Effect of element concentration on nickel release from dental alloys using a novel ion beam method

Abstract 

Objectives

Nickel chromium is widely used as a restorative material in dentistry but its biocompatibility is of concern as there are reports of patients suffering adverse effects caused by exposure to nickel-based restorations. The aim of this work was to quantify the amount of nickel released into solution from commercially available nickel-based alloys with varying compositions and to identify the potential use of thin films in further understanding the role of chromium in reducing nickel release.

Methods

Six commercially available nickel-based alloys were cast using the lost wax technique. Nickel chromium thin films were deposited onto silicon substrates by ion beam assisted physical vapor deposition. Both types of alloys were immersed into solution representative of saliva at pH 5 for 7 days. The amount of nickel released into solution was quantified by graphite-furnace atomic absorption spectrophotometry.

Results

The amount of nickel released from commercially available cast alloys did not correspond to the amount of nickel within the alloy. The total amount of chromium and molybdenum within the alloys proved to be of greater influence. Increasing the amount of chromium in the thin film alloys reduced the amount of nickel released but this was not linear.

Significance

Differences in the composition of commercial cast alloys highlighted the importance of other elements within the alloy on reducing the amount of nickel released. The use of thin film alloys can be useful in further understanding how the composition of an alloy can affect the amount of nickel released.

Keywords: Dental alloys, Nickel, Chromium, Physical vapor deposition, Sputtering, Corrosion