Influencia do meio e tempo de armazenamento na resistencia a microtração de sistemas adesivos / Influence of time and storage medium in the microtensile bond strength of adhesive systems

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The purpose of this study was to evaluate "in vitro" the microtensile bond strength of two adhesive systems applied to the dentin as a function of time and storage medium, as well as to illustrate, through Scanning Electron Microscope (SEM) images, the nanoleakage of the hybrid layer, which had its constituents evaluated by microanalysis (EDS). Eighty recently extracted bovine incisors were selected and randomly distributed into eight groups (n= 10).The buccal aspect of all teeth was sequentially abraded and planed using 320, 400 and 600 grit SiC abrasive papers until the exposure of dentin, which had a remaining thickness of 2.5 mm.The restorative procedures were executed on this exposed dentin. The Adper Scotchbond Multi-Purpose (ASBMP) and Clarfil SE Bond (CSEB) adhesive systems were used following their manufacturers instructions. Right after, a rectangular block of 8.0 x 3.0 x 4.0mm was built up over the adhesive surface with two increments of 2.0mm of thickness each of TPH Spectrum microhybrid composite resin. After the restorative procedures, the samples were perpendicularly sectioned in their long axis in the mesial-distal direction with a high precision metalografic cutting machine to obtain slices. Some of the slices had the bonding interface trimmed to an hourglass shape to obtain a bonding area of approximately 1mm2. Subsequently,the specimens were stored in water (1) or in a desmineralization/reminaralization solution (DES/RE) (2), associated with daily immersion for 1 minute in 0.05% sodium fluorite (NaF) aqueous solution for 7 (A) or 30 (B) days. After storage, the specimens were subjected to mechanical microtensile bonding test at a crosshead speed of 0.5 mm/min. The microtensile bonding strength values were statistically analyzed by ANOVA at p<0.05. For nanoleakage illustrative analysis, some of the slices obtained after sectioning of the tooth/restoration conjunction were used. Following each storage period, the slices were infiltrated with amoniacal silver nitrate (AgNO3.NH4) tracer agent, revealed, finished, polished and carbon sputtered in order to visualize the nanometer spaces within the hybrid layer using SEM. Energy Dispersive X-Ray Spectroscopy (EDS) was used to analyze the constituents of AgNO3.NH4 infiltrated specimens. The MPa values were: (G1) ASBMP 1A- 14,86Aa, (G2) ASBMP 1B-13,60Aa, (G3) ASBMP 2A- 11,86Aa, (G4) ASBMP 2B- 13,24Aa, (G5) CLSEB 1A- 13,16Aa, (G6) CLSEB 1B- 6,55Bb, (G7) CLSEB 2A- 10,27Aa, (G8) CLSEB 2B- 8,42Ba. By means of the results it was concluded that ASBMP (G1) presented the highest bonding strength values. However, the bonding strength values of ASBMP did not statistically differ from CLSEB when comparing the same period of time and storage medium (G5). For CLSEB group, G5 had the highest bonding strength values. Nevertheless, after 30 days of storage in water, a significant drop on the bond strength values was observed (G6). In the other hand, the bond strength values for ASBMP total-etch system were kept stable after the same period of time and storage medium protocol (G2). In the same manner, when CLSEB adhesive system was submitted to DES/RE cycle plus the immersion in 0.05% NaF solution for 30 days (G8), it kept the bond strength values stables and not differing from G5 and G7. For ASBMP adhesive system (G1,G2, G3 and G4), no statistically significant difference was observed among the bond strength values for the different periods of time and storage media. The SEM analysis showed less silver particles accumulation after 30 days of storage in DES/RE solution than for water. Therefore, the DES/RE medium associated with the immersion for 1 minute in 0.05% NaF solution was beneficial to the bonding longevity and hybrid layer integrity over the time

ASSUNTO(S)

tooth remineralization dentistica dentistry infiltração dentaria dental leakage remineralização dentaria

ACESSO AO ARTIGO

Documentos Relacionados