LEACHED COMPONENTS FROM DENTAL COMPOSITES IN ORAL SIMULATING FLUIDS AND THE RESULTANT COMPOSITE STRENGTHS

The aim of this study was to analyse the leached moieties of dental co mposites after storage in ethanol and organic acids of plaque and furt her evaluate the resultant effect on the diametral tensile strength (D TS) of the composites. Three commercial composites were used: Bis-GMA- based Z100, Bis-GMA/UDMA-based Heliomolar, and Bis-MPEPP-based Maratho n One. The solutions used were: 99.9% acetic acid, 99% propionic acid and 75% ethanol. Specimens (4 mm diam. x 2 mm thick) were stared at 37 degrees C in 3 mL of solution for up to 30 days. Gas chromatography/m ass spectrometry was used to characterize the leached moieties and DTS of the specimens after immersion was evaluated. Data were analysed us ing ANOVA and Tukey LSD test. The eluted substances were not all the s ame in different solutions and composites but mostly increased with im mersion time, and included diluents (TEGDMA and decamethacrylate) and some additives, such as an ultra-violet stabilizer (TINUVINP), plastic izers (dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate), initia tor (triphenyl stibine), coupling agent (gamma-methacryloxypropyl trim ethoxysilane), and phenyl benzoate. The chief polymerizing monomers we re not found. More kinds of components were found in the acetic acid a nd ethanol groups studied. The fewest kinds and quantities of leached moieties were found for Bis-GMA specimens and then Bis-GMA/UDMA ones, most of which are diluent agents. Bis-MPEPP specimens leached the most substances, which were composed mostly of a short phenyl group chain structure. The BisGMA composite showed the highest DTS (54.8 +/- 5.7 M Pa), which was not greatly affected by the length of storage. Bis-GMA/ UDMA (36.2 +/- 6.8 MPa) and Bis-MPEPP (26.1 +/- 4.5 MPa) composites we re significantly reduced (P < 0.05) after 30 days storage in the ethan ol (35-50%), in the propionic acid (25-30%), and in the acetic acid (4 0-60%). Irreversible processes such as the leaching of components occu r in fluids simulating an oral environment, which may contribute to ir reversible material degradation, especially for non-Bis-GMA-based comp osites.