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Environmental Risk Posed by Dental Materials

Dental practitioners, must recognize that some of the materials and procedures used to provide dental health services may contaminate the environment. Dentistry is a profession dedicated to promoting and enhancing oral health and well-being. Unfortunately, some of the materials that are currently in use — including heavy metals and biomedical waste — presents potential challenges to the environment.

Dental Amalgam Waste Products

During the placement and removal of dental amalgam restorations, a variety of waste products is generated:

  • Elemental mercury vapour — released from dental amalgam alloy.
  • Dental amalgam scrap — the amalgam particles that have not come into contact with the patient (i.e. particles remaining in the dappen dish following restoration placement).
  • Amalgam waste — the particles that have come into contact with patient secretions (e.g. particles generated during carving and restoration removal procedures).
  • Amalgam sludge — the fine particles present in dental office wastewater, commonly trapped in chair-side traps and vacuum filters.

Dental practitioners, are responsible for ensuring that the waste carriers used are registered and qualified to handle the wastes produced. Waste storage containers should be collected for reclamation by a registered agency. Ideally, these wastes should be recycled, but not all hazardous waste collection agencies are qualified or able to perform this service. It is important to find out what forms of dental amalgam waste are accepted by a particular waste carrier and how that company prefers the waste to be stored.

Reduction or Prevention

Regardless of the means of disposal of dental amalgam, practitioners should not flush contaminated wastewater down sinks, rinse chair-side traps or vacuum filters in sinks, nor place material containing dental amalgam in general garbage or waste to be incinerated. These practices release mercury into the environment and negate the profession’s efforts to reduce environmental mercury contamination.

Amalgam Separators

Separation technology is based on sedimentation, filtration or centrifugation of the dental amalgam particles from wastewater. Some devices use a combination of these methods, in addition to ion exchange. The proper amalgam separation unit must be selected carefully as not all units are able to work efficiently in every physical arrangement. Some units are placed before vacuum pumps, others after. Some require considerable space to house the unit, while others are compact.


Installation of chair-side traps, vacuum filters and ISO-certified amalgam separators.


An additional byproduct of traditional radiography is the lead shields contained in each film packet. Although the lead shields themselves are relatively small, the cumulative waste produced can be considerable. An added benefit of digital radiography is the reduction in lead waste production. Lead, like mercury and silver, is toxic and persists in the environment. Even at low levels of exposure, lead exerts adverse health effects on both children and adults.


Reducing environmental lead contamination by dental practitioners is an inexpensive and easy task. The lead shields from film packets have to be collected and returned periodically to the manufacturer for recycling.. The only cost is for postage. Unfortunately, some manufacturing companies report that only about 5% of products sold are returned. In part, it appears that this is due to a lack of awareness of the offered service.

Biomedical Waste

Biomedical waste encompasses materials capable of causing disease or suspected of harbouring pathogenic organisms; it includes blood-soaked gauze, tissues and syringes, although not extracted teeth. Non-sharp biomedical waste products should be stored in a yellow bag that is properly labelled with a biohazard symbol. Sharps (i.e. syringes, suture needles) should not be included in the bagged general or biomedical waste, but should be stored in a puncture-resistant, leak-proof, properly labelled container until collection and incineration.


The dentist must make sure that laboratory/surgical wastes must be collected and transferred by a registered hauler to a licensed incinerator.


Silver is another heavy metal that can enter our water system via improper disposal of dental office waste. Although silver is a component of dental amalgam, the silver thiosulfate in radiographic fixer (a solution normally used in the processing of dental radiographs) presents a greater environmental concern.


The best way to manage silver waste is through recovery and recycling. Dentists can install in-house silver recovery units to salvage the silver themselves, allowing for some monetary return on the equipment investment when the silver is later sold.

These units generally recover silver ions from the waste solution through displacement of iron ions or through a closed-loop electrolytic system that recovers not only silver for reuse, but also the radiographic fixer. Alternatively, the waste can be collected by a registered agency certified to carry and manage the waste.


Another common waste product in the dental office, unused film should also not be placed in the general waste. Unused films contain unreacted silver that can be toxic to the environment.


Safe disposal can generally be accomplished by simply contacting the supplier of the product and returning the waste for recycling. With recent advances in radiographic technology, digital imaging is becoming a popular means of obtaining dental radiographs. Among its advantages are reduced radiation exposure and the absence of chemical image processing. Therefore, incorporation of digital imaging within the dental office can greatly reduce the risk.

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