Chemical behavior of 20%-22% carbamide peroxide gels in at-home bleaching: Randomized crossover in situ trial.

OBJECTIVE: To evaluate if distinct 20%-22% carbamide peroxide bleaching gels present similar decomposition pattern and pH during the clinical use in both arches, as well as gels viscosity. METHODS: Participants randomly received treatments with carbamide peroxide gels (n = 10): OPF (OpalescencePF-20%); PNT (Polanight-22%); and WPC (Whiteness Perfect-22%) in three different days, with 2-day washout. Decomposition pattern was assessed by peroxide concentration. Both PC and pH of bleaching gels were measured in different time points in upper and lower trays during a total of 120 min of clinical use. Viscosity of bleaching gels was measured in triplicate. ANOVA and Tukey's test were applied (α = 0.05). RESULTS: Regarding decomposition pattern, no significant differences were observed for the interaction between gel, time, and tray position factors. The peroxide concentration progressively reduced until 120 min of trays use (p < 0.001), being overall more notable in lower trays (p < 0.001). Regarding pH, the lowest values were verified in WPC within time. At 120 min, an increase of pH was observed for both WPC and OPF (p < 0.001) compared to baseline means. PNT exhibited constant pH values over time. The values of viscosity were: OPF (1.682.000 ± 19 cP)a, WPC (1.388.667 ± 172.63 cP)ab, PNT (579.567 ± 0.98 cP)b. CONCLUSIONS: The bleaching gels presented overall decomposition pattern clinically equivalent, being more notable in lower trays over time. Nevertheless, distinct pH and viscosities were observed among the products. CLINICAL SIGNIFICANCE: Although the manufacturers recommend different times of use for bleaching gels with similar peroxide concentrations, the commercial products tested did not exhibit clinically relevant difference in the decomposition pattern during the 120 min of clinical procedure.

Viscosity modulation of resin composites versus hand application on internal adaptation of restorations.

OBJECTIVE: To compare the effect of the injection of viscosity modulated resin composites versus hand application without modulation, on the internal adaptation of different material to the gingival wall of class II preparations. MATERIALS AND METHODS: Class II cavities were created on mesial and distal surfaces of 60 extracted human molars, resulting on 120 tooth preparations (n = 120). The preparations were restored with four resin composites: VIS-VisCalor (Voco); GRA-GrandioSO (Voco); FIL-Filtek One Bulk Fill (3 M/ESPE); and SON-SonicFill (Kerr). Each composite was applied by two different techniques: by hand (H) or assisted (A). For the hand technique, the material was placed into the preparation using a spatula. For the assisted technique, the resin composite was heated up to 65 °C (for VIS, GRA, and FIL) or sonicated (for SON) and injected into the preparation. After the restorative procedures, the teeth were completely demineralized to allow the restoration removal. The total area of the gingival wall and the area occupied by interfacial defects of adaptation (TDA) were measured by optical microscopy and digital software. The percentage of the area occupied by the defects (%TDA) in relation to the total area was calculated. The data were analyzed by two-way ANOVA and Tukey tests. RESULTS: Significant differences were observed for the application technique (p = 0.0403) and for the materials (p = 0.0184), as well for the interaction between them (p = 0.0452). The mean (standard deviation) of %TDA and results of Tukey test for the interaction were as follows: SON/H - 1.04(0.75)a; VIS/A - 2.01(0.92)a; VIS/H - 3.62(0.99)b; GRA/A - 6.23(3.32)b; FIL/H - 7.45(3.31)bc; GRA/H - 9.21(4.53)c; SON/A - 11.26(4.04)a; FIL/A - 17.89(5.08)d. CONCLUSION: The injection of heated resin composites improves the adaptation to the walls in relation to the hand technique for VisCalor and GrandioSO but worsens for Filtek One. Sonic vibration increases the number of interfacial defects for SonicFill. CLINICAL RELEVANCE: The physical modulation of the resin composite viscosity can improve or worsen the material adaptation to the walls of class II restoration. It had a positive impact for VisCalor and GrandioSO but a negative for Filtek One and SonicFill.

Fracture resistance and stress distribution of weakened teeth reinforced with a bundled glass fiber-reinforced resin post.

