Dr. William Brown Ingersoll, 69, a retired dentist and a professor emeritus of Georgetown University School of Dentistry, died of cancer Tuesday at his home in Washington.

He had retired from private practice in early after maintaining offices here for more than 40 years.

Dr. Ingersoll became professor emeritus of the Georgetown Dental School in 1966 after serving 33 years on the faculty. He had organized and was head of the department of endodontia and periodonita.

He had served as first vice president of the American Dental Association in 1970 and 1971. President of the D.C. Dental Society in 1952 and 1953, he was its delegate to the ADA House of Delegates for 14 years.

He also was a member of the ADA's Council on Dental Therapeutics and a member of the executive committee of the D.C. Dental Society, which named him "Dentist of the Year" in 1976.

Dr. Ingersoll had served as a consultant to the Veterans Administration and the National Institutes os Health for many years. He belonged to the American College of Dentists, American Academy of Periodontology and the American Association of Endodontists.

Born in American Fork, Utah, he was an active member of the Mormon Church. He studied at the University of Utah, Brigham Young University and the University of Denver, where he received a dental degree.

He came to Washington in 1933 to teach at Georgetown.

Dr. Ingersoll also was well known as a land developer. He was one of the original developers of the Seven Corners shopping area, Willston Shopping Center and adjacent properties, including many garden apartments.

He was an officer and board member of the James Stewart Construction Co., which built the Chicago Port Authority, the Dallas Trade Mart and other major projects.

Dr. Ingersoll was a founding member of the American Land Development Association and had served as its president and board chairman.

Active for many year's in the Boy Scouts and Rotary, he was a founder of the Henlopen Acres Beach Club in Rehoboth Beach and a member of the Columbia Country Club in Chevy Chase.

He is survived by his wife, Loraine Boley Ingersoll, and a son, Joseph W., both of the home; two other sons, William B., of Springfield, Va., and Henry G., of Arlington; a daughter, Barbara J., of Falls Church, and five grandchildren.

The family suggests that expressions of sympathy may be in the form of contributions to the Georgetown University Cancer Research Center.