Shear bond strength of a veneering composite for dental alloys

Objectives: The objective of this study was to evaluate the performance of a phosphoric-ester with a functional methacrylate group as bonding agent for a veneering composite on 16 different dental alloys. Methods: Seven high noble alloys (Academy Gold-XH, Maxigold, Harmony-KF, Harmony-PF, BioUniversal-PdF, IPS d.Sign-98, Aurofluid-3), three noble alloys (Magenta, IPS d.Sign-53, IS-64), four non-precious alloys (4all, Wiron88, Pisces Plus, IPS d.Sign-30), galvanic gold and titan (Tritan) were tested. All alloys are from Ivoclar Vivadent, except Aurofluid3 (Metalor), Tritan-Ti1 (Dentaurum), Wiron88 (Bego) and galvanic gold (Hafner). Metal specimens (20x10x1mm) were grinded with silicon-carbide paper (600 grit) and sandblasted with aluminiumoxide (100µm, 2bar). Surfaces were conditioned with the phosphoric-ester primer SR Link and covered with SR Adoro Opaquer. Subsequently, SR Adoro Dentin cylinders (diameter 5mm, height 2.5mm ) were prepolymerized onto the conditioned surfaces for 20 seconds with the Quick light unit and cured for 25 minutes in Lumamat 100 (all from Ivoclar Vivadent). One group of specimens (n=8) was stored in water at 37°C for 24 hours and a second group (n=8) was thermocycled according to ISO 10477 (5-55°C, 5000 cycles, 30 seconds immersion time). Shear-bond strength was measured and data were analyzed using ANOVA and Tukey-Kramer tests (p=0.05). Results: Significant differences in shear-bond strength values were found between the alloy-groups for both storage conditions: High noble alloys showed values from 8 to 21 MPa, noble alloys from 13 to 23 MPa. Among these groups a positive effect of copper was found. For non-precious alloys and titan strength values ranged between 18 and 23 MPa. Galvanic gold produced the lowest value with 6.6 MPa. Conclusion: All measured values met the ISO requirements. SR Link performed better on non-precious alloys and on noble alloys containing copper, than on alloys with a total content of Au, Ag, Pd, Pt higher than 90%.