OBJECTIVES: To make an in vitro assessment of fracture resistance of weakened and non-weakened teeth receiving intraradicular reinforcement using Rebilda bundled glass fiber-reinforced composite posts (GT), Rebilda conventional glass fiber posts (RP), or both systems combined (GT + RP). MATERIALS AND METHODS: Eighty sound bovine incisors were prepared and divided randomly into eight groups as follows: (a) nWnR: without simulating weakness, and without intraradicular reinforcement; (b) WnR: simulating weakness, but without intraradicular reinforcement; (c) nWGT: without simulating weakness, but with GT; (d) WGT: simulating weakness, and with GT; (e) nWRP: without simulating weakness, but with RP; (f) WRP: simulating weakness, and with RP; (g) nWGTRP: without simulating weakness, but with GT + RP; (h) WGTRP: simulating weakness, and with GT + RP. The specimens were subjected to the load-to-fracture test using the DL-2000MF universal testing machine. The finite element method assessed the mechanical behavior and stress distribution in endodontically treated teeth. RESULTS: The groups nWGTRP and WGTRP presented the best results in the load-to-fracture test, with the former being better than the latter, but with no statistically significant difference (P > 0.05). However, there was a significant difference between these and the other groups (P < 0.05), except for nWRP. Stress distribution inside the canal wall was different among the groups, with promising mechanical behavior for nWGTRP and nWRP. CONCLUSIONS: The Rebilda conventional fiber post (RP), combined with the Rebilda bundled glass fiber-reinforced composite post (GT) improves the resistance and stress distribution of immature teeth. CLINICAL RELEVANCE: Longitudinal fracture is less frequent in teeth restored with GT and RP posts.

Protective Effect of Solutions Containing Polymers Associated with Fluoride and Stannous Chloride on Hydroxyapatite Dissolution.

This study investigated the protective effect of experimental solutions containing 4 polymers (polyoxirane, hydroxypropylmethylcellulose [HPMC], pectin, and an amino methacrylate copolymer [AMC]) in 2 concentrations (low and high) associated or not with sodium fluoride (F; 225 ppm F-) or sodium fluoride plus stannous chloride (FS; 800 ppm Sn2+) on the dissolution of hydroxyapatite crystals (HA). Deionized water was the control. The pretreated HA was added to a 0.3% citric acid solution (pH 3.8). An automatic titrant machine added aliquots of 0.1 N HCl at a rate of 28 µL/min, in a total reaction time of 5 min. Groups were compared with 2-way ANOVA and Tukey's test, and concentrations with Student t test (5%). The zeta potential of the HA treated with the solutions was measured. Significant differences were found for both factors and interaction (p < 0.0001). The treatments with F and FS solutions resulted in a lower amount of dissolved HA than the control. Among the polymers' solutions, only AMC was able to reduce the amount of dissolved HA, changing the surface charge of HA to positive. AMC improved the protective effect of F, but it did not affect FS. Polyoxirane and HPMC reduced the protective potential of the FS solution. No differences were found between the concentrations of the polymers. It was concluded that F and FS reduced the amount of dissolved HA. The protective effect of the experimental solutions against HA dissolution was polymer dependent. The F effect was enhanced by its combination with AMC, but the protection of FS was impaired by polyoxirane and HPMC.

Could different direct restoration techniques affect interfacial gap and fracture resistance of endodontically treated anterior teeth?

OBJECTIVES: To evaluate different direct restoration techniques on various cavity designs in anterior endodontically treated teeth (ETT). MATERIALS AND METHODS: Ninety upper central incisors (n = 90) were selected, endodontically treated, and divided into three groups (n = 30) accordingly to the cavity design: minimal endodontic cavity access (group A), endodontic access + mesial class III cavity (group B), and endodontic access + two class III cavities (group C). Three subgroups (n = 10) were then created accordingly to the restoration technique: nano hybrid composite restoration (subgroup a), glass fiber post + dual-cure luting cement (subgroup b), and bundled glass fiber + dual-cure luting cement (subgroup c). Samples underwent micro-CT scan, chewing simulation, and a second micro-CT scan. 3D quantification (mm3) of interfacial gap progression was performed; then, samples underwent fracture resistance test. Data were statistically analyzed setting significance at p < 0.05. RESULTS: Groups A and B showed significantly lower interfacial gap progression compared with group C. Subgroup b performed significantly better compared with subgroups a and c. Improved fracture strength was reported for group C compared with group A, while both subgroups b and c performed better than subgroup a. CONCLUSIONS: Cavity design significantly influenced interfacial gap progression and fracture resistance. Fiber posts significantly lowered gap progression and improved fracture resistance while bundled fibers only increased fracture resistance. A significant reduction of non-repairable fractures was recorded when fibers were applied. CLINICAL RELEVANCE: A minimally invasive approach, conserving marginal crests, should be applied whenever possible. Inserting a fiber post is indicated when restoring anterior ETT, in order to reduce gap progression, improve fracture resistance, and avoid catastrophic failures.

