Push-Out Force and Microleakage of Screw Access Hole Filling Materials in Monolithic Zirconia Implant Crowns

Purpose: To test the push-out force and marginal leakage of different screw hole-sealing methods in monolithic zirconia implant crowns. Materials and Methods: Ninety monolithic zirconia (Prettau, Zirkonzahn) specimens were milled with two different screw access hole designs: conventional smooth hole or threaded screw hole (for group PMMA-SC), and divided into five groups (n = 18) according to filling method: unbonded composite (UBC); bonded composite (BC); airborne-particle abrasion of screw hole and unbonded composite (ABR-UBC); airborne-particle abrasion of screw hole and bonded composite (ABR-BC); and PMMA screw plugs (PMMA-SC). Twelve specimens per group were subjected to static push-out force with a universal testing machine. Before testing, 6 specimens per group were stored in dry conditions, and 6 were kept in water storage (+37 degrees C) for 7 days. For the remaining specimens (n = 6), cotton pellets were placed under the screw access hole fillings, and the specimens were immersed in 0.5% basic fuchsin solution for 2 weeks. Dye in cotton pellets was dissolved in 2 ml of water, and absorbances of the solutions were measured with a spectrophotometer at 465 nm. Data are reported as mean and SD. Statistical analysis was made using a generalized linear model with logarithmic transformation. Results: PM MA-SC specimens showed the highest push-out forces (P < .0001) and lowest fuchsin penetration (P = .009). Airborne-particle abrasion increased the push-out force and decreased the microleakage in composite groups. The storage conditions affected the results of both unbonded groups. Conclusion: The design and sealing method of the screw access hole affect push-out force and microleakage.