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At least 19 recordsLinked to original sources
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↗
PubMed1997

Bleaching of a discoloured non-vital tooth: use of a sodium perborate/water paste as the bleaching agent.

Bleaching materials containing hydrogen peroxide have been used successfully for the treatment of discoloured non-vital teeth; however, their use has occasionally been associated with external root resorption. Some evidence exists that sodium perborate mixed with water is as effective as sodium perborate mixed with hydrogen peroxide. A case is presented which supports this and a step-by-step technique is described.

Adolescent↗
PubMedDate not supplied

A scanning electron microscope study of the long-term effect of bleaching agents on the enamel surface in vivo.

Vital bleaching of teeth is, increasingly, a popular esthetic desire. Bleaching agents are provided in over-the-counter as well as dental office bleaching kits. However, the effect of the bleaching agents on the enamel surface is not fully understood, and cautions approaches to their use are not usually explained to patients. In this study, an in vivo exposure of bleaching agents is used to evaluate the short and long-term effect on the enamel surface; the results are demonstrated by scanning with an electron microscope. Exposure to the bleaching agents for 14 days created an alteration of the enamel surface and caused exposure of the enamel prisms. Moreover, a 21- to 90-day post-exposure SEM evaluation demonstrated alteration of the surface enamel, indicating exposure of the enamel prismatic layer, frequently to the depth of the enamel rods and possibly the dentin.

Dental Enamel↗
PubMed2005

Effects of a 10% carbamide peroxide bleaching agent on roughness and microhardness of packable composite resins.

PURPOSE: Bleaching agents containing 10% carbamide peroxide may be applied to the surface of preexisting packable resin-based composite restorations. The aim of this in vitro study was to evaluate the effect of a 10% carbamide peroxide bleaching agent (Review, SS White, Rio de Janeiro, Brazil) on surface roughness and microhardness of three packable resin-based composites (Fill Magic condensable, Vigodent, Rio de Janeiro, Brazil; Alert, Jeneric Pentron, Wallingford, CT, USA; Definite, Degussa, Hanau, Germany). MATERIALS AND METHODS: For the control (no bleaching) and experimental (bleaching treatment) groups, 12 specimens of each material were prepared in cylindrical acrylic molds. The experimental specimens were exposed to the bleaching agent for 6 hours a day for 3 weeks. During the remaining time (18 h), they were stored in artificial saliva. The control specimens remained immersed in artificial saliva throughout the experiment. Surface roughness and microhardness measurements were performed on the top surface of each specimen. RESULTS: Analysis of variance and the Tukey test showed no significant differences in roughness among the packable composites evaluated (p = .18), but those submitted to the treatment with a 10% carbamide peroxide bleaching agent displayed significantly higher mean surface roughness than did the corresponding control group for each material. For the microhardness tests, there were significant differences among materials (p < .0001). Alert showed the highest microhardness values followed by Definite and Fill Magic condensable. CONCLUSIONS: Ten percent carbamide peroxide bleaching agents may change the surface roughness of packable composites, but they do not alter their microhardness. CLINICAL SIGNIFICANCE: Under the conditions of this study, a 3-week bleaching regimen with 10% carbamide peroxide agents affected the roughness of packable composites. Nevertheless, the surface microhardness was not affected, although there were differences among the materials evaluated inherent to their composition.

Carbamide Peroxide↗
PubMed1995

Acute toxicity of carbamide peroxide and a commercially available tooth-bleaching agent in rats.

