Luting agent

A luting agent is a dental cement connecting the underlying tooth structure to a fixed prosthesis.

There are two major purposes of luting agents in dentistry – to secure a cast restoration in fixed prosthodontics (e.g. for use of retaining of an inlay, crowns, or bridges), and to keep orthodontic bands and appliances in situ.

The introduction of adhesive resin systems made a wide range of dental materials available as luting agents.

Recently introduced agents such as resins and resin-modified glass-ionomer cement (RMGIC) are claimed to perform better clinically than some traditional ones due to their improved properties.

It has a short working time which can make it difficult to use but this can be elongated by adding tartaric acid, mixing on a cold glass slab or using a lower powder–liquid ratio.

[13] It is also very initially acidic which may cause pulpal inflammation[14] and has a very slow setting reaction, meaning hardening can take up to seven days.

Due to the presence of light-activated components (photo-initiators), this type of resin cement requires an external light source to initiate the setting reaction.

[11] Although it has the advantage of attaching restorations with minimal retentive capacity to tooth surfaces due to its high bond strength to dentine, its methacrylate constituent causes it to undergo polymerisation shrinkage when setting.

[16] The strain introduced by the shrinkage will tend to raise the tensile stresses significantly at areas where the cement is thick.

[18] Another way to look at the strain applied onto the tooth structure is to consider the configuration factor (C-factor) of the lute, especially in the case of inlay type restoration.

[1] RMGIC, also known as hybrid cements, was developed with the purpose of eliminating weaknesses of the traditional glass-ionomer (GI) to enhance its existing properties.

[19] The addition of polymerisable resins (hydrophilic methacrylate monomers) results in higher compressive and tensile strength, as well as lower solubility,[1] all of which are ideal properties of a dental luting agent.

[1] Theoretically, RMGIC benefits the teeth by releasing fluoride at the marginal area to reduce the risk of tooth decay.

[1] Eugenol (4-allyl-2-methoxy phenol) is the principal constituent of clove oil, and when mixed with zinc oxide leads to a chelating reaction.

Supposedly its therapeutic effects are supported by dentinal tubule fluid promoting the release of eugenol and its penetration towards the pulp.