Biocompatibility of nitride film coatings on dental alloy

Objective: To examine the biocompatibility of nitride film coatings on nickel-based alloy surfaces. Methods: Disc specimens (1.5mm x 12.0mm) were cut from the Ticonium™ ingot. Specimens were ground with SiC sandpapers to grip 1200 and used as controls. Specimens from the control group were selected and polished with 1.0mm alumina slurry and assigned as polished group. Titanium nitride (TiN) and titanium-aluminum nitride (TiAlN) films were deposited onto polished specimens by reactive radio-frequency sputtering. Surface characteristics were determined by X-ray diffraction (XRD), atomic force microscopy (AFM), and dynamic contact angle analyzer. Human gingival fibroblasts were used in short-term in vitro tests to assay for cell attachment and viability. Changes in cell morphology and cytoskeleton were observed using fluorescence microscopy. The MTT assay was used to assess cell proliferation at 3h, 6h, 12h, and 24h time periods (n=3) and analyzed statistically (ANOVA, Scheffe's, p<0.05). Results: The XRD pattern of TiAlN was similar to TiN and identified as B1-NaCl structure. AFM topographies clearly revealed grooves created by metallurgical grinding on the control surfaces. The surface roughness values ranged from 2.5nm to 26.5nm. The contact angles ranged from 37±2.1° to 86±5.1°. After 3h incubation, cells began to spread on the tested surfaces. The spindle-shaped fibroblasts with a well developed cytoskeleton and distinct actin fibers were observed at 24h incubation point.  The optical density values of the MMT assay at the 24h ranged from 1.2±0.2 to 2.7±0.2. The TiN and TiAlN film coated groups were statistically significant higher in cell proliferation than the polished and control groups (p<0.05). Conclusion: Cell viability and proliferation increased significantly with nitride film coatings in comparison with the control nickel-based alloy surfaces. No significant differences in the biocompatibility of the TiN and TiAlN films were determined. Supported in part: National Science Council, ROC. Grant No. 94-2314-B-010-027.