Fluoride application has an excellent effect for the prevention of dental caries, and 1.23 % acidulated phosphate fluoride (APF) gel is the most commonly used fluoride formulation for professional fluoride application.
There has been a problem, however: its excessive intake may cause toxicity in the human body. The purpose of this study was to evaluate the amount of residual fluoride present in the saliva in the mouth over time by measuring it with ¹⁹F NMR spectroscopy after the topical application of 1.23 % APF gel. After 30-minute application, a very small amount of fluoride (0.000482 %) remained in the saliva in the mouth, indicating that there
was no effect on the human body. Therefore, this study demonstrated that clinical fluoride application using 1.23 % APF gel is safe.