Effect of whitening products on sound enamel and on artificial caries lesions during a cariogenic challenge.

OBJECTIVE: To investigate the effect of fluoride-containing whitening products on sound enamel and on artificial caries lesions during a cariogenic challenge. MATERIALS AND METHODS: Bovine enamel specimens (n = 120) with three areas [non-treated sound enamel (NSE), treated sound enamel (TSE), and treated artificial caries lesion (TACL)] were randomly assigned to the four groups: whitening mouthrinse (WM: 2.5% hydrogen peroxide-100 ppm F-), placebo mouthrinse (PM: 0% hydrogen peroxide-100 ppm F-), whitening gel (WG: 10% carbamide peroxide-1130 ppm F-), and deionized water (negative control; NC). The treatments (2 min for WM, PM, and NC, and 2 h for WG) were carried out during a 28-day pH-cycling model (6 × 60 min demineralization/day). Relative surface reflection intensity (rSRI) and transversal microradiography (TMR) analyses were performed. Fluoride uptake (surface and subsurface) was measured in additional enamel specimens. RESULTS: For TSE, a higher value of rSRI was observed in WM (89.99% ± 6.94), and a greater decrease in rSRI was observed for WG and NC, and no sign of mineral loss was verified for all groups (p > 0.05). For TACL, rSRI significantly decreased after pH-cycling for all experimental groups with no difference between them (p < 0.05). Higher amounts of fluoride were found in WG. WG and WM exhibited intermediate values of mineral loss, similar to PM. CONCLUSIONS: The whitening products did not potentialize the enamel demineralization under a severe cariogenic challenge, and they did not exacerbate mineral loss of the artificial caries lesions. CLINICAL RELEVANCE: Low concentrated hydrogen peroxide whitening gel and mouthrinse containing fluoride do not intensify the progression of caries lesions.

Optical Property Stability of Light-Cured versus Precured CAD-CAM Composites.

Objective: The aim of this study was to evaluate the optical property changes after staining of precured (PC) and light-cured (LC) composites. Materials and Methods: Specimens were prepared using different LC composites (GrandioSO-Voco, Filtek Z350-3M/ESPE, Opallis-FGM, and Kalore-GC) and four PC blocks (Grandio Blocs-Voco, Lava Ultimate-3M ESPE, Brava Block-FGM, and Cerasmart-GC) from the same manufacturers (n = 20). Baseline color, gloss, translucency, and fluorescence were evaluated. The staining protocol was performed for 15 days, and the final optical properties were reevaluated. Results: The changes in each property were calculated (ΔGloss, ΔTranslucency, ΔFluorescency, ΔE ∗ 00). Data were analyzed by ANOVA and Tukey's test (α = 5%). Changes in all properties were observed after staining for all materials, with darkening and reduction of gloss, fluorescence, and translucency. Nonsignificant differences were observed between the light-cured and precured materials of the same manufacturer for ΔG and ΔT, but significant differences existed for ΔF and ΔE ∗ 00. For ΔF, the only significant differences were observed between Brava Block and Opallis (smaller). For ΔE ∗ 00, only the light-cured composites GrandioSO and Z350 showed significantly less change than the corresponding blocks. Precured composites were affected the same way as light-cured ones by the staining in relation to the reduction of gloss and translucency. Conclusion: A higher reduction in fluorescence was observed for only one brand of block and was similar for the others. The two brands of light-cured materials showed less staining, while for the others, the staining was similar. The effects of staining vary according to the composite formulation.

Glass Ionomer Versus Self-adhesive Cement and the Clinical Performance of Zirconia Coping/Press-on Porcelain Crowns.

OBJECTIVE: This split-mouth clinical study investigated the effect of luting cement on the performance of veneered yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia crowns. METHODS AND MATERIALS: A total of 60 crowns prepared with Y-TZP coping and press-on porcelain were made with a split-mouth design in 30 participants. The crowns were cemented either with glass ionomer cement (GIC) (Meron, Voco) or with self-adhesive resin cement (Bifix-SE, Voco). The restorations were assessed immediately after treatment and after 6, 12, 24, 36, and 48 months using the modified United States Public Health Service criteria. The parameters analyzed were retention, color stability, marginal discoloration, marginal adaptation, surface roughness, anatomic form, and secondary caries. The differences between the groups were analyzed by the Fisher exact test in each period of evaluation. The survival rate was analyzed with the Kaplan-Meier and log-rank test (α=0.05). RESULTS: After 48 months, 20 participants attended the recall. During the period of evaluation, 1 crown cemented with glass ionomer cement and 1 crown cemented with resin cement lost retention. Color match, marginal discoloration and adaptation, surface roughness, and anatomic form did not change in any of the periods evaluated, and no secondary caries was observed. No significant differences were found between the 2 luting cements for any of the clinical parameters analyzed, nor for the survival rates during the study. CONCLUSIONS: The type of cement did not influence the performance of the crowns after 48 months of clinical use. Both cements resulted in adequate retention rates, aesthetic and functional outcomes, and biological response.

