In vitro shear bond strength over zirconia and titanium alloy and degree of conversion of extraoral compared to intraoral self-adhesive resin cements

Objective: To evaluate the shear bond strength (SBS) over zirconia and titanium alloy and the degree of conversion (DC) of an extraoral self-adhesive resin cement compared to intraoral self-adhesive resin cements. Materials and Methods: Nine bonding protocols were carried out on zirconia 4Y-TZP and titanium alloy (Ti6Al-4V). Seven resin cements (one extraoral and six intraoral) were tested in SBS and DC measurements. Results: The highest SBS values were obtained for Monobond Plus + Multilink Hybrid Abutment (extraoral resin cement) for both titanium alloy (35.1 MPa) and zirconia (32.9 MPa). For each resin, dual-cure mode yielded significantly higher DC than self-cure mode. Nexus Universal reached the highest DC (78.4%) regardless of cure mode. Discussion/Conclusions: The extraoral self-curing resin cement associated with a universal primer showed the highest bond strength on zirconia and titanium alloy. Some intraoral dual-cure cements showed close performance when used with universal primers. No direct correlation was found between DC and SBS on the tested prosthetic materials.