Bonding to Zirconia: Relative Importance of MDP Adhesives and Sandblasting

Objectives: Bonding to crystalline ceramics is challenging because they cannot be etched. Air-particle-abrasion is commonly used for surface treatment of zirconia to increase micromechanical retention. Use of 10-MDP (10-methacryloyloxydecyl) primers also improves bonding to zirconia. Purpose: to investigate the influences of 10-MDP containing adhesives and air-particle-abrasion on the shear bond strength to translucent zirconia.
Methods: Translucent zirconia specimens were milled from 18 mm discs of Katana STML (Kuraray Noritake, Japan) and sintered (Zircom, KDF US Inc) per manufacturer’s instructions. Two surface treatments were used: wet-polished to 2000 grit SiC paper, or air-particle-abraded with 50-micron alumina particles at 1.27 cm, 0.2 MPa, 20 seconds. Four 10-MDP containing adhesives (Table 1) were used for each surface treatment. Controls included a non-10-MDP adhesive, and an etched silanated Empress CAD with the same adhesive. After adhesive application, a dual cure resin cement Duo-Link Universal (Bisco, IL) was injected into a 2.2 mm diameter plastic tube and light-cured (Valo X, Ultradent) for 60 seconds. Shear bond strengths were tested after one hour of storage in distilled room-temperature water in a standardized notched fixture (Ultradent Products Inc) at a crosshead speed of 1mm/min in a Universal testing machine (Instron, MA)
Results: Shear bond strengths are reported in Table 1. One-way ANOVA revealed significant differences among adhesives (p<0.001); Tukey’s testing revealed no differences among 10-MDP containing materials, which were superior to 2 non-10-MDP containing controls, but markedly inferior to one of the same controls when bonded to an etched glass-ceramic (p<0.05). Two-way ANOVA determined that the effect of sandblasting was highly significant (p<0.0001) and accounted for almost all of the experimental variation (mean square=1590); whereas, the type of 10-MDP adhesive was not significant (p=0.2) and had little importance (mean square=7).
Conclusions: 10-MDP containing adhesives were more effective than a non-10-MDP control adhesive, but the effect of air-abrasion was of overwhelming importance.