At-home bleaching with carbamide peroxide with concentrations below 10%: bleaching efficacy and permeability in the pulp chamber.

OBJECTIVES: To evaluate the bleaching efficacy and permeability of hydrogen peroxide (HP) in the pulp chamber of human teeth bleached with lower concentrations of carbamide peroxide gel (4%, 5% and 7% CP). MATERIALS AND METHODS: Bleaching gels with lower concentrations were formulated and a commercial standard gel, 10% CP, was used as a reference. Fifty-six human premolars were randomly divided into four groups. Applications of the bleaching gel were made for 3 h for 21 days. The bleaching efficacy was evaluated by digital spectrophotometry on 1, 7, 14 and 21 days, with analysis in the ∆Eab, ∆E00 and WID color spaces. The concentration of HP in the pulp chamber was measured in the same periods by UV-Vis spectrophotometry (µg/mL). Two-way repeated analysis of variance (ANOVA) examined bleaching efficacy and HP permeability, followed by Tukey's post-hoc test (α = 0.05). RESULTS: All groups showed significant color changes, with no statistical differences after the second and third week of bleaching (p > 0.05). The 'time' factor was statistically different (p < 0.05), increasing the bleaching efficacy throughout the treatment. The 4% CP group had lower HP levels in the pulp chamber (p < 0.05). CONCLUSIONS: The results seem promising, revealing that low concentration gels are as effective as 10% CP with the benefit of reducing the amount of HP in the pulp chamber. CLINICAL RELEVANCE: Low concentration 4% PC and 5% PC maintains bleaching efficacy, reduces the penetration of HP peroxide into the pulp chamber, and may reduce tooth sensitivity.

Influence of coating dental enamel with a TiF4-loaded polymeric primer on the adverse effects caused by a bleaching gel with 35% H2O2.

OBJECTIVE: To evaluate whether coating enamel with a polymeric primer (PPol) containing titanium tetrafluoride (TiF4) before applying a bleaching gel with 35% H2O2 (35% BG) increases esthetic efficacy, prevents changes in morphology and hardness of enamel, as well as reduces the cytotoxicity from conventional in-office bleaching. MATERIALS AND METHODS: Standardized enamel/dentin discs were stained and bleached for 45 min (one session) with 35% BG. Groups 2TiF4, 6TiF4, and 10TiF4 received the gel on the enamel previously coated with PPol containing 2 mg/mL, 6 mg/mL, or 10 mg/mL, respectively. No treatment or application of 35% BG directly on enamel were used as negative control (NC), and positive control (PC), respectively. UV-reflectance spectrophotometry (CIE L*a*b* system, ΔE00, and ΔWI, n = 8) determined the bleaching efficacy of treatments. Enamel microhardness (Knoop, n = 8), morphology, and composition (SEM/EDS, n = 4) were also evaluated. Enamel/dentin discs adapted to artificial pulp chambers (n = 8) were used for trans-amelodentinal cytotoxicity tests. Following the treatments, the extracts (culture medium + bleaching gel components diffused through the discs) were collected and applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability (alamarBlue, n = 8; Live/Dead, n = 4), oxidative stress (n = 8), and morphology (SEM). The amount of H2O2 in the extracts was also determined (leuco crystal violet/peroxidase, n = 8). The numerical data underwent one-criterion variance analysis (one-way ANOVA), followed by Tukey's test, at a 5% significance level. RESULTS: Regarding the ΔE00, no difference was observed among groups 2TiF4, 6TiF4, and PC (p > 0.05). The ΔWI was similar between groups 2TiF4 and PC (p > 0.05). The ΔWI of group 6TiF4 was superior to PC (p < 0.05), and group 10TiF4 achieved the highest ΔE00 and ΔWI values (p < 0.05). Besides limiting enamel microstructural changes compared to PC, group 10TiF4 significantly increased the hardness of this mineralized dental tissue. The highest cellular viability occurred in 10TiF4 compared to the other bleached groups (p < 0.05). Trans-amelodentinal H2O2 diffusion decreased in groups 2TiF4, 6TiF4, and 10TiF4 in comparison with PC (p < 0.05). CONCLUSION: Coating enamel with a PPol containing TiF4 before applying a 35% BG may increase enamel microhardness and esthetic efficacy and reduce the trans-amelodentinal cytotoxicity of conventional in-office tooth bleaching. The PPol containing 10 mg/mL of TiF4 promoted the best outcomes.

