demineralized enamel fragments (DE), 60 sound dentin fragments (SD) and 60 demineralized dentin fragments (DD)--were randomly fixed on the vestibular surface of the first superior molars and second superior premolars of 30 volunteers. The volunteers were divided into two groups that received bleaching or the placebo agent at different sequences and periods at a double blind 2 x 2 crossover study with a wash-out period of two weeks. Microhardness tests were performed on the enamel and dentin surface. The SE and DE submitted to treatment with OPA showed lower microhardness values than the SE and DE submitted to treatment with PLA. There were no statistical differences in microhardness values for SD and DD submitted to the treatment with OPA and PLA. The results suggest that treatment with 10% carbamide peroxide bleaching material for three weeks alters the enamel microhardness, although it does not seem to alter the dentin microhardness.

Adult↗
PubMed2002

Effects of a bleaching agent containing 35% carbamide peroxide on the immunolocalization of cyclin D and p16.

The evidences that p16 and cyclin D alterations occur in the earlier stages of many human cancers and that its immunolocalization can be used to study the cell cycle regulation, coupled with the possibility that chronic use of carbamide peroxide would induce DNA damage and cell cycle alteration, prompted us to analyse the effect of carbamide peroxide on the immunolocalization of these proteins in rat oral mucosa. Ten male Wistar rats were selected and submitted to topical application of 35% carbamide peroxide over buccal mucosa. The procedures were carried out twice a week for 3 months consecutively. The animals were killed after the last treatment and the buccal mucosa was removed and stored at -70 degrees C. Only distilled water was applied over the buccal mucosa of the control animals. The biotin-streptavidin amplified system was used for identification of cyclin D and p16 antigens and the percentage of basal and suprabasal cells positive for each one were obtained. The results did not show any difference between the experimental and control groups regarding the immunolocalization of cyclin D and p16. In conclusion, the present study showed that chronic use of carbamide peroxide does not induce cell cycle alteration in the oral mucosa of rats.

Animals↗
PubMed2001

Effects of 10% carbamide peroxide bleaching materials on enamel microhardness.

PURPOSE: To evaluate the microhardness of enamel treated with two different 10% carbamide peroxide bleaching materials at different time intervals. MATERIALS AND METHODS: Two bleaching agents were analyzed: Opalescence (OPA) and Rembrandt (REM). The control group (CON) consisted of dental fragments maintained in artificial saliva. Bleaching was accomplished for 8 hrs per day and stored during the remaining time in an individual recipient with artificial saliva. Enamel microhardness testing was performed before the initial exposure to the treatments and after 1, 7, 14, 21, 28, 35 and 42 days. RESULTS: The ANOVA, followed by the Bartlet and Tukey tests, showed significant differences for treatments (P < 0.00001) from day 7-day 42. From the 7th to the 14th day, OPA presented an increase of enamel microhardness over time while REM presented a decrease of microhardness. Statistical differences were not found between REM and the control group (OPA > CON = REM). From the 21st-35th day, enamel fragments bleached with OPA and REM presented a decrease of microhardness. Statistical differences of microhardness were verified among all the treatments (OPA > CON > REM). On the day 42, statistical differences were not found between OPA and the control group, but they were found between REM and the control group (OPA = CON > REM). The polynomial regression showed an increase of microhardness for OPA until the 21st day, followed by a decrease of microhardness up to the 42nd day. A decrease of microhardness for REM was verified. There were alterations in enamel microhardness as a function of bleaching time when using the two different 10% carbamide peroxide whiteners. Over a 42-day treatment time, bleaching with REM agent caused a decrease in enamel microhardness. The OPA agent initially increased the microhardness, then returned to the control level. Different bleaching materials with the same concentration of carbamide peroxide have different effects on the enamel.

Analysis of Variance↗
PubMedDate not supplied

In situ and in vitro effects of bleaching with carbamide peroxide on human enamel.

This study evaluated in vitro and in situ the potential adverse effects of 10% carbamide peroxide on human enamel using microhardness, calcium loss and surface morphology analysis. Twenty-four enamel slices (4 mm2) were obtained from recently extracted premolars. The specimens were polished under water-cooling down to 1,200-grade sandpaper. After initial microhardness readings (100 g), the specimens were randomly divided into two groups for in situ and in vitro conditions. The specimens were covered with 10% carbamide peroxide for eight hours. After removing the bleaching gel, the in vitro specimens were stored in deionized water and the in situ specimens, included in an intra-oral appliance, were placed in the oral cavity of four volunteers. These cycling sequences took place for 14 days. Upon conclusion of the bleaching treatment, new microhardness readings were performed on all specimens. Calcium dosage was assessed from the bleaching gel collected after initial exposure on day one, then from gel collected between days two and seven and gel collected between day eight and 14 using an atomic absorption spectrophotometer. Surface morphology was observed from two non-treated control specimens and two specimens of each experimental bleached group under SEM evaluation. Statistical analysis (ANOVA and Tukey tests) disclosed that specimens bleached in situ showed similar microhardness to unbleached specimens and had statistically higher (p < 0.01) hardness than in vitro bleached specimens. The loss of calcium in the in vitro situation at 14 days was 2.5 times higher than the in situ condition. SEM micrographs demonstrated that surface alterations were more pronounced in the in vitro condition. The adverse effects of carbamide peroxide on enamel were evident in specimens bleached in vitro but were not seen in situ. The presence of saliva could prevent the demineralizing effect of bleaching gel in situ.

