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To evaluate the efficacy of different bleaching systems on artificially created stained-remineralized caries lesions; and to assess the susceptibility of the bleached lesions to further demineralization.Human enamel specimens were sectioned, polished, demineralized, and randomly divided into six groups (n = 21) to create stained-remineralized lesions, either non-metallic (non-Met: G1, G2 and G3) or metallic (Met: G4, G5 and G6). G1 and G4 received no bleaching treatment, while G2 and G5 were treated with 15% carbamide peroxide (at-home bleaching protocol; 4 h/d×7), and G3 and G6 with 40% hydrogen peroxide (in-office bleaching protocol; 20min × 3). Susceptibility to further demineralization was tested after bleaching treatment. Lesion mineral loss and depth were measured by transversal microradiography, and color change by spectrophotometry. Outcomes were analyzed using ANOVA models followed by Fisher's PLSD tests (α = 0.05).Metallic-stained lesions were significantly darker (all p 0.001) and more resistant to bleaching (p 0.005) than non-Met ones. For both stain types, the at-home bleaching protocol was more effective than the in-office (p 0.005); however, it also increased the lesion susceptibility to demineralization (p 0.05) [ΔΔZ mean ± SD ranging from 205 ± 73 to 313 ± 188 (at home) vs. 132 ± 45 to 206 ± 98 (in office); p 0.05]. After bleaching, non-Met lesions were significantly more susceptible to demineralization (p 0.05), with the ΔΔZ ranging from 206 ± 98 to 313 ± 188 compared to Met lesions ranging from 132 ± 45 to 205 ± 73.At-home bleaching protocol presented greater bleaching efficacy compared to in-office bleaching protocol. After bleaching, metallic-stained lesions were more resistant to subsequent demineralization compared to non-metallic stained lesions.Bleaching stained-arrested caries lesions may improve aesthetics but also increase susceptibility to demineralization, depending on the type of stain involved and bleaching system used.

Objectives Desensitizing agents are usually included in the composition of bleaching agents to reduce bleaching-induced tooth sensitivity (TS). This randomized clinical trial (RCT) evaluated the risk and intensity of TS and color change after at-home bleaching with a desensitizing-containing (3% potassium nitrate and 0.2% sodium fluoride) and desensitizing-free 10% carbamide peroxide (CP) gel (Whiteness Perfect, FGM). Methods A triple-blind, within-person RCT was conducted on 60 caries-free adult patients. Each participant used the gel in a bleaching tray for 3 h daily for 21 days in both the upper and lower dental arches. The absolute risk and intensity of TS were assessed daily through the 0–10 VAS and NRS scale for 21 days. Color change was recorded using shade guides (Vita Classical and Vita Bleachedguide) and the Easyshade spectrophotometer at baseline, weekly and 30 days after the end of the bleaching. The risk and intensity of TS were evaluated by the McNemar and Wilcoxon Signed Rank tests, respectively. Color change (ΔSGU and ΔE) were evaluated by the Mann-Whitney test and a paired t-test, respectively (α = 0.05). Results No difference in the TS and color change was observed (p > 0.05). Conclusions The incorporation of potassium nitrate and sodium fluoride in 10% carbamide peroxide at-home bleaching gel tested in this study did not reduce the TS and did not affect color change (RBR-4M6YR2).

To investigate the effectiveness of two home bleaching modalities on whitening of tetracycline-stained teeth (TST).A randomized controlled trial on the bleaching effect of 15% carbamide peroxide gel loaded in tray and 6.5% hydrogen peroxide strip in subjects with TST was performed. Eligible subjects were judged independently by two assessors, and randomly assigned into the tray or the strip group. Lightness (L*), redness (a*) and yellowness (b*) were measured with colorimeter at baseline, one, two and three months. Any adverse reaction associated with bleaching were also recorded. Overall colour changes (ΔE) were analysed by one-sample and independent t-test/Wilcoxon test at significance level α=0.05.Twelve and fourteen participants were allocated to the tray and the strip group respectively. Both groups experienced noticeable and significant L*a*b* improvement at the end of the trial in comparison to the baseline (p0.05). Significant improvement was observed in the first month for the tray group (p0.05) and in the first two months for the strip group (p0.05). While greater lightness improvement was observed in the tray group over the strip group in the first month (p=0.02), the reverse was noticed in the second month (p=0.01). There was no difference between two groups at the end of this trial (p0.05) and no significant adverse reactions were observed.Over a three-month period, 6.0% hydrogen peroxide strip performed equally well as the 15% carbamide peroxide tray delivery system in TST.Home bleaching systems produce noticeable tooth whitening effect in subjects with tetracycline-stained teeth.