Effect of carbamide peroxide on biomechanical properties of vacuum-formed retainers: A split-mouth randomized controlled trial.

OBJECTIVE: To investigate the effect of tooth whitening on biomechanical properties of vacuum-formed retainers (VFRs). METHODS: Using a split-mouth, randomised controlled trial design, thirty participants were randomly allocated to receive whitening on either the upper or the lower arch, using 10 % carbamide peroxide for two weeks. Biomechanical properties such as hardness, tensile strength, and surface roughness were assessed two weeks after whitening was completed. RESULTS: Tensile strength of the whitening arch (mean ± SD: 40.93 ± 3.96 MPa) was significantly lower than that of the control (47.40 ± 5.03 MPa) (difference 6.47 MPa, 95 % CI 4.51 - 8.42, p < 0.001). Hardness and internal roughness of the whitening arch (VHN = 14.63 ± 2.29 N/mm2 and Ra = 1.33 ± 0.35 µm, respectively) were significantly greater than those of the control (12.22 ± 1.86 N/mm2 and 0.96 ± 0.29 µm, respectively) (differences 2.41 N/mm2, 95 % CI 1.56 - 3.25, p < 0.001 and 0.37 µm, 95 % CI 0.23 - 0.51, p < 0.001, respectively). The whitening arch showed greater tooth colour change (ΔE = 6.00 ± 3.32) than the control (ΔE = 2.50 ± 1.70) (difference = 3.50, 95 % CI 2.43 - 4.56, p < 0.001). CONCLUSIONS: Based on this short-term study, marked tooth colour change was achieved by whitening with VFRs as the whitening trays, but this changed the VFRs' biomechanical properties, including a decrease in tensile strength and an increase in hardness and internal roughness. CLINICAL SIGNIFICANCE: The application of carbamide peroxide in VFRs may compromise their mechanical properties.

Assessment of color changes and adverse effects of over-the-counter bleaching protocols: a systematic review and network meta-analysis.

OBJECTIVES: To assess color change efficacy and the adverse effects of varied over-the-counter (OTC) bleaching protocols. METHODOLOGY: The study included randomized clinical trials evaluating color changes from OTC bleaching agents. Nine databases were searched, including the partial capture of the grey literature. The RoB2 tool analyzed the individual risk of bias in the studies. Frequentist network meta-analyses compared treatments through common comparators (∆Eab* and ∆SGU color changes, and tooth sensitivity), integrating direct and indirect estimates and using the mean and risk differences as effect measures with respective 95% confidence intervals. The GRADE approach assessed the certainty of the evidence. RESULTS: Overall, 37 remaining studies constituted the qualitative analysis, and ten composed the meta-analyses. The total sample included 1,932 individuals. ∆Eab* was significantly higher in groups 6% hydrogen peroxide (HP) strips (≥ 14 h). ∆SGU was significantly higher in groups at-home 10% carbamide peroxide (CP) (≥ 14 h), followed by 6% HP strips (≥ 14 h) and 3% HP strips (≥ 14 h). At-home 10% CP (7-13 h) and placebo showed lower risks of tooth sensitivity without significant differences between these treatments. CONCLUSION: Considering the low level of evidence, OTC products presented satisfactory short-term effects on tooth bleaching compared to the placebo, with little to no impact on dentin hypersensitivity and gingival irritation. CLINICAL RELEVANCE: OTC products are proving to be practical alternatives for tooth whitening. However, patients should be advised about the possible risks of carrying out such procedures without professional supervision.

Effects of enamel moistening and repositioning guide color on tooth whitening outcomes: A clinical trial.

