Residual monomer leaching from chemically cured and visible light-cured orthodontic adhesives

The objective of this study was to quantify the amount of residual monomer leached from chemically cured and visible light-cured orthodontic adhesives based on Bis-GMA/TEGDMA monomers, when bonded to ceramic and stainless steel brackets. The residual TEGDMA and Bis-GMA monomer concentrations were determined by high performance liquid chromatographic (HPLC) analysis of the extracts after specimen immersion in ethanol/water solution for 15 days at 37 +/- 1 degree C. According to the results the highest monomer concentrations eluted were obtained from the chemically cured adhesive. Direct (through the bracket) irradiation of stainless steel brackets bonded to the visible light-cured adhesive showed high monomer elution as well. A polycarbonate base ceramic bracket manifested significantly greater amount of monomer release compared with ceramic brackets when combined with the visible light-cured adhesive. Indirect (from the incisal and cervical edges of the bracket) irradiation of the visible light-cured adhesive bonded to the stainless steel brackets resulted in lower residual monomer elution compared to that of directly (through the bracket) irradiated metallic brackets. No statistical difference was found between direct or indirect irradiation of the ceramic brackets tested, with respect to monomer elution from the light-cured adhesive.