A congressional study has given good marks to a cheaper, nonsurgical method of treating the gum disorders that cause millions of persons to lose their teeth every year.

The method -- several antibacterial measures by the dentist and careful daily gum and tooth cleansing by the patient -- can replace painful, expensive gum surgery in most cases, its advocates say.

If this indeed proves to be the case, the method could often substitute $125 to $500 worth of treatment by any trained dentist for $800 to $2,000 worth of gum surgery.

In short, it might virtually idle many periodontal (gum) surgeons. And this could happen at a time when many dental societies are saying that dentists in general are less busy. Apparently, fluoridation of water supplies and tooth pastes have cut the incidence of troublesome tooth decay, at the same time that dental schools have been increasing the supply of dentists.

The nonsurgical method seems to have worked so far in most of 190 patients treated by 18 Washington-area dentists, according to a study by Congress' Office of Technology Assessment.

"Clearly, we need a lot more study, but the results in the Washington area look promising," Dr. Sheldon Rovin of the University of Pennsylvania dental school said yesterday. Rovin conducted the OTA study with Richard Scheffler, a George Washington University economist.

Most periodontists still reject the gum-treating method, developed by Dr. Paul Keyes of the National Institute of Dental Research.

Keyes calls it "a rationale, not a technique or method," because, he says, "The point is not so much a fixed series of steps, because many things will work. I call it monitored and modulated therapy."

This means an analysis first to see what bacteria are doing to the troubled gums and the teeth, then therapy modified according to the way the patient responds.

The treatment starts with scrutiny of the way bacteria have attacked the gums, usually establishing themselves in pockets beneath the gum line. The microscope to observe the bacterial colonies.

The dentist cleans and scales the teeth and planes or smoothes some tooth roots. Most important, however, the patient is taught to combine daily tooth brushing and gum cleaning with daily use of an electric irrigator. The cleaning includes applying a paste of some of humankind's oldest remedies -- baking soda, peroxide and (sometimes) salt -- to attack bacteria and shrink swollen gums.

Periodically, the dentist checks on the bacteria with the microscope. About half the patients also need a few weeks on an antibiotic. After this treatment, as after gum surgery, the patient must continue the daily cleansing permanently or the bacteria will return.

The Washington dentists, say Rovin and Scheffler, treated 190 patients. After an average of 14 months, the number with bleeding gums, a prime sign of gum disease, fell from 99 to 34, and those with loose teeth from 65, to nine. No more than 5 percent have required referral to a periodontist.

"I think surgery is still needed in some cases, "Rovin said. "About one patient in three has advanced disease with deep bacterial pockets, and this usually requires surgery."

"I'm not either pro-surgery or anti-surgery," Keyes said yesterday. "I simply feel that the first order of business is to get the bacteria under control, and this does not necessarily mean surgical methods."