Adhesion of Surface Modified Zirconia to Dentin Using Resin Cement

Objectives: The aim of this pilot study was to evaluate the tensile bond strength between potassium hydrogen difluoride (KHF2) etched zirconium dioxide and bovin dentin bonded by dual cure resin cement.
Methods: Bovine teeth were extracted and cut before cast in epoxy resin with the buccal surface exposed. Embedded bovine teeth were grinded in a Struers Planopol machine with 500 grit until >5*5mm exposed dentin surface.
Zirconium dioxide rods (5*11mm rods, Starceram Z) were produced by CAD/CAM technique (n=5). Zirconium dioxide test rods were etched with KHF2 compounds at 280°C for 10 min. Non etched rods served as control.
Multilink Automix dual cure resin cement was used for cementing zirconia rods to tooth surface.
A standardized 880 gr seating load was applied during light curing from four directions; 20 sec light curing in each direction.
After cementation the specimens were stored in destilled water at 37°C for 24 h. All specimens underwent artificial aging by thermo-cycling, 500 cycles in 5°C and 55°C water baths.
Specimens were fixed i Lloyd test machine and 1mm/min tensile force was applied until break.
Both the teeth and zirconia rods were studied in light microscope.
Results: Light microscope study showed adhesive fracture between cement and dentin on three test specimens, one test specimen had a mixed cohesive (in dentin) and adhesive fracture. The control specimen had adhesive fracture both between cement-dentin and cement-zirconia.
Conclusions: The preliminary results showed no difference in tensile retention force between KHF2 etched zirconia and non-etched zirconia cemented to bovine dentin using Multilink Automix dual cure resin cement. Binding to dentin seemed to be the weakest point.
A more extensive lab study on KHF2 etched zirconia is ongoing.