EQUILIBRIUM VAPOR-PRESSURE OF MERCURY FROM DENTAL AMALGAM UNDER LOADING CONDITIONS

Earlier studies have failed to establish a consensus on the amount of mercury vapour released from dental amalgam restorations. The purpose of this study was to accurately and quantitatively measure the equilib rium mercury vapour pressure from dental amalgam. The vapour pressure was measured using a quartz crystal microbalance as a function of the load from 0-5.4 MPa. Auger spectra were collected of the as-formed and argon ion sputter cleaned dental amalgam surface. For the as-formed s urface the mercury vapour density is zero with no load and increases t o 0.6 mu g m(-3) at 5.4 MPa. Following cleaning the mercury, vapour de nsity increased to a maximum value of 15 mu g m(-3). The Auger spectra of the as-formed surfaces were dominated by features associated with carbon and oxygen. These spectral results in concert with the mercury vapour density measurements indicate that the oxide film on the as-for med surfaces inhibited the release of mercury vapour. The results of t his experiment provide an upper limit for the amount of mercury vapour released by dental amalgams. Under conditions simulating the oral cav ity this value would be reduced by oxides that form on the surface of dental amalgam restorations. (C) 1998 Elsevier Science Ltd. All rights reserved