Bond strength of composite resin to enamel bleached with carbamide peroxide

Bleaching with 35 percent hydrogen peroxide causes enamel surface changes, which result in lower bond strengths of composite resin. Although a previous SEM study showed that home bleaching with 10 percent carbamide peroxide does not cause such surface changes, the results of our study indicate that carbamide peroxide bleaching reduces the shear bond strength of composite to etched enamel. Removal of surface enamel, however, restores bond strengths to normal levels.     

Bond Strength of Composite Resin to Enamel Bleached with Carbamide Peroxide

Bleaching with 35 percent hydrogen peroxide causes enamel surface changes, which result in lower bond strengths of composite resin. Although a previous SEM study showed that home bleaching with 10 percent carbamide peroxide does not cause such surface changes, the results of our study indicate that carbamide peroxide bleaching reduces the shear bond strength of composite to etched enamel. Removal of surface enamel, however, restores bond strengths to normal levels.     

Immediate bonding to bleached enamel

This research sought to determine the shear bond strength, degree of resin infiltration and failure mode when organic solvent-based adhesives (acetone or ethanol) were used in immediate bonding to enamel bleached with 10% carbamide peroxide or 38% hydrogen peroxide systems. Seventy-two non-carious bovine incisors were randomly assigned to three groups of 24 specimens each-control group (deionized water), 38% hydrogen peroxide bleach group and 10% carbamide peroxide bleach group. Each group was further subdivided into two subgroups of 12 specimens each according to the adhesive system used to bond the resin composite to enamel surfaces. The two adhesive systems used were Single Bond, an ethanol-based adhesive, and One Step, an acetone-based adhesive. The shear bond strengths of 38% hydrogen peroxide and 10% carbamide peroxide were significantly lower compared to the non-bleached controls. Fractography revealed an adhesive failure mode in all specimens. Qualitative comparisons of resin tags present in the bleached and unbleached specimens using scanning electron microscopy (SEM) revealed few, thin and fragmented resin tags when 38% hydrogen peroxide and 10% carbamide peroxide were used.     

Reversal of compromised bonding in bleached enamel

Oxygen inhibits polymerization of resin-based materials. We hypothesized that compromised bonding to bleached enamel can be reversed with sodium ascorbate, an anti-oxidant. Sandblasted human enamel specimens were treated with distilled water (control) and 10% carbamide peroxide gel with or without further treatment with 10% sodium ascorbate. They were bonded with Single Bond (3M-ESPE) or Prime&Bond NT (Dentsply DeTrey) and restored with a composite. Specimens were prepared for microtensile bond testing and transmission electron microscopy after immersion in ammoniacal silver nitrate for nanoleakage evaluation. Bond strengths of both adhesives were reduced after bleaching but were reversed following sodium ascorbate treatment (P < 0.001). Resin-enamel interfaces in bleached enamel exhibited more extensive nanoleakage in the form of isolated silver grains and bubble-like silver deposits. Reduction of resin-enamel bond strength in bleached etched enamel is likely to be caused by a delayed release of oxygen that affects the polymerization of resin components.     

Resin bonding using an all-etch or self-etch adhesive to enamel after carbamide peroxide and/or CPP-ACP treatment

BACKGROUND: Limited evidence exists regarding the effect of carbamide peroxide and casein phosphopeptide amorphous calcium phosphate (CPP-ACP) on composite-enamel bonding. Microshear bond strengths, using either a total-etch or self-etching adhesive, to enamel treated with carbamide peroxide and/or CPP-ACP were investigated. MATERIALS AND METHODS: Twenty-six extracted human third molars were sectioned into four parts, each being allocated into one of the four groups (n=26): bleach (Polanight, 16% carbamide peroxide), CPP-ACP (GC Tooth Mousse), bleach and then CPP-ACP, or untreated (control). The surfaces were bonded with a total-etch bonding system (Single Bond) or a self-etching primer system (Clearfil SE Bond) and tested using a microshear test. RESULTS: A significant difference in bond strength was found between bonding systems. SE Bond showed the highest bond strength to untreated enamel (p < 0.05). The microshear bond strength of SE Bond decreased when the enamel was treated with carbamide peroxide, CPP-ACP or both (p < 0.05). Only combined use of carbamide peroxide and CPP-ACP significantly affected microshear bond strength with Single Bond. CONCLUSION: These findings suggest the shear bond strength of resin to enamel using a self-etching priming adhesive may be affected if the enamel is treated with a bleaching agent or CPP-ACP.     

