Fracture Strength of Zirconia Posterior Fixed Partial Dentures

Objectives: The aim of this in-vitro study was to determine the fracture strength of tooth colored zirconia fixed partial dentures (FPDs) with a different kind of cementation.

Material&Method: 96 human molars were inserted in PMMA resin to create three-unit (10mm) oral situation. The roots of the teeth were covered with an about 1mm thick layer of polyether to simulate the periodontium. 2x8 bridges of each series were made of the zirkonia materials and fixed with an adhesive bonding system (Syntac classic/Variolink2; Ivoclar-Vivadent, FL) and recommended conventional cementation: A) Digizon/GC Initial (Fuji Plus, Girrbach, G), B) Lava/Lava Ceram (Ketac Cem, 3M Espe, G) and Cercon/Cercon Ceram (Harvard, DeguDent, G). After thermal cycling and mechanical loading (TCML; 6000 thermal cycles [5°C/55°C] and 1.2x10⁶ mastication cycles [50N]) fracture strengths (UTM 1446; Zwick; v=1mm/min) of 8 FPDs of each series were determined. Statistical analysis was performed with the Mann-Whitney U-test (p=0.05).

Results:

Conclusion: There were no statistical differences between the different zirconia FPDs with conventional cementation. All FPDs showed lower fracture results with adhesive bonding, but only for Digizon the difference was statistically significant. The fracture forces of all zirconia FPDs were at a level where clinical application in posterior areas seems promising.