Recovery of silver residues from dental amalgam

A comparative life cycle assessment of dental restorative materials

OBJECTIVES

Different types of direct-placement dental materials are used for the restoration of structure, function and aesthetics of teeth. The aim of this research investigation is to determine, through a comparative cradle-to-gate life cycle assessment, the environmental impacts of three direct-placement dental restorative materials (DRMs) and their associated packaging.

METHODS

Three direct-placement dental materials; dental amalgam, resin-based composite (RBC) and glass polyalkenoate cements (GIC) are assessed using primary data from a manufacturer (SDI Limited, Australia). The functional unit consisted of 'one dental restoration' of each restorative system under investigation: 1.14 g of dental amalgam; 0.25 g of RBC (plus the adhesive = 0.10 g); and 0.54 g of GIC. The system boundary per restoration included the raw materials and their associated packaging materials for each DRM together with the processing steps for both the materials and packaging. The environmental impacts were assessed using an Egalitarian approach under the ReCiPe method using Umberto software and the Ecoinvent database. Nine different impact categories were used to compare the environmental performance of these materials.

RESULTS

Dental amalgam had the highest impact across most of the categories, but RBC had the highest Global Warming Potential. The highest sources of the environmental impacts for each restorative material were: Amalgam, derived from material use; RBC, derived from energy use in processing material and packaging material; GIC, derived from material and energy use for packaging.

SIGNIFICANCE

Less intensive energy sources or more sustainable packaging materials can potentially reduce the impacts associated with RBC and GIC thus making them suitable alternatives to dental amalgam.

Recovery of Mercury from Dental Amalgam Scrap-Indian Perspective

Aim:

The aim is to recycle mercury from dental amalgam scrap using the vacuum distillation method.

Materials and Methods:

A total of 150 g of dental amalgam scrap was taken in a round bottom flask and was subjected to vacuum distillation at 398°C. The vapor of mercury was collected in another round bottom flask.

Observation:

The procedure is carried out for mercury recovery using vacuum distillation apparatus, and mercury vapor are collected in a round bottom flask, and the silver is recovered using sucrose as reducing agent. Using 150 g of dental amalgam scrap 50%–80% of silver are recovered, and silver has a purity of 70%–80%. However, the total time required in the reduction process ranged between 303 and 600 min.

Conclusion:

Mercury could be recycled from dental amalgam scrap through vacuum distillation method at 398°C and its implication of dental amalgam scrap in an Indian perspective.