In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time. The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ. Peroxide bleaching agent effects on enamel surface microhardness, roughness and morphology. Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness. Effect of carbamide peroxide bleaching agents on tensile strength of human enamel. The Influence of Post Bleaching Treatments in Stain Absorption and Microhardness In vitro Comparison of Impact of Different Bleaching Agents on the Microhardness of Enamel. Effect on enamel microhardness of two consumer-available bleaching solutions when compared with a dentist-prescribed, home-applied bleaching solution and a control. Effects of 10% carbamide peroxide on the enamel surface morphology: a scanning electron microscopy study. Use of different concentrations of carbamide peroxide for bleaching teeth: an in vitro study. Randomized clinical trial of the efficacy and safety of a home bleaching procedure. A clinical evaluation of carbamide peroxide and hydrogen peroxide whitening agents during daytime use. Evaluation and comparison of the microhardness of enamel after bleaching with fluoride free and fluoride containing carbamide peroxide bleaching agents and post bleaching anticay application: An in vitro study Two-year clinical evaluation of tooth whitening using an at-home bleaching system. Effects of 10% carbamide peroxide treatment and sodium fluoride therapies on human enamel surface microhardness. Microhardness of demineralized enamel following home bleaching and laser-assisted in office bleaching Clinical efficacy of a degradable film-forming product containing carbamide peroxide to reduce tooth discolouration.
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 . MATERIAL S 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 result ed 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 This in situ study evaluated the microhardness of sound and demineralized enamel and dentin su bmi tted 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 r and omly 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 su bmi tted to treatment with OPA showed lower microhardness values than the SE and DE su bmi tted to treatment with PLA . There were no statistical differences in microhardness values for SD and DD su bmi tted 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 The aim of this study was to evaluate the surface roughness , microhardness and morphology of human enamel exposed to six bleaching agents ( at baseline and post-treatment ) . Human dental enamel sample s were obtained from human third molars and r and omly divided into seven groups ( n = 11 ) : control , Whiteness Perfect--10 % carbamide peroxide ( 10 % CP ) , Colgate Platinum--10 % CP , Day White 2Z--7.5 % hydrogen peroxide ( 7.5 % HP ) , Whiteness Super--3 % CP , Opalescence Quick--35 % CP and Whiteness HP--35 % HP . Bleaching agents were applied according to manufacturers ' instructions . The control group remained not treated and stored in artificial saliva . Microhardness testing was performed with a Knoop indentor and surface roughness was analyzed with a profilometer . Morphologic observations were carried out with scanning electron microscopy ( SEM ) . Results were statistically analyzed by two-way analysis of variance and Tukey 's test ( 5 % ) , and revealed a significant decrease in microhardness values and a significant increase in surface roughness post-bleaching . Changes in enamel morphology after bleaching were observed under SEM . It was concluded that bleaching agents can alter the microhardness , roughness and morphology of dental enamel surface This in vitro study evaluated the surface microhardness of human enamel su bmi tted to bleaching with 10 % carbamide peroxide ( CP ) containing calcium or fluoride . Ninety-eight dental blocks ( 5 x 5 mm2 ) with polished enamel surfaces were r and omly 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 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 r and omly 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 Objectives : This study investigated the effects of post bleaching treatments to prevent restaining and the change of enamel surface microhardness after dental bleaching in vitro . Methods : Sixty intact human incisor teeth were stained in tea solution and r and omly assigned into four groups ( n=15 ) . Then sample s were bleached for two weeks ( 8 hours daily ) by 15 % carbamide peroxide . Tooth color was determined both with a spectrophotometer and visually before bleaching ( T1 ) and immediately after bleaching ( T2 ) . Next , it was applied in group 1 fluoride ( Naf 2 % ) gel for 2 minutes , and in group 2 a fractional CO2 laser ( 10 mJ , 200 Hz , 10 s ) , and in group 3 , nanohydroxyapatite gel for 2 minutes . The bleached teeth in group 4 remained untreated ( control group ) . Then teeth placed in tea solution again . Color examinations were repeated after various post bleaching treatments ( T3 ) and restaining with tea ( T4 ) and color change values recorded . The microhardness was measured at the enamel surface of sample s. Data was analyzed using