Effect of fluoride or chitosan toothpaste and at-home bleaching in enamel roughness, tooth color, and staining susceptibility.

PURPOSE: To evaluate how fluoride- or chitosan-based toothpaste used during at-home bleaching affects enamel roughness, tooth color, and staining susceptibility. METHODS: Bovine enamel blocks were submitted to a 14-day cycling regime considering a factorial design (bleaching agent x toothpaste, 2 x 3), with n=10: (1) bleaching with 16% carbamide peroxide (CP) or 6% hydrogen peroxide (HP), and (2) daily exposure of a fluoride (1,450 ppm F-NaF) toothpaste (FT), chitosan-based toothpaste (CBT), or distilled water (control). Then, 24 hours after the last day of bleaching procedure the samples were exposed to a coffee solution. Color (ΔEab, ΔE00, L*, a*, b*) and roughness (Ra, µm) analyses were performed to compare the samples initially (baseline), after bleaching, and after coffee staining. The results were evaluated by linear models for repeated measures (L*, a*, b*, and Ra), 2-way ANOVA (ΔEab, ΔE00) and Tukey's test (α= 0.05). RESULTS: After the at-home bleaching procedure (toothpaste vs. time, P< 0.0001), the toothpaste groups presented a statistically lower Ra than the control (CBT 0.05). After coffee exposure, CBT presented lower ΔEab and ΔE00 values in the HP groups (toothpaste, P< 0.0001), and lower b* and a* values in the CP groups (toothpaste vs. time, P= 0.004). CLINICAL SIGNIFICANCE: Fluoride or chitosan delivered by toothpaste can reduce surface alterations of the enamel during at-home bleaching, without affecting bleaching efficacy.

Toothpaste Use Protocol with Dental Bleaching for a Conservative Treatment: Case Reports.

In-office bleaching is a treatment based on products that contain hydrogen peroxide (HP) while demonstrating whitening effectiveness. HP could promote alterations to surface morphologies and properties of dental tissues. The objective was describe a toothpaste protocol associated to bleaching therapy to promote a safer approach. Patient 1 (male) and Patient 2 (female) were attended, and toothbrushing (twice a day) with a dentifrice containing bioactive glass (BG) (NovaMin™) and fluoride was indicated before and during the treatment. Three bleaching sessions were made in cases, at intervals of 7 days. The gels used were 35% HP (Patient 1) and 35% HP supplied with calcium (Patient 2). The effectiveness of bleaching treatment was observed in both cases (Vita scale), with an esthetic self-acceptance. Sensitivity associated with the procedure was not reported. The indication of BG-based toothpaste is relevant in relation to enamel properties and did not affect the whitening effectiveness of dental bleaching.

Evaluation of physical properties of a nanocomposite after aging, bleaching and staining.

PURPOSE: The objective of the in vitro study was to assess the effect accelerated artificial aging, bleaching agents and coffee staining on the color, gloss, roughness and microhardness of a nanocomposite. MATERIALS AND METHODS: 120 (7 × 2 mm) were prepared and randomly divided into 2 groups (n = 60) depending on the aging. Each group was further subdivided into 6 subgroups (n = 10) according to the bleaching and staining as follows: 10% carbamide peroxide (10% CP), 10% CP + staining, 35% hydrogen peroxide (35% HP), 35% HP + staining, without bleaching treatment (WB) and WB + staining. Scanning electron microscopy was performed for qualitative analysis of the resin surface. Data were submitted to 3-way analysis of variance (ANOVA) and Tukey's test for multiple comparisons. As for ∆E, multiple comparisons were performed by using Tukey's and Dunnett's tests (α = 0.05). RESULTS: The bleaching reduced significantly the microhardness of the nanocomposite in without aging groups. All physical properties were found to be negatively changed after the aging process, with bleaching treatment with 10% CP increasing significantly the roughness and loss of gloss compared to the 35% HP. Staining reduced microhardness of both with and without aging nanocomposite as well as the color of the former (E>25), a significantly different result compared to controls. CONCLUSIONS: The bleaching reduced the microhardness of the nanocomposite, whereas the aging process changed all the properties studied. The bleaching favored extrinsic staining of the with aging nanocomposite.

