Influence of viscosity and fiber reinforcement of resin composite on fracture strength and failure mode of restored molars.

OBJECTIVE: To evaluate the fracture behavior of human molars with extensive MOD restorations using short-fiber-reinforced resin composite of varying viscosities. MATERIALS AND METHODS: Human molars were randomly divided into seven groups (n = 12): intact teeth (control); restoration using conventional high-viscosity resin composite without (Filtek Z350XT, 3M) or with fibers (everX Posterior, GC); conventional low-viscosity resin composite without (Filtek Supreme Flowable, 3M) or with fibers (everX Flow Dentin Shade, GC); bulk-fill low-viscosity resin composite (Filtek Bulk Fill Flow, 3M) or with fibers (everX Flow Bulk Shade, GC). Restorations were performed on extensive MOD preparations, following the manufacturers' recommendations for each material. Specimens underwent fracture strength testing (N) and fracture pattern (%) categorized as repairable, possibly repairable, or non-repairable. Results were analyzed using a generalized linear model (N) and Fisher's exact test (%), with α = 0.05. RESULTS: Restorations performed with high-viscosity materials showed fracture strength values similar to the control and higher than those of restorations using low-viscosity resin composites (p < 0.0001), except for the bulk-fill low-viscosity resin composite with fibers (p > 0.05). Teeth restored using low-viscosity resin composite with fibers showed a higher % of repairable and possibly repairable fractures than the control (p = 0.0091). CONCLUSIONS: The viscosity of materials mediated the fracture strength, with restorations using high-viscosity resin composites promoting values similar to the intact tooth; however, the presence of fibers influenced the fracture pattern. CLINICAL SIGNIFICANCE: Teeth with MOD cavities restored with high-viscosity resin composites showed similar fracture strength to intact teeth. Fiber-reinforced low-viscosity resin composite for the base of restoration resulted in a more repairable/possibly repairable fracture pattern.

Influence of etchant type on the shear bond strength of orthodontic brackets to enamel.

The aim of this study was to evaluate the influence of the type of etchant on the shear bond strength (SBS) of metallic brackets to enamel and the Adhesive Remnant Index (ARI) after debonding. A total of 30 mandibular and maxillary premolars were randomly distributed into groups (n = 10) treated with 1 of 3 enamel surface-conditioning agents: 35% phosphoric acid (PA), 35% glycolic acid (GA), or 35% ferulic acid (FA). The designated acid was applied to the buccal enamel surface of the tooth for 20 seconds, and the tooth was then rinsed with distilled water for 20 seconds and air dried for 5 seconds. A metal bracket was bonded to the prepared surface with light-cured orthodontic resin. After 24 hours, the bracket-tooth interface was submitted to SBS testing in a universal testing machine at a speed of 0.5 mm/min. After debonding, the enamel surface was observed under a stereomicroscope (×20 magnification) to determine the ARI. The generalized linear models showed that the PA and GA groups presented significantly higher SBSs than the FA group (P = 0.0003). The ARI was significantly higher in specimens treated with PA than with the other acids (P < 0.05; Kruskal-Wallis and Dunn tests), with a larger quantity of adhesive remaining adhered to the tooth. Both PA and GA are effective for bonding brackets, but GA resulted in a lower percentage of adhesive remnant adhered to the enamel.

Effects of in vitro erosion on surface texture, microhardness, and color stability of resin composite with S-PRG fillers.

