In vivo apatite formation induced on titanium metal and its alloys by chemical treatment

NaOH and heat treatments form an amorphous sodium titanate layer with a graded structure on the surfaces of titanium metal and its alloys. These treatments give no adverse effect on mechanical properties of the metals, Thus treated metals form an apatite layer on their surfaces in the living body by taking the calcium and phosphate ions from the surrounding fluid. This apatite layer is tightly integrated to the metal substrates through a graded structure, and bonds to the living bone in a short period, because of its structure and composition analogous to those of the bone mineral. This kind of bioactive metals are believed to be useful as bone substitutes even under load bearing conditions such as hip joints and dental implants.