This clinical trial investigated the effects of pre-application enamel moistening on the impact of a 37% carbamide peroxide whitener on tooth color changes and the influence of repositioning guide colors. Forty participants were randomly assigned to in-office tooth bleaching with either moistened enamel (experimental) or dry enamel (control). The whitener was applied for 45 min over two sessions. Tooth color was visually measured or assessed using a spectrophotometer with purple or green silicone guides. Tooth bleaching was assessed using CIE76 (ΔEab ) and CIEDE2000 (ΔE00 ) formulas and by whitening and bleaching index score changes. Moistening the enamel did not significantly affect tooth color. However, the guide color choice only impacted tooth color when measured instrumentally. At baseline, the green guide resulted in statistically significantly whiter teeth than the purple guide. Less pronounced differences in the b* coordinate between baseline and final measurements were found using the green guide. The green guide also produced lower ΔEab values and less change in indexes. In conclusion, moistening the enamel did not significantly impact tooth color changes. However, the repositioning guide color influenced the tooth bleaching measured instrumentally, except for ΔE00 .

In vitro evaluation of the effect of different bleaching varnishes: Hydrogen peroxide penetration into the pulp chamber and color change.

OBJECTIVE: To evaluate the penetration of hydrogen peroxide (HP) into the pulp chamber and the color change of different bleaching varnishes in low concentrations used for at-home bleaching. MATERIALS AND METHODS: Ninety healthy premolars were used, randomly distributed into nine groups (n = 10) according to bleaching varnish (PL, PolaLuminate; VS, VivaStyle Paint On Plus; CA, Cavex Bite&White whitening pen and; AW AlignerWhite) and time (10 and 30 min), and a control group (no bleaching). The penetration of HP was evaluated by UV-Vis spectroscopy. To evaluate the color change (ΔEab , ΔE00 , ΔWID ) a digital spectrophotometer was used (α = 0.05). RESULTS: The AW group in 10 min and the control group showed similar and lower HP penetration in the pulp chamber when compared to the other groups (p = 0.003). Increasing the application time to 30 minutes elevated the amount of HP inside the pulp chamber for all groups (p = 0.003), except for PL (p > 0.05). When applied for 30 min all bleaching varnishes showed higher color change (ΔWID ) when compared to 10 min (p = 0.04). CONCLUSIONS: For all bleaching varnishes evaluated, PolaLuminate applied for 30 min showed lower penetration into the pulp chamber and higher bleaching effects. CLINICAL SIGNIFICANCE: The use of bleaching varnishes seems promising for teeth bleaching, but it varies according to user product and protocol.

Effect of strontium fluorophosphate bioactive glass on color, microhardness and surface roughness of bleached enamel.

BACKGROUND: Undesirable effects of tooth bleaching can alter the biomechanical properties of enamel. OBJECTIVE: To determine the influence of strontium fluorophosphate bioactive glass (Sr-FPG) on color, microhardness and surface roughness of enamel bleached with 35% hydrogen peroxide. METHODS: The labial enamel of 36 extracted intact human anterior teeth were divided into 3 groups (n= 12), group 1 (HP): bleaching with 35% hydrogen peroxide only, group 2 (Sr-HP): bleaching with Sr-FPG incorporated 35% hydrogen peroxide and group 3 (HP-SrFPG): bleaching with 35% hydrogen peroxide followed by remineralization with Sr-FPG. Four consecutive eight-minute applications of the bleaching gel were done twice in all the groups. Color change (ΔE), microhardness and surface roughness were evaluated at baseline, post-bleaching and post-remineralization using spectrophotometer, Vickers hardness tester and profilometric analysis respectively. RESULTS: The mean ΔE among the groups was statistically similar (p> 0.05). Bleaching with HP significantly reduced microhardness (p< 0.05), whereas bleaching with Sr-HP and HP-SrFPG did not (p> 0.05). Post-bleaching microhardness in Sr-HP was significantly higher than HP-SrFPG (p< 0.05). An increased surface roughness was seen in Sr-HP bleached samples (p< 0.05). CONCLUSION: The addition of Sr-FPG to hydrogen peroxide significantly improved enamel microhardness than its use post-bleaching. An increase in surface roughness was seen post-bleaching with HP and Sr-HP.

Effect of antioxidant on tooth sensitivity after bleaching.