The effect of elapsed time following bleaching on enamel bond strength of resin composite.

Recent studies have concluded that carbamide peroxide bleaching agents significantly affect the bond strength of composite to bleached enamel. This study evaluated the effects of bleaching regimen with different carbamide peroxide concentrations and post-treatment times on composite bond strength to enamel. Two hundred and four flat buccal and lingual enamel surfaces obtained from erupted sound third molars were randomly divided into 17 groups (n = 12). Sixteen experimental groups comprised the evaluation of four carbamide peroxide home bleaching agents (Opalescence 10%-20% and Whiteness 10%-16%) and four time intervals after bleaching (one day, one, two and three weeks). Specimens of control group were not submitted to bleaching and were stored in artificial saliva at 37 degrees C for 10 days. The specimens of experimental groups were exposed to one daily application of carbamide peroxide for six hours for 10 consecutive days. After each daily treatment and post-bleaching, the specimens were stored in artificial saliva solution. Bonds were formed with Scotchbond MP and Z-100 composite resin, and shear bond test was carried out 24 hours after adhesive-composite application. Two-way ANOVA showed that the bond strengths were significantly different (p < 0.05). For the first two weeks post-bleaching, the bond strengths of resin to enamel were low. After a lapse of three weeks, the bond strength returned to that of the untreated control group. Increased concentration did not prolong the time needed prior to bonding.     

The effect of whitening agents on caries susceptibility of human enamel

This in vitro study evaluated whether the treatment of human enamel with whitening agents containing different concentrations of carbamide or hydrogen peroxide changes the susceptibility of enamel to caries. Twenty-four sound human incisors were selected for this study. For each tooth, the crown was sectioned into two halves in the cervical-incisal direction. One half of the sectioned tooth was treated and the other half was used as a control specimen. Each half was randomly divided into three treatment groups (eight two-halves/group). The whitening agents were 10% carbamide peroxide, 20% carbamide peroxide with fluoride and 35% hydrogen peroxide. Following pretreatment, the specimens were demineralized for four days in an in vitro microbial caries model and then analyzed using a confocal laser scanning microscope (CLSM). Results showed that there were no significant differences between the treated and controlled specimens for teeth treated with 10% carbamide peroxide or 35% hydrogen peroxide. However, specimens treated with 20% carbamide peroxide with FP (0.11% fluoride and potassium nitrate) were less susceptible to caries than their controls at p < or = 0.05. In conclusion, application of bleaching agents does not increase the caries susceptibility of human enamel.     

Postoperative dental bleaching: effect of microleakage on Class V tooth colored restorative materials

The effect of 3 percent, 11 percent, and 16 percent carbamide peroxide bleaching solutions and 35 percent hydrogen peroxide bleaching gel on microleakage of Class V composite resins, resin modified glass ionomer cements, and compomer restorative materials together with corresponding (if indicated) fourth/fifth generation bonding agents was evaluated using previously extracted human teeth. Five groups of Class V cavity preparations were placed in enamel of the facial surfaces of 200 teeth. Groups A through D included 40 restorations each (4 different restorative materials and their accompanying bonding agent multiplied by 10 teeth) treated with 3 percent, 11 percent, and 16 percent carbamide peroxide bleach and 35 percent hydrogen peroxide bleach. Group E included 40 restorations without treatment of bleach and stood as the control. The restorative materials included were: Fuji II LC resin modified glass ionomer cement, Helioprogress composite resin/-Heliobond adhesive system, Aelitefil composite resin/Allbond 2 adhesive and Dyract compomer material/Prime & Bond adhesive system. Bleaching agents included were Rembrandt 3 percent peroxide gel, Perfecta 16 percent carbamide peroxide gel, White & Brite 11 percent carbamide peroxide solution and Superoxyl 35 percent hydrogen peroxide gel. All teeth were thermally stressed for 100 cycles and microleakage were assessed by dye penetration. The results were tabulated using Analysis of Variance (ANOVA) testing procedures. The Aelitefil composite resin material behaved the least favorably (relative to microleakage) compared to the other materials when exposed to various concentrations of dental bleaching agents.     

