Dental waste: what you need to know – Rebecca Waters, Category Manager, Initial Medical

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  Posted by: Dental Design      15th June 2019

In a dental practice it’s likely that you come into contact with materials such as dental amalgam and gypsum on a daily basis. But have you ever wondered why these materials are so important to keep separate from other waste streams?

Both gypsum and amalgam can have a significant impact on the environment, so it’s necessary to understand these materials in more detail and take appropriate precautions to keep them properly segregated.

Gypsum – the unexpected threat

When we use gypsum in dental moulds, it’s difficult to believe that this material can produce potentially dangerous effects in other environments. Gypsum is chemically known as calcium sulphate dihydrate when it is found in its natural form. Through a process of calcination, it is transformed from a rock into a fine powder with the chemical name of calcium sulphate hemihydrate. It is this form of gypsum that is widely used in dentistry.[i]

Gypsum in this form is inert, meaning that it can safely be used in a wide array of situations including manufacturing, dentistry, sculpture and even children’s activities where they can use plaster of paris to make models. However, why gypsum becomes dangerous after it is disposed of is due to how it interacts with biodegradable waste.

In a landfill environment, sulphate-reducing bacteria can convert the sulphates in the material to form hydrogen sulphide gas. This only happens without the presence of oxygen, but in landfill areas, gypsum can undergo this reaction as it is likely to be buried under other waste.

Hydrogen sulphide gas is dangerous for many reasons, namely that it is highly flammable, poisonous to humans and corrosive.[ii]This means it can easily cause problems such as landfill fires, and harm any wildlife or people that are within these areas.

As such, gypsum has been banned from regular landfill sites in England since 2009 (the ban was in effect already in Scotland and Northern Ireland) and must instead be segregated to high sulphate waste sites.[iii]


Amalgam associated concerns

Much like gypsum, amalgam is dangerous to the environment because of its chemical formulation. The material is a mixture of different metals, including liquid mercury. Around 50% of the chemical makeup of amalgam is mercury, and this poses significant risks for the environment if it gets into our waterways.[iv]

This is mainly because mercury is a toxic substance. The World Health Organisation lists mercury as one of the top ten chemicals of major public concern, and this is because of its unique reaction in natural water environments. Bacteria found in the sea and in the sediment in riverbeds convert mercury into methylmercury – a substance that is easily absorbed into the bodies of marine wildlife. This either quickly poisons them or results in the formation of reproductory difficulties or other negative side effects. for that marine wildlife.

Furthermore, it’s important to consider the effect that this methylmercury has on humans, too. If people eat fish or shellfish with high mercury content, it’s likely they will suffer from mercury poisoning. Processes such as cooking do not eliminate the mercury present in seafood, and therefore there is no way to avoid mercury poisoning if the fish or shellfish is already contaminated.

Mercury poisoning can cause a number of debilitating problems. Both elemental and methylmercury are toxic to our central nervous systems, and consuming mercury can cause tremors, insomnia, memory loss and neuromuscular effects. Further complications include headaches and motor dysfunction. What makes this worse is that these effects may only become apparent when mercury has accumulated in our own bodies over time.[v] 


Proper disposal comes first

 Based on the evident harm these materials can cause, it’s vital that professionals segregate and dispose of amalgam and gypsum properly. Initial Medical can supply practices with both gypsum and specialist dental waste containers to help lessen the impact these materials make. It also offers amalgam separators for dental practices that effectively remove 99.8% of amalgam particulate and can be used on all types of suction system.

Furthermore, Initial Medical has pioneered Colour Code Characters – memorable and personality-filled embodiments of the Department of Health’s Colour Code for best practice waste disposal, with Dental Diana and Toxic Tony symbolising the two dental waste streams. Introducing these characters is a perfect way to ensure that your staff remain alert to the importance of disposing of these materials properly.


Responsible care

In the end, it’s important that dental professionals understand the materials they work with and how they can react with the outside world. Whilst gypsum and amalgam are safe when used for models or in people’s mouths, we need to be aware of where these materials could end up and whether they are harmful in these environments.



For further information please visit Tel: 0870 850 4045





[i]Singh, R., Singh, K., Agrawal, K. A Comparative Study of Physical Properties of Gypsums Manufactured in India. J Indian Prosthodont Soc. 2013 Dec; 13(4): 531–535.

[ii]Blackline Safety. H2S Gas – What you Need To know About Hydrogen Sulfide. Link:[Last accessed April 19].

[iii]Initial Medical. Gypsum Containers. Link:[Last accessed April 19].

[iv]FDA. About Dental Amalgam Fillings. Link:[Last accessed April 19].

[v]World Health Organization. Mercury and Health. Link:[Last accessed April 19].

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