Nearly three dozen Cape Ann dentists, in a rare show of professional unity, have signed onto a letter urging officials in both Rockport and Gloucester to continue adding fluoride to the drinking water of both communities.

The letter, crafted by orthodontist Dr. William Bebrin, who maintains an office in Gloucester, comes amid a growing push from a Cape Ann citizens group that opposes continued fluoridation. The group has brought the issue to both boards of health and placed a petitioned article on the warrant for Rockport Fall Town Meeting next Monday night.

The dentists’ letter, printed in full along with the full list of signees on today’s Opinion page, Page 9, includes 35 signatures in all.

The anti-fluoride group, called the Cape Ann Fluoride Action Network, has also mounted an aggressive anti-fluroridation campaign through letters to the Times and last month hosted a pair of presentations by Dr. Paul Connett, a bio-chemist and toxicologist from Binghamton, New York, who is director of the national Fluoride Action Network and has expressed concerns over the effects of fluoride on the body.

Bebrin said persistent claims by those opposed to fluoridation fueled the need for Cape Ann’s dentists to make sure officials and residents understood their positions as medical professionals.

“It’s become clear that there’s a grass-roots movement afoot on Cape Ann that is, we believe, misinformed but highly motivated to reverse something that’s been proven to work, and something that’s a great benefit to our citizens,” Bebrin said in a phone interview Monday.

Aside from differences over any negative effects of fluoride — which the dentists see as minimal — and track records showing fluoridation’s effect in fighting tooth decay, Bebrin noted flaws in other aspects of the argument to stop fluoridating local drinking water systems in the two communities.

“Some, for example, think that our current community programs can be replaced by a specific program in our schools,” he said. “But the problem with that is the practicality of it. First, a selective program such as that would be much more expensive than the community fluoridation we have now, and it would then serve only the population of students currently in our schools. That’s not sufficient.”

Bebrin also refutes the claims by anti-fluoridation activists that dentists have a beneficial stake in maintaining the status quo.