牙齿漂白剂对正畸托槽粘接强度的影响

目的:评价三种牙齿漂白剂对自酸蚀粘接系统粘接正畸托槽粘接强度的影响。方法:将100颗人前磨牙均分为四组:空白对照组(组1)、38%过氧化氢漂白组(组2)、10%过氧化脲漂白组(组3)和20%过氧化脲漂白组(组4),漂白牙齿后即刻使用自酸蚀正畸粘接系统Transbond Plus SEP将托槽粘接在牙面上,测量各组的抗剪切粘接强度,评价其剩余粘接剂指数,对结果进行统计学分析。结果:空白对照组的抗剪切粘接强度高于各漂白组,组2的抗剪切粘接强度高于组3和组4,而组4的抗剪切粘接强度最低,其差异均具有统计学意义(P<0.05)。各组的剩余粘接剂指数差异均有统计学意义(P<0.05),剩余粘接剂指数最低者为空白对照组,最高者为20%过氧化脲组。结论:在使用自酸蚀粘接系统粘接正畸托槽前应禁止使用过氧化物漂白牙齿,特别是高浓度的过氧化脲。     

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.     

Effect of tooth bleaching on bond strength of enamel-dentin cavities restored with silorane- and dimethacrylate-based materials

The aim of this study was to evaluate the influence of tooth bleaching on the push-out bond strength of a composite resin based on dimethacrylates and silorane to cavities that involve both enamel and dentin. A total of 80 bovine incisors were sectioned on the buccal surface to obtain specimens (10 × 10 mm) presenting enamel and dentin (1-mm thick each substrate). The specimens were randomly distributed into eight groups (n=10), according to the bleaching protocol (1--none; 2--10% carbamide peroxide [CP] for 21 days, six hours each day; 3--three applications of 35% hydrogen peroxide [HP] in 15-minute sessions, one session every seven days for three weeks; 4--10% CP for 18 days, six hours each day + three applications of 35% HP in 15-minute sessions, one session every seven days for three weeks) and the restorative system applied (Adper Single Bond 2 + Filtek Supreme; Filtek Silorane adhesive and composite resin). After treatment, cavities were made (1.2-mm diameter on dentin; 1.5-mm diameter on enamel) with a diamond bur. At 24 hours after restoration, a push-out bond strength test was performed at a crosshead speed of 0.5 mm/min. The bleaching treatments did not significantly affect the bond strengths of either restorative system to enamel-dentin. Regardless of the bleaching treatment, the dimethacrylate-based resin system exhibited significantly higher bond strengths to enamel-dentin than did the silorane-based system.     

Scanning electron microscopy study of dental enamel surface exposed to 35% hydrogen peroxide: alone,with saliva,and with 10% carbamide peroxide

