human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: 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 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 OBJECTIVES The aim of this study was to evaluate the efficacy , color stability , risk , and intensity of tooth sensitivity ( TS ) of combined bleaching techniques performed with 20 % or 35 % hydrogen peroxide for an in-office protocol . METHODS Thirty patients were r and omly divided into two groups and su bmi tted to a single 45-minute in-office bleaching session with 35 % hydrogen peroxide or 20 % hydrogen peroxide . At-home bleaching was performed with 10 % carbamide peroxide for two hours daily over the course of two weeks . The color was evaluated with the value-oriented shade guide Vita Classical at different periods up to 12 months after bleaching . Patients recorded the intensity of TS using a five-point verbal scale . Color change data were su bmi tted to a two-way repeated- measures analysis of variance and Tukey test ( α=0.05 ) . The absolute risk and intensity of TS were compared with the Fisher exact test and Mann-Whitney test , respectively ( α=0.05 ) . RESULTS On average , an effective and similar whitening of three units in shade guide was observed for both groups , which remained stable for 12 months . When both protocol s were compared , the one with hydrogen peroxide 35 % showed a higher risk ( p=0.02 ) and intensity of TS ( p=0.04 ) . In regard to the TS intensity , no significant difference was observed up to 48 hours after in-office bleaching ( p=0.09 ) and during the at-home bleaching phase of the study ( p=0.71 ) . CONCLUSION The combined bleaching technique using at-home bleaching associated with in-office bleaching was effective and stable over the course of 12 months , regardless of the concentration of the hydrogen peroxide used for in-office bleaching . However , the protocol with 20 % hydrogen peroxide produced lower risk and intensity of TS 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 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 This in vitro study evaluated the new formulas of bleaching products and the effect of subsequent applications of fluoride on the hardness of enamel during and after tooth bleaching . The crowns of 60 extracted intact human molars were sectioned longitudinally ; the buccal part was embedded in acrylic resin , the occlusal part was ground flat , exposing enamel and dentin , and then polished . Baseline Knoop microhardness ( KHN ) of enamel was determined . The specimens were then r and omly divided into six groups of 10 specimens , and each group was assigned to a specific 10 % carbamide peroxide ( CP ) bleaching agent . A : Opalescence , B : Opalescence PF ( 3 % potassium nitrate and 0.11 % fluoride ) , C : Nite White Excel 3 ( ACP ) , D : Opalescence + F ( acidulated phosphate fluoride 1.23 % ) , E : Opalescence PF + F , F : Nite White Excel 3 + F. The teeth were bleached for eight hours ; after each procedure , the specimens were stored in artificial saliva at 37 degrees C. Immediately after day 21 of bleaching , the specimens in groups D , E and F received fluoride 1.23 % for five minutes . KHN tests w ere performedbefore ( baseline = control ) , during ( 14 , 21 ) and two weeks ( 35 days ) after the bleaching procedure and were statistically compared using ANOVA/Tukey 's t-test ( alpha < 0.05 ) . The statistical analysis revealed no significant difference among the bleaching material s ( p = 0.123 ) . A significant enamel KHN reduction ( p < 0.001 ) was observed for all bleaching material s , with no difference among them . Two weeks after bleaching , all the groups that received fluoride showed a significant increase in microhardness . For the new bleaching formulas , the enamel was restored to a value similar to baseline 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 Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces . The aim of present study was to evaluate the effect of 10 % sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics . A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin . Subsequent to polishing , they were r and omly divided into 3 groups of 23 specimens each ; 3 for Scanning Electron Microscopy ( SEM ) analysis and 20 for hardness test . In group 1 the specimens were immersed in distilled water as control group ; in group 2 the specimens were bleached with 35 % carbamide peroxide for 30 min a week for 3 consecutive weeks ; and in group 3 the specimens were exposed to 10 % sodium ascorbate for 30 min subsequent to bleaching similar to group 1 . After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA ( P < 0.05 ) . The highest and lowest microhardness values were observed in group 1 and group 2 , respectively . However , there were no statistically significant differences in microhardness between the groups ( P = 0.12 ) . The use of 35 % carbamide peroxide alone or with 10 % sodium ascorbate does not affect bovine enamel hardness . SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface 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 morph 
    Output:
    
agent
