Effect of surface treatments on shear bond strength between CAD/CAM bioceramic and resin blocks and orthodontic metal brackets bonded to each other

This in vitro study aimed to evaluate shear bond strength (SBS) between CAD/CAM blocks with different compositions and orthodontic metal brackets, following various surface treatments and bonding procedure. Specimens were prepared from Vita Enamic, CeraSmart, Tetric CAD and Vita Mark II CAD/CAM blocks and were subjected to thermocycling for 5000 cycles. Then, the specimens were allocated into 6 groups according to the surface treatment (n = 12): control (no surface treatment); hydrofluoric acid etching (HF); air-borne particle abrasion with aluminium-oxide; tribochemical silica coating; bur abrasion; and Monobond Etch and Prime application (MEP). The surface morphology of the CAD/CAM blocks was characterized using scanning electron microscope. Then, specimens were silanized and brackets were bonded with adhesive resin. After thermocycling, the SBS test was performed until failure, and failure types were noted according to the adhesive remnant index (ARI). Data were analysed using two-way ANOVA and Tukey tests to perform pairwise analyses. The significance level was taken as α = 0.05. Both the CAD/CAM block type and the surface treatment significantly influenced SBS. Control groups of all CAD/CAM blocks demonstrated significantly the lowest SBS values. The highest SBS values were observed for Vita Mark II specimens treated with HF among all groups. Control groups showed exclusively ARI score 5, whereas surface treated groups had lower and similar scores. All groups, except the control, had reliable SBS values (above 6 MPa). Therefore, clinicians can use MEP, novel self-etching single-component ceramic primer, safely besides other surface treatments while bonding orthodontic brackets.