Mary N. Gailbreath,57, a retired director of information for the division of dental health in the U.S. Public Health Service, died of cancer Thursday at Doctors Hospital.

Before retiring in 1977, she had been assigned to the office of the assistant secertary for health of the Department of Health, Education, and Welfare. She lived in Silver spring.

Before joining USPHS in 1956, Miss Gailbreath was assistant personnel manager of The Washington Post. She joined The Post in the early 1940s and later was editor of its house pubilication. ShopTalk, and a contributing book reviewer.

She graduated from George Washington University. Where she had studied under a Post scholarship, and had been elected to Phi Beta Kappa. In 1970, she was named to the advisory council of the English department at the university.

Miss Gailbreath was born in Gainesboro, Tenn. She came to Washington with her family as a girl and graduated from Central High School.

She then worked for the state Department, the Commission of World Services of the Methodist Church in Chicago and the Doubleday Bookshops in New York City. She wrote poetry and books for children.

There are no immediate survivors.

It is suggested that expressions of sympathy be in the form of contributions to the Holland Memorial Library in Gainesboro.