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
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: 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 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 OBJECTIVES The aim of this study was to evaluate the efficacy , color stability , risk , and intensity of tooth sensitivity ( TS ) of combined bleaching techniques performed with 20 % or 35 % hydrogen peroxide for an in-office protocol . METHODS Thirty patients were r and omly divided into two groups and su bmi tted to a single 45-minute in-office bleaching session with 35 % hydrogen peroxide or 20 % hydrogen peroxide . At-home bleaching was performed with 10 % carbamide peroxide for two hours daily over the course of two weeks . The color was evaluated with the value-oriented shade guide Vita Classical at different periods up to 12 months after bleaching . Patients recorded the intensity of TS using a five-point verbal scale . Color change data were su bmi tted to a two-way repeated- measures analysis of variance and Tukey test ( α=0.05 ) . The absolute risk and intensity of TS were compared with the Fisher exact test and Mann-Whitney test , respectively ( α=0.05 ) . RESULTS On average , an effective and similar whitening of three units in shade guide was observed for both groups , which remained stable for 12 months . When both protocol s were compared , the one with hydrogen peroxide 35 % showed a higher risk ( p=0.02 ) and intensity of TS ( p=0.04 ) . In regard to the TS intensity , no significant difference was observed up to 48 hours after in-office bleaching ( p=0.09 ) and during the at-home bleaching phase of the study ( p=0.71 ) . CONCLUSION The combined bleaching technique using at-home bleaching associated with in-office bleaching was effective and stable over the course of 12 months , regardless of the concentration of the hydrogen peroxide used for in-office bleaching . However , the protocol with 20 % hydrogen peroxide produced lower risk and intensity of TS 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 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 This in vitro study evaluated the new formulas of bleaching products and the effect of subsequent applications of fluoride on the hardness of enamel during and after tooth bleaching . The crowns of 60 extracted intact human molars were sectioned longitudinally ; the buccal part was embedded in acrylic resin , the occlusal part was ground flat , exposing enamel and dentin , and then polished . Baseline Knoop microhardness ( KHN ) of enamel was determined . The specimens were then r and omly divided into six groups of 10 specimens , and each group was assigned to a specific 10 % carbamide peroxide ( CP ) bleaching agent . A : Opalescence , B : Opalescence PF ( 3 % potassium nitrate and 0.11 % fluoride ) , C : Nite White Excel 3 ( ACP ) , D : Opalescence + F ( acidulated phosphate fluoride 1.23 % ) , E : Opalescence PF + F , F : Nite White Excel 3 + F. The teeth were bleached for eight hours ; after each procedure , the specimens were stored in artificial saliva at 37 degrees C. Immediately after day 21 of bleaching , the specimens in groups D , E and F received fluoride 1.23 % for five minutes . KHN tests w ere performedbefore ( baseline = control ) , during ( 14 , 21 ) and two weeks ( 35 days ) after the bleaching procedure and were statistically compared using ANOVA/Tukey 's t-test ( alpha < 0.05 ) . The statistical analysis revealed no significant difference among the bleaching material s ( p = 0.123 ) . A significant enamel KHN reduction ( p < 0.001 ) was observed for all bleaching material s , with no difference among them . Two weeks after bleaching , all the groups that received fluoride showed a significant increase in microhardness . For the new bleaching formulas , the enamel was restored to a value similar to baseline 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 Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces . The aim of present study was to evaluate the effect of 10 % sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics . A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin . Subsequent to polishing , they were r and omly divided into 3 groups of 23 specimens each ; 3 for Scanning Electron Microscopy ( SEM ) analysis and 20 for hardness test . In group 1 the specimens were immersed in distilled water as control group ; in group 2 the specimens were bleached with 35 % carbamide peroxide for 30 min a week for 3 consecutive weeks ; and in group 3 the specimens were exposed to 10 % sodium ascorbate for 30 min subsequent to bleaching similar to group 1 . After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA ( P < 0.05 ) . The highest and lowest microhardness values were observed in group 1 and group 2 , respectively . However , there were no statistically significant differences in microhardness between the groups ( P = 0.12 ) . The use of 35 % carbamide peroxide alone or with 10 % sodium ascorbate does not affect bovine enamel hardness . SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface 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 morph 
    Output:
    