Is flossing really necessary?

Ask the doctor Q. I read recently that there is no evidence that flossing prevents cavities or gum disease. Is there any reason to keep on doing it? A. You’re right. There have been no studies in which volunteers were randomly assigned to two groups—one to floss daily and one to refrain from flossing—where the groups were followed over time to see whether those who flossed had lower rates of…