Response of Ti–Ni alloys for dental biomaterials to conditions in the mouth. Y. OSHIDA, F. FARZIN-NIA, in Shape Memory Alloys for Biomedical Applications, 2009 6.20 Oxide growth, stability and breakdown. The oxide layer forms spontaneously in air, and normally has a thickness of between 2 and 7 nm, as mentioned previously. During machining, the …