The aims of this study were to determine the etching effects of acidulated fluoride gels on high-glass-content restorations and to compare these effects with different acidulating systems. Samples of KetacFil, Fuji IX, Z100 and porcelain were separately submerged into either test solutions of 1.23% acidulated fluoride gel (APF) or solutions of the individual acidic components of APF (HF or H3PO4) combined with fluoride ions for 1–20 min at 37°C. Subsequently, the Fuji IX samples were exposed to the potential alternative acidulating solutions (polyacrylic, malic, maleic and tartaric acids) for similar time periods and assessed for roughness using profilometry and/or Scanning Electron Microscopy. The results showed that the GICs were most rapidly and extensively etched by the APF solutions. However, porcelain was etched less rapidly and Z100 showed no etching. Of the acidulated fluoride solutions tested, malic and maleic acids showed the greatest etching effect on Fuji IX followed by APF, HFF, tartaric acid, PAA and HPF. In conclusion, the acidulating system containing ortho-phosphoric acid showed the least rapid etching effects, although these effects were still a concern with long term exposure.