Previous studies have indicated that tooth-bleaching agents contain potentially hazardous chemicals. The present study evaluates the acute toxicity of a commercially available tooth-bleaching agent and carbamide peroxide, which is the active bleaching ingredient. Rats were dosed by stomach gavage, i.e., via a stomach tube, with 5, 15, and 50 mg carbamide peroxide/kg body weight and 150 and 500 mg tooth-bleaching agent/kg body weight, corresponding to 15 and 50 mg carbamide peroxide/kg body weight. Animals were killed after either one or 24 h. Autopsies were performed, and the distal part of the esophagus and the stomach were removed and processed for light microscopy investigation. Liver and kidney were evaluated histologically in animals killed after 24 h. Carbamide peroxide gave dose-dependent ulcerations of the gastric mucosa, with the 15 mg/kg body weight as the lowest observed effect level. The lesions were clearly visible after one h and seemed to be healing after 24 h. The ulcerations of the gastric mucosa were more pronounced after exposure to the tooth-bleaching agent than those observed after a comparable dose of carbamide peroxide. This may be attributed to the hydrophobic gel and the content of a carbopol (which increases the tissue adherence and retards the release of oxygen) in the bleaching agent. No apparent injury was observed in livers and kidneys. An exposure limit based on the lowest observed effect level (15 mg carbamide peroxide/kg body weight) and a safety factor of 100 were established and utilized in a risk assessment which indicated that daily human exposure during a bleaching procedure may come close to or even exceed this limit.

Acrylic Resins↗
PubMed1997

Sodium hypochlorite, bleaching agents, and the stratum corneum.

Interactions between bleaching agents containing sodium hypochlorite (NaOCl) and human stratum corneum are complex and not fully understood. The same applies when NaOCl is used as a war gas decontaminant. In this study data yielded by in vivo testing and an ex vivo bioassay are compared. Fifteen volunteers received patch tests of a neat proprietary NaOCl bleaching agent for 15, 30, 45, 60, and 90 min. No clinical reaction was seen. Reflectance colorimetry, transepidermal water loss (TEWL), and capacitance were measured for 72 hr after patch removal. Squamometry was also performed using D-Squames and colorimetry of the samples. In addition, the ex vivo corneoxenometry bioassay was conducted on various dilutions of the bleach. Data reveal that conductance and squamometry were more sensitive than TEWL to disclose the action of bleach upon the stratum corneum. Corneoxenometry proved to be a good predictive ex vivo bioassay, indicating the same information as the in vivo tests. Both squamometry and corneoxenometry appear valuable and complementary in assessing infraclinical damages of human skin by a NaOCl bleaching agent.

Adult↗
PubMed2006

Study of DNA damage induced by dental bleaching agents in vitro.

Dental bleaching is a simple and conservative procedure for aesthetic restoration of vital and non-vital discolored teeth. Nevertheless, a number of studies have demonstrated the risk of tissue damage from the contact of these agents with the oral mucosa. In the current study, the genotoxic potential associated with exposure to dental bleaching agents was assessed by the single cell gel (comet) assay in vitro. Chinese hamster ovary (CHO) cells in vitro were exposed to six commercial dental bleaching agents (Clarigel Gold - Dentsply; Whitespeed - Discus Dental; Nite White - Discus Dental; Magic Bleaching - Vigodent; Whiteness HP - FGM and Lase Peroxide - DMC). The results pointed out that all dental bleaching agents tested contributed to DNA damage as depicted by the mean tail moment, being the strongest effect observed with the highest dose of hydrogen peroxide (Whiteness HP and Lase Peroxide, at a 35% concentration). On the other hand, Magic Bleaching (Vigodent) induced the lowest level of DNA breakage. Negative and positive controls displayed absence and presence of DNA-damaging, respectively. Taken together, these results suggest that dental bleaching agents may be a factor that increases the level of DNA damage. A higher concentration of hydrogen peroxide produced higher noxious activities in the genome as detected by single cell gel (comet) assay.

Animals↗
PubMed2005

Assessment of genetic damage induced by dental bleaching agents on mouse lymphoma cells by single cell gel (comet) assay.

