HPLC analysis of residual monomer released from different adhesive systems

Objectives: The aim of this study was to evaluate the residual monomer released from three different adhesive systems which were applied to four different dentin discs under the pulpal pressure simulation. Methods: Sixty dentin discs in 4 different thicknesses (0.3 mm 30 gauge (=0,306mm) diameter perforated, 0.5 mm, 1 mm, 2 mm) obtained from human molar teeth were fixed on the orifice of the silicone hose with sticky wax, filled with distilled water. By this way, the pulpal pressure was provided under in vitro environments. Adhesive systems were applied onto the fixed dentin discs. Quartz Tungsten Halogen (QTH) light source was used for the polymerization. Calibration curves were created using standard solutions containing known amounts of each monomer evaluated. Gradient solution consisting of 75% acetonitrile and 25% water was used as mobile phase in order to determine the residual monomer levels with High Performance Liquid Chromatography (HPLC) in each 1 ml samples which were obtained in certain time periods; first second, 1 day, 1 week, 1 month. Data was analyzed two-way ANOVA and Tukey HSD tests. Results: There were statistically significant differences between adhesive systems according to the amount of residual monomers (P<.05). The significantly highest residual monomer diffusion release rate was found in where the remaining dentin thickness was 0.3 mm and was perforated with 30 gauge (0,306mm) diameter. Conclusion: The risks of direct adhesive system applications under revealed pulp conditions will be dangerous. Thus, practicians will be aware of the risks on pulp tissue and should use a liner.