Effect of energy density and delay time on the degree of conversion and Knoop microhardness of a dual resin cement.

AIM: In the present study, we evaluated the influence of the photo-curing delay time and energy density on the degree of conversion and the Knoop microhardness of a resin cement. METHODS: Seventy-eight samples were assigned to 13 groups (n = 6), one of which received no light curing (control). The samples were made of a dual-cured resin cement (RelyX ARC) with the aid of a Teflon matrix, submitted to one of the following energy densities (J/cm²): 7, 14, 20, and 28. Delay times were immediate (0), 1 min, or 2 min. After 24 h, the degree of conversion and microhardness were measured at three segments: cervical, medium, and apical. Data were submitted to three-way anova and Tukey's and Dunnett's tests, the latest of which was used to compare the control to the experimental groups. RESULTS: No interaction was observed between delay time and energy density regarding the degree of conversion. The cervical segment showed the highest values, while the apical showed the lowest. Microhardness values concerning the cervical segment in all groups were statistically different from that obtained for the control. CONCLUSION: A high-irradiance light-curing unit allows for a reduced irradiation exposure time with a short delay time, aimed at tooth restorations using a dual-cured resin cement.

Efficacy of tooth bleaching with the prior application of a desensitizing agent.

AIM: In the present study, we evaluated the efficacy of bleaching on enamel and opposite dentin surfaces using 35% hydrogen peroxide (HP) with the prior application of a desensitizing agent. METHODS: Thirty bovine dental fragments, with thicknesses of 1 mm enamel and 1.75 mm dentin, were stained in a solution of black tea. The fragments were randomly divided into three groups (n = 10) according to the following protocols: (a) 2% neutral fluoride + bleaching; (b) desensitizing agent + bleaching; and (c) without desensitizer + bleaching. The bleaching efficacy was evaluated four times: after staining with tea (baseline) and after each of the 3 weeks of bleaching, by means of the CIE Lab method using a reflectance spectrophotometer. The data coordinate L* was evaluated by an analysis of repeated measures with PROC MIXED and Tukey-Kramer's test. The ΔE values were subjected to anova and Tukey's test (α = 0.05). RESULTS: The 35% HP treatment showed greater efficacy on deep dentin after removal of the enamel stains, with increasing means during all times in all treatments. CONCLUSION: The use of a desensitizing agent prior to the bleaching session did not affect the mechanism of action of 35% HP with regard to tooth depth.

Influence of light-activation protocol on methacrylate resin-composite evaluated by dynamic mechanical analysis and degree of conversion.

The aim of this study was to evaluate the degree of conversion (DC) and to identify the viscoelastic properties: storage modulus (E'), loss modulus (E"), tangent delta (tan δ), and glass transition temperature (T g ) of a microhybrid resin-composite light-activated by three different protocols. A Filtek Z250 (3 M ESPE) shade A3 was inserted in a Teflon mold (21 mm × 5 mm × 1 mm for viscoelastic properties; and 5 mm × 1 mm for DC) and light-activated according to the following light-activation protocols: (S) 1,000 mW/cm(2) × 19 s, (HP) 1,400 mW/cm(2) × 14 s, and (PE) 3,200 mW/cm(2) × 6 s, all set up to deliver 19 J/cm(2). Viscoelastic properties was assessed by dynamic mechanical analysis (DMA) (n = 3), performed in single cantilever clamped mode. DC (n = 5) was measured by FTIR on top (T) and bottom (B) surfaces, and the data was submitted to a split-plot one-way ANOVA. For DC, there was a significant effect for surface factor and light-activation protocols factor. Top surface showed higher DC than B in all experimental conditions. Light-activation protocols S and HP resulted in higher DC than PE and were similar between them. Viscoelastic properties (E', E", tan δ, T g ) were not affected by light-activation protocols. It could be concluded that light-activation protocols influenced DC but not influenced the viscoelastic properties.