Efficacy and Safety of Bleaching Gels According to Application Protocol.

OBJECTIVES: This study evaluated bleaching efficacy, enamel microhardness, and roughness of highly concentrated hydrogen peroxide (HP) gels (35%-40%) using different application protocols. Gel decomposition and pH alteration were also analyzed. METHODS AND MATERIALS: Bovine enamel/dentin specimens were divided into groups according to the bleaching gel-Pola Office Plus (POP-SDI, 37.5% HP), Opalescence Boost (OPB-Ultradent, 40% HP), Whiteness HP (WHP-FGM, 35% HP)-and application protocol-single application (SA) and multiple application (MA) during the in-office session. Deionized water was used in control group (no bleaching). Thus, seven final groups were obtained (n=15/group). Color (CIE L*a*b*), surface microhardness (SMH), and roughness (Ra) were assessed before/after treatments. The pH of gels was measured, and HP concentration was determined with potassium permanganate titration method in different times. Data were submitted to analysis of variance and Tukey tests (5%). RESULTS: All gels presented similar and clinically acceptable bleaching efficacy (ΔE>2.7) for both SA and MA, as well as no significant differences for SMH and Ra comparing the two protocols in the same gel. Peroxide decomposition significantly increased with time, but final gel concentrations were still high after 45 minutes (32.29% POP; 38.45% OPB; and 32.74% WHP). The pH decreased over time (initial - after 45 min) for WHP (6.83±0.07 - 5.81±0.06), but minimal alterations were observed for POP (8.09±0.09 - 7.88±0.07) and OPB (7.82±0.11 - 7.87±0.07). CONCLUSIONS: Peroxide decomposition was very low for all gels tested, and pH remained stable for POP and OPB gels. Bleaching protocol did not influence whitening efficacy and hazardous effects over enamel, thus potentially there was no clinical significance. Therefore, for the products tested, there is no evidence for recommending the gel change during the bleaching session.

Assessment of Peroxide in Saliva During and After At-home Bleaching With 10% Carbamide and Hydrogen Peroxide Gels: A Clinical Crossover Trial.

CLINICAL RELEVANCE: This study suggests that at-home bleaching systems are safe in relation to toxicity based on peroxide levels in saliva since the amount of peroxide potentially ingested is much lower than the estimated toxic dose.

Pure Ormocer vs Methacrylate Composites on Posterior Teeth: A Double-blinded Randomized Clinical Trial.

CLINICAL RELEVANCE: The clinical behavior of pure ormocer composite is reliable when used in class II restorations after 24 months of evaluation.

Bioactive Materials Subjected to Erosion/Abrasion and Their Influence on Dental Tissues.

