Which of the following formulations are considered professionally applied fluoride products approved for in-office use?

The correct answer, which is 2.0% sodium fluoride, is a formulation that is widely recognized and used for professional applications in dental offices. This concentration is significant because it provides an effective concentration of fluoride to aid in the remineralization of teeth and helps reduce the risk of caries.

Professionally applied fluoride treatments typically utilize higher concentrations than those available over-the-counter. The 2.0% sodium fluoride is specifically formulated for in-office use, allowing dental professionals to apply it in a controlled manner to maximize its benefits while minimizing the risk of fluoride ingestion.

The other options, while they may contain fluoride, do not meet the same criteria for professional in-office use. For instance, 0.5% sodium fluoride and 2.5% stannous fluoride are not standard formulations for in-office applications, and while 1.23% acidulated phosphate fluoride is often used in professional settings, it's important to recognize that 2.0% sodium fluoride, specifically, is endorsed for its effectiveness and is widely accepted in clinical practice.