Amalgam, risk, benefits and the precautionary principle

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.

Recovery of silver residues from dental amalgam

Dental amalgam residues are probably the most important chemical residues generated from clinical dental practice because of the presence of heavy metals among its constituents, mainly mercury and silver.

OBJECTIVE

The purpose of this study was to develop an alternative method for the recovery of silver residues from dental amalgam.

MATERIAL AND METHODS

The residue generated after vacuum distillation of dental amalgam for the separation of mercury was initially diluted with 32.5% HNO3, followed by precipitation with 20% NaCl. Sequentially, under constant heating and agitation with NaOH and sucrose, the sample was reduced to metallic silver. However, the processing time was too long, which turned this procedure not viable. In another sequence of experiments, the dilution was accomplished with concentrated HNO3 at 90 degrees C, followed by precipitation with 20% NaCl. After washing, the pellet was diluted with concentrated NH4OH, water and more NaCl in order to facilitate the reaction with the reducer.

RESULTS

Ascorbic acid was efficiently used as reducer, allowing a fast reduction, thus making the procedure viable.

CONCLUSIONS

The proposed methodology is of easy application and does not require sophisticated equipment or expensive reagents.