Comportamento dos sistemas adesivos com fluor frente ao desafio cariogenico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The aim of this study was to investigate the behavior of fluoride-free and fluoride-containing adhesive systems subject to dynamic chemical induction of secondary caries, by means of the microtensile bond strength test, establishment of carious lesion depth and the amount of fluoride-ion release from each adhesive system. Eighty extracted bovine incisors were ground flat to expose the labial dentine surface. The Filtek Z250 composite resin and four adhesives systems, two fluoride-free (Single Bond and Clearfil SE Bond) and two-fluoride containing adhesive systems (Optibond Solo Plus and Clearfil Protect Bond), were used for the construction of bulk restorations (n=20) over the flat dentin surfaces. After bonding, half of the specimens were subjected to carious chemical induction and the other half was the control group. The specimens were serially sectioned into 6 slabs with approximately 1.0 mm width that were trimmed to a 1 mm2 cross-sectional area at the bonded interface. Nail varnish was used to cover the dentin surface, leaving an area of 4 mm2 around the bonded interface. The specimens were, then, subject to 4-day chemical cycling, comprising immersion on remineralising (RE) and demineralising (DES) solutions for, respectively, 20 hours and 4 hours per day. Microtensile bond strength test of 4 specimens from both the chemical cycling and control groups were performed using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. SEM observations of the fracture surfaces were perform to evaluate the fracture pattern of the specimens. Polarized Light Microscope was used for the establishment of carious lesion deepness at 5, 10 and 25µm from the bonded interface of the remaining two specimens subject to the chemical challenge. A specific electrode calibrated with solutions prepared with TISAB III was used to determine the amount of fluoride-ion release present in the DES-RE solutions. Data of mean bond strengths (MPa) and carious lesion depth (µm) were analyzed with ANOVA and Tukey test (?=5%). For the microtensile bond strength, regardless the adhesive system tested; there was no statistic significant difference between the specimens of control group. It was observed a significant reduction on the bond strength values for all adhesives systems after chemical cycling; however, there was no difference between the tested materials. For the deepness of carious lesion, a significant difference between the adhesive systems was only detected at the 5µm-distance, in which Optibond Solo Plus fluoride-containing adhesive system showed the smallest lesion formation. An amount of fluoride-ion release of less than 0.03 ppm (under the detection limit of the electrode) present on the DES-RE solutions was found. It could be concluded that the secondary carious reduced the restorations bond strength and the amount of fluoride-ion present at the adhesive systems was not effective in preserve the bond strength values after caries chemical induction as well as in the reduction of carious lesion deepness

ASSUNTO(S)

microscopia dentin microscopy dental caries caries dentarias dentina

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