Tensile bond strength of resin-bonded non-precious alloys with chemically and mechanically roughened surfaces.

The present study was carried out for investigation of the tensile bond strength of resin-bonded non-precious alloys after their surfaces were roughened by sand-blasting, chemical etching, or sugar crystal impressions. Fifty test specimens were cast in a Ni-Cr (Wiron 88) alloy and 50 in a Co-Cr (Wirobond) alloy. Twenty specimens of each alloy were surface-treated according to the sugar crystal impression method. The remaining specimens were first sand-blasted, and 20 specimens of each alloy were thereafter allocated for chemical etching and divided into subgroups with different etching conditions. The samples were chemically etched in strong inorganic acid solutions. After being etched, the specimens were bonded together in pairs by a chemically-curing resin cement (Panavia EX) with a force of 2 kg/cm2. After cementation, the specimens were stored under humid conditions at 37 degrees C for three wk. Prior to being tested, the specimens were subjected to 1000 thermal cyclings at temperatures between 10 degrees C and 55 degrees C. The tensile bond strength tests showed that Ni-Cr specimens sand-blasted and thereafter etched with a 50% conc. of HNO3 and a 50% conc. of HCl for two min and Co-Cr specimens sand-blasted and etched (conc. HCl for 15 min or three h) or sand-blasted alone resulted in similar high bonding values ranging between 33.3 and 37.2 MPa. Surface roughening with use of the sugar crystal impression method resulted in statistically significant lower bond strength values for both alloys (Ni-Cr, 17.9 MPa; Co-Cr, 10.2 MPa).