Fluoride is effective in strengthening weak areas of enamel to prevent decay or cavities. It is also useful to protect the gums from harmful bacteria and helps with teeth that are sensitive by blocking the tubules that run to the nerve. It is a short treatment applied at the end of your hygiene appointment. You will be asked not to eat or drink anything for at least 30 minutes and not to brush until bedtime that day. This allows the fluoride to be absorbed and the treatment to be more effective.