Long-term degradation of resin-dentin interface in vivo

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The long-term durability of bonds between adhesive resins and dentin is of significant importance for the longevity of bonded restorations. Objectives. This in vivo long-term study was carried out to evaluate the degradation of resin-dentin bonds in the oral cavity, as well as to test the hypothesis that the three-dimensional ashesive interfac would show morphological changes in vivo over time. Materials and Methods : Very shallow saucer-shaped dentin cavities were prepared in 12 intact teeth of one Japanese monkey (Macaca fuscata) under general anesthesia. The cavities were restored with Clearfil Liner Bond II and Clearfil Photo Posterior resin composite. The teeth were extracted at three different times ; immediate, 180, and 360 days after placement of the restorations. One day after sacrifice of the monkey, specimens of the three time periods were subjected to the micro-tensile bond test at a cross head speed of 1 mm/min. The surfaces of the failed bonds were observed under a field emission scamming electron microscope (FE-SEM). Results : Bond strength measurements in this study were successfully performed and were stable approximately 19 MPa during the one-year testing. Scanning electron microscopic observations of the failed surfaces revealed porosities at the top of the hybrid layr and within the adhesive resin which increased over time. Significance : Long-term bonds can be assessed in vivo using the microtensile bond test, and morphological changes of the adhesive interphase can be evaluated after the bond strength.