OBJECTIVES: To evaluate the effect of acid erosion on different physical properties of resin composite with S-PRG (surface pre-reacted glass) fillers, by conducting simulations of intrinsic and extrinsic sources. MATERIALS AND METHODS: Cylindrical samples (Ø6 vs. 2 mm) of a conventional nanohybrid resin composite (Forma, Ultradent) and of a nanohybrid resin composite with S-PRG filler (Beautifil II, Shofu) were exposed to erosive cycling (5 days), based on (n=12) remineralizing solution (control); 0.3% citric acid (pH=2.6); or 0.01 M hydrochloric acid (pH=2). Roughness (Ra), microhardness (KHN), and color (CIEL*a*b*, CIEDE2000, and Vita scale (SGU)) factors were analyzed at the initial and final time points, and the general color changes (ΔEab, ΔE00, ΔSGU) were calculated. Final images were obtained using scanning electron microscopy (SEM). The data were evaluated by generalized models, Mann-Whitney, Wilcoxon, Kruskal-Wallis, and Dunn tests (α=0.05). RESULTS: Regarding KHN, there was no difference between the groups or the time periods (p = 0.74). As for Ra, there was a significant increase in the Ra of both composites after cycling with hydrochloric acid, but only the resin composite with S-PRG filler showed a change in Ra after cycling with citric acid (p = 0.003). After cycling with citric and hydrochloric acid, the highest Ra values were found for the resin composite with S-PRG filler (p < 0.0001), corroborating the result of images (SEM) indicating loss of filler and porosities in this material. The resin composite with S-PRG filler showed higher ΔEab and ΔE00, in addition to more negative ΔSGU values and lower L* values after exposure to both acids, compared to the control (p < 0.05). CONCLUSION: The acidic conditions altered the roughness and color stability of the materials tested, pointing out that the resin composite containing S-PRG filler showed greater degradation of its physical properties than the conventional resin composite. CLINICAL RELEVANCE: Bioactive materials are relevant, considering that their properties interact with dental hard tissues; however, the S-PRG-based resin composite showed greater degradation under acidic conditions than the conventional resin composite.

Titanium dioxide nanotubes in a hydrogen peroxide-based bleaching agent: physicochemical properties and effectiveness of dental bleaching under the influence of a poliwave led light activation.

OBJECTIVES: The effects of different concentrations of titanium dioxide (TiO2) into 40% hydrogen peroxide (HP) were evaluated as regards the effectiveness of dental color change either associated with activation by polywave LED light or not. MATERIALS AND METHODS: TiO2 (0, 1, 5, or 10%) was incorporated into HP to be applied during in-office bleaching (3 sessions/40 min each). Polywave LED light (Valo Corded/Ultradent) was applied or not in activation cycles of 15 s (total time of 2 min). The color of 80 third molars separated into groups according to TiO2 concentration and light activation (n = 10) was evaluated at baseline and at time intervals after the 1st, 2nd, and 3rd bleaching sessions. RESULTS: WID value was significantly higher when using HP with 5% TiO2 in the 2nd session than the values in the other groups (p < 0.05). After the 2nd and 3rd sessions, the ΔEab value was significantly higher when activated with light (p < 0.05) for all agents containing TiO2 or not. Zeta potential and pH of the agents were not modified by incorporating TiO2 at the different concentrations. CONCLUSIONS: The 5% TiO2 in the bleaching agent could enhance tooth bleaching, even without light application. Association with polywave LED light potentiated the color change, irrespective of the presence of TiO2 in the bleaching gel. CLINICAL SIGNIFICANCE: HP with 5% TiO2 could lead to a greater tooth bleaching response in the 2nd clinical session, as well as the polywave light can enhance color change.

TiO2 nanotube-based nanotechnology applied to high-viscosity conventional glass-ionomer cement: ultrastructural analyses and physicochemical characterization.

This study characterized TiO2 nanotube (TiO2-nt) ultrastructure and morphology, and the physicochemical impact on high-viscosity conventional glass-ionomer cement (GIC). TiO2-nt was synthesized by the alkaline method (n = 3), assessed by scanning (SEM) and transmission electron microscope (TEM), and was added (3%, 5%, 7%-in weight) to KM (Ketac Molar EasyMix™). Analyses included: SEM; Energy-dispersive spectroscopy (EDS); Raman spectroscopy (RAMAN); Setting time with Gillmore needles (ST); Color (Co); Radiopacity (XR); Water sorption (WS); and solubility (SO). Quantitative data were submitted to ANOVA and Tukey's tests (chr = 0.05). External and internal TiO2-nt diameters were 11 ± 2 nm and 6 ± 0 nm, respectively. Data analyses showed: (i) TiO2-nt present into KM matrix, with a concentration-dependent increase of Ti levels into KM, (ii) physical interaction between KM and TiO2-nt, (iii) longer initial ST for the 7% group compared to KM and 3% groups (p ≤ 0.01), (iv) decreased luminosity and yellowness for the 5% and 7% groups, (v) 36% greater radiopacity for the 5% group compared to enamel, dentin, and KM, and (vi) lower SO values for the 5% group, with no significant differences on WS across the groups. TiO2-nt displayed physical interaction with KM matrix, and also modified SO, XR and Co, without affecting ST. This study provides information on the potential impact of TiO2-nt on GIC performance. TiO2-nt may be proposed to boost confidence among dental surgeons in terms of GIC's handling characteristics, success rate and differential diagnostic.