Objective To investigate the impact of tooth bleaching on oral health-related quality of life (OHRQoL) in adults using a randomised clinical trial comparing at-home and in-office bleaching. Method A total of 130 individuals were randomly allocated to two groups (n = 65) according to the type of treatment. At-home treatment was performed using 10 % carbamide peroxide (2 h/day; 3 weeks) and an in-office placebo, while 35 % hydrogen peroxide was used for in-office (1/week; 3 weeks) and an at-home placebo. Colour was assessed using the CIELAB system using a digital spectrophotometer. Objective and subjective colour change was estimated by calculating CIEDE2000 (ΔE00) and shade guide units (ΔSGU), respectively. The OHRQoL was measured using the Brazilian version of the Oral Health Impact Profile (OHIP-14). All assessments were performed at baseline and after 21 days. For bivariate analysis, the chi-square test, Student’s t-test, and Wilcoxon test were used. The effects of OHRQoL were assessed using distribution-based responsiveness. Results Objective colour change was observed at home (p = 0.033), in comparison to in-office (p = 0.429). Mean OHIP-14 scores were similar between groups at baseline (p = 0.368) and after treatment (p = 0.695). Bleaching had a moderate positive effect on the OHRQoL of adults, especially with respect to the psychological discomfort domains, social disability, and total OHIP-14 score. The perception of tooth sensitivity in the group that received at-home treatment was negatively associated with OHRQoL (p = 0.037). Conclusion The bleaching agents were highly effective and demonstrated a moderate influence on the patients’ aesthetic perception and psychosocial impact.

To compare tooth colour change and participant's satisfaction following: home (HB), in-office (IOB) and combined (CB) bleaching treatments.A group of 105 participants received HB, IOB and CB treatments. HB was performed using custom-made trays and 10 % carbamide peroxide for 14 days. IOB was performed using 37.5 % hydrogen peroxide applied in 3 cycles. CB bleaching treatment involved IOB followed by HB. Tooth colour change was assessed visually (VC-ΔVC) and using a digital spectrophotometry device (ES-ΔeVS). Participant's perception of oral health, smile and straightness and whiteness of teeth were evaluated using self-reported questionnaire. Parameters/responses were evaluated/collected prior bleaching and at recalls. Linear mixed models were used to estimate between- and within-group differences.CB resulted in significantly higher shade difference at 15 days recall (ΔVC and ΔeVS, all p ≤ 0.046). At 6 months recall, CB group demonstrated higher ΔeVS compared to IOB (p = 0.018) but the difference was not significant between the same groups when using VC (p = 0.051). Significant colour improvement was observed among all groups at 6 months recall (all within-group p 0.001) except older participants (≥40 years) who received HB (ΔeVS: within-group p = 0.060). Overall, self-perception of oral health and satisfaction with smile and whiteness of teeth were significantly improved in all groups (all within-group p ≤ 0.001). Satisfaction levels with straightness of teeth were significantly improved for CB and IOB overall and in younger (40 years) participants (all within-group p ≤ 0.013).CB treatment resulted in a pronounced colour improvement when compared to both techniques used individually. All bleaching protocols resulted in significant improvement of participants' perceived oral health and satisfaction with smile and whiteness of teeth.Accelerated whitening can be achieved using a combination of in-office and home bleaching. Patients who may accept gradual whitening of teeth can be treated effectively using a cost-effective protocol and less concentrated bleaching agents.

Objectives To evaluate the efficacy of experimental proposals of desensitizing agents during tooth bleaching. Methods 140 participants without tooth sensitivity (TS) received 16% carbamide peroxide (14 days-04 h each) (T1) or 35% hydrogen peroxide (single session-45 min) (T2). Participants used concomitantly (10 per group): desensitizing dentifrices (D1-experimental bioactive glass-ceramic; D2-commercial potassium nitrate; D3-commercial calcium and sodium phosphosilicate) in-home, daily and, desensitizing pastes (D4-experimental bioactive glass-ceramic; D5-experimental Bioglass type 45S5; D6-commercial calcium phosphate), in-office, immediately after the treatment and more 4 times. Participants in the control group did not use any desensitizing agent. We assessed TS with Visual Analogue Scale. Assessment point 1 was immediately after the first participant’s exposure to the treatments; and points 2, 3, 4, and 5 were every 72 h along the period of the study. Two-way ANOVA (considering time and desensitizing as factors) and post-hoc Tukey test (α = 0.05) analyzed the data. Results In the control group treated with 35% hydrogen peroxide, TS increased significantly on assessment points 1 and 2. The participants who used a 5% potassium nitrate dentifrice and in-office experimental pastes did not experience TS because of the 35% in-office bleaching treatment. Conclusions TS caused by 35% hydrogen peroxide in-office tooth bleaching was controlled by experimental products prepared as pastes D4-experimental bioactive glass-ceramic and D5-experimental Bioglass type 45S5, but not by D1-experimental dentifrice containing bioactive glass-ceramic. Clinical significance There is no a gold standard protocol for TS caused by tooth bleaching. The study of novel desensitizing agents that can obliterate the dentinal tubules in a faster-acting and long-lasting way may help meet this clinical need.

Objectives This randomised controlled clinical trial assessed the efficacy of color change and sensitivity after in surgery whitening with and without light activation. Methods Twenty two patients were randomly assigned to one of two different groups: Group A – in-surgery bleaching with light activated 25% hydrogen peroxide gel followed by 2 weeks at home, night time bleaching with 10% carbamide peroxide gel in a customised bleaching tray. Group B – in-surgery bleaching with 25% hydrogen peroxide without light activation followed by 2 weeks at home, night time bleaching with 10% carbamide peroxide gel in a customised bleaching tray. The efficacy of tooth whitening was assessed by determining the color change associated with the six maxillary anterior teeth. Sensitivity was self-assessed with the use of a visual analogue scale (VAS). Results Overall, there was no significant difference in shade change between the two groups immediately after the in surgery whitening phase, and at one or two weeks post in surgery treatment. With regard to sensitivity immediately following the in surgery whitening participants in Group B reported a significantly higher level of sensitivity in comparison to Group A (p = 0.03). Conclusions There was no significant difference between the shade improvements achieved by the two whitening protocols tested throughout the 2-week period of the study (p > 0.05). There was no statistical significant difference in sensitivity at the one and two week review periods, however, immediately after treatment participants in Group B reported a significantly higher level of sensitivity than participants in Group A (p = 0.03).

