The effect of cleaning methods and primer application on bond strength to zirconia

Aim: The aim of this in-vitro study was to evaluate the effect of cleaning methods and primer application on bonding to contaminated zirconia.
 
Materials and Methods: A total of 64 zirconia discs (8mm × 3mm) were fabricated with CAD/CAM. All discs were air-borne particle abraded using 50 m Al₂O_{3 particles} then divided into two main group according to application of surface cleaning after saliva contamination; A. (control test groups) (n= 16) and B. (contaminated test groups that were divided into three main test groups according to cleaning methods after contamination) (n=48) as follow; [steam cleaning (SC) (n= 16), ultrasonic cleaning (UC) (n=16), Ivoclean cleaning (IC) (n=16)]. Then, each main group was subdivided into two equal sub groups (n=8) according to primer application (Monobond N) or no primer application (NP). Composite resin discs (Nexcomp) were cemented to zirconia discs using adhesive resin cement (Multilink N). All bonded specimens were stored in water bath for 6 months. Shear bond strength (SBS) test was performed afterwards using a universal testing machine. Scanning Electron Microscope was used for failure mode examination.
 
Results:The statistical analyses were done using two-way ANOVA and serial one-way ANOVAs followed by Post hoc Tukey-HSD test at (p < 0.05). The application of primer significantly increased SBS Values of test groups compared to non-primed ones (p=0.000). The highest mean SBS (MPa) was reported for (ICP) test group (15.3±1.6 MPa) followed by (UCP) test group (11.1±2.9MPa). While the lowest mean SBS was observed for (CP) (9.5 ±3.3 MPa). There was statistically significant difference between (IC) and other test groups (C, SC, UC) (p=0.001, p=0.032, p=0.017) respectively. There was no statistically significant difference between cleaning test groups without primer application.
 
Conclusion:Within the limitations of the current study, primer application has a dual action. It proved effectiveness as a chemical surface treatment method in comparison with airborne particle abrasion (mechanical surface treatment). Surface cleaning methods without primer application were not of value. Ivoclean when conjugated with universal primer, best results obtained compared to the other surface cleaning methods.