“…In vitro [10][11][12][13][14] and in vivo [15][16][17] evidence exists that a bioinert titania-based bond coat noticeably increases the adhesion strength of the bioconductive hydroxyapatite coating thus reducing the risk of gap formation associated with concurrent invasion of connective tissue that is known to compromise implant stability. While enhanced adhesion strength has been tentatively related to the formation of a very thin Ca-Ti oxide reaction layer between titania and calcium phosphate [3,18] direct experimental evidence of the validity of this hypothesis is still lacking.…”