To evaluate clinical effectiveness, color rebound and sensitivity of 22% carbamide peroxide (CP) with 3% potassium nitrate.Twenty-one participants were enrolled and treated overnight for 2 weeks with 22% CP (Venus White, Heraeus Kulzer). Visual color measurement was performed and expressed in shade guide units (SGU) of Vita Classical (VC) and Vita Bleachedguide 3D Master (BG) shade guides. Instrumental color measurements were performed using an intraoral spectrophotometer (Vita Easyshade Compact, EC). Color measurements were taken on a canine and central incisor at baseline, 2, 3, and 4 weeks. Participants documented sensitivity and data were analysed with Wilcoxon and Bonferroni correction at the 0.05 level of significance.Mean BG SGU difference immediately, 1 and 2 weeks postbleaching compared to baseline was 4.9 (2.1), 4.5 (2.2) and 4.6 (2.0), respectively. Corresponding VC values were 7.0 (3.5), 6.4 (3.3) and 6.5 (3.4), while corresponding ΔE* values were 8.3 (4.1), 8.1 (4.0) and 7.9 (3.5). For visual shade evaluation there was a significant decrease in SGU from baseline and each subsequent week, p0.001. There was no difference between week 3 and week 4 using VC or BG. For instrumental color measurements, there was no difference from week 2 to week 3 for canines and generally no difference between week 3 and week 4 for incisors.Visual and instrumental evaluation showed rebound occurred 1 week postbleaching with 22% carbamide peroxide and 3% potassium nitrate. In general, color was stable at 2 weeks postbleaching. Participants reported low sensitivity levels with a mean value of below 2 on a 0-10 scale.This study demonstrates efficacy with overnight usage of 22% carbamide peroxide with 3% potassium nitrate and demonstrates postbleaching color is stable at two weeks with low tooth sensitivity.

Objectives To evaluate the influence of tooth bleaching on the opalescence properties of enamel. Methods Color of 38 specimens was determined by colorimetric analysis before and after bleaching in the reflectance and transmittance modes. The results were described as CIELab color coordinates. The Opalescent Parameter (OP) was calculated as the difference in yellow–blue color coordinate (CIE Δ b *) and red–green color coordinate (CIE Δ a *) between the reflected and transmitted colors. Results Mean OP value of the specimens was 18.9 (±1.6) before bleaching and 16.1 (±1.0) after bleaching. Conclusions Bleaching decreases the OP of the specimens ( p > 0.001). OP decrease was correlated with differences in b * color coordinate in the transmittance mode.

The purpose of the study was to evaluate gloss and color changes of resin composites after exposure to different bleaching agents.Products used, were: Nite White ACP (10% carbamide peroxide gel), Crest Classic and Supreme Whitestrip (6.5% and 14% hydrogen peroxide strips, accordingly). A hybrid (Herculite XRV) and a nanohybrid (Premise) resin composite were exposed to the bleaching agents. Twenty-four disk-shaped specimens per composite were subjected to bleaching by each of the agents (n=8) for up to 2 weeks. Color changes using CIE-L*a*b* system (50:50% acceptability threshold: ΔE*=3.3) were recorded after 1 and 2 weeks bleaching cycles relative to baseline measurements. In addition, gloss measurements (in gloss units) were performed at the same bleaching intervals and gloss changes were calculated.All bleaching agents tested provided decrease in gloss of both composites after 2-week bleaching (p0.05). No differences were detected among the three bleaching regimens, for up to 2-week application, in terms of color and gloss changes on both composites. After the 2-week bleaching period, hybrid composite presented higher gloss reduction (%) than nanohybrid regardless of the bleaching agent (p0.05). Color change (ΔE*) was lower than 3.3 for all composite-bleaching agent combinations. After 1- and 2-week bleaching time, the nanohybrid composite provided higher color change than the hybrid under all bleaching procedures (p0.05). No strong correlation was proved between color (ΔE*) and gloss changes caused by bleaching treatments.After 2-week bleaching cycles, composites showed significant gloss reduction (p0.05). Color alteration was below the 50:50% acceptability threshold (ΔE*3.3) and it was product-depended. There was no significant difference in color and gloss changes between the evaluated bleaching strips and 10% carbamide peroxide gel.

