Bleached Groups Research Articles

Objective comparison of three different treatment modalities in the esthetic improvement of mild-to-moderate dental fluorosis: A randomized clinical trial

Objective: To compare and evaluate esthetic improvement following resin infiltration, vital bleaching, and diode laser bleaching in mild-to-moderate fluorosis conditions immediately after treatment, 1 month, and 6 months postoperatively. Study Design: Sixteen patients with Central and lateral incisors showing mild-to-moderate fluorosis according to modified Dean's fluorosis index were selected and simple randomization was done to allocate the teeth to resin infiltration group, vital bleaching group, diode laser bleaching group, and control group. Esthetic improvement posttreatment was assessed using digital image analysis using Adobe Photoshop software and color change (ΔE) was calculated. Results: The inferential statistics included Kruskal–Wallis test and Friedman's ANOVA test. Vital bleaching showed the highest esthetic improvement followed by diode laser bleaching, vital bleaching, and control group at all the different time intervals. The results, however, were not statistically significant. Conclusion: All the three treatment measures brought about esthetic enhancement with the vital bleaching group showing slightly better results when compared with other study groups.

A novel carbamide peroxide polymeric nanoparticle bleaching gel: Color change and hydrogen peroxide penetration inside the pulp cavity.

This study evaluated the hydrogen peroxide (HP) penetration inside the pulp cavity and the color change of teeth submitted to the 15% carbamide peroxide (CP) nanoparticle bleaching gel at several application times. Premolars were divided into nine groups (n = 6) according to 15% CP bleaching agents (nanoparticle and commercial) and to application times (15, 30, 45, and 60 minutes). A negative control was exposed to ultra-purified water. After a whitening procedure, the HP concentration (μg/mL) inside the pulp cavity was assessed via spectrophotometry. The color change (ΔE* and ΔE00*) was evaluated with a spectrophotometer. Data were analyzed via two-way ANOVA and Tukey (α = 0.05). A lower concentration of HP was detected for CP nanoparticle gel after 30 and 45 minutes of whitening procedure (P = .001). The bleaching groups promoted a higher color change (ΔE* and ΔE00*) regardless of the application time (P = .0001). The CP nanoparticle gel reduced HP inside the pulp cavity, and showed effective bleaching compared with CP commercial gel. Using 15% carbamide peroxide nanoparticle bleaching gel decreased the HP penetration inside the pulp cavity and may decrease bleaching-induced tooth sensitivity in at-home bleaching.

Color stability, Roughness, and Microhardness of Enamel and Composites Submitted to Staining/Bleaching Cycles

ObjectiveTo compare the effect of two bleaching systems (bleaching gel and whitening strips) on the color change, roughness, and microhardness of enamel and two resin composites. Material and methodsTwo cavities were prepared on bovine enamel specimens (n = 16) and restored with two composites: a nano-hybrid [Herculite Ultra (HU)] and a micro-hybrid composite [TPH Spectra (TS)]. Baseline color (CIE L*a*b*), roughness (μm), and microhardness (kgf/mm2) were measured using a spectrophotometer, optical profilometer, and Vickers microhardness (VHN) tester, respectively. The specimens were stained with coffee for 14 days, and randomized into two bleaching groups: gel and strips (n = 8), then submitted to a 10-day bleaching/staining test. Color, roughness, and microhardness were re-measured. The outcomes were analyzed using two-way ANOVA and Fisher’s-PLSD test (α = 0.05). ResultsGel significantly improved the color (ΔE 4.9–8.3) and increased the roughness (Ra 0.04–0.08 μm) of all substrates (p < 0.0001) compared to strips. Enamel color was significantly improved (ΔE 5.4–8.3) compared to that of HU (ΔE 2.6–4.9) and TS (ΔE 2.0–4.9) with either gels or strips. TS roughness (0.03–0.08 μm) was significantly higher than that of enamel (0.01–0.05 μm) and HU (0.02–0.04 μm). Enamel had significantly reduced microhardness compared to HU (p = 0.0144). ConclusionGels produced the greatest color improvement and roughness compared to strips. Enamel had significant color improvement but had the greatest decrease in microhardness. Clinical significanceThere was unacceptable color change between enamel and the composites after the combined cyclic effects of staining and bleaching.

