Calcium phosphate coatings elaborated by the soaking process on titanium dental implants: surface preparation, processing and physical-chemical characterization

International audience; Dental implant manufacturers are looking for new surfaces to improve osseointegration. It is accepted that rough metallic implant surfaces promote bone mechanical anchoring and biomechanical fixation. In addition, calcium phosphate coatings favor both bone healing and apposition on implants and improve bone bonding properties. Among all the available techniques, the soaking process seems particularly attractive because of its simplicity and ability in producing a versatile bioactive coating at low temperature. The objective of the present study is to improve the titanium implant surface roughness and chemistry by optimizing the surface preparation and the soaking process parameters to produce a bioactive and adherent calcium phosphate coating. Titanium samples were sandblasted with alumina particles and acid etched to obtain a surface with an average roughness between 1.4 and 1.8 μm and micro-porosities created by the acid etching. A high surface wettability was also achieved. Moreover, acid etching favors the removal of alumina particles inlaid in the titanium substrate by sandblasting. Coatings were realized by an alternate soaking process including a centrifugation step to create a phosphate solution thin film on the implant that can afterwards react with the calcium contained in the second bath to form a CaP coating. We showed that this centrifugation step is critical and determines the coating formation, coverage and thickness. A thin covering coating (~ 2 μm) composed of apatite analogous to bone mineral was deposited. The adhesion of coating to the substrate was assessed by a pragmatic and convenient screwing/unscrewing test of the coated implant in an artificial jawbone.