Summary Objectives The study aimed to evaluate, (a) the surface morphology of acid etched/conditioned enamel following carbamide peroxide bleaching with/without casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (Tooth Mousse (MI Paste); GC Corp., Tokyo, Japan) treatment; and b) the nature of the bonded resin–enamel interfaces formed with a self-etching primer adhesive. Methods Twenty-four human adult molars were each sectioned into four, the specimens divided and treated according to four experimental groups: 1, no treatment; 2, 16% carbamide peroxide bleaching; 3, CPP-ACP paste; 4, bleaching and CPP-ACP paste. A self-etching primer adhesive (Clearfil SE Bond, CSE) was used. The specimens were further divided into four subgroups for etching/conditioning: A, CSE Primer only; B, 30–40% phosphoric acid and CSE primer; C, 15% EDTA and CSE primer; D, 20% polyacrylic acid and CSE primer. Bonded specimens were also prepared. The morphology of the etched/conditioned enamel surfaces and polished resin–enamel interfaces of the bonded specimens were observed by field-emission scanning electron microscopy (FE-SEM). Results Treatment with CPP-ACP did not inhibit phosphoric acid etching of enamel. Poorly defined enamel etch patterns were observed with the other conditioners in all the groups. The morphology of the bonded resin–enamel interfaces observed on FE-SEM for each acid etching/conditioning subgroup was similar in all the experimental groups, except after bleaching. Resin infiltration into enamel was observed with prior phosphoric acid etching and polyacrylic acid conditioning and was unaffected by experimental group treatments. Conclusions The use of a CPP-ACP paste with or without prior bleaching did not inhibit enamel etching. Enamel etching/conditioning may help improve bonding efficiency of the self-etching primer adhesive after CPP-ACP treatment.

Objectives This triple-blind, 2 × 2 crossover in situ study, was undertaken to verify whether the wear resistance of enamel and root dentine would be affected by bleaching with a 10% carbamide peroxide agent and a placebo agent. Methods Thirty slabs of each substrate (2 mm × 3 mm × 2 mm) were selected for each phase, after flattening and polishing procedures and microhardness test. After a 7-day lead-in period, one specimen of each substrate was randomly bonded on the facial surface of each one of 30 subject's upper second premolars. The volunteers received instructions on how to perform toothbrushing and application of gel in the tray. Fifteen volunteers bleached their maxillary arch with a 10% carbamide peroxide bleaching agent for a 2-week period, while the remainders used a placebo agent. After a 1-week washout period, a new set of enamel and root dentine slabs were bonded to the premolars and volunteers were crossed over to the alternate agent for 14 days. The resistance of enamel and root dentine to wear following bleaching, toothbrushing and intraoral exposure was measured with a profilometer, using reference areas. Results For enamel, ANOVA did not demonstrate significant difference between wear provided by placebo and bleaching agent ( p = 0.3713), but higher wear depth was observed for bleached root dentine ( p = 0.0346). Conclusions While overnight bleaching caused no alteration in wear resistance of enamel, root dentine showed increased tissue loss.

Objectives: The purpose of this study was to evaluate the nanohardness and elastic modulus of human enamel after treatment with tray and strip bleaching systems. Methods: Fifty-five human enamel samples were exposed to five different bleaching agents. Nanoindentations were made before and after bleaching treatments following the manufacturer’s directions using a Nanoindenter XP (MTS Systems Corporation, Oak Ridge, TN, USA). Nanohardness and elastic modulus measurements were obtained and the results were statistically analyzed using a repeated measures analysis of variance with a post-hoc Tukey–Kramer multiple comparison test. Results: Nanohardness and elastic modulus measurements showed decrease of mean values for each group except the control which remained the same. There were significant differences due to time (before and after treatment) and material effects in nanohardness (P < 0.0001) and elastic modulus (P = 0.0241). Measurements after treatment showed significant decrease in nanohardness between all groups and the control group. There was a significant difference in hardness between CP and TO after treatment. Additionally, there were significant differences in elastic modulus between the control group when compared to OB and TO after treatment. While there were significant changes in the elastic modulus due to treatment for both CP and TO, there were no significant differences between any of the groups after treatment. Conclusions: Nanohardness and elastic modulus of human enamel were significantly decreased after the application of home-bleaching systems.

This double blind randomized clinical trial evaluated the longevity of the whitening effect (6-month follow-up) of two carbamide peroxide concentrations used in at-home vital bleaching.Ninety-two volunteers with shade mean C1 or darker for the six maxillary anterior teeth were randomized into two balanced groups (n=46) according to bleaching agent concentration: 10% (CP10) or 16% (CP16) carbamide peroxide. Patients were instructed to use the whitening agent in a tray for 2h/day during 3 weeks. Shade evaluations were done with a value-oriented shade guide, and a spectrophotometer at baseline, and at 1-week and 6-month post-bleaching. Volunteers for both treatment groups had to answer questions related to dietary and oral hygiene behavior.At 6-month recall, tooth shade remained significantly lighter than at baseline, in both treatment groups, considering the color parameters: DeltaL, Deltaa, Deltab, DeltaE (p0.0001) or the tooth shade median values (p0.001). Additionally, shade median relapse at 6-month follow-up was not statistically different between CP10 and CP16 groups using the spectrophotometer (p=0.1) or the visual matching (p=0.7) analyses. Overall, subjects from CP10 and CP16 reported high consumption of beverage and food stains, which was not different between groups (p=0.5).The whitening effect remained similar 6-month after the bleaching treatment for both carbamide peroxide concentrations tested. Additionally, the high consumption of staining beverages and foods reported by patients had no influence in the whitening effect longevity at 6-month.

Objective: Carbamide peroxide and hydrogen peroxide have been used as tooth whitening agents. The aim of this paper was to determine the efficiency of several enzyme-containing whitening systems. A method to determine the rate of ‘in vitro’ tetracycline whitening was also developed. Methods: We determined the tetracycline whitening ability of carbamide peroxide and hydrogen peroxide, and the influence of peroxidase and lactoperoxidase on this tetracycline whitening rate. Results: High peroxidase and lactoperoxidase concentrations increased the rate of tetracycline decoloration obtained with carbamide peroxide or hydrogen peroxide. The decoloration rate observed was lower when the glucose/glucose oxidase system was used to generate hydrogen peroxide ‘in situ’. The presence of peroxidase increased the decoloration rate of extracted teeth obtained with carbamide. Conclusions: Enzymes such as peroxidase could be used as whitening catalysts to increase the rate of tetracycline decoloration.