Several vital bleaching systems have been introduced in response to the demand in esthetic dentistry. The active agents are commonly hydrogen peroxide or carbamide peroxide used in at-home or in-office techniques. Although generally positive results have been reported concerning the whitening ability of these agents, concerns still remain as to their effects on dental tissues. The purpose of this investigation was to evaluate the effect of these bleaching agents on the enamel surface morphology. Twelve extracted teeth were used according to three experimental protocols. In experimental protocol 1, specimens were treated with 35% hydrogen peroxide. In experimental protocol 2, after treatment with 35% hydrogen peroxide the specimens were immersed in natural saliva for 1 week. In experimental protocol 3, 35% hydrogen peroxide was applied once and 10% carbamide peroxide was applied for 1 week (12 h of 10% carbamide peroxide alternating with 12 h saliva). Scanning electron microscopy evaluation revealed that regional variation in tooth morphology surface sometimes exceeded the effects of the peroxide used according to experimental protocols. Thirty-five percent hydrogen peroxide had a tendency to promote an increase in density of pits. Precipitates were observed on specimen surfaces immersed in natural saliva according to protocol 2. A smooth and shiny surface was observed in specimens treated according to protocol 3. The potential relationship between surface alterations and differences in enamel permeability is currently under investigation. CLINICAL SIGNIFICANCE The differences in various articles written on the subject cannot be reconciled because of the lac of standardization of baseline data regarding factors such as location on the tooth, type of tooth eruption or noneruption, and age in the oral cavity. This article demonstrates that, despite changes observed in the enamel surface after bleaching, normal variation in tooth morphology may exceed the effects of 35% hydrogen peroxide and 10% carbamide peroxide on the teeth. Hence, considering the morphologic features of the tooth surface, bleaching, as described in thi study, can be considered safe for enamel.     

Effect of different bleaching techniques on enamel surface microhardness.

Conservative techniques for treatment of discolored human enamel include in-office bleaching with heat-activated 35% hydrogen peroxide, Nightguard vital bleaching with 10% carbamide peroxide, and enamel microabrasion with 18% hydrochloric acid. OBJECTIVES: In this study, these bleaching techniques were performed on 30 extracted teeth to evaluate their effects on microhardness of enamel surfaces. METHODS: The enamel surface microhardness measurements were performed 0, 24, 48, and 72 hours and 1 week after treatment. Paired t tests were performed in the statistical analyses. RESULTS: No changes were found on specimens treated with carbamide peroxide. There was a significant decrease in the surface microhardness of enamel after 0 and 24 hours when the specimens were treated with 18% hydrochloric acid (softening 85.7 and rehardening 99.4) or with 35% hydrogen peroxide (softening 85.7). However, after 72 hours, significant rehardening was observed in these groups (P <.001). CONCLUSION: According to the results, except Nightguard vital bleaching, all other techniques softened the enamel surface.     

The influence of time of hydrogen peroxide exposure on the adhesion of composite resin to bleached bovine enamel

Standard sized cylinders of a small particle light-cured resin were bonded to the flattened labial surface of young bovine incisor teeth which had been previously subjected to four different treatments: (a) immersion in 35% hydrogen peroxide and etched with 37% phosphoric acid gel for 60 s, (b) immersion in saline and etched for 60 s, (c) etched for 60 s and immersion in hydrogen peroxide, and (d) etched for 60 s and immersion in saline. Two hydrogen peroxide and saline immersion periods were used, 5 and 30 min. Specimens were stored in water at 37 degrees C for 1 and 7 days before tensile and shear testing. A total of 256 teeth were used, 8 for each treatment group, each immersion period, and each water storage period for each test. Statistical analysis of the results indicated that there was a highly significant reduction in the adhesive bond strength of the resin when the enamel was exposed to hydrogen peroxide and that the reduction was, within the limits of this study, time dependent. The bond strength was unaffected by the etching order and the period of water storage. Scanning electron microscopic examination of randomly selected fractured peroxide-treated specimens indicated that the failure occurred primarily at the bonding resin-enamel interface and that it was associated with areas of resin nonattachment and an alteration in resin quality. It is suspected that these changes were caused by the presence of residual peroxide or peroxide-related substances at or near the enamel surface.     