The effects of polishing techniques on surface roughness and gloss of different composites.

The aim of this study was to evaluate the effects of different polishing techniques on the surface roughness and gloss of various composites. A total of 360 composite cylinders (6 mm in diameter and 2 mm in thickness) were made using a silicone matrix and 1 of the following 6 restorative materials (n = 60): Admira Fusion, GrandioSO, Filtek Supreme, Filtek Z250, TPH Spectra ST, and Herculite Classic. The composite specimens were cured and then immersed in water for 24 hours. The baseline roughness was standardized with 600-grit silicon carbide paper used in a polishing device for 30 seconds. The specimens were divided into 6 subgroups (n = 10) according to the polishing technique: abrasive discs (Sof-Lex); abrasive discs (Sof-Lex) and diamond paste (Diamond Excel); abrasive rubber point (Dimanto); silicon carbide polishing brush (OptiShine); rubber spiral wheels (Sof-Lex Spiral Wheels - Diamond Polishing System); or sequential application of polishing pastes (Diamond ACI and ACII). After polishing was completed, the surface roughness and gloss were measured, and the data underwent 2-way analysis of variance and the Tukey test (P < 0.05). Statistically significant differences were observed for roughness (P < 0.001) and gloss (P < 0.001) for both factors analyzed (composite material and polishing technique). Admira Fusion exhibited the highest roughness and lowest gloss values of all of the composites, and Filtek Supreme exhibited the lowest roughness and highest gloss values. Sof-Lex Spiral Wheels and OptiShine polishing brush exhibited lower roughness and higher gloss than the other polishing techniques. The effects of different polishing techniques were material dependent, but all systems tested provided clinically acceptable results. The use of a single polishing technique for all types of composite materials might result in undesirable clinical outcomes.

Enhancing the Anti-Erosive Properties of Fluoride and Stannous with the Polymer Carbopol.

This in vitro study investigated whether Carbopol 980 polymer could potentiate the anti-erosive effect of solutions containing sodium fluoride (F) and sodium fluoride associated with stannous chloride (FS). The dissolution of hydroxyapatite treated with the experimental solutions (F [500 ppm F-], F + Carbopol [0.1%], FS [500 ppm F- + 800 ppm Sn2+], FS + Carbopol) was evaluated. Deionized water was the negative control, and a commercial mouth rinse (AmF/NaF/SnCl2; 500 ppm F + 800 ppm Sn2+; Elmex® Erosion Protection) was the positive control. The solutions were also evaluated in an erosion-rehardening protocol, with two treatments per day, using bovine enamel specimens (n = 15) and human saliva. The acid challenge was performed using 0.3% citric acid (pH 2.6) for 2 min. Microhardness was measured at different times: baseline, after the first erosive challenge, after treatment, and after the second erosive challenge. Based on microhardness values, the demineralization, rehardening, and protective potentials were calculated. The alkali-soluble fluoride on enamel surfaces was also measured. Data were analyzed using ANOVA and Tukey tests (α = 0.05). Groups treated with FS + Carbopol showed the lowest hydroxyapatite dissolution and the highest rehardening and protective potentials. The measurement of alkali-soluble fluoride on enamel surfaces was also higher in the FS + Carbopol group. Carbopol was able to significantly increase the protective effect of the fluoridated solutions in addition to optimizing the adsorption of fluoride on the enamel surface.

A randomized clinical trial of class II composite restorations using direct and semidirect techniques.

