RESIDUAL MONOMER LEACHING FROM CHEMICALLY CURED AND VISIBLE-LIGHT-CURED ORTHODONTIC ADHESIVES

The objective of this study was to quantify the amount of residual mon omer leached from chemically cured and visible light-cured orthodontic adhesives based on Bis-GMA/TEGDMA monomers, when bonded to ceramic an d stainless steel brackets. The residual TEGDMA and Bis-GMA monomer co ncentrations were determined by high performance liquid chromatographi c (HPLC) analysis of the extracts after specimen immersion in ethanol/ water solution for 15 days at 37 +/- 1 degrees C. According to the res ults 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 s howed high monomer elution as well. A polycarbonate base ceramic brack et manifested significantly greater amount of monomer release compared with ceramic brackets when combined with the visible light-cured adhe sive. Indirect (from the incisal and cervical edges of the bracket) ir radiation 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. N o statistical difference was found between direct or indirect irradiat ion of the ceramic brackets tested, with respect to monomer elution fr om the light-cured adhesive.