Effect of different polishing systems and staining solution on surface roughness and color stability of bulk fill resin composites.

PURPOSE: To evaluate the effect of polishing systems (discs or rubbers) on surface roughness (Ra) and color change (ΔE) of two bulk fill and one conventional resin composite after immersion in a dye solution. METHODS: 180 samples (10 mm x 2 mm) were separated into three groups: (1) Resin composite: Filtek One Bulk Fill (FO), Tetric N-Ceram Bulk Fill (TNC), Filtek Z350 XT (FXT) (n= 60); (2) polishing system: unpolished (control); aluminum oxide discs (Sof-Lex, AOD); cup-shaped abrasive rubber polishers (Astropol, CSA) (n= 20), and (3) immersion solutions: coffee or distilled water (n= 10). Immersion was under 5 mL of each solution for 3 hours daily, for 30 days. Measurement of Ra and ∆E was made considering two times: initial (after polishing) and final (after immersion), in addition to surface analysis by scanning electron microscopy at the end. Kruskal-Wallis, Mann-Whitney, and Dunn (α= 0.05) was used. RESULTS: For the unpolished samples after immersion in coffee, TNC (P= 0.007) showed lower ΔE than FXT and FO. For polished samples with CSA and immersed in coffee, TNC followed by FXT showed lower ΔE than in the absence of polishing. Polishing with AOD and immersed in coffee: FO had smaller ΔE than when not polished. For Ra, TNC and FO had lower values after using AOD, whereas for FXT lower Ra was noted with CSA. CLINICAL SIGNIFICANCE: The roughness and color stability of resin composites are mediated by the polished material, polishing system and dye solution. The best results were found for Tetric N-Ceram polished with aluminum oxide discs.

Can brushing with regular and whitening dentifrices influence changes in color and micromorphologic surfaces of ceramic brackets subjected to coffee staining?

The aim of the present study was to evaluate the influence of brushing with regular or whitening dentifrices on the change in color and micromorphologic surface of ceramic orthodontic brackets subjected to coffee staining. Fifty ceramic brackets were subjected to cycles of coffee staining followed by brushing according to the following groups (n = 10): C, control (no brushing); DW, brushing with distilled water; CT, brushing with Colgate Total 12 Clean Mint (regular toothpaste); COW, brushing with Colgate Optic White (containing 1% hydrogen peroxide); and CUWA, brushing with Close-Up White Attraction (containing blue covarine). The color of the brackets was assessed using the Commission Internationale de l'Eclairage (CIE) L*a*b* system at 5 different timepoints: prior to staining (baseline) and after 1, 7, 14, and 21 days of staining and brushing cycles. The surface micromorphology of the brackets was assessed at the baseline timepoint and after 21 days. Kruskal-Wallis, Dunn, Friedman, and Nemenyi tests were applied (α = 0.05) for the statistical analysis. The C group demonstrated a significant reduction in L* and a significant increase in a* and b* values over time. For the DW group, the L* value was reduced but was higher than in the C group, and there were also significant increases in a* and b* from baseline values. A significant increase in the a* and b* values was observed in all groups (P < 0.05). Total color change (∆E*) increased over the period of evaluation for all whitening groups, although only the CT group presented significantly lower ∆E* than the other dentifrices. At the end of the test period, only the COW group exhibited a surface with higher porosity. None of the dentifrices prevented the brackets from staining, but they did reduce the magnitude of color change caused by coffee. The most significant difference was found in the CT group. Micromorphologic surface changes were observed when COW was employed.

Effect of whitening dentifrices on color, surface roughness and microhardness of dental enamel in vitro.