The aim of this study was to comparatively investigate the effect of antioxidant treatment and delayed bonding after bleaching with carbamide peroxide on the shear bond strength (SBS) of a luting resin to enamel.Forty flat enamel surfaces were prepared from freshly extracted human molars using a low speed diamond saw, then divided into three bleaching groups (n=10/group) and a control group (n=10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with an antioxidant agent, 10% sodium ascorbate, while Group 3 specimens were immersed in artificial saliva for 1 week after bleaching. Specimens in Group 4 were not bleached, but immersed in artificial saliva for 1 week before bonding. Forty ceramic blocks (Empress 2, Ivoclar) were prepared and luted to teeth using a dual-curing resin cement (Variolink II, Ivoclar). The specimens were thermocycled and the SBS tests were performed using a universal testing machine (crosshead speed: 0.5mm/min). Fracture analysis of the bonded surfaces was done using a scanning electron microscope. Statistical analysis was carried out by Kruskall-Wallis and Mann-Whitney U-tests.While the samples that were immediately bonded after bleaching (Group I) demonstrated significantly lower shear bond strengths and 10% sodium ascorbate group (Group II) demonstrated significantly higher bond strengths than control group samples (p0.05), no significant differences were found among delayed bonded group and control group (p0.05).Using sodium ascorbate with a concentration of 10% may be reliable for reversing the compromised bond strength.

Objectives The purpose of this study was to evaluate the effects of a home bleaching gel containing 15% carbamide peroxide on the surface microhardness of four tooth-colored restorative materials in situ. Methods Four types of tooth-colored restorative materials, including a nanocomposite resin (Filtek Z350), a packable composite resin (Filtek P60), a polyacid-modified composite (Dyract AP), and a glass-ionomer cement (Ketac Molar Easymix), were used in this study. Each material was divided into two groups equally (n = 18): bleaching group and control group. Thirty-six Chinese volunteers were recruited and stone casts were constructed for their upper jaws. Two of the four types of restorative materials were randomly selected and mounted on the first or second molar of the cast for each subject. With respect to each material selected, two specimens from each group were put at a random side. Then custom-fabricated trays containing specimens were fabricated. The participants wore the tray in the daytime, and applied the bleaching gel for the side containing specimens of bleaching group during the night. Surface microhardness measurements were obtained on the top surface of each sample on the different time periods. Results There was a statistically significant increase in the surface microhardness of Ketac Molar Easymix due to the exposure to 15% carbamide peroxide, while it produced a significant decrease for Dyract AP. Following immersing in saliva without bleaching agent, Ketac Molar Easymix showed a significant increase in surface microhardness. Conclusions The effects of 15% carbamide peroxide on surface microhardness were material dependent. Immersing in saliva produced a surface hardening effect of glass-ionomer cement.

Objective This in situ study evaluated the influence of two home-applied bleaching agents (10% carbamide peroxide and 7.5% hydrogen peroxide) on enamel microhardness. Methods Ninety enamel slabs were obtained from human third molars and baseline Knoop hardness measurements were recorded under a 50 g load for 5 s. The specimens were attached to intra-oral devices delivered to 10 volunteers (donor of the teeth) who used the devices 24 h/day throughout the experiment. The specimens were divided in three groups, two experimental and one control; in the last group, enamel slabs were not submitted to bleaching agents, but exposed only to the action of saliva. Two custom-made trays were made for each volunteer to recover the teeth and the appliances containing the enamel slabs. The bleaching regimen was 1 h/day for 21 consecutive days. Subsequently, additional hardness measurements were recorded. Results The mean values of the baseline and final microhardness were: 348 and 352.2; 346.6 and 354.5; 342 and 340.8, for control, 10% carbamide peroxide and 7.5% hydrogen peroxide groups, respectively. One-way ANOVA of the microhardness mean values revealed no statistically significant differences among groups, the specimens treated with 7.5% hydrogen peroxide has shown a tendency (p = 0.056) to microhardness decrease. Conclusions Data suggested that the tested home bleaching agents did not change the superficial enamel microhardness.

To evaluate (a) the enamel microshear bond strength (MSBS) of a universal adhesive and (b) the effects of conditioning with a self-etching primer adhesive with/without prior bleaching and/or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application.Thirty-five molars were cut into four sections, assigned randomly to four groups (no treatment; 16% carbamide peroxide bleaching; CPP-ACP-containing paste (Tooth Mousse, TM); bleaching and TM) and treated accordingly. Specimens were divided into two for bonding with either a self-etching primer (Clearfil SE Bond, CSE) or a total-etch adhesive (Single Bond, SB). Specimens for CSE bonding were subdivided for one of four preconditioning treatments (no conditioning; 30-40% phosphoric acid (PA); 15% EDTA; 20% polyacrylic acid conditioner (Cavity conditioner, CC) and treated. The adhesives were applied and resin composite bonded to the enamel using microtubes (internal diameter 0.75mm). Bonds were stressed in shear until failure, mean MSBS calculated and data analysed using ANOVA with Tukey's HSD test (alpha=0.05). The modes of bond failure were assessed and classified.Two-way ANOVA revealed significant differences between treatments (P0.0001), conditioners (P0.0001) and a significant interaction between treatments and conditioners (P=0.001). One-way ANOVA revealed no significant differences in MSBS following any of the treatments for SB; following TM application for CSE without preconditioning; and significant differences in MSBS following bleaching with and without TM application for CSE. With preconditioning, applying PA before CSE post-bleaching and either PA or CC before CSE post-TM application, resulted in significant differences in MSBS (P0.05).The use of conditioners prior to bonding with the self-etching primer adhesive system on treated enamel may significantly improve bond strengths.