ANOVA , Tukey HSD test and Dunnett T3 ( α = 0.05 ) . Results : Directly after bleaching ( ΔE T3-T2 ) , the treatment with nanohydroxyapatite showed significantly the least color lapse in colorimetric evaluation . In experimental groups , the color change between T3 and T4 stages ( ΔE T4-T3 ) was significantly lower than control group ( P < 0.05 ) . Different methods of enamel treatment caused a significant increase in surface microhardness compared to control group ( P < 0.05 ) . Significance : Application of fluoride , fractional CO2 laser and nanohydroxyapatite as post bleaching treatments are suggested for prevention of stain absorption and increasing the hardening of bleached enamel BACKGROUND Various agents are used these days for increasing the esthetics . One such procedure is bleaching that offers various advantages , as it is minimal invasive and cheap option to color the teeth and remove stain . The altered enamel after the bleaching process shows surface demineralization and porosities . The present study aim ed to evaluate the effect of different bleaching agents on the microhardness of enamel . MATERIAL S AND METHODS A total of 100 freshly human extracted maxillary premolar teeth were selected for the study . Teeth with sound tooth structure were included for the study . All the specimens were r and omly divided into four groups with 25 specimens in each group depending upon the type of bleaching agent used : Group A , artificial saliva ( Control group ) ; Group B , 35 % hydrogen peroxide ( HP ) ; Group C , 25 % HP ; Group D , 10 % carbamide peroxide ( CP ) .  Knoop Hardness Number ( KHN ) was calculated at 24 , 48-hour , and 7-week interval . RESULTS Results showed no statistical significant differences between the microhardness of enamel of different groups ( p < 0.005 ) . A slight fall in the value of KHN was seen in all the groups , except for the control group , although the results were statistically nonsignificant ( p > 0.005 ) . CONCLUSION Although nonsignificantly , all the bleaching solutions produced some amount of alterations in the microstructure of enamel . More studies with higher study groups and more advanced estimation technologies are required to minimize microstructure alterations and promote for better outcome of bleaching procedures BACKGROUND There exists limited data in the literature regarding the efficacy and safety of consumer-available , paint-on bleaching solutions . PURPOSE The purpose of this in vitro study was to evaluate the effect of two consumer-available , paint-on bleaching products on enamel microhardness against a control and a dentist-prescribed , home-applied ( DPHA ) bleaching product . MATERIAL S AND METHODS Eighty enamel slabs were obtained from extracted human teeth and r and omly divided into four treatment groups : ( 1 ) control ; ( 2 ) Opalescence ( Ultradent Products , Inc. , South Jordan , UT , USA ) ; ( 3 ) Crest Night Effects ( Procter & Gamble , Cincinnati , OH , USA ) ; and ( 4 ) Colgate Simply White Night ( Colgate-Palmolive Co. , Piscataway , NJ , USA ) . Opalescence is a carbamide peroxide DPHA product , whereas Crest Night Effects and Colgate Simply White Night are consumer-available products . The specimens in groups 2 to 4 underwent 2 weeks of treatment for 8 h/d . Specimens were maintained in artificial saliva at 37 degrees C between treatments . Subsequently , one-half of the specimens in groups 2 to 4 ( n=10 ) underwent an additional seven treatments for 8 h/d , while the other half were stored in artificial saliva , receiving no further treatment . Microhardness was measured as Knoop hardness numbers ( KHNs ) at baseline and after 1 , 7 , 14 , and 21 treatment days . The results were analyzed for statistical significance both intra- and intergroups using analysis of variance ( p=.05 ) . RESULTS A statistically significant reduction in mean KHN was observed compared with baseline at 1 , 7 , 14 , and 21 treatment days for group 4 and at 7 treatment days for group 3 . When compared with the control or DPHA product , group 4 was the only treatment that result ed in significantly lower mean KHNs at 7 , 14 , and 21 treatment days . CONCLUSION When evaluating enamel microhardness , consumer available , paint-on bleaching solutions may adversely affect enamel microhardness compared to a control and 10 % carbamide peroxide DPHA bleaching solution . CLINICAL SIGNIFICANCE With numerous consumer-available bleaching products on the market , it is crucial to be judicious in their selection and use . The results of this in vitro study showed that the consumer-available , paint-on bleaching solutions adversely affected enamel microhardness at some time during the study . Consumers should be made aware of this effect on enamel 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 . MATERIAL S 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 br and of bleaching agent and duration of application time . However , these alterations revert to almost normal within 3 months OBJECTIVE This in vitro study compared the shade changes in extracted teeth during 2 weeks ' whitening with 5 % , 10 % , or 16 % carbamide peroxide . METHOD AND MATERIAL S After color calibration , the sole examiner selected 110 extracted unrestored , noncarious teeth , shade A3 or darker on a value-oriented guide . The teeth were r and omly distributed into equal color groups . The control group ( 11 teeth ) was treated with 0.9 % saline , while the experimental groups ( 33 teeth each ) were treated with 5 % , 10 % , or 16 % carbamide peroxide . The solutions remained on the teeth for 8 hours . The teeth and tray were rinsed with tap water for 2 minutes , then rehydrated in 0.9 % saline for 16 hours in the humidifier . The shade was assessed , and the process was repeated daily for 2 weeks . RESULTS Repeated- measures analysis of variance indicated a significant difference in overall shade values between the control and all carbamide peroxide-treated groups at days 8 and 15 . A Kaplan-Meier Survival Analysis indicated a quicker two-tab color change for the 10 % and 16 % groups than the 5 % group . However , continuation of the 5 % treatment to 3 weeks result ed in shades that approached the 2-week 10 % and 16 % values . CONCLUSION Lower concentrations of carbamide peroxide take longer to whitening teeth but eventually achieve the same result as higher concentrations . Higher concentrations may cause increased sensitivity The safety and efficacy of a home-use carbamide peroxide tooth-whitening procedure were evaluated in a double-blind experimental design . Fifty-two adults were r and omly assigned to experimental and control ( placebo gel ) groups . The products were applied in a custom-fitted tray and used for 5 consecutive nights in accordance with the manufacturer 's recommendations . Tooth color changes from baseline were measured with a small-area colorimeter . Concurrently , electric pulp test and periodontal indices were measured . At the end of 6 months , the teeth in the active group had a statistically significant greater mean color change that did the placebo controls . The mean color change differed significantly by tooth type . No statistically significant changes in vitality , sulcus depth , or Gingival Index were found in the treatment group BACKGROUND Vital tooth bleaching for esthetic reasons has gained in popularity during the last few years . However , few studies have investigated the efficacy of daytime bleaching products . The purpose of this double-blind in vivo study was to evaluate the efficacy of 20 percent carbamide peroxide , or CP , and 7.5 percent hydrogen peroxide , or HP , during daytime use . The degree of color change , any color relapse , and tooth or gingival sensitivity were evaluated . METHODS Twenty-four patients participated in this study . The bleaching gels were r and omly applied to the right and left maxillary anterior teeth . Patients were shown how to place the two bleaching agents in a custom tray for one hour , twice a day for two weeks . Patients returned in one , two , three , six and 12 weeks for color evaluation with the colorimeter and shade guides as well as to have color slide photographs taken . The authors evaluated sensitivity by asking the patients to record daily for 21 days any tooth or gingival sensitivity they experienced . RESULTS Use of the 20 percent CP result ed in significantly more lightness than the 7.5 percent HP during the first 14 days of the study , but at the end of the study , there was no significant difference between products with regard to tooth lightness . In addition , the authors found no statistically significant difference between products with regard to gingival or tooth sensitivity . CONCLUSIONS Both CP and HP are effective at-home bleaching agents when daytime bleaching is preferred . CLINICAL IMPLICATION S Dentists who choose to use daytime bleaching can select either CP or HP Aims and Objectives : The purpose of the study was to evaluate and compare the microhardness of enamel after the application of anticay on bleached enamel with fluoride containing and fluoride free bleaching agent . Material s and Methods : Twenty freshly extracted teeth decoronated and divided mesiodistally into two halves were r and omly divided into five groups with 10 sample s in each group . The enamel surface was treated as follows : Group 1 - no treatment , Group 2 - fluoride free bleaching agent , Group 3 - fluoride containing bleaching agent , and Group 4 - fluoride free bleaching agent followed by anticay application . The sample s were subjected to indentation to test the microhardness using Vicker 's hardness analyzer . Conclusion : Enamel microhardness significantly increased in sample s where anticay was used after the application of bleaching agent PURPOSE The purpose of this study was to evaluate the 2-year effectiveness of a carbamide peroxide at-home bleaching gel used to provide tooth lightening treatment . MATERIAL AND METHODS Twenty-nine patients participated in the original study , during which they treated their maxillary teeth with a 10 % carbamide peroxide gel nightly for 2 weeks . Shades were determined before and after treatment by comparison with a Vita shade guide . Twenty-four patients ( a recall rate