Tooth filling materials Dental amalgams & alternative materials

5. What are the possible health effects of alternative tooth filling materials?

• 5.1 How toxic are the different components of alternative materials ?
• 5.2 What are the possible negative effects on health associated with alternative materials ?

5.1 How toxic are the different components of alternative materials ?

Tooth fillings are increasingly done using alternative materials such as composites, glass ionomer cements, compomers, giomers and sealants. Some of these alternative materials are chemically very complex and not necessarily free from concerns about health effects.

Composites contain many different components, including a resin base and ceramic filler. The product is supplied as a paste that is filled into the tooth cavity. The resin is then typically hardened using visible blue light.

Used since the 1970s, glass ionomer cements are formed when glass powder and a type of polymer react with each other. The reaction hardens the material and attaches it firmly to the tooth.

Other materials, such as compomers have been introduced since the 1990s to combine specific advantages of composites and cements.

Sealants are pastes or liquids that are used to seal small surface defects such as pits and fissures in permanent teeth to prevent caries.

Clearly these alternative restorative materials are complex chemically, with different components, properties, and setting reaction mechanisms. They can thus interact with the patient’s tissues in many different ways.

Substances of particular concern are:

• ions leaching from different types of glass used as filling material ;
• acids used to etch teeth and set the fillings; and
• the small organic molecules (monomers) that react to form polymers, the basis of many alternative materials. Some of the monomers may not have reacted during placement and therefore low levels may remain in the set filling.

Although there is very limited data available, some monomers are known to be toxic to cells and others cause allergic reactions. Some of these substances are irritants when used by themselves. The effects they cause vary depending on the substance and on the type of body tissue with which they come into contact. In addition, many alternative materials release ions. In vitro studies have shown that some of these releases (such as fluorides) are beneficial or too low to be harmful, while others (such as copper, aluminium and iron) may reach concentrations capable of harming cells.

As restorations degrade or erode over time, they release substances that can be absorbed through the skin, the gut, and through the lungs. It is very difficult to determine exposure to the different substances because there are no obvious indicators that could be measured and because the volumes of the materials used are very small and these materials set quickly. In addition, the starting materials change chemically when they set and it is likely that their toxicity also changes.

Although laboratory studies show that some of these leached substances are harmful to cells, the concentrations emitted by restorations during placement and thereafter are usually too small to be considered a significant health problem.

When some alternative materials set, they shrink and leave a gap between the tooth and the restoration. Improvements in techniques and products have led to smaller gaps but some microorganisms can fit underneath restorations and cause harmful effects to the dental pulp.

Dental workers are exposed to some of the components of alternative materials when they prepare and place fillings. There is very limited information on the level of exposure to components of alternative materials present in the air. More...

5.2 What are the possible negative effects on health associated with alternative materials ?

Alternative tooth-coloured materials contain a complex mixture of chemicals that react with each other inside the tooth cavity and also interact with the surrounding tissues. Some of the components of these materials are highly toxic to gum and pulp cells grown in the laboratory and others can cause mutations. However, these properties may not necessarily lead to negative health effects in dental patients.

Many of the components of alternative materials and their degradation products can cause local allergic reactions in dental patients (mouth) and workers (hands). Such allergic reactions can also affect other parts of the body such as the face, arms or legs. Allergic reactions are more common in dental workers than in patients, probably because the exposure is highest when handling resin-based restorative materials.

Wearing gloves when handling these materials does not prevent very small molecules released from alternative materials to reach the skin, and these molecules may induce reactions in persons sensitive to them. Such reactions can be avoided by not touching these substances even when wearing gloves.

Many alternative materials are hardened by shining visible blue light onto them. The powerful light sources now used for this purpose may constitute an additional risk for adverse effects, both to patients and dental personnel. Eye protection is extremely important. Though these dental curing units are generally considered safe certain people should avoid their use, for instance individuals with certain cataract and other eyesight problems, patients sensitive to light or those on photosensitising medication. Certain electrical equipment used for dental curing may pose a risk to people with electrical implants such as pacemakers.

The full chemical specification of alternative restorative materials is not always divulged and it may be difficult to ascertain exactly what they contain. In the absence of data, it may not be possible to provide a scientifically sound statement on the safety of individual products. There are very limited scientific data available concerning exposure of patients and dental personnel to these substances.

Nevertheless, these alternative materials have now been in clinical use for well over thirty years, and this use has revealed little evidence of clinically significant adverse events. The commercially available materials have either changed substantially or been improved considerably during this time, with reduced exposure to harmful components through improved hardening processes. More...