Acid-base reaction and fluoride release profiles in visible light-cured polyacid-modified composite restoratives (compomers)

Objective. The aim of the study was to evaluate the extent of the acid-base reaction and F- release in Compoglass (Vivadent) and Dyract (Dentsply/DeTr ey) restoratives. Methods. For evaluation of the extent of the acid-base reaction, two groups of three specimens (7 mm x 5 mm x 1 mm) were prepared for each material. T he first group was immersed in distilled water, while the second was kept i n dark and dry conditions. Micro-MIR FTIR spectroscopy was used to determin e the extent of the acid-base reaction on directly irradiated material surf aces immediately after irradiation and following water storage for 30 min, 3 d, 1, 2, 4, 8 and 12 wks. The in-depth extent of the acid-base reaction o f the specimens stored in water for 4 weeks was studied by sequential spect ra acquisition after removal of the uppermost 20, 70, 100, 240 and 400 mu m layer by controlled grinding and 1 wk re-immersion in water of the 400 mu m reduced specimens. For the F- release measurements, five disk-shaped spec imens (10 mm x 1.5 mm) were prepared from each material and stored in disti lled water. The amount of F- released for the storage periods reported abov e was measured using an ionometer with an F- electrode. Statistical analysi s was performed by ANOVA, Scheffe's test and regression analysis. Results. Storage in water promoted the development of an acid-base reaction on directly irradiated surfaces which reached a saturation point after 4 w eeks. Depth profiling of the 4 wk immersed specimens revealed high salt con centration at the uppermost 100 mu m layer. Re-immersion in water for 1 wee k of the 400 mu m reduced specimens increased the salt concentration again at the uppermost region. Statistically significant differences were found i n the acid-base rates and the in-depth salt yields between the materials (p < 0.05). The fluoride release after a 1 week initial "bursting" period was stabilized below 2 mg l(-1) (p > 0.05) in both products. No positive corre lation was found between acid-base reaction and fluoride release. Significance. The development of a carboxylate-rich surface layer on polyac id-modified composite restoratives after water storage may explain their to wer wear resistance compared with resin composites. The dynamic nature of t hese surfaces may provide several advantages regarding their interaction po tential with hard dental tissues and their anticariogenic properties, but a lso some disadvantages concerning the quality of the surface texture obtain ed. (C) 1998 Academy of Dental Materials. Published by Elsevier Science Ltd .