RESUMEN
OBJECTIVE: To evaluate the mechanical stability and the proteolytic activity of bonds created by a two-step, etch-and-rinse adhesive applied to cross-linked and air-dried etched dentin. METHODS: Flat dentin surfaces were produced in 64 extracted sound human molars. The dentin was etched with 35% phosphoric acid for 15 seconds, and then the teeth were divided into groups according to the cross-linking solution applied on the etched dentin. Group 1: 5% grape seed extract (GSE), Group 2: 5% glutaraldehyde, Group 3: Gluma Desensitizer, or Group 4: deionized water (control). Solutions were applied for 60 seconds, followed by rinse and blot drying. Then, the teeth were separated into two subgroups where the etched dentin was kept moist or air-dried. The adhesive was applied followed by a composite resin buildup. After 24 hours, the teeth were cut into beams (0.81 mm²) that were tested for microtensile strength immediately or after 12 months of aging in a 37°C saliva-like buffer. Additional teeth (n=32) were bonded as described and cut into 0.5-mm-thick slabs. The slabs were prepared for nanoleakage (scanning electron microscopy) and in situ zymography (EnzChek Protease Assay Kit). Bond strength data were submitted to ANOVA and Tukey tests (α =0.05). RESULTS: Significant reduction in immediate bond strength (ca 65%) and increase in proteolytic activity was seen when the etched dentin was air dried without previous cross-linking biomodification. Conversely, bond strengths did not differ from those produced on wet dentin when collagen was cross-linked before air drying, irrespective of the solution applied. For both moist and air-dried etched dentin, collagen cross-linking resulted in mechanically stable bonds and reduced proteolytic activity after 12 months of storage. CONCLUSION: Bonds produced by the application of a two-step, etch-and-rinse adhesive to cross-linked, air-dried, etched dentin were mechanically stable and revealed reduced proteolytic activity after 1 year of aging.
Asunto(s)
Recubrimiento Dental Adhesivo , Recubrimientos Dentinarios , Colágeno , Resinas Compuestas/química , Resinas Compuestas/uso terapéutico , Recubrimiento Dental Adhesivo/métodos , Cementos Dentales/uso terapéutico , Dentina , Recubrimientos Dentinarios/química , Recubrimientos Dentinarios/uso terapéutico , Ensayo de Materiales , Cementos de Resina/química , Cementos de Resina/uso terapéutico , Resistencia a la TracciónRESUMEN
Reaction times were measured in an absolute judgment experiment involving either the location of a point on a screen, or the direction of a moving point, or its velocity. Stimuli were chosen to be almost perfectly detectable and discriminable when presented pairwise to avoid confusions at the sensory coding level. Typical results associated with absolute judgment tasks were observed, as to the amount of information transmission and anchoring effects. More in particular, latencies appear to be a direct function of the number N of alternatives. For N constant, responses are much slower for velocity than for both location and direction. This difference itself is a direct function of N, and, presumably, drops to zero for N = 1, i.e., when stimulus uncertainty vanishes. These observations support the idea that the difference should not be attributed to some velocity-specific integration of space and time but to some performance decision strategies in evaluation of magnitude.