OBJECTIVE: This prospective study evaluated the clinical performance of large class II restorations made with different techniques over 24 months. MATERIALS AND METHODS: Thirty patients received two class II restorations (n = 60) using a nanohybrid composite and different restorative techniques (direct (DT), semidirect (SDT)), in a split-mouth randomized design. The same adhesive system was applied for all restorations. For DT, the restorative material was applied directly inside the tooth preparation. For SDT, a tooth preparation impression was obtained using alginate and a silicone flexible die was prepared. The restoration was made chairside on the model and additionally light cured. After that, it was cemented in preparation using resinous cement. All restorations were evaluated using the FDI criteria after 7 days, 6, 12, and 24 months postoperatively. RESULTS: After 24 months, 24 patients attended the recall and 48 restorations were evaluated. Fisher's statistical analysis (5%) showed no difference between the techniques. Nevertheless, Friedman's test showed significant differences for some criteria after 12 months of evaluation for both techniques. Postoperative sensitivity was reported in one DT restoration. Also, after 24 months, one SDT restoration presented marginal fracture, which was deemed unsatisfactory. CONCLUSIONS: After a 24-month follow-up, no significant difference between the tested techniques was detected. The restorations performed with both techniques produced clinically acceptable restorations. CLINICAL RELEVANCE: This study demonstrated the viability of applying two different operatory techniques (direct and semidirect) for class II resin composite restorations.

Nanofilled bis-acryl composite resin materials: Is it necessary to polish?

STATEMENT OF PROBLEM: Manufacturers of the recently introduced nanofilled bis-acryl composite resins no longer recommend polishing to produce interim restorations; however, whether this advice is appropriate is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the type of interim resin material, polishing procedure, and artificial staining on surface roughness, gloss, and color. MATERIAL AND METHODS: Disk-shaped specimens were prepared from 1 unfilled acrylic resin (Duralay) and 3 bis-acryl composite resins (Structur 3-nanofilled, Systemp C&B-microhybrid, Proviplast-microhybrid). The specimens of each material were assigned to 2 subgroups (n=15): polished and unpolished. Surface roughness (Ra-µm), gloss (UB), and color (ΔE) were analyzed at baseline and after 14 days of artificial staining. Roughness and gloss data were separately analyzed by 3-way ANOVA and color by 2-way ANOVA, followed by the post hoc Tukey test (α=.05). RESULTS: The baseline roughness of all materials was significantly reduced by the polishing procedure, whereas the baseline gloss was increased (P<.001). Only the unpolished Proviplast had a significant increase in Ra values after aging. Structur 3 had higher gloss than Systemp C&B and Proviplast. The acrylic resin had the lowest color change after staining. CONCLUSIONS: The polishing procedure produced smother and glossier surfaces for all the materials tested. The nanofilled bis-acryl composite resin material had higher gloss than the microhybrid bis-acryls tested, but it was not different from the acrylic resin. The 14 days of artificial staining did not promote significant changes in Ra or gloss values, except for Ra in the unpolished Proviplast subgroup, indicating excellent performance of the materials. The acrylic resin had the highest color stability.

Influence of Surfactants and Fluoride against Enamel Erosion.

This study investigated the effect of surfactants associated with sodium fluoride (NaF) on enamel erosion prevention, using an erosion-remineralization in vitro model. Sodium lauryl sulfate (SLS), polysorbate 20 (P20), and cocoamidopropyl betaine (CAPB) were tested, at concentrations of 1.0 and 1.5%, and associated or not with NaF (275 ppm). The control groups were distilled water and the NaF solution. Bovine enamel samples (n = 12) were prepared and submitted to a 5-day cycling model: acid challenge (0.3% citric acid, pH 2.6, 4×/day), human saliva (2 h, 4×/day), and the treatment solutions (2 min, 2×/day). The protective potential of the agents against initial erosion was assessed by microhardness and the surface loss by profilometry. Enamel surface wettability was determined by goniometry, protein adsorption was measured by spectroscopy (FTIR), and the KOH-soluble fluoride was quantified. Goniometry showed that SLS and CAPB increased enamel wettability. No differences were found among the surfactants regarding protein adsorption. Microhardness showed that SLS reduced NaF protection. P20 (1 and 1.5%) and CAPB 1.5% presented a protective effect, but lower than the NaF solution. Profilometry showed that CAPB protected enamel, but no agent associated with NaF promoted a higher protection than the NaF solution alone. KOH-soluble fluoride analysis showed that all surfactants reduced the fluoride adsorption on the enamel surface. Therefore, the surfactants tested (except for P20) changed the enamel surface energy. The SLS decreased the protective potential of NaF on initial erosion, but no tested agent interfered with the protective effect of NaF on enamel erosive wear.

Fluorescence properties of demineralized enamel after resin infiltration and dental bleaching.