OBJECTIVE: The objective of this study was to evaluate the effect of erosion or erosion-abrasion on bioactive materials and adjacent enamel/dentin areas. METHODS AND MATERIALS: Enamel and dentin blocks (4×4×2 mm) were embedded side by side in acrylic resin, and a standardized cavity (1.2×4×1.5 mm) was prepared between them. Preparations were restored with the following materials: composite resin (Filtek Z350, control); experimental composite containing di-calcium phosphate dihydrate particles (DCPD); Giomer (Beautifil II), high viscosity glass ionomer cement (GIC, Fuji IX); and a resin-modified GIC (Fuji II LC). The specimens were submitted to two cycling models (n=10): erosion or erosion-abrasion. The challenges consisted of five-minute immersion in 0.3% citric acid solution, followed by 60-minute exposure to artificial saliva. Toothbrushing was carried out twice daily, 30 minutes after the first and last exposures to acid. Dental and material surface loss (SL, in µm) were determined by optical profilometry. Data were analyzed with Kruskal-Wallis and Dunn tests (α=0.05). RESULTS: Under erosion, for enamel, only the GIC groups presented lower SL values than Z350 (p<0.001 for Fuji IX and p=0.018 for Fuji II LC). For dentin, none of the materials showed significantly lower SL values than Z350 (p>0.05). For material, the GICs had significantly higher SL values than those of Z350 (p<0.001 for Fuji IX and p=0.002 for Fuji II LC). Under erosion-abrasion, the enamel SL value was significantly lower around Fuji II LC compared with the other materials (p<0.05). No significant differences were observed among groups for dentin SL (p=0.063). The GICs and Giomer showed higher SL values than Z350 (p<0.001 for the GICs and p=0.041 for Giomer). CONCLUSION: Both GIC-based materials were susceptible to erosive wear; however, they promoted the lowest erosive loss of adjacent enamel. Against erosion-abrasion, only Fuji II LC was able to reduce enamel loss. For dentin, none of the materials exhibited a significant protective effect.

Do Tooth- and Cavity-related Aspects of Noncarious Cervical Lesions Affect the Retention of Resin Composite Restorations in Adults? A Systematic Review and Meta-analysis.

PURPOSE: The purpose was to perform a systematic review and meta-analysis based on the following research question: do tooth- and cavity-related aspects of noncarious cervical lesions (NCCLs) affect the retention of composite restorations? METHODS: Randomized clinical trials (RCTs) that evaluated the retention rate of resin restorations in NCCLs were included for the identification and comparison of their characteristics. The search was conducted in PubMed and adapted for Scopus, Web of Science, Latin American and Caribbean Health Sciences Literature database (LILACS), Brazilian Library in Dentistry (BBO), Cochrane Library, and System for Information on Grey Literature in Europe (SIGLE) without restrictions until July 2018. Unpublished and ongoing trial registries were also searched. The Cochrane Collaboration tool was used for assessing risk of bias. The quality of the evidence was graded using the Grading of Recommendations: Assessment, Development and Evaluation. Using the random effects model, a meta-analysis was conducted for each aspect (arch distribution, tooth location, wear facets, dentin sclerosis, shape, size, depth, occluso-gingival distance, and margin location). RESULTS: We retrieved 6738 articles. After removal of duplicates and nonrelevant articles, 24 RCTs remained. The anterior tooth location favored the retention rates of restoration of NCCLs (relative risk [RR], 1.08; 95% confidence interval [CI], 1.00-1.16). The presence of wear facets is a risk factor for the retention of restorations (RR, 0.91; 95% CI, 0.83-0.99). The evidence was moderate for arch distribution and low or very low for all other factors because of heterogeneity, imprecision, and inconsistency. CONCLUSION: The tooth location and the presence of wear facets can affect the retention of composite resins in NCCLs.

Effect of Calcium and Fluoride Addition to Hydrogen Peroxide Bleaching Gel On Tooth Diffusion, Color, and Microhardness.

OBJECTIVES: The aim of this study was to evaluate the effect of calcium and fluoride addition to a 35% hydrogen peroxide (HP) bleaching gel with regard to its diffusion through the tooth structure, enamel microhardness, and bleaching efficacy. METHODS AND MATERIALS: Eighty specimens (6 mm in diameter and 2 mm in height; 1 mm/enamel and 1 mm/dentin) were obtained from bovine incisors that were polished and divided into four groups (n=20) according to the remineralizing agent added to the gel: Ca = 0.5% calcium gluconate; F = 0.2% sodium fluoride; Ca+F = 0.5% calcium gluconate and 0.2% sodium fluoride; and control = no agent. Initial microhardness and color were assessed. The samples were positioned over simulated pulpal chambers filled with acetate buffer solution to capture the HP. Gels were applied over enamel for 30 minutes, and HP diffusion was assessed by spectrophotometry two hours after bleaching. Microhardness was measured immediately after bleaching and then the specimens were immersed into artificial saliva for seven days for final color assessment. Data were analyzed by one-way analysis of variance followed by Tukey test. RESULTS: Bleaching reduced microhardness for all groups (p=0.0001), but the Ca+F and F groups showed lower reductions after bleaching. The addition of Ca, F, and Ca+F decreased the peroxide penetration through the tooth structure (p=0.0001), but there were no differences in color change for ΔL (p=0.357), Δa (p=0.061), Δb (p=0.823), and ΔE (p=0.581). CONCLUSION: The addition of calcium and fluoride in the gel did not affect bleaching efficacy, but it was able to reduce both the peroxide diffusion and the bleached enamel microhardness loss.

