Due to their strength, flexibility, and biocompatibility, titanium alloys are often used for joint and bone implants. Chromium and cobalt alloys, as well as stainless steel are also, though somewhat less commonly, used for bone implants for similar reasons. Shape-memory alloys have biomedical applications in procedures such as angioplasty where they can prevent blood vessels from becoming reblocked. Ceramics, though they include good chemical and corrosion-resistant properties, are notoriously brittle. Researchers therefore have sought ways of combining desirable ceramics with other materials to tailor properties such as strength and elasticity to meet system requirements. Composites, functionally gradient materials, and coatings have been studied to optimise material choices. Ceramic coated, biocompatible metals seem to offer an excellent compromise between the strength and flexibility of metals and the ability of ceramics to be incorporated into biological systems.