Influence of different airborne-particle abrasion pressures, cleaning methods, and artificial aging on zirconia...

Airborne-particle abrasion (APA) with alumina combined with a primer or luting resin containing a phosphate monomer has been well established for resin bonding to zirconia. However, a standardized method for bonding to zirconia is unavailable, as some factors including the optimal pressure of airborne-particle abrasion, the cleaning method, and the luting resin system are still unclear because of the limited available data.

The purpose of this in vitro study was to evaluate the influence of different airborne-particle abrasion pressures and different cleaning methods of zirconia on the tensile bond strength (TBS) of 2 luting resins system containing methylacryloyloxydecyl-dihydrogenphosphate (MDP) either in the primer or in the luting resin.

A total of 128 disk specimens were milled from zirconia blocks and divided into groups according to the pressure of airborne-particle abrasion of either 0.1 MPa or 0.25 MPa (n=64). The specimens were then divided into 2 subgroups and were either cleaned in an ultrasonic device in isopropanol or with oil-free air stream (n=32). The subgroups were further divided according to the luting resin (n=16) and the bonding surfaces were perpendicularly luted to the acrylic resin tubes filled with a composite resin (Clearfil F II) with either an MDP-containing primer and a luting resin or with a self-adhesive MDP-containing luting resin. Each of the 8 groups was further divided into 2 subgroups (n=8) with either 3-days water storage at 37 °C or 150-days water storage with additional thermal cycling (37 500 thermal cycles between 5 °C and 55 °C) for artificial aging. The TBS was evaluated with a universal testing machine. All specimens underwent failure mode analysis. Statistical analysis was performed with 4-way ANOVA and, if required, with 3-way ANOVA (α=.05).

The mean ±standard deviations ranged from 57.0 ±11.1 MPa to 61.5 ±7.1 MPa after 3 days and from 32.3 ±11.7 MPa to 61.0 ±12.4 MPa after 150 days. The pressure of airborne-particle abrasion and the cleaning method had no significant effect on the TBS (P>.05), whereas the luting resin and artificial aging significantly influenced the TBS (P<.05).

Irrespective of the pressure of airborne-particle abrasion and the cleaning method, the use of an MDP-containing luting resin for bonding to zirconia was found to be more advantageous compared with an MDP-containing primer and luting resin because of higher bond strength and no significant decrease after artificial aging.