Effect of Remineralizing Gels on Microhardness, Color and Wear Susceptibility of Bleached Enamel.

OBJECTIVES:: To evaluate the effect of a remineralizing gel combining fluoride and calcium silicate/phosphate or a sodium fluoride gel on bleached enamel microhardness, color, and wear susceptibility. METHODS AND MATERIALS:: Two hundred forty bovine enamel-dentin samples were prepared. Baseline analysis of Knoop microhardness, color coordinates (L*a*b*), and surface profile were performed. According to the baseline microhardness values, specimens were stratified into six groups (n=40): NC (negative control)-no treatment; BL (positive control)-bleaching with 40% hydrogen peroxide gel (Opalescence Boost, Ultradent); BL/Rs-bleaching + application of calcium silicate/phosphate gel (Regenerate Serum, Unilever - Rs); Rs/BL-Rs + bleaching; Rs/BL/Rs-Rs + bleaching + Rs; and BL/F-bleaching + 2% sodium fluoride gel. After the treatment described for each group, color change (ΔE) and microhardness were evaluated again. To evaluate abrasion susceptibility, samples were randomly divided into two subgroups, according to the toothpaste used (Cp-Close Up or Rt-Regenerate), and underwent 100,000 brushing strokes. The profile of each sample was evaluated and the mean wear calculated. The data were analyzed by ANOVA and Tukey tests. RESULTS:: All bleached groups showed a significant reduction of microhardness in relation to the negative control. The groups treated with remineralizing gels showed a significantly higher microhardness and less wear than the positive control, although nonsignificant differences were observed among them. Nonsignificant differences in ΔE were found among bleached groups. The groups brushed with Regenerate toothpaste showed significantly less wear than those brushed with Close Up toothpaste. CONCLUSIONS:: The remineralizing gels did not interfere with bleaching efficacy. However, all the treatments minimized the surface hardness reduction caused by the bleaching procedure and enamel loss after abrasion. Regenerate toothpaste resulted in less enamel abrasion.

Bond Stability of a Universal Adhesive System to Eroded/Abraded Dentin After Deproteinization.

OBJECTIVE: Erosive/abrasive challenges can potentially compromise bonding to dentin. Aiming to improve the quality and stability of bonding to this substrate, this study investigated the combined effect of erosion and toothbrush abrasion on the microtensile bond strength (µTBS) stability to dentin using a universal adhesive system in total and self-etching modes, associated or not associated with deproteinization. METHODS: Bovine dentin specimens were divided into five groups according to the organic matrix condition (n=20): control (C); erosion (E); erosion + abrasion (EA); erosion + sodium hypochlorite (EH); erosion + abrasion + sodium hypochlorite (EAH). The groups were further divided (n=10) according to the mode of application (total or self-etching) of a universal adhesive. After the bonding procedure, composite blocks were built up, and the samples were cut to obtain sticks for µTBS testing. For each specimen, one-half of the sticks was immediately tested, and the other one-half was tested after artificial aging (5000 thermocycles, 5°C and 55°C). RESULTS: Three-way analysis of variance (α=5%) showed a significant difference for the triple interaction ( p=0.0007). Higher µTBS means were obtained for the EH and EAH groups compared with the E and EA groups. The control group showed immediate µTBS values similar to that of the E and EA groups for both bond strategies. CONCLUSIONS: Erosion and erosion/abrasion did not significantly influence the immediate µTBS to dentin. Artificial aging reduced µTBS values for the groups C, E, and EA using the total-etching mode. Deproteinization maintained the bond stability to artificially aged eroded and eroded/abraded dentin.

Nd:YAG laser irradiation associated with fluoridated gels containing photo absorbers in the prevention of enamel erosion.

