Evaluation of Bonding Stability Between Treated Y-TZP and Resin Cements

Objective: To evaluate the influence of four surface treatments on the bond strength between two resin cements and an yttria-stabilized zirconia (Y-TZP).

Method: The study was divided in two phases. In the first phase, forty plates (8mm x 6mm x 1mm) of Y-TZP were randomly assigned to four groups (n=10) according to surface treatment: control (no treatment); airborne-particle abrasion (Al₂O₃-50µm); MDP-based primer (Kuraray); and the Rocatec-System (3M ESPE). The treated plates were further divided into 2 subgroups according to resin cement: RelyX^TMARC (ARC-conventional) (3M ESPE) and RelyX^TMUnicem (UCem-self-adhesive) (3M ESPE). The cement was placed in a PVC tube (∅=0.75mm x 0.5mm in height) that was on the surface of each specimen.  After water storage (37^oC/24h), the specimens were submitted to a micro-shear bond strength (µSBS) test. In the second phase of the study the stability of the bond was investigated. The methodology was repeated, but the new specimens were stored in distilled water (37°C) for 6 months prior to testing.

Result: Surface treatments significantly influenced the µSBS (p<0.05). For all surface treatments, UCem recorded significantly higher µSBS when compared with ARC (p<0.05). For both resin cements, the best result was produced with the MDP-based primer. The highest values were 36.2±2.1MPa for UCem/MDP and 37.4±2.3MPa for UCem/Rocatec-system. After water storage, a number of specimens spontaneously separated in the control group and Al₂O₃ group (their results were excluded from statistical analysis). For the remaining groups, all groups presented a drop in µSBS after storage (p<0.05) except for ARC/Rocatec-system. For UCem/Rocatec, the drop was 54.8% and for UCem/MDP-primer the drop was 52.8%. The drop for ARC/MDP-primer was 42.5%.

Conclusion: Within the limitations of this study, it was concluded that aging in water for 6 months reduced the bond between the self-adhesive resin cements tested and Y-TZP ceramics.