Push-out Force of Screw-hole Filling Materials in Zirconia Implant Crowns

Objectives: The screw-retained implant crowns are preferred when possible as the excess cement can cause problems on peri-implant health. The aim of this study was to compare push-out force of screw access hole filling materials in zirconia dental implant crowns using different filling methods.
Methods: Partially yttrium stabilized zirconia (PSZ) (Prettau, Zirkonzahn,Italy) crowns (cylinder shape, Ø10mm) were milled (M5, Zirkonzahn) on titanium bases (Brånemark 4.1, Zirkonzahn) and sintered in non-vacuum sintering furnace (1500°C, Zirkonofen 600/V2, Zirkonzahn). Two different design of screw hole were milled: conventional smooth hole or threaded screw hole using special thread milling burs. For smooth screw hole filling methods (n=6/group) were: 1) restorative (Filtek™ Supreme XTE universal restorative (3M ESPE)), 2) adhesive (Scotchbond universal adhesive) + restorative, 3) grit blasting (50µm, 2,5bar Renfert) + restorative, 4) grit blasting+adhesive+restorative. 5) PMMA A3 resin screw plugs were milled.for filling the threaded screw holes. The specimens were subjected to static mechanical testing with a universal testing machine (Model LR30, Lloyd, UK). Filled screw access holes were loaded until failure. Statistical evaluation was made using ANOVA.
Results: Results: ANOVA revealed significant differences among filling methods (p<0.05). Results are presented in Table 1.

Different superscript letter indicates statistical significant differences (p<0.05, Tukey)
Conclusions: Grit blasting of zirconia surface in screw access hole increases push-out force of universal adhesive and restorative filling material. Prefabricated PMMA screw plug showed comparable force.