Effects of remaining dentin thickness on the bond strength of bleached dentin

BackgroundThe bond strength of resin composites to dentin was reported to be related to either the remaining dentin thickness (RDT) or bleaching treatment. However, information is limited regarding the effects of RDT on the bond strength of bleached dentin. The present study aimed to investigate the effects of RDT on the microshear bond strength (μSBS) of resin cement to bleached dentin.MethodsA total of 120 dentin specimens were prepared and randomly divided into 2 groups: a bleaching group (group B) and a control group (group C). Hydrogen peroxide with a concentration of 35% (Ultradent, USA) was applied on the dentin surface for 2 × 1 d for group B, while no bleaching treatment was performed for group C. After the treatment, the specimens were finished and polished to obtain different RDTs (2, 1, and 0.5 mm) and divided into 3 groups of 20 specimens each. The bonding procedure was performed using Panavia V5 (Kuraray, Japan) with a bonding area of 0.785 mm2. For each group, half of the specimens were subjected to 5000 thermal cycles (subgroup T), while the other half did not receive thermocycling (subgroup N) (n = 10). The specimens were then subjected to the μSBS test using a universal testing machine. Data were analyzed by a three-way analysis of variance (α = 0.05). The fracture modes of the specimens were confirmed with a measuring microscope. Representative specimens with different fracture modes were observed with scanning electron microscopy (SEM).ResultsThe μSBS values were significantly affected by bleaching treatment (p < 0.001), whereas no significant effect was observed for thermocycling (p = 0.293). In terms of RDT, a significantly different μSBS value was found among the subgroups with different RDTs in group C (p = 0.003). However, the RDT did not significantly affect the μSBS values of bleached dentin in group B (p = 0.779). The μSBS values were significantly lower in group B than in group C (p < 0.001). A higher percentage of adhesive failure was observed in group B than in group C.ConclusionBased on the present findings, it can be concluded that the RDT did not affect the bond strength of resin cement to bleached dentin.Clinical significanceSince RDT did not affect the bond strength of resin cement to bleached dentin, bonding procedures should not be performed immediately after intracoronal bleaching, even if the dentin is planned to be removed due to a tooth preparation process.

Changes in enamel after bleaching pre-treatment with non-thermal atmospheric plasma

The aim of this study was to evaluate color change, mineral composition and topography of the enamel after the pre-treatment with non-thermal atmospheric plasma (NTAP) followed by 38% hydrogen peroxide (HP) bleaching.Buccal enamel of bovine incisors teeth was stained with black tea solution and then divided into five groups (n = 12), according to the plasma application time: PL1 (one minute) or PL2 (2 min) and number of HP applications: HP1 (one) and HP3 (three). The following groups were investigated: HP3, PL1+HP1, PL1+HP3, PL2+HP1 and PL2+HP3. Four color measurements: initial (untreated), after staining and after bleaching (first and second sessions), were performed using an intraoral spectrophotometer (Vita Easyshade). Energy Dispersive X-ray Spectroscopy (EDX) was used to analyze the mineral composition of the enamel before and after two bleaching sessions. Laser confocal microscopy was used to analyze the enamel topography.The pre-treatment with NTAP did not improve the whitening results. The use of NTAP preserves the concentration of calcium and phosphorus, only HP3 group experimented a significant decrease in the mineral concentration. All the bleached groups, with or without NTAP treatment increased their enamel roughness.The application of NTAP did not influence the color change, but it was important to maintain the mineral composition of bleached teeth. All the groups increased their roughness level.

