Objectives: The objective of this study was to investigate the buffer capacity of typical and experimental restorative materials during a carious and intrinsic erosive attack. Methods: Samples with a small cavity (130 µl) were milled out of composites, a compomer, a giomer, a pulp capping liner, a glass ionomer cement, a PMMA block, extracted teeth and an experimental dual-curing composite containing a bismuth-doped bioactive glass using CEREC MC XL (Sirona) to create a standardized surface. 80 µl of acid (lactic acid with a pH of 4.5 or hydrochloride acid with a pH of 2.6) was added. The change of pH was measured over a period of 12 minutes using a calibrated pH-electrode (In Lab nano, Mettler Toledo). Before and after this test the surface of each sample was electron-microscopically analyzed. Results: After the HCl acid attack the compomer, giomer and the glass ionomer cement showed some buffering effect while composites and PMMA had no relevant buffering effect. The experimental bioactive glass-containing composite buffered most effectively and performed similar to the positive control group (liner). Following the lactic acid attack smaller pH changes were measured as compared to the HCl. However a neutral pH was induced by the majority of the tested materials. The electron microscopy showed transformation in the surface of all materials after an acid attack Significance: The results indicate that bioactive agents can increase the pH in vitro and therefore may be of advantage during an acid challenge. Keywords: buffer capacity, pH, secondary caries