PURPOSE: To evaluate the effects of different white spot lesion (WSL) treatments associated with dental bleaching on the fluorescence of dental enamel. METHODS: 80 flat enamel disks (3 mm diameter and 1 mm thick) were obtained from bovine incisors. The initial fluorescence (fluorescent emission or Delta E*ab- FL units) of the specimens was measured using a spectrophotometer. Artificial caries was created in all specimens, and the measurements were repeated. The specimens were divided into four groups according to the treatment applied (n = 20): CON (control) - immersion in ultrapure water for 8 weeks; SAL - immersion in artificial saliva for 8 weeks; FL - daily application of 0.05% sodium fluoride for 1 minute/artificial saliva for 8 weeks; and ICON - resin infiltration (Icon). After the treatments, the assessments were repeated. Dental bleaching using 35% hydrogen peroxide gel was performed on all specimens for 30 minutes, and the measurements were made again after 7 days. Data were submitted to ANOVA and Tukey tests across the treatments for each moment of evaluation. RESULTS: Fluoride and saliva remineralization were not able to change enamel fluorescence, even after bleaching. Only resin infiltration increased the enamel fluorescence; however, after bleaching, all groups presented similar values. Icon increased translucency immediately after application, but bleaching reduced it to its initial values. CLINICAL SIGNIFICANCE: Changes of fluorescence in infiltrated enamel might lead to unsatisfactory esthetics under certain conditions such as ultraviolet light.

Influence of interim cements on the optical properties of interim restorations.

STATEMENT OF PROBLEM: Even if the appropriate resin shade is selected for an interim restoration, how the optical characteristics of the interim cement affect the esthetics of the interim restoration is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effects of interim cements on the optical properties of interim restorations. MATERIAL AND METHODS: Twenty dentin disks (6×1 mm) were obtained from the labial surface of bovine incisors. Disks of acrylic and bis-acrylic resins (n=20) with the same dimensions were prepared and cemented over the dentin using the following cements: Bifix Temp (resin-based; VOCO), ClearTemp LC (resin-based; Ultradent Products, Inc), Provicol (VOCO), TempCem NE (Coltène). The same dentin and resin disks were used for all cements. After cementation, the color difference (ΔE00), translucency parameter (TP), and fluorescence of the dentin/cement/resin combinations were compared with each other and with a control group (C), in which a transparent liquid (polyethylene glycol 400; LabSynth) was applied. Color and translucency were evaluated with a spectrophotometer (CM-2600; Konica Minolta) and fluorescence with a spectrofluorophotometer (RF-5301PC; Shimadzu). ΔE00 and TP data were analyzed using 2-way ANOVA. For fluorescence, 1-way ANOVA was used. The Tukey test was used for multiple comparisons (α=.05). RESULTS: ΔE00 values were significantly influenced by the interim material (P<.001) and the interim cement (P<.001). Bifix Temp showed the lowest significant ΔE00 values (P<.001). The highest ΔE00 values were observed for TempCem NE. No differences were observed between the interim resins with respect to TP (P=.318). The lowest translucency values were measured for TempCem NE, followed by Provicol, ClearTemp LC, Bifix Temp, and the control group (P<.001), with no significant differences among the interim resin-based cements. Among the cements, Bifix Temp and TempCem NE yielded fluorescence similar to that of the natural tooth for both interim resins. A similar result was found for bis-acrylic resin combined with Provicol. CONCLUSIONS: Cementation with interim resin-based cements resulted in better esthetics. However, the high fluorescence of the ClearTemp LC may reduce the esthetics of interim restorations in environments with predominantly UV light.

Effect of whitening mouthrinses on enamel toothbrush abrasion.

