SALEM - Oregon's perennial tug-of-war over adding fluoride to the water supply in cities with more than 10,000 residents resurfaced Tuesday at the state Capitol, with a familiar cast of adversaries facing off over the benefits and risks of mandated fluoridation.

Two-thirds of the U.S. population drinks from fluoridated water supplies, which dentists have long said helps to curb tooth decay.

In Oregon, though, only 41 water systems fluoridate, leaving the state ahead of only New Jersey and Hawaii in the percentage of residents who drink fluoridated water.

Fluoridation bills have stalled in the last three legislative sessions, but proponents are hoping their cause falls on more sympathetic ears this year.

In front of the House Health Policy subcommittee Tuesday, Gordon Empey, a dentist who works as a consultant to the state Department of Human Services, said tooth decay can be reduced by 18 to 40 percent with fluoridation of community drinking water.

It's also cost-effective, Empey said, citing a recent study showing that Oregonians who don't drink fluoridated water spend $15 million a year on preventable tooth decay work.

But fluoride opponents - a loose-knit coalition of local control advocates, environmentalists and small-government proponents - argue that research is beginning to show that the health benefits of fluoride have been overstated.

“Fluoride should never be forced on anyone,” said Kimberly Kaminiski, an organic farmer who directs Oregon Citizens for Safe Drinking Water.

Fluoride opponents counter that it doesn't make sense to add a chemical to clean water, and bolster their case with a recent advisory from the American Dental Association that recommends limiting the use of fluoridated water when preparing baby formula.

They also cite evidence that increasing the levels of fluoride in water can cause a white spotting of the tooth surface - but Empey and other dentists testified that that's a cosmetic issue, often barely visible to the naked eye.

Water systems in cities such as Salem, Forest Grove, Coquille, Florence, Astoria and Corvallis do fluoridate, and advocates for local control argue that such decisions should remain on a community-by-community basis.

In a letter to health committee members, David Shaff, the administrator of the Portland Water Bureau, said mandated fluoridation would cost the city up to $4 million upfront, and then $600,000 in annual operating costs.

Some cities have gone further: In November, the Ashland City Council passed an ordinance making it illegal to put fluoride, or anything else that would act as medication, in the city's water supply.

Members of the Health Policy subcommittee voted 5-1 Tuesday to send the bill on for a hearing in front of the full House Health Care committee.

The bill is HB 3099.