Resistance to fracture of metal ceramic and all-ceramic crowns.

This study evaluated the fracture resistance of three types of all-ceramic crowns and compared these to the fracture values of metal ceramics. Uniform metal ceramic specimens; veneered, cast glass-ceramic; and porcelain fused to two different dispersion-strengthened ceramic cores (Hi-Ceram and In-Ceram) were investigated. The metal ceramic specimens demonstrated a significantly higher resistance to fracture than did the Hi-Ceram or veneered glass-ceramic units but did not significantly differ from the In-Ceram specimens. The metal ceramic crowns showed cracks only in the ceramic layer, whereas the all-ceramic specimens underwent global fracture.