OBJECTIVES: This study aimed to investigate the effect of antioxidant (sodium ascorbate) on tooth sensitivity after two in-office bleaching techniques (light-activated and chemical bleaching). MATERIALS AND METHODS: Ten patients aged 18-25 were bleached in four groups according to bleaching materials and/or antioxidant used. Group A: Maxillary right quadrant received light-activated bleaching with antioxidant. Group B: Maxillary left quadrant received light-activated bleaching without antioxidant. Group C: Mandibular right quadrant received chemical bleaching without antioxidant. Group D: Mandibular left quadrant received chemical bleaching with antioxidant. The tooth sensitivity was recorded using Numerical Rating Scale (NRS) and Schiff Scale (SS) immediately after treatment, 1 day, 1 week, 2 weeks, and 1 month follow-up periods. RESULTS: Group B exhibited higher sensitivity values than Group A. This difference was statistically significant on the first day after treatment (p = 0.027* in NRS and p = 0.046* in SS). Furthermore, antioxidant incorporation in Group D led to a reduction in teeth sensitivity values compared to Group C. This disparity was highly significant on the first day after treatment (p = 0.001* in NRS and p < 0.001** in SS). CONCLUSIONS: The antioxidant (10% sodium ascorbate) reduces the intensity of tooth sensitivity at the different follow-up periods, especially after 1 day from bleaching. CLINICAL SIGNIFICANCE: Using 10% sodium ascorbate after bleaching is advisable to reduce post-operative tooth sensitivity.

EFFECTS OF PROFESSIONAL ORAL HYGIENE AND TEETH WHITENING ON THE MICROELEMENT COMPOSITION OF ENAMEL.

OBJECTIVE: Aim: The objective of this study is to investigate the impact of professional teeth cleaning and the substances used in modern dentistry for whitening on the microelement composition of tooth enamel. PATIENTS AND METHODS: Materials and Methods: To study the morphology and microelement composition of the enamel, scanning electron microscopy was performed using the MiraLM microscope equipped with a Schottky field emission electron gun from Tescan. RESULTS: Results: A comparative analysis between the areas subjected to mechanical cleaning and those where it was not applied revealed a significant difference in the research results, particularly in carbon, which changed from 25.16±1.04 to 32.02±1.8. An analysis of the enamel's chemical composition before and after whitening revealed a decrease in carbon from 45.91±1.20 to 42.46±1.74. The change in phosphorus content was determined to be from 9.77±0.39 to 9.56±0.75. A decrease in calcium from 15.96±0.64 to 15.21±1.22 and magnesium from 0.07±0.01 to 0.01±0.01 was also observed. CONCLUSION: Conclusions: Professional dental hygiene does not have a direct impact on the microelement composition of enamel, such as the levels of calcium, phosphorus, fluoride, and other microelements. However, it can have an indirect and temporary influence due to the use of abrasive materials that affect dental deposits, pellicle, and the surface layer of enamel. Teeth whitening can affect the microelement composition of enamel, but these changes are mostly temporary and associated with processes of demineralization/ remineralization and oxygenation.

Effects of the application of sodium ascorbate after in-office bleaching on the penetration of hydrogen peroxide, color change, and microtensile bond strength.

This study aimed to evaluate the effects of the application of 10% sodium ascorbate (SA) after in-office bleaching on the penetration of hydrogen peroxide (HP) into the pulp chamber, color change, and microtensile bond strength (µTBS) to the resin-enamel interface. Thirty premolars and thirty molars were randomly divided into three groups (n = 20 each). One group was exposed to deionized water (negative control). The other two groups were bleached with 35% HP in a single session for 3x15 minutes for each application. However, in only one of them, SA was applied for 10 minutes after bleaching. After, the concentration (µg/mL) of HP in each pulp chamber was evaluated by UV-Vis spectrophotometry. Color changes (ΔEab, ΔE00, and ΔWID) were evaluated with a digital spectrophotometer before and in the first week after bleaching. After treatment, molars were restored and sectioned to obtain resin-enamel interface sticks for µTBS at a crosshead speed of 1 mm/min until failure. The HP concentration and µTBS data were analyzed using one-way ANOVA and Tukey tests, and color changes were analyzed by t-tests (α = 0.05). SA application significantly improved the µTBS values and reduced the HP concentrations within the pulp chambers (p < 0.0001). The application of SA significantly interfered with the color changes after bleaching when compared to the control group (p < 0.05). Application of 10% SA after in-office bleaching successfully reduced the penetration of HP into the pulp chamber; however, it decreased color change.

The effect of tooth bleaching using violet LED (405-410 nm) on the properties of resin-based composites.