Comparative evaluation of the effect of chemical and diode laser activated bleaching techniques on enamel surface and subsurface

Objective: The aim of this study was to compare diode laser-activated bleaching effect versus chemical bleaching on enamel surface and subsurface of human mandibular incisors concerning morphology and chemical profile.Materials and Methods: Forty extracted human, caries and defect-free mandibular incisors were divided into four groups by dividing their labial surface longitudinally into two halves. The distal halves of 20 teeth were assigned for chemical bleaching protocol using 38% hydrogen peroxide, their mesial halves represented their control. The other 20 teeth were assigned by the same method into laser-activated bleaching group and its control. The morphology and chemical profile of the surface and subsurface of the labial enamel were investigated, chemical profile of the subsurface was investigated at 50 and 100 μm depth.Results: The enamel surface of chemically bleached group showed surface irregularities, porosities and erosive areas, ternary diagram of its chemical profile presented a slight shift to an area of less mineralized enamel. Morphology of the subsurface of chemically bleached enamel showed structural defects in prisms configuration and channels extending from surface defects through the enamel, its ternary diagram presented a shift to a demineralized area at both depths examined. Enamel surface of laser-bleached teeth appeared as a molten glazed surface and presented almost no shift in the ternary diagram. Subsurface of laser-bleached teeth showed loss of prismatic enamel integrity and presented a shift to a more mineralized area at 50μm depth and to a demineralized area at 100μm depth.Conclusion: Laser-activated bleaching caused less enamel surface irregularities than chemical bleaching, but its effect was more deleterious on the morphology of the enamel subsurface. Concerning enamel chemical profile, subsurface enamel of chemically bleached teeth was more affected than that of the laser-bleached teeth.

Optical changes of human dentin after non-vital bleaching and effect of Er,Cr:YSGG laser on micro-shear bond strength of a self-etch and an etch-and-rinse adhesive system.

The aim was to evaluate the optical changes of bleached human dentin and the efficacy of Er,Cr:YSGG laser on micro-shear bond strength (μSBS) of two adhesive systems for immediate and delayed applications. Seventy-two human dentin specimens (1mm) were obtained. Colour measurements of 30 specimens (control and bleaching groups) were made at baseline, after bleaching and a 7-day delay. Differences at colour (ΔE00), translucency (ΔTP00) and whiteness (ΔWID) were calculated by recorded data. Forty-two specimens were used to compare μSBS of a self-etch (Clearfil SE Bond [SE]) and an etch-and-rinse (Prime&Bond NT [PBNT]) adhesive to bleached dentin. Additional to a negative group, six groups were contemplated for each adhesive, considering the time of composite application (immediate, delayed) and whether additional surface treatment by laser (1W, 2W) or not. Colour and μSBS data were statistically analysed. For optical analysis, only ΔE00 and ΔWID calculated for the difference between baseline and bleaching were found significantly different for control and bleaching groups. Whiteness of bleached specimens was remarkably decreased after a 7-day delay. Despite immediate applications of SE showing lower μSBS than negative control, delayed applications showed no significant differences except that of the 2W laser etching. For PBNT, laser etching increased μSBS for both of the immediate and delayed applications, and no significant difference was observed from negative control. Related with the preferred adhesive system, Er,Cr:YSGG laser etching can be an alternative for optimal bond strength of immediate restorations, but the clinicians should always keep in mind that perceived colour and whiteness will change by the passing time which can affect the shade match.

The efficacy and complications of several bleaching techniques in patients after fixed orthodontic therapy. A randomized clinical trial.

This study aimed to evaluate the efficacy and complications of several bleaching methods in patients with discolored teeth after orthodontic treatment. This randomized clinical trial involved 60 volunteers (31 women, 29 men) aged 14 to 30 years, who finished fixed orthodontic therapy at least three months before the study commencement and complained of discoloration on upper front teeth. The subjects were divided into four groups by treatment. The patients in group 1 received home bleaching, whereas those in groups 2 to 4 underwent in-office bleaching using a diode laser, a plasma arc and no light source, respectively. Tooth color was measured at baseline, one hour after the end of the bleaching procedure, and one week later, and the color alteration between different stages was compared among the groups. The severity of tooth sensitivity and the occurrence of other post-treatment complications were recorded. The color change between baseline and one week after treatment was greatest in the home-bleaching and the laser-assisted bleaching groups, and lowest in the plasma-arc bleaching group, although the difference between the groups was not significant (p > 0.05). Tooth sensitivity over 24 hours after bleaching was lowest in subjects who had undergone laser-assisted bleaching and highest in those who had received in-office bleaching without light (p < 0.05). All methods were effective in managing tooth discoloration after orthodontic treatment. Home bleaching produced favorable color alteration. Amongst the in-office approaches, laser-assisted bleaching should be considered as the best option, as it produced effective results with lowest tooth sensitivity and over a shorter period of time.

