The microstructure of Ti-Ta and Ti-Nb alloys diffusion bonded to a 99.7 wt% Al2O3 ceramic for dental implants is subdivided into a reaction double layer containing the phases TiAl and Ti3Al, a transition region of coarse α-Ti plates in ß-Ti, and the unaffected bulk metal, the α-Ti/ß-Ti structure of which can be refined by annealing at 800 °C for 1 hour after bonding. Optimized joints fabricated by diffusion bonding in a high vacuum at 1,200 °C from a 99.7 wt% Al2O3 ceramic and Ti-Ta alloys fitted in their thermal contraction behavior to that of the ceramic by the addition of 30 to 40 wt% Ta showed a fracture resistance of 2.3 MN/m3/2. Approximately 80% of the bend test specimens notched at the Ti-Ta/alumina interface failed by crack extension parallel to the interface within the ceramic, which is typical for a metal-ceramic bond of high to medium interfacial strength. Schlagwörter: bond strength, dental implant, interfacial microstructure