PURPOSE: To evaluate the color, surface roughness and microhardness of human dental enamel subjected to brushing with whitening dentifrices. METHODS: The enamel samples (4 x 4 x 2 mm) were darkened using 0.2% chlorhexidine and black tea, and were randomly divided into seven groups (n= 15) for brushing cycles with only water; control; conventional dentifrice (Colgate Maximum Anticaries Protection); dentifrice containing 2% hydrogen peroxide (Colgate Luminous White Advanced); dentifrice containing sodium tripolyphosphate (Sensodyne True White); dentifrice containing activated charcoal (Black is White); and dentifrice containing blue covarine (Close Up White Now). The samples were submitted to 1,000 and 30,000 brushing cycles. The color values (CIE L*a*b*), surface roughness (Ra) and microhardness (Knoop) were recorded at four time points: baseline, after staining, after 1,000 and after 30,000 brushing cycles. The data were submitted to statistical analyses using paired t-test, ANOVA and Tukey. RESULTS: The color analysis, roughness and microhardness results showed interaction between the effect of the dentifrices and the time point (P< 0.001). The bleaching dentifrices brought about color changes (ΔE) significantly greater than those obtained with conventional dentifrices and the control; however, there were no significant color changes among the bleaching dentifrices. When the color coordinates were evaluated individually, the L* values increased and the a* and b* values decreased throughout the experiment. The conventional toothpaste and the toothpastes containing blue covarine, activated charcoal or hydrogen peroxide promoted a statistically significant increase in the surface roughness of the samples after the last brushing cycle. The sodium tripolyphosphate dentifrice caused a progressive reduction in roughness. The microhardness increased statistically after 30,000 cycles for the conventional toothpaste, blue covarine and hydrogen peroxide. It was concluded that the whitening dentifrices lightened the samples, which evidenced greater luminosity and reduction in reddish and yellow tones. Moreover, they did not have deleterious effects on microhardness, and caused acceptable changes in surface roughness. CLINICAL SIGNIFICANCE: Dentifrices with different whitening strategies changed the color of the samples, resulting in samples with greater luminosity and reduced reddish and yellowish tones. They also caused changes in surface roughness within the acceptable clinical limit and did not have a deleterious effect on the microhardness of dental enamel.

Influence of infrastructure design and ceramic coverage material on stress development in posterior crowns.

PURPOSE: To evaluate the influence of the infrastructure design and type of ceramic coverage on residual stresses after occlusal loading of crowns with yttria-stabilized zirconium oxide (Y-TZP) infrastructure, analyzed by means of the finite element method. METHODS: 3D models of a mandibular first molar total crown were constructed with two different types of infrastructures: a coping with a uniform thickness of 0.3 mm, and an anatomic coping with a thickness ranging from 0.3 mm to 1.5 mm, depending on the external anatomy of the crown, and three types of ceramic coverages: feldspathic, leucite- and lithium disilicate-reinforced types. Fusion 360 software ( Autodesk) was used to simulate occlusal loading of 300 N in an area of 1 mm² on the internal slopes of the mesial vestibular cusps. RESULTS: Higher tensile stress values ( σ1 positive) were observed for the ceramics with anatomic copings (800.3 MPa for feldspathic; 800.1 MPa for leucite, and 799.0 MPa for lithium disilicate), in comparison with the groups of uniform coping (482.0 MPa for feldspathic, 480.0 MPa for leucite, and 479.4 MPa for lithium disilicate). Stress distribution in all the groups followed the same type of pattern, with stresses developing in the load application region and following in the direction of the facial-lingual regions of the coverage crowns. The main maximum peaks of tensile strength were located below the points of load application and on the internal surface of the crown in the distolingual direction. The magnitudes of tensile stress on the anatomic coping ceramics were higher than on the uniform coping ceramics; the different coverage ceramics used did not influence the stress distribution pattern. CLINICAL SIGNIFICANCE: Ceramics on copings with a uniform shape resulted in lower values of internal stress development, in comparison with the anatomic-shaped copings, irrespective of the coverage ceramic used.

At-home, in-office and combined dental bleaching techniques using hydrogen peroxide: Randomized clinical trial evaluation of effectiveness, clinical parameters and enamel mineral content.

