John David, who is 4-years-old is in for his 6-month cleaning appointment

John David, who is 4-years-old is in for his 6-month cleaning appointment. The dentist has recommended that John David receive his first fluoride treatment at today's appointment. When the dentist walks out of the room, John's mom says she already has her son use over the counter fluoride everyday. And she stated the there is already fluoride in the tap water that they drink. What could you tell her to convince her that the fluoride treatment is better.
-What are all the vitamins and there functions and uses, what do they help you with health wise?