Going in line with the example in the question, there are different coating on implants used to stimulate specific responses. For example the Hydroxyapatite coating on a titanium implant to convert fibrous tissue to bone around loaded implant. The implant itself would have to go through the CDRH and probably be a class 1 device as there are already an abundance of titanium implants, and the specialized coating could be considered a class 2 as it has special and unique health benefiting aspects, though not as extreme as a class 3 device.
Link: http://bjj.boneandjoint.org.uk/content/jbjsbr/75-B/2/270.full.pdf