Analysis of Variance↗
PubMedDate not supplied

Carbamide peroxide bleaching: effects on enamel surface hardness and bonding.

Three 10% carbamide peroxide home bleaching agents were evaluated to determine their effects on tensile bond strength of resin to enamel and enamel surface hardness. Eighty extracted bicuspid crowns were divided into four groups (three bleaching agents and control), and treated with the bleaching agents for five consecutive days. A bonding site on the buccal surface of each crown was etched with phosphoric acid and an orthodontic bracket bonded in place. The specimens were thermocycled and loaded to failure in an Instron Universal Testing Machine. Five hardness specimens per group were measured prebleaching and after five days' exposure. Analysis by one-way ANOVA indicated no significant differences in bond strength between the four groups (P > 0.05). There were also no differences in pre- or postbleaching Knoop hardness values for the four groups (P > 0.05). This study indicated that in short-term regimens 10% carbamide peroxide does not significantly affect enamel surface hardness or bonding ability.

Analysis of Variance↗
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↗
PubMedDate not supplied

Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment.

OBJECTIVES: To evaluate the effects of home bleaching (carbamide peroxide) on enamel surface morphology and the degree of acid dissolution. METHODS: Buccal surfaces of 15 caries-free human premolars were used in the study. The 15 teeth were cut in half in a buccal-lingual direction at midline; in total, 15 pairs of specimens were obtained. Group A consisted of five pairs that studied surface morphology change and Group B consisted of 10 pairs that studied the susceptibility of bleached enamel to acid dissolution. Tooth halves were prepared following a fluoride-free prophylaxis paste cleaning. One half of the tooth was untreated (control), and the other half was bleached (experimental) for eight hours daily for 10 days using 10% carbamide peroxide. Tooth samples were then stored in distilled water for seven days, after which scanning electron microscopy (SEM) was performed on Group A. Only halves from the same tooth were compared to rule out natural variations between teeth. Group B was etched with 37% phosphoric acid before being examined by SEM. The severity of the acid attack was graded from I to V, and the grades of each pair were compared. RESULTS: Results of the SEM observation showed that surface porosity slightly increased after bleaching, and more surface dissolution by phosphoric acid was seen with bleached, compared to unbleached, enamel.

Carbamide Peroxide↗
PubMed2004

Effect of nonvital bleaching with 10% carbamide peroxide on sealing ability of resin composite restorations.

AIM: To (i) determine the effect of nonvital bleaching with 10% carbamide peroxide on the sealing ability of resin composite restorations bonded with a self-etching adhesive system; and (ii) compare the effects of antioxidant treatment and delayed restoration after bleaching on marginal seal. METHODOLOGY: Forty-eight noncarious maxillary incisors were divided into four groups (n=12) after conventional root canal treatment was completed. In group 1, access cavities were restored with a self-etching adhesive system and resin composite. In the remaining three groups, 10% carbamide peroxide bleaching gel was placed into the access cavities for periods of 8 h per day for 1 week. They were then restored in the same manner as group 1. Group 2 consisted of specimens restored immediately after bleaching. Group 3 specimens were treated with the antioxidant, 10% sodium ascorbate, whereas group 4 specimens were immersed in artificial saliva for 1 week before restoration. Ten specimens in each group were then subjected to dye leakage; the remaining 2 specimens were examined in a SEM (Jeol/JSM 5200, Tokyo, Japan). The dye penetration was assessed with the standard scoring system. Statistical analysis was carried out using the Kruskal-Wallis and the Mann-Whitney tests. RESULTS: Groups 1, 3 and 4 exhibited similar leakage patterns and significantly less leakage than group 2 (P<0.0083). SEM examination of groups 1, 3 and 4 specimens demonstrated close adaptation of resin composite to cavity walls, whereas group 2 specimens did not. CONCLUSION: Nonvital bleaching with 10% carbamide peroxide adversely affected the immediate sealing ability of resin composite restoration; both 10% sodium ascorbate treatment and a 1-week delay in restoration following bleaching improved the reduced sealing ability of resin composite.

Antioxidants↗
PubMed2002

Effects of 10% carbamide peroxide on the enamel surface morphology: a scanning electron microscopy study.