PURPOSE: To conduct a clinical evaluation of dental bleaching techniques using hydrogen peroxide (HP), regarding tooth sensitivity, gingival irritation, subject's perception of color change, and calcium (Ca) and phosphorous (P) concentrations in enamel. METHODS: 75 volunteers were distributed according to the bleaching technique (n=25): (a) at-home: 10%HP (Opalescence GO) for 15 days of continuous use (1 hour per day); (b) in-office: 40%HP (Opalescence Boost) in three clinical sessions (40 minutes each session); (c) combined: one initial session with 40%HP, and the rest with 10%HP for 15 days of continuous use. Clinical evaluations and Ca and P concentration collections were obtained before, during bleaching treatment, and 15 days after conclusion of treatment. The generalized linear models were used to evaluate the data for VITA Classical scale, CIELAB, tooth sensitivity, degree of acceptability of the technique, Ca and P concentrations and to determine the ΔE variables and color change perception. Gingival irritation was analyzed by Fisher's Exact test. The total frequencies for each time interval (regardless of bleaching technique) were compared at 50% by the chi-square test. RESULTS: The in-office technique presented the lowest tooth sensitivity, but all techniques caused an increase in sensitivity over time (P< 0.0001). All techniques resulted in lower Ca and P concentrations in enamel at each time point, compared with the baseline concentrations. Calcium concentrations did not differ significantly among the treatments (P= 0.9360). Phosphorus concentration at the 8th day was higher for the in-office technique group (P< 0.05). All the bleaching techniques were effective in altering color, with ΔE values higher than 3.3, without any significant differences (P= 0.3255). Higher occurrence of gingival irritation was observed for at-home and combined techniques. The combined technique seemed to promote a color change faster than the other techniques. CLINICAL SIGNIFICANCE: All the dental bleaching techniques proved equally effective in promoting tooth color change. These techniques may reduce calcium and phosphorous content in enamel. The at-home and the combined techniques may cause greater dental sensitivity than the in-office technique, and led to a higher prevalence of gingival irritation.

TiF4 Incorporated into a Self-etching Primer in Different Concentrations: Antimicrobial Properties and Effects on Demineralisation Inhibition Around the Restoration/Enamel-Dentin Interface.

PURPOSE: To apply titanium tetrafluoride (TiF4) in an aqueous solution or incorporated into the primer of a self-etching adhesive (Clearfil SE Bond) as dentin pre-treatment and evaluate its antimicrobial effect, determine the minimum bactericidal concentraion (MBC) against Streptococcus mutans and Lactobacillus casei and analyse its potential to inhibit the development of carious lesions at the restoration interface. MATERIALS AND METHODS: For MBC, an aqueous solution or primer with different concentrations (in %) of TiF4 were used (from 0.0 to 4.0). Also, 50 cavities were prepared at the enamel/dentin junction of third molars and received the following dentin pre-treatments (n = 10): Clearfil SE Bond (CL); aqueous solution of 2.5% TiF4 + CL (T2.5%); aqueous solution of 4% TiF4 + CL (T4%); 2.5% TiF4 incorporated into the primer (P2.5%); 4% TiF4 incorporated into the primer (P4%). Cavities were restored and submitted to pH cycling to create artificial caries lesions. Microhardness tests were performed after sectioning the restorations to assess the demineralisation at margins. RESULTS: ANOVA and Tukey's tests showed that TiF4 in aqueous solution presented MBC against S. mutans and L. casei of over 2.0%. TiF4 in the primer of a self-etching adhesive presented MBC of over 1% for L. casei. For enamel, CL showed no significant differences in microhardness between the depths. CONCLUSIONS: The aqueous solution had an antimicrobial effect against Streptococcus mutans and Lactobacillus casei of over 2.0%. Pretreatment with the aqueous solution or primer did not inhibit demineralisation at enamel or dentin restoration interfaces.

Influence of Core-Veneer Thickness Ratio on the Fracture Load and Failure Mode of Zirconia Crowns.

PURPOSE: To evaluate the influence of different core-veneer thickness (CVT) ratios on fracture loads and failure modes of zirconia crowns with or without thermomechanical cycling (TC). MATERIALS AND METHODS: Forty yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) cores were veneered with a pressable ceramic and divided into four groups (n = 10): group 1 - 1:3 CVT ratio (0.5-mm core, 1.5-mm veneer); group 2 - 1:1 CVT ratio (1.0-mm core, 1.0-mm veneer); groups 3 and 4 - identical to groups 1 and 2, respectively, except that they underwent TC (1,000,000 cycles with an 84-N load applied at a 4-Hz frequency, temperature cycling at 4°C, 37°C, and 55°C - 30 seconds each). Loads were applied axially to the central fossa of the crowns with a 1 mm/min crosshead speed at 200 N until failure. RESULTS: Two-way ANOVA showed that the crowns with a 1:3 CVT ratio had a lower mean fracture load than crowns with a 1:1 CVT ratio (group 1 = 1666.4 ± 466.4 N; group 2 = 2156.6 ± 472.3 N). TC had no effect on the fracture load for crowns with the same CVT ratio. The failures observed for the crowns in groups 1, 3, and 4 were fractures within the veneering ceramic, which exposed the core. The failure severity of fractures for group 2 was less extensive, characterized by chipping within the ceramic veneer. CONCLUSION: Crowns with a 1:1 CVT ratio had higher fracture load values and more conservative failures. TC had no effect on the fracture load of the ceramic crowns.

