Which approach regarding increasing the fixation of professionally applied topical fluoride is INCORRECT?

Raising the pH of the fluoride solution is not an effective approach to increase the fixation of professionally applied topical fluoride. Fluoride is most effective in a slightly acidic environment. An optimal pH allows fluoride ions to be efficiently absorbed by the enamel. If the solution becomes too alkaline, it can hinder the uptake of fluoride into the enamel, thus reducing its effectiveness in remineralizing and protecting against caries.

The other strategies listed effectively enhance fluoride fixation. Increasing the concentration of fluoride can allow for a greater amount of fluoride ions available for uptake, thereby improving the remineralization process. Prolonging the exposure time allows for more fluoride to penetrate the enamel surface, maximizing the potential for fixation. Pre-treating the enamel with a mild acid like 0.5% phosphoric acid can help remove surface debris and create a more receptive surface, enhancing fluoride uptake. All these methods are based on the principles of improving fluoride absorption and retention within the enamel structure.