BACKGROUND: Several studies have been published about the effect of carbamide peroxide on enamel surface morphology. However, only a few studies have been carried out under intraoral conditions. The purpose of this study was to investigate the effect of two commercially available 10% carbamide peroxide bleaching products (Colgate Platinum and Starbrite) on the enamel surface morphology under intraoral conditions. MATERIALS AND METHODS: Twenty-four subjects were divided into two groups and assigned a product to use for 2 weeks. Epoxy resin replicas obtained from the maxillary right central incisors of the subjects before, immediately after, and 3 months after the bleaching procedure were examined under a scanning electron microscope. RESULTS: Immediately after the bleaching procedure, the surface porosity of enamel had increased in the Colgate Platinum group, whereas erosive surface alterations were observed in the Starbrite group. At 3 months, the surface morphology of enamel in the Colgate Platinum group was similar to the untreated enamel surface. In the Starbrite group, erosive defects on the enamel surface had decreased within 3 months, and the appearance of the enamel surface was almost the same as the untreated enamel. CONCLUSION: Even though both bleaching agents caused alterations in the surface morphology of enamel, these alterations were reversed within 3 months following treatment. CLINICAL SIGNIFICANCE: The results of this study suggest that 10% carbamide peroxide bleaching products cause alterations in enamel surface morphology immediately after bleaching, and the degree of these alterations depends on the brand of bleaching agent and duration of application time. However, these alterations revert to almost normal within 3 months.

Adult↗
PubMed2003

In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time.

PURPOSE: This study evaluated the effect of two home bleaching regimens (1 h/day versus 7 h/day for a total of 21 days) on the microhardness of superficial enamel treated with 10% carbamide peroxide gel. MATERIALS AND METHODS: Rectangular enamel specimens (2.5 x 2.5 x 1 mm) were obtained from human third molars and mounted on the palatal aspect of removable orthodontic retainers. Nine enamel specimens were mounted in each of 10 retainers, used by 10 volunteers during the active phase of the study. Modified 0.089 cm thick bleaching trays were fabricated for each participant. Each bleaching tray fit a participant's arch and the retainer containing the enamel specimens. Enamel specimens were treated with a 10% carbamide peroxide bleaching gel (Nite White Excel 2Z, Discus Dental, Culver City, CA, USA) for either 1 h/day (n = 30) or 7 h/day (n = 30), both for 21 days. Three enamel specimens in each retainer were never treated and served as controls. The retainers were worn by the participants whether or not they underwent bleaching. This simulated the natural action of the saliva/oral fluids on the enamel specimens. Enamel specimens were subjected to pre- and post-treatment microhardness measurements. Post-treatment Knoop hardness numbers were compared with baseline values and analyzed statistically. RESULTS: Bleaching treatment resulted in a nonsignificant reduction in microhardness values when compared with values of the control nontreated specimens (1.7% and 2.5% reduction in hardness for 1 h/day and 7 h/day, respectively). There was no difference in microhardness between the different treatment regimens. CONCLUSION: Home bleaching with 10% carbamide peroxide for up to 7 h/day for 21 days does not significantly affect enamel microhardness. CLINICAL SIGNIFICANCE: Bleaching with 10% carbamide peroxide for 1 h/day or 7 h/day for a total of 21 days is safe for human enamel.

Adolescent↗
PubMed1995

Carbamide peroxide bleaching of teeth with dentinogenesis imperfecta discoloration: report of a case.

Carbamide peroxide dental bleaching has gained much popularity in the past 5 years. Because tooth discoloration caused by dentinogenesis imperfecta involves deep, dark, dentinal stain, practitioners might believe that affected teeth would be resistant to color improvement by bleaching. This article reports the successful use of carbamide peroxide at-home bleaching in a teenager with dentinogenesis imperfecta. Six-month treatment results are shown.

Adolescent↗
PubMed2004

Factors affecting mercury release from dental amalgam exposed to carbamide peroxide bleaching agent.

PURPOSE: To assess, in vitro, the effects of aging and surface polishing on mercury release from dental amalgams exposed to 10% carbamide peroxide at two pH levels. METHODS: Samples of fresh and aged amalgam, polished and unpolished, were treated with 10% carbamide peroxide at pH 4.5 and at pH 6.5 for periods of 1, 4, 7, 10 and 13 days. At each time period, mercury concentrations in solution were measured using a cold-vapor atomic absorption mercury analyzer system and compared to control samples treated with phosphate buffer. RESULTS: Amalgam samples exposed to 10% carbamide peroxide released significantly more mercury in solution than samples exposed to phosphate buffer controls. Mercury release was time-dependent and significantly higher in aged amalgam than in fresh amalgam (P < 0.001). Mercury release was also pH-dependent and higher in unpolished amalgam.

Analysis of Variance↗