Changes to Glazed Dental Ceramic Shade, Roughness, and Microhardness after Bleaching and Simulated Brushing.

PURPOSE: To evaluate shade stability, surface roughness, microhardness, and compressive strength of a glazed feldspathic ceramic subjected to bleaching and simulated brushing. MATERIALS AND METHODS: Eighty-eight glazed feldspathic ceramic specimens were made from microparticulate leucite and divided into eight groups (n = 10). The whitening products used were: Opalescence Trèswhite Supreme (Ultradent), Opalescence®\ PF 15% (Ultradent), and Oral-B 3D White Whitestrips. All substances for whitening were used for 4 hours/day for a period of 14 days; the control group was not bleached. Next, half of the specimens were individually brushed. Microhardness and surface roughness data were subjected to three-way ANOVA and Tukey test. The diametrical tensile strength data were subjected to two-way ANOVA. The shade change data were analyzed using Kruskal-Wallis, Mann-Whitney, and the Student-Newman-Keuls test. The significance level was set at 5%. RESULTS: Glazed feldspathic ceramic surface microhardness was significantly affected by bleaching agents (p = 0.007). Initially, glazed ceramic microhardness was significantly higher than that observed after contact with the bleaching agents, whether or not brushing was performed. The specimens submitted to bleaching in preloaded trays presented lower surface roughness values after brushing (p = 0.037). The surface roughness was significantly lower in the brushed specimens (p = 0.044). The diametrical tensile strength was not significantly affected by the application of bleaching agents (p = 0.563) or by brushing (p = 0.477). When the specimens were brushed, however, shade change was significantly influenced by the bleaching agent used (p = 0.041). CONCLUSIONS: Bleaching agents associated with brushing cycles can alter surface properties and shade stability of glazed feldspathic ceramics, though such findings may not reflect the performance of unglazed feldspathic ceramics.

Chitosan incorporated in a total-etch adhesive system: antimicrobial activity against Streptococcus mutans and Lactobacillus casei.

The aim of this study was to investigate the antimicrobial effect of an experimental adhesive system containing chitosan (0.2% and 0.5%) against Streptococcus mutans and Lactobacillus casei. Twenty-four extracted human third molars were used, and 4 cavities were prepared in each tooth. The teeth were contaminated with either S mutans (n = 12 teeth, 48 cavities) or L casei (n = 12 teeth, 48 cavities) microorganisms. One cavity in each tooth received 1 of the following treatments: negative control (no treatment [NC]), positive control (Adper Single Bond 2 [SB]), an experimental adhesive containing chitosan 0.2% (CHI2), or an experimental adhesive containing chitosan 0.5% (CHI5). After sealing of the cavities and an incubation period, dentin scrapings were collected from each cavity for microbiological evaluation. Analysis of variance and Tukey tests revealed no statistically significant differences among the SB, CHI2, and CHI5 groups (P > 0.05), but all 3 differed significantly from the NC group (P ≤ 0.05). The concentrations of chitosan did not influence the antimicrobial effect against S mutans and L casei, presenting a similar effect to that of a conventional 2-step adhesive system.

Effect of high- or low-concentration bleaching agents containing calcium and/or fluoride on enamel microhardness.

The aim of this in vitro study was to evaluate enamel microhardness following bleaching treatments using either high- or low-concentration hydrogen peroxide (HP) agents containing calcium and/or fluoride. Sixty enamel blocks were bleached with 1 of 6 different bleaching agents (n = 10). The high-concentration HP agents were Whiteness HP Maxx (35% HP), Whiteness HP Blue (35% HP, 2% calcium gluconate), Pola Office+ (37.5% HP, 5% potassium nitrate), and Opalescence Boost (38% HP, 1.1% fluoride ion, 3% potassium nitrate). The low-concentration HP agents evaluated were Pola Day (9.5% HP) and White Class (10% HP, potassium nitrate, calcium, fluoride). High-concentration agents were applied in 3 sessions, whereas low-concentration agents were applied for 14 days. Knoop microhardness measurements were taken on the surface of the enamel before bleaching, at various timepoints during bleaching, and 14 days after the final bleaching treatment. The 2-way analysis of variance test showed that microhardness values were significantly influenced by the bleaching agent (P < 0.001) and application time (P < 0.001). The Tukey test showed that enamel bleached with Whiteness HP Maxx or White Class presented lower microhardness values than did the enamel treated with the remaining products. There was a reduction in micro-hardness values up to the end of the treatment. The results showed that the composition, concentration, and application protocol for each bleaching agent influenced the enamel microhardness values in that the microhardness decreased over time, regardless of the agent used or the addition of calcium and/or fluoride.

