The thickness of the oxide layer is usually from 20 to 100 Ao, with the oxygen-rich oxides nearer to the surface, and the oxygen-poor oxides nearer the alloy. It is necessary for oxides to form in a controlled environment because contaminants from the air and the metal will be incorporated into the oxide layer and adversely affect the ability of the alloy to osseointegrate with the bone.
The low degradation of commercially pure titanium or titanium alloy in tissues is one of its assets for use in restorative procedures (Craig, Power and Wataha, 2004, 316). Trace amounts of elements have been shown to be released from these alloys into bone, the levels released are less than one part per billion in most cases, and their effects appear to minimal. Trace amounts have also been found in lung, liver, spleen, and kidney, with no ill effects noted. Titanium alloy may be coated with ceramic films to combine the high strength of the alloy with the favorable integrative characteristics of the ceramics (318). The thickness of the ceramic coating varies from 50 Śm to 100 Śm and is sprayed on to the metal alloy. It has several characteristics that influence its porosity, crystallinity, composition, strength, and thickness. Studies suggest that these layers promote a strong bone-implant bond more quickly, and promote biointegration rather than osseointegration, but the ceramic coats degrade over time, and this e