[In vitro evaluation of mercury leakage from dental amalgam using atomic absorption spectrophotometry]

The use of silver amalgam as a tooth filler is under constant critical review because of its mercury content. After a review of the literature on this subject, in vitro spectrophotometry was used to assay the release of mercury by these amalgams in basal conditions.

The experiment was conducted in two phases using standard doses of amalgam. In Phase 1 Black Class I cavities were created in extracted teeth that were big enough to take the required dose of amalgam. In some cases the material was inserted in a single operation, while in others the amalgam was introduced in three stages. Some of the cavities were cleansed with cotton buds bathed in ethyl alcohol, while others were not. All the drilled teeth were imbued in a bath of artificial saliva held at a constant temperature. In the second experiment, crushed amalgam was immersed in a similar bath of artificial saliva but otherwise untreated. The saliva was assayed after different time lapses using atomic absorption spectrophotometry and the FIAS technique.

The results showed extremely variable but always modest quantities of free mercury in the artificial saliva.

The findings suggest that not all the mercury available in the amalgamation phase is involved in the formation of the crystalline reticulum and that the percentage of mercury bonded is different every time. While the titre of free mercury encountered was always extremely low and hard to predict, it cannot be ignored.