T. PLEIN*, M. ROSENTRITT, M. BEHR, R. LANG, G. HANDEL
(Department of Prosthetic Dentistry, University of Regensburg, Germany)
The fracture resistance of all-ceramic systems is of major concern in the clinical application of these materials. In this in vitro study the influence of different abutment-materials on the in vitro fracture strength of all-ceramic three-unit fixed partial dentures was determined. Dies were produced of human teeth (third molars), LCP Vectra B 950 (Ivoclar, Schaan, FL) and a non-precious alloy (Biosil F, Degussa, Hanau, G). Twenty-four all-ceramic Empress 2 (Ivoclar, Schaan, FL) three-unit fixed partial dentures were resin bonded (Syntac classic/ Variolink II, Ivoclar, Schaan, FL) to divergent dies. All abutments were supported by an artificial periodontal membrane. Forces of physiological magnitude (50 N, 1.2 mio. times) and occlusal direction were applied in all three test groups in an artificial oral environment (Thermalcycling: 6000 cycles 5°/55° C, each 2 min). The fracture strength was tested in a universal testing instrument (Zwick, Ulm, G; initial speed: v=1mm/min). Medians and 25%/75% percentiles were calculated. Statistical analysis was performed using Mann-Whitney-U and Kruskal-Wallis-test (p<0.05).
In comparison to values found for fixed partial dentures luted on human teeth, the fracture strength of fixed partial dentures on LCP-, Co/Cr-abutments were slightly higher. There was no significant difference between the fracture strength of bridges bonded to the divergent dies. In contradiction to conclusions found for all-ceramic crowns the fracture strength of an all-ceramic three-unit fixed partial denture seems not to be depen-dent on the modulus of elasticity of the supporting material.