Characterization of Composite Hydroxylapatite (HA) Coatings for Medical and Dental Devices

Abstract

Porous metallic/bioceramic composite coatings, produced by plasma arc deposition incorporating highly crystalline hydroxylapatite (HA) in a porous structure of titanium or cobalt-chromium-molybdenum, have been developed for medical and dental device applications. An otherwise brittle and weak HA coating has been anchored by a porous metallic underlayer which is strongly bonded to the substrate. Implants with such coatings have the advantage of mechanical fixation by bony ingrowth into the porous metallic structure coupled with enhanced biocompatibility achieved through the use of HA. This combination produces a more stable bone/implant interfacial region as compared to that achieved by a HA coating applied directly on the implant surface. Once bony ingrowth has taken place, strong bonding has been achieved even if bone resorption of the HA were to take place. Various thicknesses, densities and pore sizes of such composite coatings have been applied to dental and orthopedic devices and have been implanted in the U.S.A., Japan, and Europe showing excellent post insertion clinical results. Physical, mechanical, and chemical properties of selected coatings have been characterized and are reported herein.

A Methodological Study for the Analysis of Apatite‐Coated Dental Implants Retrieved From Humans

“…25 Aluminum oxide powder (Al 2 O 3 ) is employed to flash the metallic surface prior to the hydroxyapatite plasma spraying process and may also adhere to the surface. 26 Both the Al 2 TiO 3 from the metallic surface and any residual aluminum oxide particles, exposed as a result of coating loss, may explain the aluminum peak observed with EDAX in all the failed specimens in our study. As previously reported, 27 aluminum can also be detected at the metallic-hydroxyapatite-coating interface of noninserted implant specimens.…”

Structure and shear strength of implants with plasma coatings

“…3 2016 strong joint between them during the early step of inte gration. The interface can be formed using a porous plasma titanium coating, the elastic modulus of which is 0.05 to 0.25 of the elastic modulus of the bulk material; this decreases the concentration of stresses on the interface [27][28][29][30][31][32]. The conventional porous titanium coating has a higher specific surface area, 71 μm 2 /μm as com pared to 43.8 μm 2 /μm for titanium after abrasive treat ment, which increases the carrying ability of the inter face at equivalent strength of the joint [33].…”

“…The formation of the surface relief in TCP Ti coatings leads to the increase in their specific surface as com pared to conventional porous titanium coatings by a factor of six, from 71 to 413 μm 2 /μm [33,36]. TCP Ti coatings have higher shear strength relative to the implant surface than conventional porous coatings that are composed of spherical particles (70 and 18 MPa, respectively) at the porosity of 46% [29,37]. Low strength of the conventional porous coatings is due to the presence of only point contacts between sprayed particles.…”