Spectrophotometric analysis of dental bleaching after bonding and debonding of orthodontic brackets

IntroductionThe aim of this study was to evaluate the bleaching effect after aging simulation in teeth submitted to bonding and debonding of orthodontic brackets. Materials and methodsFor this study, 90 human premolars were selected, and randomly divided into 6 groups: control, bleaching, and other 4 groups submitted to bleaching after bonding and debonding brackets using different methods. Color measurement of sample through the CIE L*a*b* system was performed in three moments: T1 – after brackets debonding, T2 – after staining cycling, and T3 – after bleaching. For evaluation of results among the components L*, a* and b*, the two criteria analysis of variance and the multiple comparison Tukey test (p < 0.05) were used. ResultsStatistically significant difference was observed among the groups submitted to brackets bonding and debonding through self-conditioning adhesive system and tungsten drill, also the control and bleaching groups between the moments T1 e T2. ConclusionBonding and debonding brackets methods tested in this study showed influence on the sample color change, and after the tooth bleaching process, only the group without brackets previous bonding achieved the color value presented before the staining and aging of samples in the brackets absence.

Effectiveness of Different Laser-Assisted In-Office Bleaching Techniques: 1-Year Follow-Up.

Objective: The aim of this study was to evaluate color longevity after different bleaching techniques. Background: Laser-activated bleaching methods are gaining popularity due to decreased chair time and increased patient compliance. However, the longevity of such methods has not been stated clearly. Methods: Sixty patients were divided into the following three groups (n = 20); group 1: chemical bleaching with 35% hydrogen peroxide (HP) gel, group 2: bleaching with 35% HP gel with diode laser activation, and group 3: bleaching with 35% HP gel with Er,Cr:YSGG laser activation. Color changes (ΔE*) were calculated by using two different formulas: (i) CIELAB (ΔEab) and (ii) CIEDE2000 (ΔE00) with a spectrophotometer before treatment, 24 h after treatment 3, 6, and 12 months after treatment. Evaluation of postoperative sensitivity was performed before and immediately after treatment, followed by re-evaluation 24 h and 1 week after treatment. Results: For ΔEab calculation, no significant difference was observed during both intra- and inter-group evaluations (p > 0.05). For ΔE00 calculation, no significant intergroup difference was observed (p > 0.05), whereas significant intragroup differences between the values of after treatment, 6-12 months. In the chemical bleaching group, increased postoperative sensitivity was observed after 24 h (p < 0.001). In the diode-laser-activated group, postoperative hypersensitivity was detected at 24 h and 1 week. No significant hypersensitivity was observed in the Er,Cr:YSGG-laser-activated group (p > 0.05). Conclusions: All three techniques provided efficient bleaching. Chemical and diode-activated bleaching methods resulted in slight sensitivity after application, whereas Er,Cr:YSGG-laser-activated bleaching did not cause sensitivity.

Influence of low-level laser therapy on inflammation, collagen fiber maturation, and tertiary dentin deposition in the pulp of bleached teeth.