This study evaluated the combined effect of Nd:YAG laser irradiation and fluoridated gels containing photo absorbers against enamel erosion. Enamel specimens from bovine teeth were polished, eroded (10 min, with 1% citric acid, pH = 2.6), and randomly allocated into the experimental groups (n = 8), according to the different surface treatments: fluoridated gels (F: 9047 ppm F and F + Sn: 9047 ppm F and 3000 ppm Sn), with or without photo absorbers (E: erythrosine and MB: methylene blue), and associated or not with Nd:YAG laser irradiation (in contact; 0.5 W; 50 mJ; ~41.66 J/cm2; 10 Hz; 40 s; pulse duration of 120 µs). A placebo gel (PLA) associated or not with laser was used as control. All gels had pH = 4.5 and were applied for 2 min. Laser irradiation was performed during gel application. The specimens were then submitted to a 5-day erosion-remineralization cycling model using 0.3% citric acid (pH = 2.6), 4×/day. Enamel surface loss (SL) was analyzed by optical profilometry in the end of the cycling (in µm). Data were analyzed by ANOVA and Tukey tests (α = 0.05). Means (SD) of SL for the groups were the following (different superscript letters imply significant difference among groups): PLA (21.02 ± 1.28)a, PLA + laser (19.20 ± 0.96)ab, laser (17.47 ± 1.50)b, F + Sn + E + laser (13.69 ± 0.62)c, F + E + laser (13.52 ± 1.16)c, F (13.10 ± 1.08)c, F + laser (11.94 ± 1.44)cd, F + Sn + MB + laser (11.90 ± 4.02)cd, F + MB + laser (11.42 ± 1.42)cd, F + Sn (11.12 ± 1.20)cd, and F + Sn + laser (10.35 ± 0.89)d. In conclusion, all fluoridated gels and the Nd:YAG laser irradiation reduced erosion development, but the combination of treatments did not promote further protection. The addition of photo absorbers to the fluoridated gels did not influence the anti-erosive effect of the combination of laser plus fluoridated gels.

Microleakage and Shear Bond Strength of Composite Restorations Under Cycling Conditions.

OBJECTIVES: The aim of this study was to evaluate microleakage and shear bond strength of composite restorations under different cycling conditions. METHODS AND MATERIALS: Class V cavities were prepared in the buccal and lingual surfaces of 30 human molars (n=60). A further 60 molars were used to prepare flat enamel and dentin specimens (n=60 each). Cavities and specimens were divided into six groups and pretreated with an adhesive (self-etch/Clearfil SE Bond or etch-and-rinse/Optibond FL). Composite was inserted in the cavities or adhered to the specimens' surfaces, respectively, and submitted to cycling (control: no cycling; thermal cycling: 10,000 cycles, 5°C to 55°C; thermal/erosive cycling: thermal cycling plus storage in hydrochloric acid pH 2.1, 5 minutes, 6×/day, 8 days). Microleakage was quantified by stereomicroscopy in enamel and dentin margins after immersion in silver nitrate. Specimens were submitted to shear bond strength testing. Statistical analysis was done by two-way analysis of variance and Kruskal-Wallis tests (p<0.05). RESULTS: Microleakage in enamel margins was significantly lower in the control group compared with thermal cycling or thermal/erosive cycling. Erosive conditions increased microleakage compared with thermal cycling (significant only for Clearfil SE Bond). No significant differences were observed in dentin margins. Bond strength of enamel specimens was reduced by thermal cycling and thermal/erosive cycling when Clearfil SE Bond was used and only by thermal/erosive cycling when Optibond FL was used. No differences were observed among dentin specimens. CONCLUSIONS: Thermal/erosive cycling can adversely affect microleakage and shear bond strength of composite resin bonded to enamel.

Is resin infiltration an effective esthetic treatment for enamel development defects and white spot lesions? A systematic review.