不同过氧化物对牙釉质结构和硬度的影响

目的:探究30%过氧化氢(hydrogen peroxide,HP)、22%过氧化脲(carbamide peroxide,CP)、3%过硼酸钠(sodium perborate,SP)对离体牙漂白后牙齿釉质表面结构和硬度的差异。方法:筛选正常人离体牙标本并随机分为A、B、C、D 4组,分别用生理盐水、30%过氧化氢、22%过氧化脲、3%过硼酸钠对4组牙齿进行漂白处理,最后对离体牙进行电镜扫描(×2000)和维氏硬度测定并进行统计分析。结果:实验组与对照组相比,扫描电镜显示: 30%过氧化氢和3%过硼酸钠组,其釉质表面呈散在的孔状,蜂窝状破坏,说明牙齿出现了不同程度的脱矿、溶解;22%过氧化脲组牙齿釉质表面结构基本完整,无明显脱矿和溶解现象;硬度测定结果显示:组间两两比较存在差异性(P＜0.05),漂白后4个组牙齿硬度大小是:对照组＞22%过氧化脲组＞3%过硼酸钠＞30%过氧化氢。结论:3种过氧化物漂白试剂中22%过氧化脲对牙釉质结构和硬度的影响最小。     

Influence of prolonged light-curing time on the shear bonding strength of resin to bleached enamel

This study evaluated the effect of prolonged light-curing time using a light-emitting diode unit (LED) on the shear bond strength of a resin composite to enamel immediately after bleaching. The enamel surfaces of human molars were divided into four groups: one control and three bleaching groups. One bleaching group (CP) was exposed to a 10% carbamide peroxide bleaching agent and bonded after 24 hours. The other two bleaching groups (HP) were bleached with a 38% hydrogen peroxide bleaching agent, then bonded either within one hour (HPA) or after 24 hours (HPB). All groups were subdivided into two subgroups and cured for two different times (20 or 40 seconds) with an LED unit. Shear bond strength (SBS) was tested with a universal-testing machine and the data were analyzed by ANOVA and post-hoc tests. Scanning electron micrographs of representative specimens were taken. A significant difference was seen between the control and HPA groups for both curing times (p = 0.000). However, neither the CP nor HPB groups showed any significant differences compared with the control groups (p > 0.05). Two-way ANOVA showed that a significant effect of the curing time factor was recorded for all groups (p = 0.000). Prolonged curing time, using an LED unit with a light intensity of 500 mW/cm2, increased resin-enamel bonding strengths for the control and bleached groups when bonding was performed after 24 hours of immersion in deionized water. However, the SBS was still compromised when bonding was performed immediately to enamel bleached with 38% HP.     

Evaluating the bonding of two adhesive systems to enamel submitted to whitening dentifrices

The aim of this study was to evaluate by micro-shear bond strength test, the bond strength of composite resin restoration to enamel submitted to whitening dentifrices. Forty bovine teeth were embedded in polystyrene resin and polished. The specimens were randomly divided into eight groups (n=5), according to the dentifrice (carbamide peroxide, hydrogen peroxide and conventional dentifrice) and the adhesive system (Prime & Bond 2.1 and Adper Single Bond 2). Dentifrice was applied for 15 minutes a day, for 21 days. Thirty minutes after the last exposure to dentifrice, the samples were submitted to a bonding procedure with the respective adhesive system. After that, four buttons of resin were bonded in each sample using transparent cylindrical molds. After 24 hours, the teeth were submitted to the micro-shear bond strength test and subsequent analysis of the fracture mode. Data were submitted to analysis of variance and Fisher's PLSD test (alpha = 0.05). The micro-shear bond strength showed no difference between adhesives systems but a significant reduction was found between the control and carbamide groups (p = 0.0145) and the control and hydrogen groups (p = 0.0370). The evaluation of the failures modes showed that adhesive failures were predominant. Cohesive failures were predominant in group IV The use of dentifrice with peroxides can decrease bonding strength in enamel.     