We evaluated the effects of low-level laser therapy (LLLT) using an infrared laser (IRL) and a red laser (RL) on the pulp of molar teeth in rats after dental bleaching to assess inflammation, collagen fiber maturation, and tertiary dentin formation. Eighty Wistar rats (Rattus norvegicus, albinus) were randomly divided into eight groups with 10 hemimaxillae in each of the following: control; bleached (Ble, 35% hydrogen peroxide [H2O2]); Ble-1IRL and Ble-1RL (one IRL [808nm, 30s, 3J] or RL [660nm, 15s, 1.5J] application immediately after H2O2); Ble-3IRL and Ble-3RL (three [immediately, 24h, and 48h] IRL or RL applications after H2O2); and 3IRL and 3RL (three IRL or RL applications without bleaching). The rats were euthanized after 2 and 30days for histological evaluation of inflammation (hematoxylin-eosin) and maturation of collagen fibers (picrosirius red). Additionally, the dentin deposition in the specimens obtained at 30days was quantified via microtomography of the pulp chamber volume. Statistical analyses were performed (P < 0.05). Initially, severe damages to the pulp were observed in the Ble and Ble-1RL groups. Ble-1IRL and Ble-3RL groups showed lower inflammation. The bleached groups had a greater amount of mature collagen fibers than the control group. The Ble-3IRL group had a greater number of immature fibers than the Ble group. At 30days, there was an absence of inflammation and equal proportion of mature and immature collagen fibers. All bleached groups showed a reduction in the volume of the pulp chamber. Three consecutive applications of RL and one IRL application can minimize damage to the pulp of bleached teeth, whereas three IRL applications can minimize pulp fibrosis. However, LLLT did not prevent deposition of tertiary dentin. This study describes LLLT protocols capable of minimizing inflammation and maturation of collagen fibers in pulp tissue after dental bleaching. However, the protocols proved insufficient for reducing the formation of tertiary dentin in bleached teeth.

Effects of 16% Carbamide Peroxide Bleaching on the Surface Properties of Glazed Glassy Matrix Ceramics.

Objective To determine the influence of the home bleaching agent, Opalescence PF, on the surface roughness and microhardness of glazed glassy matrix CAD-CAM ceramics. Materials and Methods. The 28 sintered leucite- and lithium disilicate-reinforced ceramic specimens (IPS Empress CAD and IPS e.max CAD) were divided into control and bleached groups. The home bleaching agent was applied to specimens of bleached groups for 7 days. The surface roughness and microhardness of all specimens were measured. A scanning electron microscope was used to evaluate the surface properties. The data were statistically analyzed by two-way ANOVA. Results The control e.max CAD showed the lowest surface roughness values. For both Empress and e.max CAD, surface roughness was significantly higher for the bleached group (p < 0.05). No significant differences in microhardness were observed. Conclusions According to our study, patients should be careful when using home bleaching agents because whitening agents can affect the mechanical properties of full ceramic restorations like e.max CAD and Empress CAD. Ceramic polishing may be required in clinical situations where ceramic restorations are accidentally exposed to bleaching gels.

Influence of pain-relieving therapies on inflammation and the expression of proinflammatory neuropeptides after dental bleaching treatment

ObjectivesTo minimize the tooth sensitivity caused by in-office bleaching, many dentists use non-steroidal anti-inflammatory drugs and topical desensitizing gels containing potassium nitrate and sodium fluoride. This study aimed to evaluate the influence of these substances on inflammation and the expression of substance P and calcitonin gene-related peptide in pulp nerve fibers.Materials and MethodsSeventy-two rats were divided into 6 groups as follows: GI, control; GII, only dental bleaching; GIII, only ibuprofen; GIV, ibuprofen administered 30 minutes before and after the bleaching treatment and every 12 hours until the analysis; GV, only topical application of a desensitizing agent; and GVI, topical application of a desensitizing agent before dental bleaching. Placebo gel was applied to the upper left jaw and the bleaching agent was applied to the upper right jaw in all groups. Subsequently, the groups were divided into 3 subgroups based on the time of analysis: 0, 24, and 48 hours after bleaching (n = 8). The rats were euthanized and the maxillae were processed and evaluated by histopathological and immunohistochemical analyses. The data were analyzed using the Kruskal-Wallis test, followed by the Dunn test (p < 0.05).ResultsIn the bleaching groups, the inflammatory process and expression of neuropeptides decreased over time. The animals in which a desensitizing agent was applied showed better results within 24 hours.ConclusionsThe use of a desensitizing agent had positive effects on inflammation and pain-related neuropeptide expression, minimizing the painful effects of dental bleaching treatment.

Improving shear bond strength of metallic brackets after whitening.

