An Electric Polarization Of Plasma Sprayed Hydroxyapatite Coatings In Alkaline Solution And Its Effects On The Properties Of Coatings

As an ideal substitute and restoration materials of hard tissue, plasma sprayed hydroxyapatite coatings have obtained an excellent success in clinical application. However, during plasma spraying process, hydroxyapatite would appear the phenomena which including decomposition, dehydroxylation and amorphorization etc. due to special thermal history. These phenomena affected the mechanical and biological properties of coatings. Hence, it was essential to post-treat of coatings for improving the integrative properties of coatings.In this study, we put forward a novel post-treatment method for plasma spraying hydroxyapatite coatings, which based the mechanism integration of the existing various plasma spraying coatings post-treatment methods. The novel post-treatment method meant electric polarizing post-treatment in alkaline solution (PAS). First of all, an optimized electric polarizing post-treatment condition was selected by orthogonal experimental design. And then, we studied the physical, chemical, mechanical properties and preliminary in vitro, in vivo biological properties of coatings which post-treated by PAS and water vapor treatment (WVT).The physical and chemical investigating results showed that PAS treatment not only improved the crystallinity and structure integrity of coatings, but also transformed additional phase into hydroxyapatite phase. The surface of coatings which post-treated by PAS has less crack and still keeps the morphology of porous samdwich. Compared with WVT treatment, the PAS treatment made the coatings higher hydrophilic with higher surface energy and more negatively charged. The in vitro stability of coatings which post-treated by PAS was more than that of WVT. The bonding strength between coatings and substrate treated by PAS method was appreciably lower than that post-treated by WVT method, but it still met the relevant requirements of the ISO 13779-2:2000 standard.The preliminary in vitro biological properties were studied by FCS immersion, protein immersion, cell culture etc. FCS immersion results showed that the calcium and phosphorus adsorption ability of coatings which post-treated by PAS was better than that of WVT. Protein immersion results indicated, compared with WVT treatment, PAS made the coatings have better protein adsorption ability. MTT results showed protein immersion promoted the cell growth and proliferation on coatings which post-treated by PAS. Fluorescence coloration and SEM observation results indicated that protein immersion could keep the cell on coatings which post-treated by PAS have normal morphology and improve the adhesion and growth of cell.The preliminary in vivo biological properties were further investigated by animal experiment. General histological examination and put-out strength results revealed that new bone had generated between coatings and host bone after coatings were implanted. As the time of coatings implantation increased, amount of bone contact and push-out strength augmented in the same way. After 1 month implantation, amount of bone contact and push-out strength of coatings which post-treated by PAS are obviously more than that of WVT. After 2, 3 months implantation, however, the former had no remarkable difference with the latter. Consequently, compared with WVT treatment coatings, PAS made the coatings having better initial fixation.