HPLC ANALYTICAL STUDY OF METHACRYLIC MONOMERS RELEASED FROM DENTAL COMPOSITE MATERIALS

The widely used high performance liquid chromatography (HPLC) is an analytical technique based on the crossing of a solvent (mobile phase), under high pressures, through a stainless steel column packed with very small particles (stationary phase). This technique allows a very efficient separation of the components of a mixture and an easy detection with high sensitivity. In the normal phase HPLC, the column is filled with silica particles and the mobile phase has low polarity or it is non-polar. The polar compounds of the mixture passing through the column are retained longer by the polar silica whereas are poorly dissolved into the non-polar mobile phase. The non-polar analytes pass instead more quickly through the column. In the largely used reversed phase HPLC, the silica surface is conversely made non-polar by attaching long hydrocarbon chains. A mixture of water and a polar solvent is used as mobile phase. In this case, the polar molecules of the mixture passing through the column are strongly attracted by the polar solvent but not by the hydrocarbon chains attached to the silica of the stationary phase; the polar molecules will therefore easily move with the solvent through the column. Non-polar compounds will instead tend to interact with the hydrocarbon groups of stationary phase slowing their way through the column. Triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) are methacrylic monomers present in dental auto- and photo-polymerizable resins. Many in vitro studies have shown that the polymerization of the above mentioned compounds is never complete and the uncured monomers are released in the oral environment, causing possible local adverse effects. The evaluation of the amounts of the methacrylic monomers released from composite resins is therefore very important and HPLC technique is particularly suitable to this purpose. HPLC is however not limited to qualitative and quantitative analysis of methacrylic monomers but can be also applied to the study of their metabolism. The present work summarizes the recent results about the detection of TEGDMA and HEMA in complex systems like cells and culture media by HPLC, evidencing its key role in the investigations of the substances involved in cytotoxic processes. Moreover the great specificity and sensibility of the used method allow to relate the concentration values of methacrylic monomers to their cytotoxic effects, in particular when such molecules are used in presence of N-acetyl cysteine, helping to clarify its mechanism of detoxification.