OBJECTIVES: To determine if resin infiltration is an effective treatment for improving the esthetic appearance of tooth discoloration resulting from development defects of enamel (EDD) and white spot lesions (WSL) by means of a systematic review. DATA SOURCES: A comprehensive search was performed in PubMed, Scopus, Web of Science, LILACS, BBO Library, Cochrane Library, and SIGLE, as well as in the abstracts of IADR conference, and in the clinical trials registry. STUDY SELECTION: Clinical studies in patients with whitish tooth discoloration, in which the resin infiltration technique was applied, were included. Color masking was the primary outcome. The methodological quality and risk of biases of included papers was assessed using MINORS criteria for non-randomized (NRS) comparative studies and Cochrane Collaboration for randomized clinical trials (RCT). RESULTS: From a total of 2930 articles, 17 were assessed for eligibility and 11 remained in the qualitative synthesis. Four NRS and seven RCT studies were selected, the latter consisting of four full-text studies and three conference abstracts. Two studies were excluded from the quality assessment, due to overlapping results. The number of participants (treated teeth) ranged from 18 to 21 (38-74) in the NRS, and 20-83 (20-231) in the RCT studies. Post-orthodontic WSL were the most frequent treated lesions. Initial condition was used as control in the NR studies. In the RCT, resin infiltration was compared to non treatment, remineralization, or bleaching. Overall, partial or complete color masking of affected teeth was reported immediately after resin infiltration. Only two studies followed original outcomes up to one year and reported maintenance of original color masking. Two NR studies were assessed as "moderate" and one as "high" quality. Two RCT were classified as "low" risk of bias in the chosen key domains. The remaining four studies were considered "unclear" or "high" risk of bias. CONCLUSION: Although the partial or total masking effect of enamel whitish discoloration has been shown with resin infiltration, there is no strong evidence to support this technique based on the present clinical studies. CLINICAL SIGNIFICANCE: Enamel whitish discolorations in esthetically compromised areas are clinically undesirable. Minimally invasive approaches used as attempts to minimize the discoloration include the resin infiltration technique. The evidence for clinical recommendation of this technique is not strong, thus, further RCT studies with long-term follow-ups should be conducted.

Toothbrushing abrasion susceptibility of enamel and dentin bleached with calcium-supplemented hydrogen peroxide gel.

UNLABELLED: The objective of this study was to evaluate enamel and dentin susceptibility to toothbrushing abrasion, after bleaching with 7.5% hydrogen peroxide (HP) gel supplemented or not with 0.5% calcium gluconate (Ca). Toothbrushing was performed immediately and 1h after bleaching, with two suspensions (high and low abrasivity). Bovine enamel and dentin specimens were divided into 12 groups (n=10) according to the bleaching gel (with and without Ca), slurry abrasivity (high or low) and elapsed time after bleaching (immediately and after 1h). As control, a group was not bleached, but abraded. The treatment cycle (7 d) consisted of bleaching (1h) and toothbrushing (135 strokes/day) immediatelly or after 1h of artificial saliva exposure. Surface roughness and surface loss (µm) were measured by profilometry and analysed by three-way ANOVA (5%). Surface roughness means were significantly influenced by slurry abrasivity (p<0.0001). For enamel loss, significant triple interaction was observed (p<0.0001). HP-bleached groups and immediately brushed with high-abrasive slurry exhibited increased loss (1.41±0.14) compared to other groups (µm). Control and HP+Ca-bleached groups brushed after 1h with low abrasive slurry presented the lowest loss (0.21±0.03/0.27±0.02). For dentin loss, significant interaction was observed for bleaching and interval factors (p<0.001). 7.5%HP-bleached groups and immediately brushed showed significantly higher loss (8.71±2.45) than the other groups. It was concluded that surface roughness increased when high abrasive was used, independently of bleaching. 7.5%HP increased enamel and dentin loss, mainly with high abrasive slurries. Calcium supplementation of bleaching gel reduced surface loss. Additionally, in order to minimize tooth wear susceptibility, it is recommended to delay brushing after bleaching. CLINICAL RELEVANCE: After bleaching gel application, postponing toothbrushing is recommended, as well as brushing with low abrasive dentifrices. Additionally, supplementation of hydrogen peroxide gel with calcium-based remineralizing agent potentially reduces tooth loss after abrasion.

Longitudinal Evaluation of Bond Strength to Enamel of Dental Adhesive Systems Associated with Nd:YAG Laser.

