Effect of alloy and surface treatment on adhesive cement strength

Maximal crown retention to compromised preparations stresses the ability of an adhesive cement to bond to a metal restorative material, and surface treatment of metal type selected may play an important role.

Purpose:Evaluate the tensile strength of an adhesive resin cement to base and noble metal alloys having different surface treatments.

Methods:Cylindrical rods (9.5-mm diameter, 10.0-mm long) of a base (Rexillium NBF) and noble metal (IPS d.SIGN 53) alloy were fabricated. Rod ends were flattened perpendicular to the rod axis, and were subjected to a degassing cycle to form an oxide layer. Control groups were not additionally treated, the others received sandblasting (50µm alumina) or a metal primer application (Alloy Primer, J Morita USA). Sections were joined using an adhesive resin cement (RelyX ARC, 3M/ESPE) (n=10-12/group). After water storage (24h, 37°C) and thermocycling (500x, 5°-55°C) rods were debonded in tension in a universal testing machine and recorded in MPa. A Rank-based pair-wise comparison was used for each pair of treatments for each of the two metal types (each comparison performed at a significance level of 0.0083, overall error rate for comparisons 0.05). The two metals were compared separately for each of the three treatments using an adjusted significance level of 0.017 for each comparison, maintaining an overall error rate of 0.05.

Results:A significant interaction occurred between metal type and surface treatment (p = 0.019). No significant difference in strength was noted between oxide or sandblasting treatment for either metal type. Respectively: Noble (3.2±2.0, 2.8±1.5) Base (1.6±1.4, 3.6±3.4). However primer treatment significantly enhanced strength compared to oxide or sandblasting treatment for both metals. Noble/primer (9.4±7.2) Base (12.2±5.1) (each comparison p < 0.001).

Conclusions:Metal-primer pre-treatment of either type alloy significantly improved tensile strength compared to oxide only or sandblasting.