Monomer release in saliva after bonding orthodontic brackets

Researchers have measured substances from bonding materials in patient saliva at different time points.

“Understanding what is released from dental materials in real clinical situations is essential for assessing patient exposure. Studies like this help us build a clearer picture of when and how these substances appear in the mouth,” says Hilde Molvig Kopperud, CTO at NIOM

What is this about?

When orthodontic brackets are bonded to teeth, adhesive materials are used between the bracket base and the enamel. These materials contain various methacrylate-based monomers. The question in this study was whether these substances are released into saliva during and after bracket placement.

A research team from NIOM, the University of Bergen and two orthodontists now in orthodontic practices collected saliva from 30 patients aged 10–18. Samples were taken before the brackets were bonded, immediately after bonding, and again at the first follow-up visit 4–6 weeks later. The samples were analysed using gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS).

The goal was to identify which monomers, if any, appear in saliva, how much is present, and whether the release continues over time.

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What did the researchers find out?

The analyses showed that three monomers—poly-EGDMA, HEMA and BMAEPH—were present in saliva immediately after bracket bonding. The amounts varied between patients. These substances originate from both the adhesive applied to the bracket and the primer used on the tooth surface.

Before treatment started, none of the monomers were detected. At the follow-up visit 4–6 weeks later, the substances were no longer measurable in any patient. This means that, using the analytical methods applied in the study, the release appears to occur only shortly after the bonding procedure.

The researchers also found undeclared components in the bonding materials during the initial screening. This underlines the importance of accurate product information for clinical use and risk assessment.

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Key results

• Monomers from orthodontic bonding materials were detected in saliva immediately after bracket placement.
• The release was temporary; no measurable amounts were found 4–6 weeks later.
• The detected monomers were poly-EGDMA, HEMA and BMAEPH.
• Individual variation between patients was considerable.
• Some components in the adhesive system were not listed in the manufacturers’ safety data sheets.

Overall, the study indicates that exposure to monomers during orthodontic bracket bonding is short-lived. Further work may explore bonding procedures with reduced primer use and improved transparency in material composition.