BACKGROUND: The objective of this study was to evaluate the effect of bleaching techniques, including or not the use of violet light (405-410 nm), on resin-based composites' color, surface roughness, nanohardness, and elastic modulus. METHODS: Ninety-six disk-shaped specimens (12 mm x 2 mm; n = 12) were prepared using Filtek Z350 XT (Z350) and IPS Empress Direct (ED) resin-based composites. After 24 h, specimens were stained in red wine for 28 days. After staining, specimens were divided into four experimental groups: 40 % Hydrogen Peroxide (HP); Violet Light (VL); 40 % Hydrogen Peroxide associated with Violet Light (HP+VL), and a control group - no treatment (NT). Specimens were evaluated at six experimental times: initial (24 h after light curing); after staining and after the 1st, 2nd, 3rd, and 4th bleaching sessions regarding the color change (ΔE00, L*, a*, b*, and WID); roughness (Ra), nanohardness and elastic modulus (GPa). Two-way analysis of variance for repeated measures was performed (α=0.05 %). RESULTS: There was a statistically significant difference between staining and the 1st bleaching session for all ED groups (p<0.05). After the last bleaching session, there were no differences between the experimental and the control groups of both resin-based composites. Bleaching using violet light did not change the roughness, nanohardness and elastic modulus of the tested resin-based composites (p>0.05). CONCLUSIONS: Although hydrogen peroxide and violet light remove pigments from resin-based composites without affecting their surface roughness, nanohardness, and elastic modulus, the color change was similar to the one obtained by immersion in distilled water.

Evaluation of Enamel Surfaces Treated with a Desensitizing Agent Containing CPP-ACP Before or After In-Office Bleaching.

PURPOSE: To evaluate the effects of desensitizing MI Varnish (GC America) applied before or after bleaching on the mineral component of enamel and surface topography. MATERIALS AND METHODS: The coronal portions of 10 freshly extracted bovine teeth were segmented for a total of 40 specimens. Enamel specimens obtained from each tooth were randomly divided into four groups (n = 10): Group A = no bleaching; Group B = bleaching with 40% hydrogen peroxide (HP); Group C = MI Varnish applied before bleaching; and Group D = MI Varnish applied after bleaching. The calcium (Ca) and phosphorus (P) levels of the specimens in each group were determined by energy dispersive spectroscopy (EDS). Morphologic changes were observed using scanning electron microscopy (SEM). One-way ANOVA and Tukey HSD tests were used for statistical analyses (α = .05). RESULTS: The mean Ca content of Group B was significantly lower than those of Groups A, C, and D (P < .05). The mean Ca content of Group C was significantly lower than that of Group A (P < .05). There was no significant difference in Ca content between the other groups (P > .05). The mean P content of Group A was significantly higher than those of Groups B to D (P < .05). There was no significant difference in P content between Groups B to D (P > .05). CONCLUSIONS: Application of MI Varnish before or after in-office bleaching was effective in reducing mineral loss. However, applying MI Varnish after bleaching was more effective.

Hybrid light applied with 37% carbamide peroxide bleaching agent with or without titanium dioxide potentializes color change effectiveness.

BACKGROUND: The effectiveness of dental color change was assessed by incorporating titanium dioxide (TiO2) into 37% carbamide peroxide bleaching agent associated with hybrid light. METHODOLOGY: Fifty bovine incisors were selected to receive the bleaching treatment, and separated into five groups (n = 10): 35% hydrogen peroxide (HP) (Whiteness HP, FGM/HP); 37% carbamide peroxide (CP) (Whiteness SuperEndo, FGM/CP); CP + hybrid light (HL) (CP HL); CP + 1% TiO2 (CP TiO2); CP TiO2 + hybrid light (CP TiO2 HL). The bleaching gels were applied to the dental surface for 30 min. Hybrid light (Whitening Plus, DMC/infrared laser diodes + blue LEDs +violet LEDs) was applied with 1 min of active light, alternating with 1 min of pause. A spectrophotometer (VITA Easyshade® Advance, Vita) was used to determine the color of the dental elements at baseline and time points after the 1st, 2nd and 3rd bleaching sessions. Color change effectiveness was evaluated using Vita Classical, CIEL*a*b*, WID and ΔEab, ΔE00 and ΔWID parameters. RESULTS: Generalized mixed linear models for repeated measures (α = 5%) showed significant decrease in Vita Classical scores and a* and b* values, as well as an increase in L* and ∆WID values for all the groups. Higher color change values for ΔEab were observed for CP HL and CP TiO2 HL, while those of ΔE00 and ΔWID were higher for CP TiO2 HL at the end of the bleaching treatment. CONCLUSION: Hybrid light applied with TiO2 incorporated into CP potentiated the effectiveness of the color change in the tooth structure.

