February AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 1 9 4 6 iTSSe TSS iTSSe TSS JTST HIGHLIGHTS PLASMA-SPRAYED HYDROXYLAPATITE COATINGS AS BIOCOMPATIBLE INTERMEDIARIES BETWEEN INORGANIC IMPLANT SURFACES AND LIVING TISSUE Robert B. Heimann The present contribution discusses critical aspects of the thermal alteration that HAp particles undergo when pass- ing along the extremely hot plasma jet. This heat treatment leads to dehydroxylated phases such as oxyhydroxylapatite/ oxyapatite as well as thermal decomposition products such as tri- and tetracalcium phosphates, and quenched phases in the formof amorphous calciumphosphate of variable compo- sition. The contribution also includes studying the influence that bioinert TiO 2 bond coats have on adhesion, crystallinity, and composition of HAp coatings. Moreover, the question is being addressed whether oxyapatite might exist as a (meta) stable phase or whether its occurrence is merely an ephem- eral event. In addition, the article deals with the role that HAp coatings are playing during in vitro interaction with simulated body fluid resembling the composition of extracellular fluid. The biological and biomechanical advantages of using HAp coatings formedical implants aswell as salient aspects of their biomineralization and osseointegration is discussed in some detail (Fig. 1). THERMAL SPRAY COATINGS ON ORTHOPEDIC DEVICES: WHEN AND HOW THE FDA REVIEWS YOUR COATINGS Limin Sun Thermal spray coatings are commonly applied to med- ical devices for various reasons, e.g., surface roughening, bi- ological fixation, and similarity of chemical composition to bone minerals. Generally, to introduce a thermal spray-coated device to the U.S. market, a premarket review by the U.S. Food and Drug Administration (FDA) is required. This article aims to improve understanding regarding FDA reviewof thermal spray coatings in orthopedic medical device marketing applications and expectations for information to be submitted as part of this process. While different thermal spray technologies and materials have been used for coatings on medical devices, thermal spray coatings often seen by the FDA on orthopedic devices include plasma-sprayed titanium (Ti) coatings and hy- droxyapatite (HA) coatings as well as Ti/HA dual coatings. The coated devices are mostly metals (e.g., Ti alloy, cobalt-chro- mium alloy, stainless steel alloys) and some polymers (e.g., polyetheretherketone). The FDA does not clear or approve in- dividual coatings or materials; rather, coatings and materials are evaluated as part of the final, finished medical device in the context of the specific device’s technological characteris- tics and intended use. MICROSTRUCTURAL EVOLUTION AND SINTERING OF SUSPENSION PLASMA- SPRAYED COLUMNAR THERMAL BARRIER COATINGS Omkar Aranke, Mohit Gupta, Nicolaie Markocsan, Xin-Hai Li, and Björn Kjellman Suspension plasma spray (SPS) is capable of producing coatings with a porous columnar structure, and it is also a more cost-effective process compared to traditional electron beamphysical vapor deposition (EB-PVD). Although TBCs with a columnar microstructure that are fabricated using SPS typ- ically have lower thermal conductivity than EB-PVD, they are T he Journal of Thermal Spray Technology (JTST), the official journal of the ASM Thermal Spray Society, publishes contributions on all aspects—fundamental and practical—of thermal spray science, including processes, feedstock manufacture, test- ing, and characterization. As the primary vehicle for ther- mal spray information trans- fer, its mission is to synergize the rapidly advancing thermal spray industry and related industries by presenting research and development efforts leading to advancements in implementable engineering ap- plications of the technology. Articles from the December and January issues, as selected by JTST Editor-in-Chief Armelle Vardelle, are highlighted here. The December issue is a special edition on “Biomaterials: Thermal Spray Processes and Appli- cations.” The first two articles highlighted below are from this issue. The January edition features papers based on presenta- tions at ITSC 2018. In addition to the print publication, JTST is available online through springerlink.com . For more informa- tion, visit asminternational.org/tss. Fig. 1 — Ball-and-spoke model of hydroxylapatite with space group P6 3 /m. The mirror planes m through z=1/4 and 3/4 are shown perpendicular to the screw axis 6 3 . 12