Micro-shear bond strength and surface micromorphology of a feldspathic ceramic treated with different cleaning methods after hydrofluoric acid etching

Objective

The aim of this study was to evaluate the effect of feldspathic ceramic surface cleaning on micro-shear bond strength and ceramic surface morphology.

Material and Methods

Forty discs of feldspathic ceramic were prepared and etched with 10% hydrofluoric acid for 2 minutes. The discs were randomly distributed into five groups (n=8): C: no treatment, S: water spray + air drying for 1 minute, US: immersion in ultrasonic bath for 5 minutes, F: etching with 37% phosphoric acid for 1 minute, followed by 1-minute rinse, F+US: etching with 37% phosphoric acid for 1 minute, 1-minute rinse and ultrasonic bath for 5 minutes. Composite cylinders were bonded to the discs following application of silane and hydrophobic adhesive for micro-shear bond strength testing in a universal testing machine at 0.5 mm/min crosshead speed until failure. Stereomicroscopy was used to classify failure type. Surface micromorphology of each treatment type was evaluated by scanning electron microscopy at 500 and 2,500 times magnification.

Results

One-way ANOVA test showed no significant difference between treatments (p=0.3197) and the most common failure types were cohesive resin cohesion followed by adhesive failure. Micro-shear bond strength of the feldspathic ceramic substrate to the adhesive system was not influenced by the different surface cleaning techniques. Absence of or less residue was observed after etching with hydrofluoric acid for the groups US and F+US.

Conclusions

Combining ceramic cleaning techniques with hydrofluoric acid etching did not affect ceramic bond strength, whereas, when cleaning was associated with ultrasound, less residue was observed.     

Effect of different monomer-based composites and acid etching pre-treatment of enamel on the microleakage using self-etch adhesives systems

Objective. To evaluate quantitatively the marginal microleakage of restorations carried out with self-etching adhesives with or without prior phosphoric enamel acid etching of silorane or methacrylate resin-based composite restorations subjected to thermal cycling. Materials and methods. Forty cavities were prepared at the proximal surface of bovine incisors and randomly divided according to the etching of the enamel and restorative system used. The groups were restored with methacrylate [Adper SE Plus adhesive (3M ESPE) + Filtek Z250 (3M ESPE)] or silorane [Filtek LS adhesive (3M ESPE) + Filtek LS composite (3M ESPE)] restorative systems, light-cured using a LED unit (Bluephase 16i, Vivadent). After restorative procedure and thermocycling (1000 cycles), the specimens were immersed in methylene blue for 2 h. The specimens were triturated and the powder was used for analysis in an absorbance spectrophotometer. Data were statistically analyzed by 2-way ANOVA (alpha = 0.05). Results. No statistical difference between the restorative materials tested with or without previous acid etching of enamel in Class II marginal microleakage was observed (p > 0.05). Conclusions. The use of acid etching prior to self-etching adhesives did not interfere on the microleakage of methacrylate- or silorane-based restorations.     

Microtensile bond strengths of composite to dentin treated with desensitizer products

PURPOSE: This study was designed to analyze the influence of desensitizing procedures on dentin bond strength. MATERIALS AND METHODS: Forty bovine incisors were used, divided into four groups (n = 10): G1: control; G2: Gluma Desensitizer (Heraeus Kulzer); G3: Oxa-Gel (Art-Dent); G4: low-intensity laser (MMOptics). The buccal surface was wet ground flat with 180-, 400- and 600-grit silicon carbide abrasive paper to expose midcoronal dentin and create a uniform surface. After the application of the desensitizing agents to the exposed dentin, the specimens were etched with 35% phosphoric acid for 30 s, and an adhesive (Single Bond) was applied and light cured. A 4-mm high crown of composite resin (Filtek Z250) was then built up. Specimens were trimmed to an hourglass shape with cross sections of 1 mm2. Each specimen was individually fractured by a microtensile testing machine at a crosshead speed of 0.5 mm/min. The data, recorded in MPa, were analyzed with one-way ANOVA and the Duncan test (p = 0.05). RESULTS: Specimens treated with dentin desensitizers (except Gluma) yielded significantly lower mean bond strengths than nontreated control specimens. The mean values in MPa (+/- SD) were: G1: 13.4 (6.2); G2: 13.2 (4.8); G3: 7.15 (4.3); G4: 7.21 (4.6). CONCLUSIONS: Among the desensitizing agents studied, only Gluma Desensitizer did not detrimentally influence the bond strength values. It is a useful material for dentin desensitization.     

Foraging differences in cattle: Fecal analysis of three racial categories in a harsh environment

Feces from three racial categories of cattle being raised together in a degraded, desertic-thorn forest environment in northwestern Mexico were compared for plant epidermal cell content. There were statistically significant group differences for approximately one-third of the plant material found in the feces. The proportional fecal differences between racial categories were similar to those found previously for B-system blood types. The feces ofBos taurus-like cattle contained a greater variety of plants than did those ofB. indicus-like animals. The findings have implications for studies of behavioral evolution, the effects of cattle on ecology, and cattle husbandry.The research was supported, in part, by University of California Faculty Research Grants awarded to R.M.M. and C.J.B. M.C.T.P. was on a training grant from the Applied Sciences Unit, Department of Scientific Affairs, Organization of American States.     

Does a meso‐caval shunt have positive effects in a pig large‐for‐size liver transplantation model?

In pediatric liver transplantations with LFS grafts, higher incidences of graft dysfunction probably occur due to IRI. It was postulated that increasing the blood supply to the graft by means of a meso‐caval shunt could ameliorate the IRI. Eleven pigs underwent liver transplantation and were divided into two groups: LFS and LFS+SHUNT group. A series of flowmetric, metabolic, histologic, and molecular studies were performed. No significant metabolic differences were observed between the groups. One hour after reperfusion, portal flow was significantly lower in the recipients than in the donors, proving that the graft was maintained in low portal blood flow, although the shunt could promote a transient increase in the portal blood flow and a decrease in the arterial flow. Finally, it was verified that the shunt promoted a decrease in inflammation and steatosis scores and a decrease in the expression of the eNOS gene (responsible for the generation of nitric oxide in the vascular endothelium) and an increase in the expression of the proapoptotic gene BAX. The meso‐caval shunt was responsible for some positive effects, although other deleterious flowmetric and molecular alterations also occurred.