Dental compomer

The setting reaction is similarly a polymerisation process of resin monomers (e.g. urethane dimethacrylate) which have been modified by polyacid groups, and is induced by free radicals released from a photoinitiator such as camphorquinone.

[2] Also in compomer is fluoroaluminosilicate glass which, when broken down by hydrogen ions through an acid-base reaction, releases fluoride.

To aid water absorption and fluoride release, some of the resins in the compomer matrix are more hydrophilic (e.g. glycerol dimethacrylate).

[1] The source of the hydrogen ions that break the fluoroaluminosilicate glass particles apart are certain resin monomers that have a carboxyl group attached.

Some compomers instead source their hydrogen ions from a methacrylated polycarboxylic acid copolymer that is similarly used in some resin modified glass ionomer cements.

[1][3] Fluoride is a mineral which helps strengthen our teeth and protects them from decay, and it is found in many dental products including toothpaste.

Compomers and glass ionomer cements are able to release fluoride over extended periods, and this may help to reduce the risk of a tooth decaying further.

[5] On the other hand, Richard van Noort (2013) states that, due to recent developments, modern compomers are now capable of releasing the same amount of fluoride over the lifetime of the restoration as glass ionomer cements.

As such, water equilibrium is reached within days rather than weeks, months or even years in the case of dental composite materials.

This property has the advantage of compensating for the polymerisation shrinkage during the setting reaction, thus reducing any gap that develops at the cavity margins.

Compomers have poorer mechanical properties than dental composites, with a lower compressive, flexural and tensile strength.

[1] It is important to note that compomers do not bond to tooth tissue like glass ionomer cements; this is the same issue with dental composites.