Inhibition of demineralization around the enamel-dentin/restoration interface after dentin pretreatment with TiF4 and self-etching adhesive systems.

OBJECTIVES: The objective of this study was to evaluate the inhibition of demineralization around enamel-dentin/restoration interface after dentin pretreatment with 2.5% titanium tetrafluoride (TiF4). MATERIALS AND METHODS: Forty dental class V cavities at the cementoenamel junction were distributed into four groups (n = 10), according to the presence or absence of TiF4 and to the adhesive system (Clearfil SE Bond/CL and Adper EasyOne/AD), and restored with a resin composite. A dynamic pH cycling model was used to induce the development of artificial caries lesions. After sectioning the dental blocks, Knoop microhardness tests were performed at different depths (20, 40, and 60 µm from the occlusal margin of the restoration) and at different distances (100, 200, and 300 µm from the adhesive interface). Repeated measures three-way analysis of variance (ANOVA) and Tukey's test were used (α = 0.05). RESULTS: For enamel, there were no differences in the microhardness values for CL, AD, and TiF4-AD at depths, regardless of the distances. Considering each depth, there were no significant differences among treatments. For dentin, ANOVA showed no significant interaction among the independent variables treatment*distance*depth (p = 0.994), no significant interaction between treatment*depth (p = 0.722), no significant interaction between treatment*distance (p = 0.265), no significant interaction between depth*distance (p = 0.365), and no significant effect on treatment (p = 0.151), depth (p = 0.067), or distance (p = 0.251). CONCLUSIONS: Dentin pretreatment of the cavity walls with TiF4 before self-etching adhesive systems was not effective in inhibiting demineralization around the enamel-dentin/restoration interfaces. CLINICAL RELEVANCE: The mechanism of incorporating fluoride in enamel and dentin of the cavity walls to inhibit demineralization around restorations seems ineffective when using TiF4 as a dentin pretreatment.

TiF4 improves microtensile bond strength to dentin when using an adhesive system regardless of primer/bond application timing and method.

OBJECTIVES: This study evaluated the bond strength of a two-step conventional adhesive system to dentin pretreated with 2.5 % titanium tetrafluoride (TiF(4)) according to application timing (before or after acid conditioning) and primer/adhesive application method (active or passive). MATERIALS AND METHODS: Dentin surfaces were randomly treated with different adhesive procedures (n = 6): etching with phosphoric acid (PA) + primer/adhesive (Adper Single Bond 2/3M ESPE) actively applied; PA + primer/adhesive passively applied; TiF(4) before PA + primer/adhesive actively applied; TiF(4) before PA + primer/adhesive passively applied; TiF(4) after PA + primer/adhesive actively applied; and TiF(4) after PA + primer/adhesive passively applied. A composite block was built onto the tooth, which was sectioned into sticks (adhesive area of approximately 1 mm(2)). Microtensile bond strength tests and the failure mode were determined. RESULTS: Two-way ANOVA revealed no significant interaction between TiF(4) application timing and primer/adhesive application method (p = 0.184). The use of TiF(4), before or after PA significantly increased bond strength values (p < 0.001). There was no significant difference in bond strength values when using TiF4 before or after PA. The primer/adhesive application method had no influence on bond strength, regardless of whether TiF(4) was used (p = 0.906). Failure mode was predominantly adhesive. CONCLUSIONS: The use of TiF(4) promoted higher immediate bond strength to dentin. The conventional adhesive system may be applied either actively or passively, regardless of TiF(4) application timing. CLINICAL SIGNIFICANCE: Pretreatment with TiF(4) increased bond strength in a conventional two-step adhesive system to dentin, regardless of the primer/adhesive application method and the timing of dentin pretreatment.

Influence of an arginine-containing toothpaste on bond strength of different adhesive systems to eroded dentin.

