Dentists say too much fluoride can be almost as harmful for a young person’s teeth as not enough fluoride. Dental researchers at the University of Iowa say fluoride comes from many sources now — not just drinking water, but juices, milk, cereal and baby foods — which has some advantages.Dr. Steve Levy is a professor of dentistry at the U-of-I and co-author of the study. It found 70-percent of soft drinks have significant levels of the cavity-fighting chemical — so young kids shouldn’t drink too much soda. Levy says older children and adults can easily handle the fluoride in one or two cans of soda per day.Dr. Levy says too much fluoride can lead to fluorosis, which in severe cases can stain teeth orange or brown.