Bioglass coated metal substrate

A prosthesis or surgical implant suitable for cement-free bonding to bone consisting essentially of a metal substrate of sufficient strength for the intended use coated at least on the portions thereof to be bonded to the bone of the recipient with a coating of about 0.2 mm to about 2 mm thickness of a biologically active glass or glass-ceramic of uniform composition and thermal coefficient of expansion and substantially free of flaws resulting from the release of thermo-mechanical stresses, the surface of said substrate at its interface with said glass coating being roughened, to a degree sufficient to substantially increase the surface area of said substrate without permitting substantial mechanical interlocking between said metal surface and said glass coating, and oxidized, and said glass coating being bonded to said surface of said metal substrate by ion diffusion at said interface, wherein the thermal coefficients of expansion of said metal substrate and said glass or glass-ceramic coating are substantially different.