Anti-fluoridation activists work very hard to deny that ingested fluoride has a beneficial role. They take description of the “topical” mechanism that fluoride in saliva plays in inhibiting tooth decay out of context to deny any other role of fluoride. Even then they distort the research to claim fluoride must be applied as toothpaste – it doesn’t. Anything to deny a role for fluoridated water (see Fluoridation – topical confusion and Topical confusion persists).
But research findings do support a beneficial role of ingested fluoride during teeth development – that is on pre-erupted teeth. This was illustrated again in a recent paper reporting incidence of tooth decay in South Korean children. One group lived in an area where there had been no water fluoridation. The other group in an area where fluoridation had stopped 7 years before.
Cho et al (2014)* found children of age 11, who drank fluoridated water during their first 4 years (before eruption of their first permanent teeth), had significantly less tooth decay at than children of age 6, who had not had access to community water fluoridation during their first 4 years (see figure below – results for decayed missing and filled teeth (DMFT) expressed as a ratio of results for children in previously fluoridated area divided by results for children in never-fluoridated area).
The DMFT ratio for the 11 year old children, who had received fluoridated water in the first 4 years during tooth development, is much lower than 1 (the result expect of fluoridated water had no effect). The difference is statsically significant for 11 year olds, but not the 8 year olds. The data shows a clear beneficial effect of fluoride ingested during tooth development.
*Cho, H.-J., Jin, B.-H., Park, D.-Y., Jung, S.-H., Lee, H.-S., Paik, D.-I., & Bae, K.-H. (2014). Systemic effect of water fluoridation on dental caries prevalence. Community Dentistry and Oral Epidemiology.