Scanning electron microscopy observations on the penetration and structure of resin tags in bleached and unbleached bovine enamel

The purpose of this study was to determine the effect of hydrogen peroxide on the ability of composite resin to penetrate bovine enamel etched with phosphoric acid. In a previous investigation, the flattened enamel surfaces of extracted bovine incisors were immersed in either saline (control) or 35% hydrogen peroxide (experimental) for 5 or 30 min before or after acid etching with 37% phosphoric acid gel for 60 s. A standard-sized light-cured resin cylinder was then bonded to the enamel surface. The specimens were stored in a water bath at 37 degrees C for 1 day or 7 days, after which the enamel-resin bond was tensile tested to failure. Sixteen of the failed specimens (eight control and eight experimental) were randomly selected for the present scanning electron microscopic study to evaluate the appearance of the resin tags at the resin-enamel interface. In the control specimens, the tags were well defined and contiguous with resin which was uniformly adherent to the enamel surface. In the experimental specimens, large areas of the enamel surface were free of resin. When tags were present, they were fragmented, poorly defined, and penetrated to a lesser depth than in the saline controls. The changes observed suggest that there may be interaction between resin and residual peroxide at or near the enamel surface.     

Influence of carbamide peroxide-based bleaching agents on the bond strength of resin-enamel/dentin interfaces

In this bond strength study, a bleaching agent containing 10% carbamide peroxide was applied over composite-teeth bonded interfaces of two adhesive systems applied to enamel and dentin. Sixteen human third molars were used for bonding procedures. Single Bond (SB) and Clearfil SE Bond (CB) were applied to enamel and dentin according to the manufacturers' instructions. A resin composite cube-like structure was incrementally built on the bonded surfaces. The restored teeth were sectioned into 0.7 mm thick slices that were trimmed at enamel or dentin bonded interfaces to an hourglass shape with a cross-sectional area of approximately 0.5 mm2. Specimens were assigned to 8 groups (n = 10) according to the following factors under study: dental substrate (enamel and dentin); adhesive system (SB and CB) and treatment (10% carbamide peroxide and not bleached/control). The bleaching gel (Opalescence) was applied at the bonded interfaces for 6 hours during 14 days and after daily treatment specimens were stored in artificial saliva. Unbleached specimens were stored in artificial saliva for 14 days. Specimens were tested for tension and the data were analyzed by three-way ANOVA and Tukey's test (p < 0.05). Enamel tensile bond strength of CB was reduced after carbamide peroxide application. The bleaching treatment did not alter dentin bond strength of both adhesives. The results suggest that bleaching significantly affects bond strength of CB to enamel, but no influence on bond strength to dentin was noted for both adhesive systems.     

Tensile bond strength of brackets after antioxidant treatment on bleached teeth

Various studies have reported a significant reduction in tensile bond strength of brackets when bonding is carried out immediately after bleaching. The purpose of this investigation was to determine the effect of an antioxidant agent on the tensile bond strength values of metal brackets bonded with composite resin to human enamel after bleaching with carbamide peroxide (CP). A total of 80 extracted premolar teeth were randomly divided into three bleaching groups of 10 per cent CP and an unbleached control group. The specimens in group 1 were bonded immediately after bleaching; group 2 were stored in an artificial saliva solution for 7 days after bleaching; group 3 were treated with 10 per cent sodium ascorbate, immediately before bonding, whereas the unbleached specimens in group 4 had no treatment before bonding. Tensile bond strengths were established in MPa. To evaluate the amount of resin left on the enamel surfaces after debonding, the adhesive remnant index (ARI) scores were used. The tensile bond strength data were analyzed with the Kruskal-Wallis test and pairwise comparisons were made by the Mann-Whitney U test at a significance level of P < 0.05. The brackets bonded immediately after bleaching revealed significantly lower tensile bond strengths than those of unbleached enamel (P = 0.000). No statistically significant differences in tensile bond strength were noted when the delayed-bonding (P = 6.000) and antioxidant-treated (P = 0.2757) groups were compared with the control group. The antioxidant treatment immediately after bleaching was effective in reversing the tensile bond strength of brackets.