Objective Aim of the in vitro study was to evaluate the time period needed to re-establish enamel surface microhardness after bleaching with fluoridated (0.5% F − as NaF) and unfluoridated carbamide peroxide (CP) bleaching gels under a daily de- and remineralization protocol. Materials and methods Ninety enamel specimens were prepared from bovine incisors and prepared for Knoop microhardness determination. The samples were divided into five groups and bleached for 7 days (8 h per day) with experimentally designed neutral and acidic 10% CP gels: A (0.5% F − , pH 7.0), B (0.5% F − , pH 5.5), C (no F − , pH 7.0) and D (no F − , pH 5.5). Group E served as control and was not bleached. After each 8-h bleaching period the samples were subjected to a de- and remineralization protocol. In the following 5 days, the specimens were not bleached, but stored in artificial saliva for 8 h instead; the daily de- and remineralization cycles were maintained during this period. Knoop microhardness determinations were conducted at baseline, after each bleaching interval and after completion of each daily de- and remineralization cycle. A repeated measures two-way ANOVA statistical analysis and a comparison of confidence intervals was conducted to check for hardness recovery during the post-bleaching period. Results After completion of bleaching therapy on day 7 a statistically significant hardness loss was observed for all bleaching groups in the range of about 7–15% hardness reduction as compared to baseline. The fluoridated gels proved significantly less hardness loss than the unfluoridated gels. In the following period, from days 8 to 12 recovery of hardness to baseline data was observed in the fluoridated groups (A and B) after the first de-/remineralization cycle on day 8 (group A) and after the second 8-h remineralization period on day 9 (group B), respectively. Hardness of the specimens treated with the unfluoridated bleaching gel C returned to baseline values after day 10. The samples of group D did not show recover of hardness data during the 5-day post-bleaching period. Conclusion Fluoridated 10% carbamide peroxide bleaching gels support re-hardening of bleached enamel with a shorter period needed for hardness recover as compared to unfluoridated gels.

Objectives To assess the efficacy of a bleaching enzyme-based toothpaste. Material and methods A randomized clinical trial was carried out, comprising 48 participants with teeth exhibiting color A3 or higher according to the Vita Classical guide. One-half of the sample received the bleaching enzyme-based toothpaste (White Kin ® ), while the other received placebo toothpaste. Both products were supplied in identical containers and had the same composition except for the active components. The teeth color was measured with a spectrophotometer. The patients were instructed to brush their teeth three times a day during 3 min with the assigned product, during 12 weeks. The color measurements were repeated after 3, 6, 9 and 12 weeks of treatment. Color variation was based on the CIE L * a * b * coordinates, Δ E and the EW index. The relationship of these variables at different observation times were performed using a generalized estimating equations model, which evaluated the effect of treatment, time and interaction. Results The patients using the bleaching enzyme-based toothpaste showed an increase in lightness (80.14 -treatment- versus 79.25 -control group-) and a reduction in component b *. Δ E was found higher in the treatment group ( p = 0.064), close to statistical significance. Conclusions The bleaching enzyme-based toothpaste could be potentially efficient in the modification in tooth color progressing from the third to ninth week of treatment, tending to stabilize after the ninth week. Clinical relevance A very low carbamide peroxide concentration, with the incorporation of lactoperoxidase, tooth paste, tends to offer clinically satisfactory results, in terms of modifications in tooth color, nevertheless no significant differences were founded when compared to the control group, with an oral hygiene controlled along the study.

Objective Aim of the study was to evaluate the influence of carbamide peroxide (CP) on enamel fluoride uptake by comparing enamel fluoride uptake from a 1% amine fluoride (AmF) gel with the fluoride acquisition from a 10% carbamide peroxide agent supplemented with 1% AmF. Materials and methods Three enamel cylinders (4 mm in diameter) were prepared from the buccal surfaces of 60 bovine incisors. One sample of each tooth was used for determination of baseline fluoride content of the respective tooth. The two remaining samples were allocated to the experimental series 1 or 2, respectively. Each series consisted of five experimental groups (A–E, n = 12) and differed with respect to the length of the treatment period with the gels (A–D). The experimentally designed gels (pH 5.5) used in the study were as follows: A (10% CP), B (10% CP, 1% F− as AmF), C (1% F− as AmF), D (no CP, no F−) and were formulated on the same basis. The enamel samples were covered for 4 h with the respective gel at 37 °C and were then transferred to artificial saliva for 20 h (series 1). The samples of group E served as controls and were not treated with a gel. In series 2, treatment with the gels and storage in saliva was conducted seven times. Finally, the samples were assessed for KOH-soluble and structurally bound fluoride. Results Only the enamel samples treated with the fluoridated bleaching gel (group B) and with the amine fluoride gel (group C) exhibited significant fluoride acquisition. Thereby, both gels showed significantly lower uptake in series 1 as compared to series 2. Both KOH-soluble and structurally bound fluoride acquisition was significantly higher in group C than in group B. Conclusion Treatment with a carbamide peroxide gel supplemented with amine fluoride causes less fluoride acquisition in enamel than a pure amine fluoride gel. Under the conditions of the study, it is assumed that carbamide peroxide seems to influence enamel fluoride uptake.