ABSTRACTObjective: To evaluate a protocol for bonding metallic brackets after bleaching with hydrogen peroxide (HP). Methods: 60 extracted maxillary premolar were randomly divided into an unbleached control group and two groups bleached with a solution of 35% hydrogen peroxide prior to bonding. The teeth in one of the treated groups were bonded immediately after bleaching; while the other group was treated with 10% sodium ascorbate immediately after bleaching and before bonding. The teeth in all groups were stored in an artificial saliva solution for 7 days after bonding. The shear bond strength data was measured in megapascals (MPa) and the fail attempts were verified. The significance level was established at p< 0.05. Results: The unbleached group, in which brackets were bonded to untreated enamel, had the highest bond strength values (11.0 ± 5.7MPa) in comparison to the bleached group (7.14 ± 40MPa), in which brackets were bonded to recently bleached enamel. Slightly improved bond strength was observed in the antioxidant group (8.13 ± 5.4MPa), in which the teeth were bleached and then the antioxidant was applied to the teeth before bonding. Unbleached and bleached groups showed statistically significant difference for shear bond strength (p=0.03) and load strength (p=0.03); no significant differences were noted between unbleached and antioxidant groups (p=0.52).Conclusion: The antioxidant treatment applied immediately after bleaching was effective in reversing the reduction in shear bond strength of brackets after tooth bleaching.

The effect of in-office bleaching applications on the color and translucency of composite resins

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Labor and birth outcomes in term low-risk adolescent pregnancies

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Influence of light and laser activation of tooth bleaching systems on enamel microhardness and surface roughness.

Objective:The objective of this study was to compare the effects of light and laser activation of in-office tooth bleaching systems on enamel microhardness and surface roughness.Materials and Methods:Twenty-five enamel slabs were divided into three treatment groups: light-activated bleaching, laser-activated bleaching, and control. The baseline data were recorded for enamel microhardness (Vickers microhardness [VMH]) and surface roughness (Roughness average, Ra). The specimens were cured for 10 min upon hydrogen peroxide application for the light-activated bleaching group and activated with a laser source, 8 cycles, 10 s per cycle for the laser-activated group. The changes in VMH and Ra at days 1, 7, and 28 were evaluated. Kruskal–Wallis, Friedman, Wilcoxon, and Mann–Whitney tests were used to analyze both VMH and Ra between the treatment groups at different time intervals.Results:There were a significant reduction in VMH values and significant differences between days 1, 7, and 28 against the baseline in the light-activated bleaching group (P = 0.001). The Ra values revealed significant differences in both light- (P = 0.001) and laser-activated (P = 0.033) groups.Conclusion:Light activation of a bleaching agent caused a reduction in enamel microhardness and an increase in surface roughness when compared to laser activation.

Comparison of the effect of bleaching with 15% carbamide peroxide and 35% hydrogen peroxide on flexural strength of Cention N in selfcured and dual-cured polymerization modes.

Background. The use of bleaching agents might result in microstructural changes in tooth structure and in restorative materials. This study compared the effects of bleaching with %15 carbamide peroxide and %35 hydrogen peroxide on the flexural strength of Cention N restorative material using the self-cured and dual-cured polymerization modes. Methods. Sixty bar-shaped samples of Cention N restorative material were included in this in vitro study and assigned to three groups (n=20) randomly: control, bleaching with %15 carbamide peroxide and bleaching with %35 hydrogen peroxide. Each group was divided into two subgroups: samples polymerized in the self-cured mode and samples polymerized in the dual-cured mode. Then the flexurals trengths of the samples were determined. Two-way ANOVA was used to compare flexural strengths between the three groups in two polymerization modes, followed by post hoc Tukey test. Statisticals ignificance was defined at P<0.05. Results. The difference in the mean flexural strength was significant in terms of the bleaching regimen (P<0.001), with significantly lower flexural strength in the two bleaching groups compared to the control group. However, the mean flexural strengths were not significantly different in terms of the polymerization mode applied (P=0.14). Conclusion. The application of %15 carbamide peroxide and %35 hydrogen peroxide bleaching agents decreased the flexural strength of Cention N restorative material. Irrespective of the bleaching regimen, there was no significant difference in the flexural strength of Cention N between the self-curing and dual-curing polymerization modes.

