Effect of silane coupling agents and alloy primers on adhesion to titanium

Titanium-ceramic adhesion is known to be not ideal yielding to ceramic fractures especially in extensive implant reconstructions. Intraoral repair actions could be performed chairside using adhesion promoters. This study evaluated the adhesion of resin composite to titanium alloy using different silane coupling agents and alloy primers in combination with surface conditioning methods after aging.

Titanium alloy disks were embedded in PMMA and wet polished to 1200 grit silicon carbide abrasive. Silanes and alloy primers used in combination with surface conditioning methods were as follows: 1) Al2O3 (50 µm) and Alloy Primer (Kuraray); 2) Al2O3 (50 µm) and V-Primer (Sun Medical); 3) SiO2 (30 µm) and Silane (ESPE-Sil) (CoJet System, 3M ESPE); 4) Al2O3 (50 µm) and Silane (ESPE-Sil); 5) Al2O3 (50 µm) and Cesead II Opaque Primer (Kuraray); 6) Al2O3 (50 µm) and Alloy Primer and Clearfil SE Bond Primer and Clearfil Porcelain Bond Activator (Clearfil Repair System, Kuraray). A thin layer of Sinfony opaquer was then applied, polymerized and a direct resin composite (Quadrant Photoposterior, Cavex) was adhered onto the conditioned titranium surfaces using polyethylene molds. After thermocycling (6000 cycles at 5-55 °C), specimens were submitted to shear loading in the Universal Testing Machine (crosshead speed: 1 mm/min). Failure types were classified as adhesive, cohesive in resin and a combination of adhesive and cohesive failures (mixed) after debonding. The data (MPa) were analyzed statistically using One-way ANOVA and Tukey's tests.

Significant difference was observed between the groups (P<0.05) (1-way ANOVA). Significantly higher results were obtained from Groups 1 (25.4±7) and 6 (26.3±5) than those of other groups (11.4±3 - 22.6±9) (P<0.05) (Tukeys' test). Group 2 presented the lowest mean bond strength among all groups (11.4±3) (P<0.05). While Group 1 showed mainly cohesive (4 out of 10) and mixed failures (6 out of 10) and no adhesive failures, other groups presented mainly adhesive and mixed failures.

Conditioning titanium surfaces with 50 µm Al2O3 followed by Alloy Primer or silane mixture of Clearfil Repair system delivered the most stable repair bond strength of the resin composite to titanium compared to other alloy primers and silanes tested.