Dental bleaching is a simple and conservative procedure for aesthetic restoration of vital discoloured teeth. However, dental bleaching agents may represent a hazard to human health, especially by causing DNA strand breaks. Genotoxicity tests form an important part of cancer research and risk assessment of potential carcinogens. In the current study, the genotoxic potential associated with exposure to dental bleaching agents was assessed by the single cell gel (comet) assay in vitro. Six commercial dental bleaching agents (Clarigel Gold - Dentsply; Whitespeed - Discus Dental; Nite White - Discus Dental; Magic Bleaching - Vigodent; Whiteness HP - FGM and Lase Peroxide - DMC) were exposed to mouse lymphoma cells in vitro. The results pointed out that all dental bleaching agents tested contributed to the DNA damage as depicted by the mean tail moment. Clear concentration-related effects were obtained for DNA damaging, being the strongest effect observed at the highest dose of the hydrogen peroxide (Whiteness HP and Lase Peroxide, at 35% concentration). On the contrary, Whitespeed (Discus Dental) induced the lowest level of DNA breakage. Taken together, these results suggest that dental bleaching agents may be a factor that increases the level of DNA damage as detected by the single cell gel (comet) assay.

Animals↗
PubMed2001

Cytotoxicity of intracanal bleaching agents on periodontal ligament cells in vitro.

Intracoronal bleaching of nonvital teeth is a simple and conservative procedure for esthetic restoration of discolored teeth. However it is possible that damage to the periodontal ligament may occur if the bleaching agents contact this tissue. The purpose of this study was to examine the cytotoxicity of intracanal bleaching agents on human periodontal ligament (PDL) cells in vitro. Three bleaching agents, 30% hydrogen peroxide (H2O2), 2.0 g/ml sodium perborate (SP) solution, and 2.0 g/ml SP in H2O2, were diluted from 10(-3) to 10(-7) with Eagle's minimal essential medium and incubated with PDL cells isolated and cultured from extracted teeth. Cytotoxicity was assessed quantitatively by determining the amount of lactic dehydrogenase activity released from the cells after exposure to the agents for 24 or 72 h. Dose-response curves were plotted, and TD50 values (dilution causing the release of 50% of control lactate dehydrogenase activity) and 95% confidence limits determined. The rank order of the TD50 values after exposure for 24 h was SP in H2O2 (most toxic) > H2O2 > SP solution (least toxic). After 72 h SP in H2O2 still produced the greatest cytotoxic effect. However the SP solution was more cytotoxic than H2O2 at this time point. It is concluded that the mixture of SP with H2O2 was the most toxic to the PDL cells in vitro.

Borates↗
PubMed1995

Role of saliva and salivary components as modulators of bleaching agent toxicity to human gingival fibroblasts in vitro.

Mild oxygenating agents generating H2O2 are used for effective at-home tooth bleaching, but can cause gingival ulcers in some patients. There are concerns about the possible pathological effects of relatively long-term exposure of oral tissues to bleaching agents. Previous work in our laboratory showed that a bleaching agent, which generates approximately 3% H2O2 from carbamide peroxide, was toxic to human gingival fibroblasts in vitro, but that the toxicity was abolished by treatment with the H2O2-destroying enzyme catalase. The purpose of the present study was to determine if whole saliva, the salivary enzyme lactoperoxidase (LP) (which, like catalase, removes H2O2), or salivary mucin protected fibroblasts from bleaching agent toxicity. The cells were exposed to 0.05% agent with or without saliva, LP, mucin or catalase (as a positive control based on our previous study) and assessed for effect on viability/morphology (by microscopic observation), proliferation (by [3H]-thymidine incorporation), and the production of fibronectin (FN) and type I collagen (by ELISA). While the bleaching agent at 0.05% caused cell death, the cells appeared viable and morphologically normal when treated with the bleaching agent and LP (> or = 0.1 microM), saliva LP, and catalase from agent inhibition of proliferation (P < or = 0.04) and FN production (P < or = 0.01). Mucin had statistically insignificant or no protective effect as assessed by the above parameters. Treatment with saliva, LP, mucin, and catalase gave complete or partial protection from agent-inhibition of collagen production (P < or = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Catalase↗
PubMed2002

The effect of bleaching agents on the microhardness of dental aesthetic restorative materials.

