Effect of cementation techniques on fracture load of monolithic zirconia crowns

The aim of this study was to evaluate the effect of cement on the fracture load of monolithic zirconia crowns with different yttria content (3 and 5mol%). A total of 62 monolithic zirconia crowns, 40 3Y-zirconia crowns (Prettau®Zirconia, Zirkonzahn) and 22 5Y-zirconia crowns (Prettau® 4 Anterior®, Zirkonzahn) were produced to a shallow chamfer molar preparation. The 3Y-crowns were divided into four groups and attached to composite abutment duplicates (SDR® flow+, Dentsply DeTrey GmbH) using the following four cementation techniques; 1: Self-adhesive resin-based cement, 2: Pre-treatment with air-abrasion and self-adhesive resin-based cement, 3: Zinc phosphate cement 4: Glass-ionomer cement. The 5Y-crowns were divided into two groups and attached to the duplicates with; 1: Self-adhesive resin-based cement, or 2: Air-abrasion pre-treatment and self-adhesive resin-based cement. All crowns were loaded axially (0.5mm/min) on the occlusal surface until fracture occurred. Among the 3Y-zirconia groups, the zinc phosphate cement group fractured at lower loads compared to the resin-based cement groups, with and without air-abrasion, (