EFFECT OF A NEW MERCURY-FREE ALLOY ON EXTRACTED TEETH
A new, mercury-free, direct-filling, metallic powder material is being investigated as a substitute for conventional dental amalgam. A dilute acid is used to deliver the powdered metal to the tooth preparation. This study used extracted human teeth with class I cavity preparations to evaluate possible effects of the mild acid on the tooth dentin and any interpositional varnish or liner. The teeth were divided into four groups (n=5) to receive either no treatment, copal varnish, polyamide varnish or adhesive resin liner before restoration with the new alloy. Visible light microscopy (LM) and scanning electron microscopy (SEM) were used to evaluate the alloy/tooth interface. Twenty teeth restored with spherical amalgam were separated into the same four pretreatment groups to serve as controls. All teeth were sectioned, polished, and examined with LM and SEM to evaluate the retention of sealant and/or surface degradation of the tooth. Samples consistently revealed retention of both varnishes, under all conditions. The adhesive resin liner showed considerable disruption and loss of liner from the dentin surface. There was a zone of reacted dentin in the samples restored with the new alloy and no liner, while the adhesive liner had a reacted zone of dentin with both the new alloy and the amalgam. The source of the resin reacted zone was consistent with the formation of a dentin hybrid zone. Data from this experiment contributes to in-vitro microleakage information and suggests the alloy and acidic vehicle do not adversely affect tooth dentin.