Influence of liquid films on mercury vapor loss from dental amalgam

Objectives: The aim of this study was to determine the effect of aqueous liquid films on Hg emission from of dental amalgam. Methods: Amalgam specimens (4 mm dia. ×4 mm long) made from ten alloys were uniformly abraded on wet ASTM 600 grit SiC paper, quickly dried and covered by liquid films of a thickness that approximated the thickness of saliva films on tooth surfaces in vivo. Distilled water and two formulations of artificial saliva were tested. After abrasion and film placement, the specimens were immediately inserted in a plastic tube which was then closed. After 30 min, the Hg vapor that had collected in the tube was measured using a Jerome 411 Hg analyzer. Hg emission from abraded surfaces exposed to air was also measured and used for comparative purposes. The test results were compared using ANOVA and Tukeyʹs contrast test (p=0.05). Results: Hg emission from abraded surfaces under liquid films was one to two orders of magnitude less than Hg emission from abraded surfaces exposed to air. Significance: In vitro measurement of Hg vapor emission from abraded surfaces exposed to air should not be used to estimate directly the Hg vapor release from dental amalgam restorations in vivo.