Effects of Hydrofluoric Acid Concentrations, Commercial Brands, and Adhesive Application on the Bond Strength of a Resin Luting Agent to Lithium Disilicate Glass Ceramic.

OBJECTIVES: To evaluate the surface topography/roughness and bond strength of a resin luting agent to a lithium disilicate glass ceramic after etching with different concentrations of hydrofluoric acid (HF) and commercial brands. METHODS: For bond strength evaluation, 260 lithium disilicate glass ceramic (EMX) discs were randomly distributed into 13 groups based on concentrations of HF and commercial brands (n=20): 5% and 10%, Lysanda (LY5 and LY10); 5% and 10%, Maquira (MA5 and MA10); 5% and 10%, FGM (FG5 and FG10); 4.8%, Ivoclar Vivadent (IV5); 5% and 10%, PHS do Brasil (PH5 and PH10); 5% and 10%, BM4 (BM5 and BM10); 9%, Ultradent Inc (UL10); and Dentsply (DE10). A further random distribution (n=10) was made based on the application (+) or absence (-) of an adhesive layer. Resin luting agent cylinders (1 mm in diameter) were added on EMX surfaces, light-cured, and stored for 24 hours in deionized water at 37°C. On a universal testing machine (DL 500, EMIC), specimens were submitted to a microshear bond strength test at a crosshead speed of 1 mm/min until failure. A representative etched EMX disc from each group underwent surface topography analysis using field-emission scanning electron microscopy (n=1), and five (n=5) etched EMX discs from each group were tested for surface roughness. Data were statistically analyzed using analysis of variance and Tukey test (α=0.05). RESULTS: A less conditioned and smoother surface was observed for 5% HF compared to 10%. Additionally, commercial brands of HF were shown to affect bond strength. When the adhesive layer was not used (-), a 10% concentration promoted higher bond strengths to EMX. However, when adhesive was applied (+), the concentrations of HF and commercial brands had no effect on bond strength results. CONCLUSIONS: A 10% concentration of HF results in higher bond strength than a 5% concentration. If an adhesive layer is applied, neither this distinction nor the influence of commercial brands is observed.

Effect of Mouth Rinse Treatments on Bleached Enamel Properties, Surface Morphology, and Tooth Color.

OBJECTIVE:: To evaluate, in vitro, the effect of mouth rinse exposure on bleached enamel. METHODS:: Enamel/dentin bovine blocks (4×4×2 mm) were bleached with 35% hydrogen peroxide (HP) and were submitted to immersion twice daily for 14 days with different rinses (n=10), including those involving: distilled water (C [control]), 225-ppm NaF (FM, Colgate Plax Classic), essential oil (EM, Listerine Tartar Control), 1.5% hydrogen peroxide (HPM, Colgate Plax Whitening), and 2% hydrogen peroxide, pyrophosphates, and 225-ppm NaF (HPM+P, Colgate® Luminous White). The specimens were stored in a remineralizing solution during all experiments. Analyses of color (ΔE, L*, a*, b*) and roughness (Ra) were performed at the baseline, after HP, and after exposure to the rinse. The cross-sectional microhardness (CSMH) and images by scanning electron microscopy (SEM) were assessed at the end. The data were subjected to analysis of variance (ANOVA) (ΔE), repeated measures ANOVA (Ra), and split-plot ANOVA (CSMH), followed by the Tukey test. The L*, a*, and b* values were analyzed by generalized linear models (α=0.05). RESULTS:: Color changes were not statistically different in the groups. Ra increased in all groups after bleaching; however, it was reestablished in C, FM, and HPM+F and increased in EM after 14 days of the rinse. EM and HPM reduced the CSMH values differing from C and promoted alterations on the enamel surface visualized by SEM. CONCLUSION:: The mouth rinses did not affect the whitening efficacy or promote benefits on bleached enamel properties. Moreover, the 1.5% hydrogen peroxide- or essential oil-based mouth rinses affected the bleached enamel properties, promoting an alteration in morphologic surface and mineral loss in depth.

Effect of Toothpaste Use Against Mineral Loss Promoted by Dental Bleaching.

AIM: To investigate the effect of different toothpaste formulations used prior to dental bleaching with 35% hydrogen peroxide (HP) on the mineral content and surface morphology of enamel. METHODS: Seventy bovine enamel blocks (4×4×2 mm) were submitted to in vitro treatment protocols using a toothbrushing machine prior to dental bleaching or a placebo procedure (n=10) as proposed in the following groups: unbleached control (PLA), bleached control (HP), and brushing with differing toothpastes prior to HP bleaching, including: potassium nitrate toothpaste containing sodium fluoride (PN), sodium monofluorophosphate/MFP toothpaste (FT), arginine-carbonate (8% arginine) (PA) or arginine-carbonate (1.5% arginine) toothpaste (SAN), and toothpaste containing bioactive glass (NM). Phosphorus concentration in gel ([P]) was evaluated (µg of P/mg of gel), and the elemental levels (wt%) of Ca, P, and Na as well as the proportion between Ca and P and spectra graphics were determined using an energy-dispersive X-ray spectrometer (EDS). The surface morphology was assessed using scanning electron microscopy (SEM). The data were subjected to analysis of variance and the Tukey test (α=0.05). RESULTS: HP demonstrated the greatest [P] values in gel, being statistically different from PLA. The [P] of NM was statistically similar to PLA. HP showed a significant decrease in the Ca% and Ca/P values when compared to PLA in EDS analysis. PA showed Ca/P values statistically different from HP. In accordance with SEM analysis, the PA, SAN, and NM groups presented a smooth and uniform enamel surface, while HP and FT demonstrated some alterations in morphology. CONCLUSION: The toothpastes containing bioactive glass or arginine carbonate used prior to dental bleaching were effective in protecting enamel against mineral loss promoted by the whitening procedure.

Effect of Cigarette Smoke on Resin Composite Bond Strength to Enamel and Dentin Using Different Adhesive Systems.

OBJECTIVE: To evaluate the microshear bond strength of composite resin restorations in dental blocks with or without exposure to cigarette smoke. METHOD: Eighty bovine dental blocks were divided into eight groups (n=10) according to the type of adhesive (Scotchbond Multi-Purpose, 3M ESPE, St Paul, MN, USA [SBMP]; Single Bond 2, 3M ESPE [SB]; Clearfil SE Bond, Kuraray Medical Inc, Okayama, Japan [CSEB]; Single Bond Universal, 3M ESPE [SBU]) and exposure to smoke (no exposure; exposure for five days/20 cigarettes per day). The adhesive systems were applied to the tooth structure, and the blocks received a composite restoration made using a matrix of perforated pasta. Data were statistically analyzed using analysis of variance and Tukey test (α<0.05). RESULTS: For enamel, there was no difference between the presence or absence of cigarette smoke (p=0.1397); however, there were differences among the adhesive systems (p<0.001). CSEB showed higher values and did not differ from SBU, but both were statistically different from SB. The SBMP showed intermediate values, while SB demonstrated lower values. For dentin, specimens subjected to cigarette smoke presented bond strength values that were lower when compared with those not exposed to smoke (p<0.001). For the groups without exposure to cigarette smoke, CSEB showed higher values, differing from SBMP. SB and SBU showed intermediary values. For the groups with exposure to cigarette smoke, SBU showed values that were higher and statistically different from SB and CSEB, which presented lower values of bond strength. SBMP demonstrated an intermediate value of bond strength. CONCLUSION: The exposure of dentin to cigarette smoke influenced the bonding strength of adhesives, but no differences were noted in enamel.