Tantalum Nitride-Decorated Titanium with Enhanced Resistance to Microbiologically Induced Corrosion and Mechanical Property for Dental Application

Abstract

Microbiologically induced corrosion (MIC) of metallic devices/implants in the oral region is one major cause of implant failure and metal allergy in patients. Therefore, it is crucial to develop practical approaches which can effectively prevent MIC for broad clinical applications of these materials. In the present work, tantalum nitride (TaN)-decorated titanium with promoted bio-corrosion and mechanical property was firstly developed via depositing TaN layer onto pure Ti using magnetron sputtering. The microstructure and chemical constituent of TaN coatings were characterized, and were found to consist of a hard fcc-TaN outer layer. Besides, the addition of TaN coatings greatly increased the hardness and modulus of pristine Ti from 2.54 ± 0.20 to 29.88 ± 2.59 GPa, and from 107.19 ± 6.98 to 295.46 ± 19.36 GPa, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy studies indicated that TaN coating exhibited higher MIC resistance in comparison to bare Ti and TiN-coated coating in two bacteria-containing artificial saliva solutions. Moreover, the biofilm experiment showed that the TaN-decorated Ti sample possessed good antibacterial performance. The SEM and XPS results after biofilm removal demonstrated that TaN film remained its integrity and stability, while TiN layer detached from Ti surface in the bio-corrosion tests, demonstrating the anti-MIC behavior and the strong binding property of TaN coating to Ti substrate. Considering all these results, TaN-decorated Ti material exhibits the optimal comprehensive performance and holds great potential as implant material for dental applications.

Fig 1. XRD patterns (a) and XPS survey scan spectra (b) of the pristine Ti, TiN-coated and TaN-coated Ti: (bi) XPS wide spectra; the high-resolution Ti 2p spectra for the pristine Ti (bii), TiN-coated Ti (biii), and Ta 4f spectrum for TaN-coated Ti (biv).

Fig 2. Surface characteristics of the pristine Ti, TiN-coated Ti and TaN-coated Ti samples: (a) SEM images, the insets show the water contact angle of the corresponding materials; (b) in situ SPM images; and (c) surface roughness, root-mean-square roughness (RMS) and average roughness (Ra) are used to present the surface roughness.

Fig 3. Hardness (a) and elastic modulus (b) vs. depth curves for the uncoated Ti, TiN-coated Ti, and TaN-coated Ti samples.

Fig 4. Open circuit potentials (a) and potentiodynamic polarization curves (b) of the uncoated Ti, TiN-coated Ti, and TaN-coated Ti in AS, AS-S.mu, and AS-A.vi solutions, respectively.

The inset table in (b) shows the corrosion current density (I _corr) of the samples.

Fig 5. Representative EIS spectrum plots of the pristine Ti, TiN-coated Ti, and TaN-coated Ti in AS, AS-S.mu, and AS-A.vi solutions: Nyquist plots (a), Bode plots (b), and the equivalent electrical circuit model (c).

Fig 6. Biofilm formation observation of the pristine Ti, TiN-coated Ti, and TaN-coated Ti after 14 days of incubation with mixed bacteria: SEM images of bacteria and EPS (a), WLI images (b), and Live/dead cell staining of CLSM.

In WLI images, the brown represents bacterial cells, and the orange represents substrates. Red arrows in (a) point to the secreted EPS of bacteria. * represents p < 0.05 compared with other groups.

Fig 7. The SEM micrographs (a) and in situ SPM (b) of the pure Ti, TiN-coated and TaN-coated surfaces exposed to medium with and without the mixed bacteria for 7 and 28 days after the removal of biofilm and corrosion products.

Fig 8. The XPS high-resolution spectra of Ti 2p and O 1s for bare Ti (a), Ti 2p and N 1s for TiN-coated Ti (b), and Ta 4f and N 1s for TaN-coated Ti samples (c) in medium with and without the mixed bacteria for 28 days after the removal of biofilm and corrosion products.