OBJECTIVES: This study evaluated the durability of bond strength to enamel using total-etch (Single Bond/SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with neodymium:yttrium-aluminu-garnet (Nd:YAG) laser irradiation through the uncured adhesives. METHODS: Bovine incisors were worn to expose an area of enamel and were divided into four groups: group 1 (control) SB + polymerization; group 2 (control) CSEB + polymerization; group 3 (laser) - SB + Nd:YAG laser (174.16 J/cm(2)) + polymerization; and group 4 (laser) CSEB + Nd:YAG (174.16 J/cm(2)) + polymerization. Blocks of composite were fabricated and stored for 24 hours or 12 months, sectioned into beams, and submitted to microtensile tests. Results were analyzed by three-way analysis of variance (ANOVA) (adhesive, technique, and storage time) and Tukey tests. RESULTS: ANOVA revealed significant differences for adhesive × technique and technique × storage time (p<0.05). The mean values (MPa) for interaction adhesive × technique (standard deviation) were as follows: SB/control = 35.78 (6.04)a; SB/laser = 26.40 (7.25)b, CSEB/control = 26.32 (5.71)b, CSEB/laser = 23.90 (7.49)b. For interaction technique × storage time the mean values were as follows: control/24 hours = 32.58 (6.49)a; control/12 months = 29.52 (8.38)a; laser/24 hours = 29.37 (5.71)a; laser/12 months = 20.92 (6.5)b. Groups with the same letters showed no statistically significant differences. CONCLUSION: Scanning electron microscope analysis showed evident areas of micromorphological alterations in lased samples after 12 months of water storage. Nd:YAG laser irradiation of enamel through unpolymerized total-etch adhesive significantly reduced bond strength compared with the control. Bond strength decreased when enamel samples irradiated with Nd:YAG laser through unpolymerized adhesives were stored in water for 12 months.

Effect of hydrogen peroxide concentration on enamel color and microhardness.

OBJECTIVES: The aim of this study was to investigate the effect of hydrogen peroxide gels with different concentrations (20%, 25%, 30%, and 35%) on enamel Knoop microhardness (KNH) as well as on changes in dental color (C). METHODS: Cylindrical specimens of enamel/dentin (3-mm diameter and 2-mm thickness) were obtained from bovine incisors and randomly divided into six groups (n=20), according to the concentration of the whitening gel (20%, 25%, 30%, 35%, control, thickener). After polishing, initial values of KNH0 and color measurement, assessed by spectrophotometry using the CIE L*a*b* system, were taken from the enamel surface. The gels were applied on the enamel surface for 30 minutes, and immediate values of KNHi were taken. After seven days of being stored in artificial saliva, new measures of KNH7 and color (L7* a7* b7*, for calculating ΔE, ΔL, and Δb) were made. Data were submitted to statistical analysis of variance, followed by Tukey test (p<0.05). RESULTS: Differences in gel concentration and time did not influence the microhardness (p=0.54 and p=0.29, respectively). In relation to color changes, ΔE data showed that the 35% gel presented a higher color alteration than the 20% gel did (p=0.006). CONCLUSION: Bleaching with 35% hydrogen peroxide gel was more effective than with the 20% gel, without promoting significant adverse effects on enamel surface microhardness.

Color masking of developmental enamel defects: a case series.

Developmental defects involving color alteration of enamel frequently compromise the esthetic appearance of the tooth. The resin infiltration technique represents an alternative treatment for color masking of these lesions and uniformization of tooth color. This technique is considered relatively simple and microinvasive, since only a minimal portion of enamel is removed. This article illustrates the color-masking effect with resin infiltration of fluorosis and traumatic hypomineralization lesions with a case series. The final esthetic outcomes demonstrated the ability of the resin infiltrant to mask the color of white developmental defect lesions, resulting in satisfactory clinical esthetic improvements. However, in more severe cases, the color-masking effect was not complete.

Influence of pH on the effectiveness of hydrogen peroxide whitening.

OBJECTIVE: To evaluate the influence of pH on the bleaching effect of hydrogen peroxide on chromogen agents. METHOD: Hydrogen peroxide 50% was mixed with red wine or with an alcoholic solution of tobacco in glass cuvettes, resulting in final peroxide concentrations of 16.97% and 21.12%, respectively. The pH of this mixture was measured and adjusted with 3.3 M HCl solution or 2.5 M NaOH solution to obtain the final pH values of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0. After mixing, the color of these solutions was evaluated in a reflectance spectrophotometer; readings were repeated after 10 minutes for the wine solution and 20 minutes for the tobacco solution. Ten samples were prepared for each solution at each pH. Color changes (Delta E) were calculated. The data were statistically analyzed using analysis of variance one-way and Tukey tests, with a significance level of 5%. RESULTS: There were significant differences among the different pH values for the wine and tobacco solutions (p=0.0001). The Tukey test showed that for both solutions, pH 9.0 resulted in a significantly greater bleaching effect than the other values tested. CONCLUSION: The efficacy of hydrogen peroxide bleaching is directly proportional to the increase in its pH.