Dr. John Francis Brazinsky, 86, who practiced dentistry in Washington for more than 45 years before his retirement in 1972, died Monday at a hospital in Las Vegas, Nev. He had a heart ailment.

He had maintained homes in Las Vegas and Carmel, Calif., since 1974.

Dr. Branzinsky graduated in 1924 from the Georgetown University School of Dentistry and later was a member of the faculty and assistant dean for many years. He had experimented in the design of insulated fillings and crowns and had done work on Adm. Richard E. Byrd and his men before they left for their Antarctica expedition in 1930.

Dr. Brazinsky was born in Shenandoah, Pa. He served with the Army in France in World War I and was wounded in the Meuse-Argonne campaign. He received the Purple Heart. He also was honored by England's Royal Society of Health.

He was a member of the D.C. Dental Society, the American Dental Association, the American Lithuanian Society, the Knights of Columbus and the Congressional Country Club.

His wife, Frances Holt Brazinsky, died in 1974.

Survivors include a son, Dr. John Holt Brazinsky of Carmel; a daughter, Jeanne B. Scarff of Las Vegas; a brother, Peter, and two sisters, Agnes Wasley and Julia Goulden, all of Shenandoah, and eight grandchildren.

The fimily suggests that expressions of sympathy be in the form of contributions to the library of the Georgetown University School of Dentistry.