Influence of flowable composite and restorative technique on microleakage of class II restorations.

AIM: The aim of the present study was to evaluate the microleakage in class II cavities restored with dental composite by varying the thickness of two flowable composite resins and the restorative technique. METHODS: A total of 130 cavities were prepared on proximal surfaces of bovine teeth and randomly divided in 13 groups. Twelve experimental groups were performed using flowable composite resin as the liner, and they were divided according to the type of flowable composite resin (Filtek Z350 Flow-Z350F and SureFil SDR Flow-SUR), the thickness of the flowable composite (0.5, 1, or 2 mm), and the restorative technique (flowable composite applied at the cavosurface angle or amelodentinal junction) (n = 10). A control group was performed without using a flowable composite. Following restorative procedures and thermocycling, the samples were immersed in Methylene Blue for 2 h, and prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed (α = 0.05). RESULTS: There was no significant difference between the flowable composites (P > 0.05). The restorative techniques influenced microleakage and were flowable composite dependent (P ≤ 0.05). The lower thickness of the flowable composite provided less microleakage (P ≤ 0.05). CONCLUSION: The use a lower thickness of a flowable composite resin provided less microleakage, suggesting a better sealing tooth-restoration interface.

Effect of polymerization mode and time of adhesive system on microleakage in composite resin restorations.

AIM: To quantify the microleakage on restorations carried out with a two-step etch-and-rise adhesive system and nanofilled composite resin after thermal and mechanical loading cycling. METHODS: Ninety cavities were prepared on proximal surfaces of incisive teeth, and were randomly divided according to the photoactivation time (10, 20, or 30 s) and light-curing mode (Quartz Tungsten Halogen (QTH) lamps, 450 mW/cm(2); Light Emitting Diode (LED) second generation, 1100 mW/cm(2); or LED third generation, 700 mW/cm(2)) of an adhesive system (n = 10). Following restorative procedures and thermal and mechanical loading cycling, the samples were immersed in Methylene Blue for 2 h. The samples were ground, and the powder was prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed by anova and Tukey's test at the 5% level of significance. RESULTS: There were no significant statistical difference in microleakage between the light-curing mode (P = 0.1212) and light-curing time (P = 0.2043). CONCLUSION: Different curing modes and increasing the curing time were not factors that influenced the process of microleakage.

Effectiveness of dental bleaching in depth after using different bleaching agents.

OBJECTIVES: This study evaluated the effectiveness of low- and high-concentration bleaching agents on enamel and deep dentin. STUDY DESIGN: Stained bovine incisors fragments were randomized placed into 10 groups (n=5), according to the sample thicknesses (2.0 mm or 3.5 mm) and bleaching agent: 10% carbamide peroxide (CP) (4 h a day/21 days); 6% hydrogen peroxide (HP) with calcium (1:30 h a day/21 days); HP 20% with calcium (50 min a day/3 sessions with a 7-day interval); HP 35% (3 x 15 min a day/3 sessions with a 7-day interval); HP 35% with calcium (40 min a day/3 sessions with a 7-day interval). The samples were stored in artificial saliva during the experiment. The color change was evaluated using a spectrophotometer at the initial analysis, after artificially staining with black tea and after each of the bleaching weeks, and data was expressed in CIE Lab System values. The L* coordinate data was submitted to analysis of variance and Tukey-Kramer test and the ?E values data was submitted for analysis of variance in a split-plot ANOVA and Tukey's test (?=0.05). RESULTS: None of the bleaching agents tested differed from the reflectance values on the enamel surface. For deep dentin HP 20% and HP 35%, both with calcium, showed the lowest reflectance values, which differed from CP 10%. CONCLUSION: It is concluded that high concentration hydrogen peroxide with calcium was less effective in deep dentin than 10% carbamide peroxide. Key words:Dental bleaching; hydrogen peroxide; carbamide peroxide; dental staining.