The aim of this study was to evaluate the bond strength of different adhesive systems to eroded dentin following toothbrushing with an arginine-containing toothpaste. Sixty standardized 3 × 3 × 2-mm fragments of root dentin (n = 10) were prepared. After all surfaces except the buccal surfaces were impermeabilized, specimens were subjected to an erosive wear protocol and stored for 24 hours at 37°C. The specimens underwent 1000 toothbrushing cycles with an arginine-containing toothpaste, an arginine-free toothpaste (positive control group), or artificial saliva (negative control group). Following application of a self-etching or an etch-and-rinse adhesive to the buccal surfaces of the specimens, 6-mm-high composite resin blocks were built up in 2-mm increments. After 24 hours' storage in 100% relative humidity, microtensile test specimens with an approximate area of 1 mm² were prepared. The test was performed at a speed of 0.5 mm/min until specimen fracture, and the failure patterns were evaluated using a stereoscopic loupe. Two-way analysis of variance revealed no significant difference between the toothpastes, the adhesive systems, or the interactions between toothpaste and adhesive system in terms of the bond strength to eroded dentin (P > 0.05). The predominant failure pattern was adhesive in all groups. It was concluded that a toothpaste containing arginine did not interfere with the bond between either the self-etching or the etch-and-rinse adhesive system and eroded dentin.

Antimicrobial Potential of Papain Chemomechanical Agent on Streptococcus Mutans and Lactobacillus Casei Followed by the Use of Self-Etching Adhesive Systems.

OBJECTIVE: This study evaluated the antimicrobial effect of papain-based gel (Papacárie/ P) followed by self-etching adhesive systems with MDPB monomer (Clearfil Protect Bond/ PB) and without (Clearfil SE Bond/ Cl) on Streptococcus mutans (Sm) and Lactobacillus casei (Lc). STUDY DESIGN: The dentin of twenty human teeth was exposed to prepare four cylindrical cavities in each tooth. The cavities were incubated with Sm or Lc. One cavity from each tooth served as contamination control (positive control group); the other three were treated with P, P+CL and P+PB. The cavities were sealed and after 72 h, dentin samples were collected and microbial cultivation was performed. Microbial count was undertaken (CFUs/mg) according to the morphological characteristics for Sm and Lc. Analysis of variance and Tukey's test were applied (α=5%). RESULTS: For Sm, groups P+Cl and P+PB had lower microbial count than group P (no statistical differences between P+Cl and P+PB). For Lc, group P+Cl had microbial count similar to group P. There was statistical difference between cavities treated with P and P+PB but none between groups P+Cl and P+PB. After using P, both self-etching adhesives showed antimicrobial potential, although Clearfil Protect Bond proved better against Lc. CONCLUSIONS: Both self-etching adhesives used after application of Papacárie showed antimicrobial potential, although Clearfil Protect Bond proved more effective against Lactobacillus casei.

Toothpastes containing abrasive and chemical whitening agents: efficacy in reducing extrinsic dental staining.

This in vitro study evaluated the efficacy of toothpastes containing abrasive and chemical whitening agents in reducing the extrinsic discoloration of dental enamel. Sixty slabs of dentin from human teeth were sealed so that only the enamel surface was exposed. The enamel surfaces were photographed for initial color assessment. Staining was performed by immersing the dental slabs in 0.2% chlorhexidine solution for 2 minutes and then in black tea for 60 minutes. This process was repeated 15 times. Photographs were taken at the end of the staining process, and the slabs were divided into 5 groups (n = 12), 3 to be brushed with toothpastes containing chemical whitening agents (2 containing phosphate salts and 1 containing phosphate salts plus hydrogen peroxide) and 2 to represent control groups (ordinary/nonwhitening toothpaste and distilled water). The dental slabs were subjected to mechanical toothbrushing with toothpaste slurry or distilled water, according to each group's specifications. After brushing, more photographs were taken for color analysis. The results showed a significant reduction in luminosity after the staining process in addition to an increase in the colors red and yellow (P < 0.001). After brushing, there was a significant increase in luminosity and a reduction in both red and yellow (P < 0.001). However, there was no observed difference between the changes in color values in dental enamel slabs brushed with whitening toothpastes and the changes found in slabs brushed with ordinary toothpaste. The whitening toothpastes did not outperform an ordinary toothpaste in the removal of extrinsic staining.