Changes in Optical Characteristics and Surface Topography of CAD/CAM Materials after Bleaching Applications: An AFM Evaluation.

To evaluate the effect of in-office and at-home bleaching agents on color changes (ΔE00 ), translucency (TP00 ), whiteness (WID ), surface roughness (Ra ), and surface topography (Rsk and Rku ) of a resin nano-ceramic and a polymer-infiltrated ceramic network CAD/CAM material. Sixty specimens (6 mm × 7 mm × 1.3 mm) were prepared from Lava Ultimate (LU) and Vita Enamic (VE). The specimens were divided into 6 groups according to the bleaching agents applied (n = 10/group): control, Perfect Bleach Office + (PBO), Opalescence Boost (OB), Perfect Bleach (PB) with 10% and 16% carbamide peroxide and Whiteness Perfect (WP). ΔE00 values were calculated before and after bleaching procedures with a spectrophotometer using the CIEDE2000 formula. ΔTP00 and ΔWID values were calculated for each material. Ra , Rsk , and Rku values of the specimens were evaluated with an Atomic Force Microscope. Two-way ANOVA was used for statistical analyses of the parameters measured after bleaching. For pairwise comparisons, Tukey test was performed. For LU, no statistically significant difference among the ΔE00 values of the groups was observed (p = 1.000). For VE, only WP group presented significantly higher values (2.12 ± 2.66) than the other groups (p < 0.001). For both materials; ΔTP00 values of at-home bleaching groups were significantly higher than in-office bleaching groups and control group (p < 0.001). For VE, ΔWID values did not demonstrate statistically significant difference (p = 1.000); however, for LU, PBO applied group showed statistically higher ΔWID values (3.00 ± 2.38) (p = 0.010) and WP applied group showed lower ΔWID values (0.47 ± 0.31) than the other groups (p = 0.030). For both LU and VE, there was no statistically significant difference among the groups regarding Ra (F = 4.544), Rsk (F = 2.369), and Rku values (F = 2.391) (p = 1.000). All of the VE groups presented Ra values higher than 0.2 µm. The optical properties of LU and VE after bleaching applications were affected by the contact time with bleaching agents rather than concentration. Bleaching procedure had no effect on the surface properties of these materials.

Bleaching gel mixed with MI Paste Plus reduces penetration of H2O2 and damage to pulp tissue and maintains bleaching effectiveness.

MI Paste Plus remineralizer (Rem) strengthens dental structures after bleaching. We investigated the effect of Rem on the penetration of hydrogen peroxide (H2O2), bleaching effectiveness, and pulp inflammation after bleaching. Bovine disks were grouped as follows (n = 10): control (untreated), bleached (Ble; 35% H2O2, 30min), Ble-Rem (H2O2 followed by Rem, 30min), Rem-Ble (Rem followed by H2O2), Rem-Ble-Rem (Rem before and after H2O2), and Ble+Rem (mixture of Rem with H2O2, 1:1, 30min). The penetration of H2O2 was quantified and bleaching efficacy was analyzed. Upper rat molars (n = 10) received the same treatments at random. The rats were euthanized after twodays and 30days, and their jaws were removed for histological analysis. Statistical tests were performed (P < 0.05). The bleached groups, except Ble+Rem (P > 0.05), showed significant H2O2 penetration compared with control (P < 0.05). Color alteration analysis showed that ΔL and ΔE were significantly higher in the bleached groups than those in control (P < 0.05); the Δb of the bleached groups differed from that of control at 24h (P < 0.05). At twodays, necrosis or inflammation was observed in the bleached groups compared with control (P < 0.05), except Ble+Rem, which was similar to control (P > 0.05). At 30days, tertiary dentin formation was significant in the bleached groups (P < 0.05), except Ble+Rem (P > 0.05). The mixture of MI Paste Plus and bleaching gel reduces H2O2 penetration and pulp damage and maintains bleaching effectiveness. Because bleaching can damage dental tissues, we studied a new bleaching protocol that reduces damage to the pulp tissue while maintaining bleaching efficiency: a single application of 30min of MI Paste Plus mixed with 35% H2O2 bleaching gel (1:1).