Effects of experimental bleaching gels containing co-doped titanium dioxide and niobium pentoxide combined with violet light.

OBJECTIVES: The objective of the study is to evaluate the bleaching potential of 6% hydrogen peroxide (6% HP) gels containing NF_TiO2 or Nb2O5 irradiated with a violet LED light and the effects on enamel mineral content and surface morphology. METHODS: Particles were synthesized, and experimental gels were chemically analyzed by preliminary and accelerated stability tests, pH, and HP decomposition rate. Bovine enamel blocks were treated with 6% HP gels containing (n = 10): 5% NF_TiO2, 5% Nb2O5, 2.5% NF_TiO2 + 2.5% Nb2O5 or without particles (6% HP), irradiated or not with LED, and the control was treated with 35% HP. Color (∆E00) and whitening index (∆WID) variations, surface microhardness (SH), average roughness (∆Ra), Ca-P concentration (EDS), and enamel morphology (SEM) were assessed. Bleaching was performed in 3 sessions of 30 min and 7-day intervals. Data were submitted to two- (pH, decomposition rate, ∆E00, and ∆WID) or three-way ANOVA and Bonferroni (SH), Kruskal-Wallis (∆Ra), and Dunnet tests (α = 0.05). RESULTS: No changes in the gel's color, odor, or translucency were observed. The pH (6 to 6.5) remained stable over time, and light irradiation boosted the HP decomposition rate. NF_TiO2 and Nb2O5-containing gels displayed higher ∆E00 and ΔWID when light-irradiated (p < 0.05). Nb2O5 and Nb2O5 + NF_TiO2 decreased enamel SH (p < 0.05), but no SH changes were found among groups (p > 0.05). No differences among groups were noted in ∆Ra, Ca-P content, and enamel morphology after treatments (p > 0.05). CONCLUSION: Experimental light-irradiated 6% HP gels containing NF_TiO2 or Nb2O5 were chemically stable and exhibited bleaching potential comparable with 35% HP. CLINICAL RELEVANCE: Low-concentrated HP gels containing NF_TiO2 or Nb2O5 and light-irradiated stand as a possible alternative to in-office bleaching.

Effect of experimental bleaching gels with polymers Natrosol and Aristoflex on the enamel surface properties.

Natrosol and Aristoflex® AVC polymers are widely applied in the cosmetic industry and have recently been applied as a thickener option in the composition of dental bleaching gels, with the purpose to reduce the adverse effects on enamel mineral components. The aim of this study was to evaluate the color variation (ΔE* ab, ΔE00, ∆WID), surface roughness (Ra), and mineral content quantification (Raman Spectroscopy) of dental enamel after bleaching treatment with experimental gel-based on 10% carbamide peroxide (CP), containing Carbopol, Natrosol, and Aristoflex® AVC. Sixty bovine teeth were randomly divided into 6 groups (n=10): Negative Control (NC) - no treatment; Positive Control (PC) - Whiteness Perfect 10% - FGM; CP with Carbopol (CPc); CP with Natrosol (CPn); CP with Aristoflex® AVC (CPa); NCP - no thickener. Data were analyzed, and generalized linear models (∆WID -T0 x T1) were used for repeated measurements in time for Ra and with a study factor for ΔE* ab and ΔE00. For the evaluation of the mineral content, data were submitted to one-way ANOVA and Tukey tests. For enamel topographic surface analysis the Scanning Electron Microscope (SEM) was performed. A significance level of 5% was considered. ΔE* ab and ΔE00 were significantly higher for CPc, CPn, CPa, and NCP groups. (∆WID) showed a significantly lower mean than the other groups for NC in T1. After bleaching (4-hour daily application for 14 days), Ra was higher in the CPc, CPn, and PC groups. For CPa, Ra was not altered. No significant difference was found in the quantification of mineral content. CPa preserved the surface smoothness more effectively. Aristoflex® AVC is a viable option for application as a thickener in dental bleaching gels, presenting satisfactory performance, and maintaining the whitening efficacy of the gel, with the advantage of preserving the surface roughness of tooth enamel without significant loss of mineral content.

