High load bearing, high reliable all-ceramic dental bridges by the direct ceramic machining process

F. Filser, H. Lüthy, P. Kocher, P. Schärer, L.J. Gauckler

All-ceramic dental bridges are highly desired as they offer the advantages of a metalfree treatment. Due to the weak mechanical properties of traditional dental ceramics ceramic bridges have to be designed up to now with thick connectors (about 16 to 20 mm2) for bearing the mastication loads in the posterior region (880 N).Zirconia in its tetragonal yttria stabilized polychrystal form (TZP) offers highest strenght combined with highest toughness. However, TZP is difficult to machine in its dense state and has therefore found only limited application for dental bridges. A new Direct Ceramic Machining (DCM) process uses porous, easy-to-machine TZP blanks and machines the frameworks in an enlarged shape to compensate for the sintering shrinkage. We compare the load bearing and reliability of frameworks and bridges fabricated by the DCM process to other dental ceramic materials and evaluated their failure probability.