Researchers at the Harvard Dental School believe small dosages of the antibiotic tetracycline can help treat periodontal disease, the major cause of tooth loss in adults.

Majorie K. Jeffcoat, assistant professor of Periodontology at the Dental School, said yesterday tetracycline would not replace surgical treatment but instead would function as an "adjunct to therapy."

Periodontal disease is a bacterial infection of the gum that destroys the tissue and bone that support the teeth. Tetracycline concentrates in the pockets between the gums and teeth and slows the rate of bone loss, Jeffcoat said.

Working with beagles for three years, Jeffcoat and Ray Williams, assistant professor of Periodontology at the Dental School, found that dogs who received tetracycline have a slower rate of bone loss than those who did not receive the drug.

Jeffcoat said there are still unanswered questions about the effectiveness of tetracycline because some beagles are resistant to the drug. Some humans might be resistant or develop a resistance to the drug, she said, adding, "We don't know if the same bacteria is involved in humans."

Sigmund S. Socransky, associate clinical professor of Oral Biology, and Jeffrey M. Gordon, a researcher at Forsyth Dental Center this year began testing tetracycline treatment on humans.

"By itself, tetracycline will not prove useful because the layers of bacteria in periodontal disease are to great for the drug to penetrate and inhibit," Gordon said, but he added that the drug will probably be effective in conjunction with other therapy.