Abstract
To understand the degradation mechanisms of commercially available one bottle-type ceramic primer, we prepared one bottle-type experimental ceramic primer consisting of gamma-methacryloxy-propyl-trimethoxysilane, gamma-MPTS, and 90% ethanol solution. The effects of aging of the experimental primer on the hydrolysis and condensation behavior of gamma -MPTS and on the bonding efficacy of gamma-MPTS at the interface between cement and ceramic were studied. We used two lamina bond porcelain primers (LB), that had been aged for 20 months and newly purchased. Experimental primer was aged at 20 degrees C. After aging, we measured 29Si NMR spectrum of the gamma-MPTS and the shear bond strength of the cement to silane-treated ceramic by varying aging periods. When the LB was aged for 20 months, the mean bond strength decreased from 26 to 11 MPa. To understand the degradation mechanism in the bond strength, the effects of aging of experimental primer on molecular species of gamma-MPTS were examined. With prolonging its aging period, the methoxy group of the silicone functional portion in the gamma-MPTS hydrolyzed and the hydrolyzed gamma-MPTS species condensed together. The molecular weight of condensed gamma-MPTS species increased. On the other hand, when the dimer species of gamma-MPTS were produced, a maximum mean bond strength of 28 MPa was observed. Thereafter, the bond strength dropped down and leveled off at 16 MPa. When the LB was aged for 20 months, the bond strength dramatically decreased. This decrease in the mean bond strength was probably attributed to ester exchange reaction of the methoxyl group in the gamma-MPTS by the ethanol used as diluent solvent.
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