Effect of non-vital tooth bleaching photoactivated with blue or violet LED on color and microhardness.

BACKGROUND: To evaluate the efficacy of dental bleaching protocols using 35% hydrogen peroxide photoactivated with violet LED on color and microhardness of endodontically treated teeth. METHODS: Forty specimens were selected and randomized into 4 groups (n = 10): C - Control, HP - 35% hydrogen peroxide, HP + BL - 35% hydrogen peroxide + blue LED, HP + VL - 35% hydrogen peroxide + violet LED. Three bleaching sessions were performed for each group. Color analysis was performed 7 days after each bleaching session. Two-way repeated measure ANOVA and Bonferroni test were used to evaluate the effect of different bleaching protocols and evaluation times on the dependent variables (∆E and ∆L). Dentin microhardness was measured 24 h after the third bleaching session. Data were evaluated by ANOVA and Tukey's test at a significance level of 5%. RESULTS: Differences on ∆E and ∆L were verified after the first and second bleaching sessions (p < 0.05) and showed stability after the third one, for all the groups. No differences were observed among HP, HP + BL, and HP + VL groups, regardless of the evaluation time (p > 0.05). HP and C showed the greatest and smallest reduction in dentin microhardness (p < 0.05), respectively. No difference between HP + BL and HP + VL protocols (P > 0.05) was observed. CONCLUSIONS: High concentration hydrogen peroxide (35%) photoactivated with violet LED bleached endodontically treated teeth effectively. However, the same protocol negatively affected the dentin microhardness, but not in the same level of 35% HP solely used.

The in vitro effect of solutions with or without sugar in dental bleaching.

The interaction of bleaching technique (in-office or at-home) and solutions (deionized distilled water with and without sugar, red wine with and without sugar, coffee with and without sugar) on the effectiveness of in vitro dental bleaching was evaluated. Hydrogen peroxide (HP) 37.5% gel was used for in-office bleaching, 3 applications of 8 min each, 3 sessions with an interval of 7 days. At-home bleaching was performed with 10% Carbamide peroxide (CP), 2 h/day, for 30 days. The enamel vestibular surfaces (n = 72) were subjected daily to test solutions for 45 min, washed with distilled water for 5 min and stored in artificial saliva. The enamel color analysis was performed with a spectrophotometer through color variation (ΔE) and luminosity variation (ΔL). Roughness analysis was performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Enamel composition was determined by energy dispersive X-ray spectrometry (EDS). The results were submitted to one-way analysis of variance (ANOVA) for ΔE, ΔL and EDS and two-way for AFM. For ΔE and ΔL there was no statistically significant difference. An increase in roughness was observed on the surface when exposed to a sugar-water solution for at-home bleaching and a lower concentration of Ca and P in the deionized water solution with sugar. Solutions containing or not sugar did not influence the bleaching potential, however the presence of sugar in the water solution increased the surface roughness with CP.

Effectiveness and Safety of Over-the-Counter Tooth-Whitening Agents Compared to Hydrogen Peroxide In Vitro.

(1) This study investigated the whitening effect, cytotoxicity and enamel surface alterations induced by different over-the-counter (OTC) bleaching agents in comparison to hydrogen peroxide. (2) Human teeth (n = 60) were randomly assigned into 6 groups (n = 10), stained with coffee solution for 7 d, followed by a whitening period of 7 d with either placebo, bromelain, sodium bicarbonate, sodium chlorite, PAP or hydrogen peroxide. Color measurements were performed with a spectrophotometer. Scanning electron micrographs (SEM) were taken to assess the enamel structure. Cytotoxicity of the tested substances was assessed based on the cell viability of primary human fibroblasts. (3) The application of all whitening gels resulted in a greater color difference of the enamel (ΔE) in comparison to the negative control. Hydrogen peroxide caused the greatest color difference. Bromelain and PAP treatment showed no enamel surface changes, in contrast to hydrogen peroxide treatment, which showed very mild interprismatic dissolution. Bromelain was the only non-cytotoxic agent. (4) The maximum effect achieved by all OTC bleaching agents was the removal of stains, whereas hydrogen peroxide was capable of further whitening the teeth. Bromelain treatment was neither cytotoxic, nor resulted in enamel surface alterations, and its whitening effect was less, yet still effective, compared to hydrogen peroxide.

