Deposition, heat treatment and characterization of two layer bioactive coatings on cylindrical PEEK

Abstract

Polyether ether ketone (PEEK) rods were coated via ion beam asssited deposition (IBAD) at room temperature. The coating consists of a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to increase bioactivity. A rotating substrate holder was designed to deposit an even coating on the cylindrical surface of PEEK rods; the uniformity is verified by cross-sectional measurements using scanning electron microscopy (SEM). Deposition is followed by heat treatment of the coating using microwave annealing and autoclaving. Transmission electron microscopy (TEM) showed a dense, uniform columnar grain structure in the YSZ layer that is well bonded to the PEEK substrate, while the calcium phosphate layer was amorphous and pore-free in its as-deposited state. Subsequent heat treatment via microwave energy introduced HA crystallization in the calcium phosphate layer and additional autoclaving further expanded the crystallization of the HA layer. Chemical composition evaluation of the coating indicated the Ca/P ratios of the HA layer to be near that of stoichiometric HA, with minor variations through the HA layer thickness. The adhesion strength of as-deposited HA/YSZ coatings on smooth, polished PEEK surfaces was mostly unaffected by microwave heat treatment, but decreased with additional autoclave treatment. Increasing surface roughness showed improvement of bond strength.

Hydroxyapatite coating on PEEK implants: Biomechanical and histological study in a rabbit model

“…YSZ is used as a thermal barrier coating in high temperature applications and its columnar grain structure helps mediate residual film stresses caused by heat treatment. Recent studies have shown these coatings to exhibit high adhesion strength to PEEK substrates, indicating potential for a robust method for implant surface preparation [24]. In addition, an in vitro study using MC3T3 cells showed promising bone growth on coated samples that underwent post-deposition heat treatments [21].…”

PEEK Physical Surface Modification: Evaluation Of Particles Leaching Process

“…PEEK materials also exhibit radiolucent characteristics, implants manufactured from PEEK are compatible with imaging diagnoses, unlike metal implants 3 . Its heat resistance and chemical compatibility with various sterilization techniques, coupled with low cost molding techniques, led PEEK to be a practical and economical material for the manufacturing of medical devices 4 .…”

Modificação da superfície do poli (éter-éter-cetona)

“…Este polímero também possui características radiolúcidas, ou seja, os implantes fabricados a partir do PEEK são compatíveis com diagnósticos de imagem, ao contrário dos implantes metálicos. A sua resistência ao calor e compatibilidade química com várias técnicas de esterilização, juntamente com técnicas de moldagem de baixo custo fazem do PEEK um material prático e econômico para a fabricação de dispositivos médicos [3,4,5,6,7,8,9]. O PEEK trata-se de uma resina termoplástica, semicristalina de cadeia linear aromática interconectadas por grupos cetona (C=O) e éter (-O-).…”

“…Sem a osseointegração (interação do implante com o osso), os implantes podem afrouxar ou migrar, causando dor, deformidade ou deficiência ao paciente. A energia de superfície relativamente baixa do PEEK também pode limitar a osseointegração, e potencializar a encapsulação fibrosa, diminuindo a cicatrização de feridas nas aplicações que exigem a integração [2,8,14,15]. Algumas estratégias têm sido utilizadas para superar o carácter inerte do PEEK.…”