Elution study of acrylic monomers from orthodontic materials using high performance liquid chromatography (HPLC).

Purpose: Main goal of the study was the identification and quantitative analysis of monomer elution from materials commonly used in fixed orthodontic therapy. Studies have shown severe health effects of monomers including cytotoxic, allergenic or mutagenic potential and endocrine changes. This in vitro study focusses primarily on five resins which are usually processed intraorally and remain in the oral cavity long-term.

Methods: We tested the elution of monomers from specimens (7.5 mm × 1.5 mm) immersed in artificial saliva at body temperature (37 °C) for 30 min to 5 weeks. The used method is in accordance with DIN EN ISO 10993-13. The five tested materials were BrackFix® (Voco GmbH, Cuxhaven, Germany), Triad®Gel (DeguDent GmbH, Hanau, Germany), and Transbond™ XT, LR and Plus (3M Unitek, Monrovia, CA, USA). All aliquots were analyzed using high performance liquid chromatography (HPLC). Data were statistically analyzed.

Results: All five analyzed materials eluted substances over a period of 5 weeks. Identified substances included bisphenol A (BPA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA). BPA eluted from Transbond™ Plus, XT, LR and BrackFix®. The cumulated mean values after 35 days ranged from 16.04 to 64.83 ppm, depending on the material. TEGDMA eluted with a mean of 688.61 ppm from Transbond™ LR. UDMA with a mean of 1682.00 ppm from Triad®Gel. For each material the highest concentrations of all these substances were found in the first elution period. Other substances that were not equivocally identified or of low concentration also eluted.

Conclusion: Using the described method, it is possible to qualitatively and quantitatively determine the in vitro elution of monomers from orthodontic materials. The concentrations of the substances identified were below the current maximum recommended intake. However, a cumulative effect and low-dose effects should be considered for both patients and dental professionals, especially for young patients. Measures to reduce exposure patients and practitioners are suggested.