Summary Objectives There is still some controversy in the dental literature whether carbamide peroxide bleaching causes demineralization of teeth. One of the reasons for this controversy is that there is as yet no reliable, non-destructive in vitro metod for assessing mineral loss in bleached teeth. The objective of this study was to investigate the possible demineralization effect of 10% carbamide peroxide bleaching agent on enamel and dentine non-destructively. Methods μCT images were obtained of 12 human molar tooth sections. These sections had 10% carbamide peroxide applied for eight hours a day over a period of 15 days. Further tomographic images were obtained and the mineral content prior to and post bleaching assessed. Results A total of 144 regions were evaluated using the image processing language available in the work station. The application of 10% carbamide peroxide was found to cause demineralization of the enamel extended to a depth of 50 μm below the enamel surface (Paired t -test, p Conclusions This study confirmed that μCT was indeed a highly suitable method for assessing mineral content of dental enamel after bleach application. It is recommended that application of bleaching agents should be carefully considered in patients susceptible to caries and tooth wear.

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% H 2 O 2 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.

Objectives This parallel randomized clinical trial evaluated the efficacy of two treatments for removing fluorosis stains. Methods Seventy individuals living in an area endemic for fluorosis, with at least four maxillary anterior teeth presenting fluorosis with a Thylstrup and Fejerskov index from 1 to 7, were randomized into two treatment groups (n = 35): GI – enamel microabrasion or GII – microabrasion associated with at-home bleaching. Microabrasion was performed using 37% phosphoric acid and pumice and, at-home tooth bleaching was performed with 10% carbamide peroxide. Areas of enamel opacities were recorded by digital camera at baseline and 1-month (1 M) after treatment. Two blinded examiners evaluated the reduction in the area (mm2) of opacity using software. Two visual analogue scales were used: one for recording tooth sensitivity and/or gingival irritation ranging from 1 (none) to 5 (severe) and the other to evaluate participant satisfaction with the treatment used ranging from 1 (no improvement) to 7 (exceptional improvement). Results 1 M after treatment, both groups showed a significant reduction in the area of enamel opacity (p = 0.0001) and there was no difference between groups (p = 0.1). Most of the participants from both treatment groups reported no or mild tooth sensitivity and gingival irritation (p > 0.05). Participants reported that they were happy with the improvement in dental appearance, however, individuals from GII reported that they were happier than those from GI (p = 0.004). Conclusions Both treatment protocols were effective in reducing fluoride stains, however, when home bleaching was associated to enamel microabrasion, patients reported a major satisfaction with dental appearance.

Objectives This study aimed to assess changes in oral health-related quality of life (OHRQoL) in individuals enroled in a double-blind randomized clinical trial conducted to evaluate the efficacy and safety of two carbamide peroxide concentrations used in at-home vital bleaching in the city of Pelotas, Southern Brazil. Methods Ninety-two volunteers with a shade mean of C1 or darker for the six maxillary anterior teeth were randomized into two balanced groups (n = 46) according to bleaching agent concentration: 10% or 16% carbamide peroxide. The patients were instructed to use the whitening agent in a tray for 2 h once a day for three weeks. To assess changes in OHRQoL, participants completed the oral impact on daily performance (OIDP) at the start and one week after the completion of treatment. Because there was no difference with regard to whitening effect or tooth sensitivity during or after treatment the two groups were merged for the analyses of the current article. Before-and-after changes in OIDP scores were assessed by chi-square and McNemar tests (p Results Mean pre- and post-treatment OIDP scores varied from 0.42 to 0.60. When the frequency of impacts for different activities were compared, there was an increase in difficulty in cleaning teeth (p = 0.02) and a significant reduction in smiling and showing teeth with embarrassment (p = 0.03). Regarding the symptoms and main oral conditions that generated impact, there was higher number of participants reporting pain (p = 0.05) after treatment. In opposite, significant decrease was observed in individuals reporting being unhappy with their appearance (p = 0.03). On the contrary, it was showed a decrease in impacts resulting from dental colour was observed after bleaching (p = 0.03). Conclusion Quality of life is complex and encompasses different domains. Although positive impact of the dental bleaching was detected, with patients showing more their teeth without embarrassment, difficult in dental hygiene and pain resulting from the treatment were also reported, and this can negatively impact daily performances. Dentists must consider these aspects when performing aesthetics procedures.

