The inflammatory response of epithelial cell to corrosion products from recast palladium –silver alloy

Abstract

In dentistry, there is an increase in alternative metals such as palladium or silver to add into noble metal alloys in order to improve properties and reduce cost. Apart from using other metals to replace gold or platinum, reuse is another way to save the cost. There are many studies on the recast dental alloys on mechanical properties and how many percentages of new alloys needed to add in the recasting process. It has been well accepted that amount of new and used alloys would affect the mechanical and physical properties. The biocompatibility of the alloys, however, has not been extensively investigated. It is reported that metal ions releasing from recasting alloys, might influence on the biocompatibility of the alloy, but the mechanisms is not yet clear. In the gingival sulci, the metal restoration margin is in close proximity to the sulcular epithelium, therefore the epithelial cells may encounter the released metal ions as an external stimulus. To investigate the epithelial inflammatory responses to corrosion products from recast palladium-silver alloy. Three specimens of each group from first cast, second cast and fourth cast Pd-Ag alloy (10*5*1mm3) were submerged in artificial saliva for 15 days. Microstructure of alloys were observed by a scanning electron microscope (SEM). The corrosion products from alloys were measured by an inductively coupled plasma mass spectrometry (ICP). To study the biocompatibility property, the oral epithelial cells cultured in monolayer were challenged by corrosion product from recast alloys. Quantitative RT-PCR was used to examine the expression of proinflammatory cytokines-specific mRNA, including IL-1β and TNF-α. Microstructure were changed after recasting. Palladium ion was more found after recast. In a reverse transcriptase PCR, IL-1β mRNA levels in response to corrosion product of second and fourth recast group were significantly higher than first cast group. We suggest that the corrosion product from recast Pd-Ag alloy induce epithelial cells to secrete IL-1β which is a proinflammatory that is also found in inflammed gingival tissue. This research give more information and understanding on biocompatibility of recast palladium-silver alloy by observing their corrosion behavior and potential cytotoxic effect i.e. presence of inflammatory response.