For many years now, mercury has been recognised as a dangerous neurotoxin that can cause serious health problems. Indeed, according to the World Health Organisation (WHO), mercury is rated as one of the top 10 chemicals or groups of chemicals of major public health concern.
However things aren’t always as simple as they may seem. Dental professionals will be aware that mercury is a key component of dental amalgam, and there is a significant ongoing debate within the profession as to the impact and potential toxicity of dental amalgam fillings. The issue here is that on one level, all humans are exposed to some small dose of mercury, and there are a number of key factors that determine whether health effects occur. These include the type of mercury concerned, the dose, the duration of exposure, and the route of exposure (inhalation, ingestion or dermal contact).
Dangers
While the debate certainly still rages regarding the toxicity of mercury within the context of a dental filling, in other dental contexts, the dangers of mercury exposure are far more clear-cut. In 1996 Parsell et al, published an article on ‘Mercury release during autoclave sterilisation of amalgam’. In the study, it was found that mercury vapour levels within the room where amalgam was exposed to steam autoclave sterilisation reached levels that constitute an unnecessary health risk to members of the dental team.
This should perhaps come as no surprise to readers: the heat generated in the sterilisation process causes mercury to turn into a vapour – a dangerous form of the element that can easily be inhaled by clinical staff. While the dangers of autoclaving amalgam-filled teeth such as in the Parsell study would perhaps appear obvious to many readers in a modern context, the dangers of mercury vapour from autoclaves still exist to this day.
This is because tools used in the placement or removal of dental amalgam can also be contaminated with amalgam containing mercury prior to sterilisation. Heating instruments that have been used in such instances can also therefore cause mercury to vaporise. This vapour will then emit from the autoclave after the door is opened at the end of the cycle, and can also potentially enter vital parts within the autoclave, resulting in contamination, and possible malfunction and failure of the unit. To complicate matters further, if there is a suspicion that the failure of the autoclave is mercury linked, then the engineers tasked with trying to repair the fault do themselves run the risk of being contaminated.
Naturally, if mercury is found in the autoclave then steps must be taken to decontaminate the unit before it can be returned to use.
In some instances, where mercury has vaporised then re-settled within inaccessible vital parts, it may not be possible to service or repair the autoclave at all.
Reducing the risk
To minimise the risks associated with mercury there are several steps you can take to reduce the chance of biological or mechanical contamination. Firstly, you should ensure that any dental instruments used for placing or removing amalgam are thoroughly decontaminated and inspected before entering the sterilisation phase of the cycle.
Beyond precautionary measures such as decontamination and inspection, you can also take steps to improve the safety of the local working environment. Autoclaves should for example be situated in a location where air circulation is high, and ideally, where an exhaust fan can remove contaminated air.
Autoclaves are an important part of the decontamination cycle and are considered an integral part of any modern dental practice. Though they are of course designed to facilitate the sterilisation of pathogens, dental team members should be aware that there are still other dangers within the dental practice setting. Though the debate over mercury in dental amalgam still rages to this day, there can be no mistaking the danger of vaporised mercury released during the high temperatures of the sterilisation cycle.
References available on request.