Basically, the pH. APF has a low pH 3.5, enabling it to deliver fluoride at a faster rate into enamel than NSF with its pH of 7.0. Because APF is acidic it can etch and dull composite and ceramic restorations in adults, which causes increased staining and may affect the longevity of cosmetic work. APF can also etch sealants causing marginal break down. NSF’s neutral pH is the best option for patients with these indications. NSF in most cases tastes better than APF because it doesn’t have a sour aftertaste. With Pediagel, both the APF and NSF taste great.