of 83 % ) were recalled for evaluation 2 years after the initial bleaching treatment . The shade of the maxillary incisors was evaluated and compared with shades before , immediately after , and at 6 months and 2 years after initial treatment . Data were analyzed using a repeated- measures analysis of variance . RESULTS At 2 years after bleaching with a 10 % carbamide peroxide gel , the median shade was D2 , a six-increment difference from the baseline median of D3 . Twenty of 24 patients ( 83.3 % ) had a shade change of two or more units , which is the threshold value for bleaching efficacy using American Dental Association guidelines . The lightening result remained statistically significant ( p < .0001 ) at 2 years . CLINICAL SIGNIFICANCE Although some reversal of the lightening effect occurs over time following the original bleaching treatment , loss of the lighter color appears to be gradual for most patients . Although the longevity of the lightening effect remains to be determined , this clinical trial indicates that the majority of patients have a satisfactory result 2 years after treatment This study sought to evaluate the microhardness of enamel su bmi tted to 10 % carbamide peroxide treatment  and different methods of remineralization involving sodium fluoride ( NaF ) .  Non-erupted third molars were used and 75 enamel blocks with st and ardized dimensions ( 4.0 x 4.0 x 2.0 mm ) were obtained . Enamel blocks were r and omly divided into five groups ( n = 15 ) : one control ( no bleaching and no fluoride treatment ) , one receiving a 10 % carbamide peroxide treatment , one receiving 10 % carbamide peroxide plus acidulated phosphate fluoride , one receiving 10 % carbamide peroxide with 0.2 % NaF , and one receiving 10 % carbamide peroxide and 0.05 % NaF. There were no differences among four of the groups ( p > 0.05 ) ; the group receiving 10 % carbamide peroxide only was different from all other groups ( p < 0.05 ) . Based on these results , NaF therapies are recommended during carbamide peroxide bleaching treatments Background There is little data regarding the effect of tooth whitening on microhardness of white spot lesions . This study was conducted to investigate the effect of home-bleaching and laser-assisted in-office bleaching on microhardness of demineralized enamel . Material and Methods Forty bovine incisors were selected and immersed in a demineralizing solution for 12 weeks to induce white spot lesions . Enamel blocks were prepared and r and omly assigned to two groups of 20 each . The first group underwent home bleaching with 15 % carbamide peroxide which was applied for 8 hours a day over a period of 15 days . In the second group , in-office bleaching was performed by 40 % hydrogen peroxide and powered by irradiation from an 810 nm gallium-aluminum-arsenide ( GaAlAs ) diode laser ( CW , 2W ) . This process was performed for 3 sessions every seven days , in 15 days . The specimens were stored in Fusayama Meyer artificial saliva during the experiment . Surface microhardness was assessed before and after the bleaching therapies in both groups . Results Microhardness decreased significantly following both home bleaching and laser-assisted in-office bleaching ( p<0.05 ) . There were no significant differences in hardness values among the two groups either before ( p=0.131 ) or after ( p=0.182 ) the bleaching procedures . Conclusions Tooth whitening through home bleaching or laser-assisted in-office bleaching can result in a significant reduction in microhardness of white spot lesions . Therefore , it is suggested to take protective measures on bleached demineralized enamel . Key words : White spot lesion , bleaching , laser , microhardness , demineralized enamel , home bleaching , in-office bleaching The methods used to lighten tooth discolouration while conserving the tooth structure have attracted much attention in a society which places a high value on esthetics . The purpose of this article is to present a home bleaching agent that uses a film-forming preparation containing carbamide peroxide ( CP ) which , while degrading , serves as a slow release delivery system of the bleaching agent . The efficacy of the preparation containing 3 % CP and 10 % CP on reduction of tooth discolouration is evaluated by a Chromameter in a double-blind placebo-controlled study . The effect of the tested bleaching agent on the gingival status , plaque accumulation and pulp sensitivity is also assessed
The results of this meta- analysis showed no significant changes in enamel microhardness when using the 10 % carbamide peroxide bleaching gel over periods of 7 , 14 and 21 days
Several studies have investigated the effect of bleaching on dental tissues .
The evaluation of the effect of home bleaching with 10 % carbamide peroxide is important for assessing alterations in enamel microhardness that may affect dental health in terms of resistance to masticatory forces .
This meta- analysis was performed in order to determine scientific evidence regarding the effects of home vital bleaching with 10 % carbamide peroxide gel on the microhardness of human dental enamel .