Zirconia-based ceramics offer strong restorations in dentistry, but the adhesive bond strength of resin cements to such ceramics is not optimal. The aim of the present study was to evaluate the effect of both primer types and ultrasonic cleaning on bonding to zirconia ceramics.A total number of forty zirconia discs were constructed from prefabricated blanks of zirconia. The discs were mounted on acrylic blocks and randomly divided into two equal main groups (n = 20) According to ultrasonic cleaning. Without ultrasonic cleaning and with ultrasonic cleaning. Every group was subdivided
into three subgroups according to type of primer (n= 10) Monobond S primer and Monobond Plus primer Forty composite resin blocks were cemented to zirconia discs by (Variolink II) with its corresponding adhesive components. Shear bond strength of each sample was measured using a universal testing machine at a crosshead speed of 1 mm/min. Shear bond strengths were analyzed through Two-way ANOVA/Tukey tests Treated zirconia ceramic surfaces were examined using scanning electron microscopy. Data was collected and statistically analyzed. Monobond Plus group recorded higher
shear bond strength than Monobond S group. Monobond Plus primer improved bonding to zirconia ceramic while the cleaning method had little or no effect.