PURPOSE: To evaluate the effect of whitening mouthrinses used before toothbrushing on enamel microhardness and wear. METHODS: 80 polished bovine enamel specimens were randomly assigned into four groups according to the mouthrinses tested (n=20): PW: Plax Whitening - 1.5% hydrogen peroxide (HP); LW: Listerine Whitening Pre-Brush Rinse - 2% HP; U: Ultradex - Chlorine dioxide; C: Control - Artificial saliva. The specimens were immersed in the mouthrinses for 1 minute and brushed with 10 strokes, using a dentifrice containing sodium fluoride. After treatments, they were immersed in artificial saliva for 30 minutes. A total of 540 cycles were performed simulating 9 months of use. Enamel surface was assessed with a Knoop microhardness tester and by a contact profilometer before and after treatments to obtain the surface microhardness (KHN) and enamel loss (µm) values. The specimens were immersed in artificial saliva for an additional 30 days and microhardness was measured again. Data were analyzed by ANOVA and Tukey's tests (5%). RESULTS: Significant differences were observed in KHN (P= 0.0001) and wear (P= 0.0001). Results of Tukey's for KHN: U-320.08±13.86a, PW-323.58±32.75a, LW-331.66±24.74a, C-354.24±16.40b. Wear (µm) : PW-10.03±0.94a, LW-9.92±0.81a, U-8.88±1.02b, C-6.56±0.91c. Groups followed by the same letters do not present significant differences. After 30 days in saliva, there was no significant difference for SMH among the groups. CLINICAL SIGNIFICANCE: The continuous use of whitening mouthrinses can increase the enamel abrasion potential promoted by daily toothbrushing; therefore, they should be used with caution.

Effect of whitening toothpastes on wear and roughness of ormocer and methacrylate-based composites.

PURPOSE: To investigate the effects of whitening toothpastes over the wear and surface roughness of ormocer and methacrylate composites. METHODS: Cylindrical specimens (n=120) were prepared using methacrylate-based composites (Filtek Z350 XT, TPH3 and GrandioSO) and a pure-ormocer composite (Admira Fusion). Brushing abrasion (100,000 strokes) was performed using whitening toothpastes containing different abrasives: alumina (Colgate Ultrawhite), perlite (CloseUp Whitening) and sodium bicarbonate (Kin Progressive Whitening). Wear and roughness alteration were evaluated. Additional analyses of microhardness, degree of conversion and scanning electron microscopy were also performed. RESULTS: Data were separately analyzed with Kruskal-Wallis and ANOVA tests. Statistically significant differences were found for the composites and whitening toothpastes (P<0.05). For all toothpastes, GrandioSO showed lower wear than Z350 XT and Admira Fusion, although non-significant differences in relation to TPH3 were observed. For perlite and bicarbonate-based toothpastes, Z350 XT, Admira Fusion and TPH3 did not present significant differences among them for wear. For alumina-based toothpaste, Z350 XT showed higher wear than TPH3, while Admira Fusion showed intermediate values. Higher wear and roughness alteration were observed after using alumina-containing toothpaste. All composites tested showed increased roughness after brushing. Z350 XT presented the lowest roughness alteration, while Admira Fusion the highest. CLINICAL SIGNIFICANCE: The alumina-containing whitening toothpaste significantly increased the wear and roughness of composites in relation to the other abrasives tested. However, using the ADA standards, the wear promoted by all whitening toothpastes tested would be considered clinically acceptable for all materials. The type of organic matrix in a composite is not the main factor that determines the wear rate, but also its interaction with the inorganic fillers and the filler content. The composite GrandioSO showed the lowest overall wear values, while Z350 XT resulted in the smoothest surfaces.

Effects of artificial staining on bulk-filled resin composites.

PURPOSE: To evaluate the color stability of bulk-fill resin composites (RC) in comparison to conventional RC submitted to artificial staining. METHODS: 15 specimens of each RC were prepared. Five bulk-fill RC [X-tra Base (XB), Filtek Bulk-Fill Flowable (FBF), Admira Fusion X-tra (AD), Tetric N-Ceram Bulk-Fill (TB), and Filtek Bulk-Fill (FB) ], and two conventional RC [GrandioSO (GO) and Filtek Z350XT (FXT) ] were used. After preparation of the samples, the specimens were immersed in a staining broth for 5 weeks and repolished. The color change was assessed using a spectrophotometer. Data were analyzed using one-way ANOVA, Tukey's tests, and paired t-test. RESULTS: The bulk-fill flowable (XB and FBF) presented color change clinically acceptable (ΔE< 2.7) after staining. Among the bulk-fill regular resins, only AD presented clinically acceptable values (ΔE= 1.99). Regarding the conventional resins, GO presented a significantly lower color change than the other resins, but was not significantly different from AD. For all the resins, except AD, the repolishing procedures resulted in a significant decrease of color change. Tested resins did not present the same behavior under staining, despite their similarities. All the resins stained above the perceptibility threshold (ΔE> 1.2). After repolishing, the color change was reduced overall. CLINICAL SIGNIFICANCE: Color stability of resin composites was related to the properties of the resin material. The staining degree was related to the replacement of the restorations and repolishing contributes to the maintenance and longevity of these composites.

