Effectiveness of wet and dry mercury vapour suppressant systems in a faculty of dentistry clinic.

The objective of this study was to determine the effectiveness of a liquid and a dry commercial mercury vapour suppressant system. Measurements were made in a student dental clinic, using a mercury vapour detector for periods up to 76 weeks. The two products examined were Mercon vap liquid in a stock jar and the Mercon tainer dry jar system. Amalgam scrap jars were removed from the study when the mercury vapour concentration in the jars exceeded the arbitrary cut-off criterion of 0.05 mg Hg m(-3). Results showed that the mercury vapour concentration in the liquid system exceeded the cut-off criterion in 44 weeks or less, whereas the dry system remained below the detection limit (0.01 mg Hg m(-3)) for the maximum measurement period of 76 weeks. It was concluded that the dry system is more effective and reliable than the liquid system. The reliability of the liquid system may be influenced by contact of amalgam scrap with the portion of the inner wall of the jar that is not covered by liquid. It is proposed that amalgam scrap contaminates the wall with mercury during its insertion.