This study investigated the effects of three home bleaching agents on the microhardness of various dental aesthetic restorative materials. The restorative materials were: feldspatic porcelain, microfilled composite resin and light-cured modified glass-ionomer cement and the bleaching agents Nite-White (16% carbamide peroxide), Opalescence (10% carbamide peroxide and carbapol jel) and Rembrandt (10% carbamide peroxide jel). A total of 90 restorative material samples were prepared 1 cm diameter and 6 mm thick and kept in distilled water for 24 h before commencing bleaching which was carried out for 8 h day-1 for 4 weeks. Microhardness measurements were then made using a Tukon tester. Statistically significant differences with respect to unbleached controls were found only for the feldspatic porcelain and microfilled composite resins (P <0.05) for Nite-White and Opalescence. All the bleaching agents decreased the microhardness of the porcelain and increased that of the light cured modified glass-ionomer cement. For the composite resin, whereas Nite-White increased its microhardness, the other bleaching agents decreased it. There were no significant differences between the bleaching agents for any of the restorative materials.

Aluminum Silicates↗
PubMed2004

Safety and efficacy of a nightguard bleaching agent containing sodium fluoride and potassium nitrate.

OBJECTIVES: Transient sensitivity during bleaching is generally reported to affect 67% of patients. While most people tolerate this sensitivity, some find it impossible to continue treatment. The purpose of this study was to determine the safety and efficacy of an experimental, low-sensitivity bleaching agent. METHOD AND MATERIALS: Twenty-two participants bleached for a minimum of 6 hours per night over a 2-week period. The bleaching agent used, Experimental Product E, is a 10% carbamide peroxide gel containing potassium nitrate and sodium fluoride. Evaluations were performed at baseline and 1,2,13, and 26 weeks. Color change was measured using a value-ordered Vita classic shade guide and a colorimeter. Sensitivity of the teeth, gingiva, tongue, and/or throat was measured daily using a patient log. RESULTS: The median color change after 2 weeks was eight tabs. Approximately 36% reported sensitivity during the active whitening phase of the study. As a group, participants reported sensitivity during 13.7% of the total days spent whitening. CONCLUSION: Experimental Product E was shown to be safe. Participants experienced minor sensitivity during the active bleaching phase only. Experimental Product E was shown to be an effective bleaching agent for the subjects tested in this study.

Adult↗
PubMed1998

In vitro evaluation of the cytotoxicity of a bleaching agent.

Cell cultures of L929 and BHK21/C13 cells were used to evaluate the toxicity of a newly introduced bleaching agent (Colgate Platinum) compared to hydrogen peroxide, an established bleaching agent. The cell reaction was determined by a quantitative technique at 24 h and 72 h. Both bleaching materials had a dose-dependent effect on cell viability. Concentrations of hydrogen peroxide causing a 50% decrease in cell number (50% inhibition dose-ID50) were calculated as 0.00034% after 24 h and 0.00001% after 72 h in L929 cells. The ID50 of hydrogen peroxide was found to be 0.00016% after 24 h and 0.00007% after 72 h in BHK21/C13 cells. The ID50 of Colgate Platinum was 0.00074% after 24 h and 0.00045% after 72 h in L929 cells and 0.00055% after 24 h and 0.00024% after 72 h in BHK21/C13 cells. The results showed that, in vitro, both bleaching agents were cytotoxic to fibroblasts and the new bleaching agent was less toxic than hydrogen peroxide.

Animals↗
PubMed1993

[An epidemiologic survey on the cosmetic use of bleaching agents by the women of Bamako (Mali)].

In Mali, the cosmetic use of bleaching agents by black people has become a social phenomenon. How wide is this practice is not precisely known. We report the results of a survey conducted in Bamako among women aged from 15 to 45 years in order to evaluate the prevalence of this practice and its socio-economic factors. Two-hundred and ten women were questioned during the cluster survey. Among these, 53 (25 p. 100) used bleaching agents which were topical cortico-steroids (37), hydroquinone-containing products (21), mercury derivatives (11) and products of unknown composition (16). Dermatological side-effects were observed, but they did not hinder the use of these agents. Bleaching was particularly frequent in unmarried women (39 p. 100), literate women (34 p. 100) and female students (45 p. 100).

Administration, Topical↗
PubMed2005

Effect of bleaching agents on bonding to pulp chamber dentine.