Effect of pH on whitening efficacy of 35% hydrogen peroxide and enamel microhardness.

OBJECTIVE: This study aimed to evaluate the effect of 35% hydrogen peroxide at different pH values and the degree of tooth staining on whitening efficacy and enamel microhardness. MATERIALS AND METHODS: 90 enamel-dentin specimens were obtained from bovine incisors. They were randomly divided into 2 groups (n = 45), 1 group was immersed in a staining broth for 14 days, and another group was not stained and kept in distilled water at 37°C. Twenty-four hours after the staining procedure, each group was distributed into 3 subgroups that were whitened by 35% hydrogen peroxide with different pH values (5, 7, and 8.4) for 30 minutes. The color was measured at baseline and 7 days after whitening. Microhardness was measured at baseline, immediate, 24 hours, and 1 month after the whitening procedure. Data were submitted to 2-way analysis of variance (ANOVA) and the Tukey test for multiple comparisons for color analysis. Repeated measures ANOVA and the Tukey test were used to analyze microhardness data. RESULTS: The color change of the stained groups (ΔE00 = 4.6) was significantly higher than that of the nonstained groups (ΔE00 = 3.7). Microhardness value decreased significantly immediately after whitening for all subgroups and did not return to initial values. For each measurement time, microhardness was not significantly different among subgroups with different pH values. CONCLUSIONS: Despite the effectiveness of 35% hydrogen peroxide, changes on gel pH did not affect the whitening efficacy, and the enamel was superficially demineralized, regardless of pH values. CLINICAL SIGNIFICANCE: Independently of the pH value of whitening gel, enamel undergoes superficial demineralization and with a reduction in superficial microhardness that does not return to the initial values. However, using hydrogen peroxide with different pH values does not alter the whitening effect.

Bond Strength to Eroded Enamel and Dentin Using a Universal Adhesive System.

PURPOSE: To evaluate the influence of previous acid etching on the bond strength of a self-etch universal adhesive system on sound and eroded enamel and dentin. MATERIALS AND METHODS: Flat enamel and dentin surfaces were obtained from bovine incisors (n = 44) and divided into two groups according to the exposure to erosive conditions: sound (without erosion) and eroded (after erosive challenge with 0.3% citric acid, pH 2.6, 5 min, 4x/day, 5 days). Each group was then divided into two subgroups (n = 11) according to the application or not of 37% phosphoric acid before applying a universal self-etch adhesive. Single Bond universal adhesive (3M ESPE) was applied and composite blocks were built up using Amelogen Plus (Ultradent). Sticks (1 × 1 mm) were obtained and the microtensile bond strength (µTBS) was assessed using a universal testing machine at a speed of 1 mm/min. Data were analyzed with two-way ANOVA and Tukey's tests (p < 0.05). RESULTS: For enamel groups, significant differences were observed for erosive challenge (p = 0.034) and acid etching (p = 0.047), but not for the interaction between them (p = 0.182). The means ±â€¯SD (MPa) for the erosive conditions were: sound, 25.02 ±â€¯5.82a; eroded, 28.45 ±â€¯5.92b; and for acid etching: without, 24.89 ±â€¯5.39a; with, 28.58 ±â€¯6.23b (different superscript letters indicate significant differences). For dentin, both the erosive condition (p = 0.936) and acid pretreatment (p = 0.084), as well as their interaction (p = 0.107), did not affect the bond strength. CONCLUSION: The erosive challenge and previous acid etching significantly increased the bond strength of the tested universal adhesive to enamel but not to dentin.

Influence of previous acid etching on bond strength of universal adhesives to enamel and dentin.

The objective of this study was to evaluate the effect of acid pretreatment on the bond strength of composite resin bonded to enamel and dentin with 2 different universal self-etching adhesives. The null hypothesis was that the acid treatment performed prior to adhesive application would not significantly change the bond strength to enamel or dentin for either universal adhesive tested. A sample of 112 bovine incisors were selected and embedded in acrylic resin. Half were ground until a flat enamel surface was obtained, and the other half were polished until a 6 × 6-mm area of dentin was exposed, resulting into 2 groups (n = 56). The enamel and dentin groups were divided into 2 subgroups according to the adhesive system applied: Futurabond U or Scotchbond Universal. Each of these subgroups was divided into 2 additional subgroups (n = 14); 1 subgroup received phosphoric acid pretreatment, and 1 subgroup did not. The bond strength was assessed with a microtensile test. Data from enamel and dentin specimens were analyzed separately using 1-way analysis of variance. The acid pretreatment did not significantly change the bond strength of the adhesives tested, either to enamel (P = 0.4161) or to dentin (P = 0.4857). The acid etching pretreatment did not affect the bond strength to dentin and enamel when the tested universal multipurpose adhesive systems were used.

