Approximately 40 people will participate in this study. This study will compare two different methods of fluoride application. Both methods are currently used in dental practice and both have been shown to be effective. If the participant chooses to participate in this study, participant will be asked to either wear a small tray that has been custom made to fit into the mouth into which fluoride is placed and worn for 5 minutes at bedtime, or participant will be asked to brush fluoride onto the teeth for 2 minutes at bedtime. Participant will be randomly assigned to use one of these methods of fluoride application: participant will not be allowed to choose which method of application you prefer. Participant will be asked to use fluoride every night while enrolled in the study. The fluoride that is used in the study is approved by the United States Food and Drug Administration and is commercially available with a prescription. After the study is over, participant will need to continue to use fluoride every night for life to help reduce the risk for dental cavities in the future.