Multi-Scale Characterisation and Mechanical Adhesion in PVD-Deposited Ca-SZ Coating for Implantable Medical Devices

Abstract

Oral implantology faces a multitude of technical challenges in light of current clinical experience, underlining the need for innovation in implantable medical devices in both mechanical and biological terms. Objectives: This study explores the influence of the thickness factor of calcium-doped zirconia (Ca-SZ) coatings deposited by PVD on their intrinsic mechanical properties and the determinism of the latter on adhesion to the TA6V alloy substrate after mechanical loading for applications in dental implantology. Methods: Three separate thicknesses of 250 nm, 450 nm and 850 nm were evaluated in terms of mechanical strength, modulus of elasticity and adhesion to the substrate, in accordance with ISO 20502:2005. Results: The results show an increase in apparent modulus of elasticity with thickness, reaching values of around 25.05 GPa and 36.3 GPa, close to the cortical bone for the 250 nm and 450 nm thick coatings, respectively. Adhesion tests show a progressive improvement up to 450 nm, followed by a similar observation at 850 nm, underlining the importance of optimal thickness to balance mechanical protection and biomechanical compatibility. Furthermore, the initial roughness and topography of the substrate were not influenced by the different thicknesses of the Ca-SZ coating. Conclusions: Together, these results reinforce the potential of Ca-SZ coatings to minimise stress shielding in dental implants.

Keywords: Ca-SZ; Young’s modulus; adhesion; biomechanics; coating.

Figure 1

Three ×50 SEM micrographs of TA6V surfaces coated with 250 nm (a), 450 nm (b) and 850 nm (c) thick Ca-SZ (magnification ×50).

Figure 2

Elemental EDS maps of Ca-SZ coatings of thicknesses 250 (a–c) 450 (d–f) and 850 nm (g–i).

Figure 3

Three-dimensional surface profile of bare TA6V compared with TA6V surfaces coated with 250, 450 and 850 nm thick Ca-SZ.

Figure 4

Evolution of topographic parameters Sa and Sq as a function of the thickness of the deposited Ca-SZ coating.

Figure 5

SEM micrograph after scratch test of the Ca-SZ coatings at thicknesses of 250 (A), 450 (B) and 850 nm (C) associated with the critical loads measured (LC1, LC2 and LC3) for each thickness.

Figure 6

SEM micrograph after scratch test of a bare TA6V surface (A) compared with 250nm thick Ca-SZ coatings (C). (B,D) are end-of-track images at ×500 magnification.

Figure 7

EDS profiles of scratch tracks after scratch testing on a 250, 450 and 850 nm thick Ca-SZ coating. The spectra show the elemental distributions of zirconium (green), titanium (blue) and oxygen (red for 250 and 450 nm, pink for 850 nm) along the track, illustrating the evolution of the coating’s coverage and resistance as a function of its thickness. The tendency of the track is indicated by the yellow arrow at the bottom of the column for each coating thickness.