In vitro effectiveness of different dental bleaching protocols using violet LED.

PURPOSE: There has been growing demand for dental bleaching worldwide, however, despite being effective, hydrogen peroxide (HP) can negatively affect the dental structure. Thus, new techniques, such as violet LED light have emerged and need to be studied. The aim of this study was to analyze and compare the effectiveness of violet LED light alone or combined with 35% HP gel. METHODS: Six different tooth bleaching techniques (n = 10) were performed in intrinsically pigmented bovine teeth: G1 - 35% HP (1x/week for 4 weeks, 45 min of gel application); G2 - 35% HP (1x/week for 4 weeks, 15 min of gel application); G3 - violet LED (1x/week for 4 weeks); G4 - violet LED (2x/week for 2 weeks); G5 - violet LED (4x/week for 1 week); G6 - Violet LED + 35% HP (hybrid technique, 1x/week for 4 weeks, 15 min of gel application). Specimens were submitted to color evaluation at predetermined times using Konica Minolta® spectrophotometer, and the surface morphology (n = 3) was qualitatively analyzed by Scanning Electron Microscope (SEM). Data of the color change test were analyzed considering a 5% level of significance. RESULTS: There was significant difference in color (p <0.05) for all groups after bleaching protocols. SEM analysis revealed that the greatest change in surface occurred in Group G1, with demineralization of the dental enamel. When considering the same time interval, there were no statistical differences for axis L*, but differences were shown for axis a* (G2, G3, G4 ≥ G1, G5 ≥ G6) and b* (G1, G2, G3, G4, G5 > G6). Regarding the comparison of ΔE00 between groups, results showed statistical difference between groups, with G1 ≥ G2, G5, G6 ≥ G3, G4. CONCLUSION: Bleaching protocols with less time (15 min) or no exposure to 35% HP (violet LED, 4x/week) could promote bleaching results as those obtained by the conventional technique using 35% HP for 45 min, with no enamel surface changes, showing to be a promising alternative to tooth bleaching.

A new approach for professional dental bleaching using a polymeric catalyst primer.

OBJECTIVE: Evaluate the influence of a polymeric catalyst primer (PCP) on esthetic efficacy (EE), degradation kinetics of hydrogen peroxide (H2 O2 ), and trans-amelodentinal cytotoxicity (TC) of bleaching gels. MATERIALS AND METHODS: The following groups were established: G1: No treatment (NC, negative control); G2: PCP; G3: 10% H2 O2 ; G4: PCP + 10% H2 O2 ; G5: 20% H2 O2 ; G6: PCP + 20% H2 O2 ; G7: 35% H2 O2 (positive control); G8: PCP + 35% H2 O2 . To determine EE, enamel/dentin discs (E/DDs) were stained and subjected or not to bleaching protocols for 45 min. To assess TC, the E/DDs were adapted to artificial pulp chambers. The extracts (culture medium + gel components diffused through E/DDs) were applied to odontoblast-like MDPC-23 cells. The viability (VB), oxidative stress (OxS), morphology (SEM), amount of H2 O2 diffused and the production of hydroxyl radical (OH• ) were assessed (two-way ANOVA/Tukey/paired Student t-test; p < 0.05). RESULTS: The highest EE was found in G8 (p < 0.05), and G4, G6, and G7 did not differ statistically (p > 0.05). In G4, the limited H2 O2 diffusion reduced OxS and increased cell VB (p < 0.05). CONCLUSIONS: Coating the enamel with PCP containing 10 mg/ml of manganese oxide before applying the 10% H2 O2 bleaching gel maintains the EE of conventional in-office bleaching and minimizes the toxic effects of this esthetic therapy. CLINICAL SIGNIFICANCE: Coating the enamel with a PCP before applying the bleaching gel may potentiate the EE of the conventional in-office tooth bleaching and reduce the toxicity of this professional therapy to the dental pulp.