Improved bonding of zirconia substructures to resin using a "glaze-on" technique

To investigate the influence of applying thin intermediary coatings of acid-etchable glasses on the shear bond strength between a methacrylate resin based cement and an yttria-stabilized zirconia dental ceramic substrate.

The upper and lower surfaces of 110 sintered yttria-stabilised tetragonal zirconia polycrystalline disc-shaped specimens were polished using sequential grades of Silicon Carbide, then air-abraded with 25 μm diameter alumina particles. Specimens were randomly allocated to 11 groups (A-K) (n=10), group A acting as control. The upper surface of Group A specimens was subjected to a tribochemical coating regime (CoJet, 3M ESPE). Five glazing ceramics were applied and fired according to the manufacturer's recommended firing regime. The glaze was etched with 10% HF acid and all specimens coated with a silane primer. Two differing storage regimes were employed (wet storage vs thermocycling). Shear bond strength testing specimens were created by cementing resin-based composite cylinders to the centre of the prepared ceramic surface using Rely-X Unicem (3M ESPE) resin based cement. Shear bond strength testing was performed and load at failure recorded.

A factorial analysis of variance at a 95% significance level demonstrated that all glazing techniques resulted in a significant increase in the shear bond strength compared with using the resin based cement alone (P<0.01), with the different glazing ceramics resulting in significant differences in mean shear bond strength (P=0.008). The differences were a function of the storage state (wet storage vs thermocycling (P=0.013)).

The glazing techniques used in the current investigation resulted in a significantly enhanced shear bond stress to the resin based cement when compared with the current 'gold standard' - tribochemical coating.