Influence of de/remineralization of enamel on the tensile bond strength of etch-and-rinse and self-etching adhesives.

PURPOSE: To evaluate the bonding behavior of resin composite and different adhesives applied to demineralized or remineralized enamel. METHODS: Bovine tooth crowns were polished to prepare a 5 mm2 enamel bonding area, and divided into five groups (n= 48) according to the surface treatment: CONT (sound enamel control), DEM (demineralized with acid to create white spot lesions), REMS (DEM remineralized with artificial saliva), REMF (DEM remineralized with sodium fluoride) and INF (DEM infiltrated with Icon resin infiltrant). The surface-treated teeth were divided into two subgroups (n= 24) according to adhesive type: ER (etch-and-rinse; Single Bond Universal) and SE (self-etching; Clearfill S3 Bond), and further subdivided into two categories (n= 12) according to aging process: Thermo (thermocycling) and NA (no aging). Composite blocks were made over bonded enamel and sectioned for microtensile bond strength (MTBS) testing. Data were analyzed with three-way ANOVA and post-hoc Tukey's test (α= 0.05). RESULTS: Significant differences were observed for enamel surface treatment (P< 0.0001), adhesive type (P< 0.0001) and aging (P< 0.0001). CONT and INF groups had higher MTBS than the other groups; Single Bond Universal had higher MTBS than Clearfil S3 Bond; thermo-aging resulted in lower MTBS irrespective of adhesive type and surface treatment condition. The predominant failure mode was mixed for all groups. Enamel surface infiltrated with Icon does not interfere with adhesive resin bonding procedures. CLINICAL SIGNIFICANCE: Treatment of enamel surface containing white spot lesions or cavities with cavosurface margins in partially-demineralized enamel can benefit from infiltration with a low viscosity resin infiltrant prior to adhesive bonding of resin composites.

Effect of home-bleaching gels modified by calcium and/or fluoride and the application of nano-hydroxyapatite paste on in vitro enamel erosion susceptibility.

OBJECTIVE: This in vitro study compared the effect of bleaching agents modified by the addition of calcium and/or fluoride and the application of a nano-hydroxyapatite paste after bleaching, on the susceptibility of enamel to erosion. MATERIALS AND METHODS: Bovine enamel cylindrical samples (3 mm diameter) were assigned to six groups (n = 20 specimens/group) according to the bleaching agent: no bleaching (C-control), 7.5% hydrogen peroxide gel (HP), HP with 0.5% calcium gluconate (HP+Ca), HP with 0.2% sodium fluoride (HP+F), HP with calcium and fluoride (HP+Ca+F) and HP followed by the application of a nano-hydroxyapatite agent (HP+NanoP). The gels were applied on the enamel surface (1 h) followed by cyclic erosive challenges (Sprite Zero®-2 min), for 14 days. The paste was applied after bleaching for 5 min (HP+NanoP). The enamel surface alteration was measured by contact profilometry (µm) (after 7 and 14 days). RESULTS: C-control (mean ± SD: 2.29 ± 0.37 at 7 days/4.86 ± 0.72 at 14 days) showed significantly lower loss compared to the experimental groups. HP+Ca (3.34 ± 0.37/6.75 ± 1.09) and HP+F (4.49 ± 0.92/7.61 ± 0.90) presented significantly lower enamel loss than HP (4.18 ± 0.50/10.30 ± 1.58) only for 14 days and HP+Ca+F (4.92 ± 1.03/8.12 ± 1.52) showed values similar to the HP+F group. The HP+NanoP (5.51 ± 1.04/9.61 ± 1.21) resulted in enamel loss similar to the HP after 14 days. CONCLUSIONS: It was found that 7.5% hydrogen peroxide increased the susceptibility of enamel to erosion. The addition of calcium or fluoride to the bleaching gel reduced the erosion effect, while the nano-hydroxyapatite agent did not provide any protective effect.