AIM: To determine the effect of intracoronal bleaching agents on adhesion of bonding agents to pulp chamber dentine. METHODOLOGY: Forty extracted human maxillary anterior teeth were randomly divided into four groups of 10 teeth each. Bleaching agents were sealed in pulp chambers for 7 days, as in clinical use. Group 1 (control): distilled water, group 2: 35% hydrogen peroxide, group 3: sodium perborate mixed with water, and group 4: sodium perborate mixed with 35% hydrogen peroxide. Teeth were stored in saline at 37 degrees C for 7 days. After the bleaching agent was removed, teeth were leached in water for a further 7 days prior to bonding. The crown was cut vertically from mesial to distal and the labial pulp chamber dentine was prepared for bonding with Clearfil SE-Bond and filled with resin composite (Clearfil AP-X). The bonded specimens were kept moist at 37 degrees C for 24 h. Microtensile bond strengths were determined using a universal testing machine. Additional teeth were prepared using the same bleaching procedures to investigate the scanning electron microscopic appearance of the dentine surface. RESULTS: Mean values (+/-SD) of microtensile bond strength for the experimental groups were: group 1: 5.29 +/- 2.21 MPa, group 2: 5.99 +/- 1.51 MPa, group 3: 9.17 +/- 1.65 MPa and group 4: 3.99 +/- 1.31 MPa. Dentine treated with sodium perborate in water (group 3) had significantly higher mean bond strength when compared with the other three groups (P < 0.05, Tukey's test). Mean bond strength was lowest when dentine was treated with sodium perborate plus hydrogen peroxide (group 4). CONCLUSIONS: In terms of subsequent bond strength during restoration, sodium perborate mixed with distilled water appears to be the best intracoronal bleaching agent.

Borates↗
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

An atomic force microscopy study on the effect of bleaching agents on enamel surface.

OBJECTIVES: The aim of the present study was to evaluate the effect of three peroxide-containing bleaching agents, Opalescence, Nite White and a 30% hydrogen peroxide solution, on enamel surfaces using Atomic Force Microscopy (AFM). METHODS: Fifteen non-carious human incisors (ten maxillary and five mandibular, extracted for periodontal reasons) were used. The teeth were divided randomly into three groups of five, according to the bleaching agents. The labial surface of each tooth was imaged by AFM before and after treatment. Each bleaching agent was applied for a total of 28 h (in individual 4 h treatments). The specimens were examined only after 28 h of treatment. RESULTS: On comparing the AFM images of untreated and treated enamel, surface alterations were observed after 28 h of treatment with Opalescence, Nite White and 30% hydrogen peroxide solution. Several grooves present in the enamel surface of untreated teeth became deeper after the bleaching procedure. The depths of the grooves increased in each case. The increase in the depth of grooves was more pronounced in the case of the 30% H2O2 solution. CONCLUSION: Home-use bleaching agents are capable of causing enamel surface alterations. It is hypothesized that the peroxide-containing bleaching agents affect the organic phase of enamel. Peroxides can affect not only the surface but also the inner structure of enamel. As a result of its low molecular weight, hydrogen peroxide can penetrate into the enamel. Thus, inner oxidative effects are more likely to occur in the subsurface enamel where more organic material is present and oxidation is capable of altering the outer enamel and the surface.

Acrylic Resins↗
PubMed1989

An in vitro comparison of different bleaching agents in the discolored tooth.

Extracted teeth with intact crowns were stained to compare and evaluate the effectiveness of four bleaching agent combinations. Forty-two permanent and 12 deciduous teeth were used. The bleaching agents were placed into coronal pulp chambers and then evaluated and rated at 1-, 3-, 7-, and 14-day and 6-month intervals. New sodium perborate combined with fresh Superoxol was the most effective bleaching agent with 93% success (the final shade was as light as the prestained shade). New sodium perborate and 1-yr-old Superoxol was 73% successful. New sodium perborate with distilled water and old sodium perborate with distilled water were both 53% successful. Deciduous teeth demonstrated a response to bleaching agents similar to that of permanent teeth. Color regression after 6 months was found in 4% of the cases. When it occurred, the degree of color regression was minimal.

Borates↗