Tooth filling materials Dental amalgams & alternative materials

1. Introduction

Dental amalgam is a combination of one part liquid mercury with one part of a metallic alloy which mainly contains silver and tin. It has been used for over 150 years to restore decayed teeth, and its use has stirred controversy from the earliest days. To make the amalgam, mercury is mixed with the other metals to form a paste that can be fitted to the tooth cavity. The mixture sets relatively fast to form a hard alloy.

At the time of the introduction of amalgam into dentistry, gold could be used in some types of dental restorations, but its cost prohibited widespread use. In the 19th Century, there were no other synthetic materials that had both the required mechanical properties and the ease of placement. As a metallic alloy, amalgam did not look particularly good, but the increasing prevalence of dental caries at the time meant that this was a minor consideration. The even more profound increase in caries throughout the twentieth century, through the widespread use of refined sugars in foodstuffs, resulted in the increased use of dental amalgam fillings.

Although dental amalgam is extremely strong and durable and may still be considered a material of choice for some fillings in the back teeth, it has some drawbacks:

• It is not tooth-coloured so it is very visible, even more so in front teeth.
• It does not adhere to the surface of the tooth cavity, so dentists have to drill out relatively large holes in the teeth to securely fasten the filling.
• It contains mercury that is toxic in some forms. There is concern that mercury could be released during placement, normal corrosion and wear, and removal of a filling, and that it could lead not only to local effects in the mouth but also to effects in the body as a whole, for instance on the nervous system.

In recent years, alternative tooth-coloured materials have been developed for dental restorations and are increasingly used across the EU. These include composite materials, glass ionomer cements and a variety of hybrid structures.

This report considers whether mercury and the other components of amalgams and alternative restorative materials are safe for dental patients and workers. These alternatives include any chemicals used for the adhesion of the filling materials to the tooth and any light sources used to harden the material. The whole life-cycle of the restoration is taken into account: from manufacture, through placement, to degradation or wear in use and removal.

The report also assesses the exposure of the general population to mercury from dental amalgams released into the environment for instance through wastewater from dental offices (when fillings are placed or removed), and emissions into air from crematoria. Similar considerations on effects on the environment and indirect effects on humans are made for alternative materials although there is much less information available on these.

The toxicity of mercury has been extensively researched and there is a wide variety of scientifically-based sources of information on its health effects. However, some of the alternative materials are relatively new and little is known about their safety. More...