Objectives To evaluate the effects of experimental protocols on bleaching effectiveness and hydrogen peroxide (HP) diffusion through enamel and dentine. Methods Enamel/dentine discs were subjected to six bleaching sessions, consisting of 1 or 3 applications of 17.5% or 35%-HP gel for 5/15 min, or 37% carbamide peroxide (CP) gel for 10/20 min. Discs undergoing the regular protocol (35%-HP; 3 × 15 min) constituted the positive control group. Colour change (ΔE) was assessed (CIE L * a * b * system) after each session. HP diffusion was quantified (sessions 1, 3, and 6) in enamel/dentine discs adapted to artificial pulp chambers. Data were analysed by Pillai's Trace and Bonferroni test, or by one-way ANOVA and SNK/Tamhane's test ( α = 5%). Results All tooth-bleaching protocols significantly increased the Δ E values. A reduction in HP diffusion and no significant difference in Δ E compared with the positive control were observed for the following bleaching protocols: 17.5%-HP 3 × 15 min, at the 4th session; and 35%-HP 1 × 15 and 3 × 5 min, at the 5th session. HP diffusion in the 37%-CP 3 × 20 min bleaching protocol was statistically similar to that in the positive control. The other experimental bleaching protocols significantly decreased HP diffusion through enamel/dentine discs, but the Δ E values were statistically lower than those observed in the positive control, in all sessions. Conclusion Shortening the contact time of a 35%-HP gel or reducing its concentration produces gradual tooth colour change and reduced HP diffusion through enamel and dentine. Clinical significance A reduction in HP concentration, from 35% to 17.5%, in a bleaching gel or shortening its application time on enamel provides a significant tooth-bleaching improvement associated with decreased HP diffusion across hard dental tissues. Therefore, these protocols may be an interesting alternative to be tested in the clinical situation.

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

The aim of this study was to investigate the effect of home bleaching agents on the color and translucency of resin composites.Thirty disc shaped specimens (1mm thick) were fabricated from each resin composite (Reflexions, Grandio, Gradia Direct, Clearfil Majesty Esthetic, Ceram-X Mono) and divided into 3 subgroups as carbamide peroxide (CP, Opalescence 10% PF), hydrogen peroxide (HP, 10% Opalescence Treswhite Supreme) and control group (n=10). Baseline CIE L*a*b* color coordinates were measured with spectrophotometer and translucency parameters (TP) were calculated. CP and HP groups were treated with bleaching agents according to manufacturers' instructions and control group was stored in distilled water (DW) for 14 days. Color and translucency measurements were repeated and color differences were calculated, ΔE values3.3 were considered as clinically unacceptable.Clinically unacceptable color change was detected for all resin composites exposed to bleaching agents and there was significant color difference between the control group and bleached specimens (P0.05). However no significant color difference was found between CP and HP groups. Intragroup comparison revealed that Ceram-X Mono showed the highest color change but there was no significant difference among the other tested materials for both CP and HP groups. Intergroup comparison of TP values of CP, HP and control groups at the end of 14th day revealed that there was no statistical significant translucency difference among the groups.Application of CP and HP resulted in clinically unacceptable color change for all resin composites. Translucencies of the resin composites were not affected by bleaching procedure.The results of this in vitro study suggest that patients should be informed regarding a potential color change of existing resin composite restorations with the use of home bleaching agents.

This study examined the effect of nano-carbonate apatite (n-CAP) to prevent re-staining and the change of enamel surface after dental bleaching in vitro.Twenty-four bovine specimens were bleached for 2 weeks with 10% carbamide peroxide (CP). After bleaching, the specimens were divided into the following four groups: distilled and deionized water (DDW, negative control), 10% n-CAP, NaF (positive control) and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP, positive control). Each group was subjected to pH cycling for 7 days. The specimens were treated for 4 min 3 times per day and re-staining was induced naturally by artificial saliva in the remineralization process. After pH cycling, the changes in colour were evaluated with spectrophotometry and scanning electron microscopy (SEM). The difference in colour between before and after pH cycling was evaluated using an ANOVA and Tukey test.After pH cycling, the colour difference of n-CAP group was significantly lower than that of the DDW and CPP-ACP groups (p0.05). SEM showed that n-CAP particles were deposited regularly on the damaged surface compared to the other groups.10% n-CAP could significantly maintain the initial colour and protect the damaged enamel structure after bleaching.

Summary Objectives The aim of this study was to evaluate the separate contribution of enamel (E) and dentine (D) to the colour change of tooth which subjected to 10% carbamide peroxide (CP) gels using a novel recombined enamel–dentine (Recombined-ED) study model. Methods 120 enamel–dentine (ED) samples (four homogeneous premolar ED from each patient; total = 30 × 4 ED) were involved in the present study. Two homogeneous ED samples were bleached with 10% CP and the other two ones were stored in artificial saliva for one, two or four weeks. After treatment, four kinds of layers were prepared from each four homogeneous ED samples by removing enamel or dentine part: bleached-enamel (BE), bleached-dentine (BD), control-enamel (CE) and control-dentine (CD). Initial and final colour records of samples were taken with a spectrophotometer in CIELab system. The contribution of enamel/dentine to the colour change of tooth (CTCC) was calculated by measuring the colour difference ΔE between two different enamel–dentine combinations (ΔE between BE/BD and CE/BD for enamel; ΔE between BE/BD and BE/CD for dentine). Translucency parameter (TP) was obtained by calculating the colour difference between enamel on black and white backings. Results ED and recombined-ED were significantly correlated in L*a*b* values both for unbleached samples and bleached samples. Bleaching resulted in a significant colour change (ΔE) of E, D and ED samples. The TP of BE was significantly lower than that of CE. The CTCC of enamel was significantly higher than that of dentine all through the time points. Conclusions Enamel played a more important role than dentine in tooth bleaching due to the changes in translucency and colour.