Varying Composition of IBA-PVD Thin Films to Determine Ni Release

Objectives: NiCr cast alloys are widely used in dentistry as a cheap alternative to the more noble alloys. Unfortunately the biocompatibility of the alloy is a concern. The objective of this present study was to use thin films prepared by an Ion Beam Assisted-Physical Vapour Deposition (IBA-PVD) method so that the biocompatibility of materials with controlled chemistry could be studied in detail compared to conventionally cast dental alloys. Methods: Thin films with varying composition of NiCr and NiMo were deposited onto Si substrates using an IBA-PVD technique with the same surface finishes. The composition of each test piece was determined using scanning electron microscopy fitted with an energy dispersive x-ray (SEM-EDX) detector. Each test piece was placed into phosphate buffered saline solution used as artificial saliva for a week. The amount of Ni released into the solution was determined using graphite furnace atomic absorption spectrophotometry (GFAAS). Results: All samples showed that the amount of Ni released into the solution increased as the amount of Cr and Mo in the alloy decreased, with some interesting trends as the composition of the alloy varied. A comparison of microstructure and EDX maps has been used to explain and evaluate the cause of Ni release compared to cast dental alloys of similar composition. Conclusion: The amount of Cr and Mo both play a similarly important role in the release of Ni from both IBA-PVD thin films and conventionally cast NiCr dental alloys. As similar trends were observed for IBA-PVD films and dental cast alloys, the use of such films, where the composition of the alloy can be closely controlled may be valid as a quick and easy way to undertake similar element release investigations in the future.