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PURPOSE: The aim of this study was to investigate the fracture strength and fracture mode of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) posterior three-unit FDPs with varying connector dimension and abutment core thickness. MATERIALS AND METHODS: Seventy 3-unit posterior FDP cores made of Y-TZP were divided into 7 groups with varying connector dimensions and abutment core thicknesses. All the FDPs underwent a simulated aging process including veneering, firing applications, thermocycling, and cyclic preloading. Finally the FDPs were subjected to load until fracture. RESULTS: Significant difference was seen between the different subgroups (p < 0.05). Groups with the same connector dimension showed no significant difference in fracture strength. All fractures of the specimens involved the connector. CONCLUSIONS: Within the limitations of this in vitro study, it can be concluded that the strength of an all-ceramic Y-TZP FDP beam depends more on the connector dimension than on the thickness of the abutment core. Results indicate that the minimum abutment core thickness of an all-ceramic Y-TZP FDP might be reduced, compared to the recommended thickness, without reducing the strength of the reconstruction. This indication, however, needs to be verified by further studies before being considered generally applicable.
Ambré et al. (2013) studied this question.