Howe was born in North Providence, R. I. in 1864. He was the younger of two children and only son of James Albert Howe and Elizabeth Rachel (Rogers) Howe, both of English and Scottish stock. His father was a Baptist minister who became dean of the Cobb Divinity School at Bates College in Lewiston, Maine. Young Howe spent his childhood in Lewiston.
He attended the Nichols Latin School and Bates College, receiving the B. A. degree in 1887. Unwilling to enter the ministry, as his father would have liked, and with no other career apparently available, he accepted an offer to serve an apprenticeship with the family dentist. The work kindled his interest, and at the end of the year he entered the Philadelphia Dental College, receiving the D. D. S. degree in 1890.
He established a successful practice in Lewiston and – at first, on a part-time basis – a second one in Boston. In 1903 he gave up his office in Maine and settled in Boston. His practice flourished, and he gained a reputation as a dentist who took an unusual interest in the well-being of his patients. Endowed with a keen intellect and an independent turn of mind, Howe was troubled from the beginning of his career by the feeling that he was being asked to treat the symptoms rather than the disease and that dentistry ought not to be isolated from medicine.
Dentistry at this time was essentially technique-oriented, concerned with repairing or removing diseased teeth, with little attention to the cause, cure, or prevention of dental disease. It was widely believed that pyorrhea and caries were produced by chemical or bacterial substances in the mouth, that a clean tooth would not decay, and that bad teeth could cause bodily illness. Howe questioned all these views. He had observed that bacteria was normally present even in healthy mouths, and he early became convinced that diet and nutrition were important factors in the condition of the teeth and that bad teeth were usually the result rather than the cause of poor health. Howe was among the first to seek answers to such questions through application of the scientific method.
To explore the problem of dental decay, he set up a private laboratory in connection with his office, and in his spare time he studied the chemical composition of saliva, collected from his patients, and its secretion of medicinal and other substances ingested by the body. He was conscious of having an inadequate background in physiology and biological chemistry, and so, to widen his knowledge, he formed acquaintanceships with Lawrence J. Henderson and Otto Folin at Harvard, who encouraged his investigations. Howe's work attracted considerable attention, and in 1915, at the age of fifty, he was appointed chief of research at the newly opened Forsyth Dental Infirmary for Children, in Boston. Thereafter, he gradually gave up his private practice and devoted the remainder of his long life to research and to the reform of dental education. With a well-equipped laboratory and the assistance of a trained bacteriologist, Howe investigated the role of oral microorganisms in producing caries, and particularly the etiology of pyorrhea, a disease then widely and erroneously believed to be caused by the same oral amoebas that were responsible for dysentery. Using material from the mouths of children at the infirmary, he was able to show that the amoebas often present were harmless organisms that could exist in entirely healthy mouths.
One of Howe's most important contributions, made during his early years at the Forsyth, was a method of treating diseased teeth instead of extracting them. By introducing ammoniated silver nitrate into the affected tooth and root canals and then precipitating the silver so that it formed a sterile filling, he was able to check the spread of carious lesions and save the tooth. This method, which became widely adopted, was the first chemotherapeutic treatment of dental caries.
The relation between nutrition and dental disease remained a major interest. In experiments with guinea pigs and, later, with rhesus monkeys, Howe showed that diets deficient in vitamins brought about profound deterioration in the tooth and bone structure, similar to that observed in scurvy, and that an antiscorbutic diet would initiate repair. Having demonstrated that general health could directly affect dental health, he began an intensive – and, for a long time, lonely – battle against the prevalent theory that decaying teeth could act as foci for bodily infection and against the common medical practice of ordering the wholesale extraction of teeth as a means of curing a patient's illness.
In 1927 Howe was made director of the Forsyth Infirmary, a post he held until his death. During his years as director, he oversaw the training of more than five hundred interns, many of whom came from abroad and later were instrumental in advancing the progress of dentistry in their own countries. Howe formed strong personal and professional ties with such stalwarts at the Harvard Medical School as Walter B. Cannon, Hans Zinsser, and the pathologist S. Burt Wolbach. With Wolbach he collaborated on a number of fundamental studies on the pathological consequences of deficiencies in vitamins A and C.
Howe also taught at the Harvard Dental School as assistant professor of dental research (1917 - 1925) and as Thomas Alexander Forsyth professor of dental science (1925 - 1940), but he was critical of the curriculum: in his opinion it paid too much attention to dental repair and not enough to the whole man. In 1937 he was appointed to a university committee to consider the future course of dental education at Harvard and was influential in the eventual conversion of the Harvard Dental School to the School of Dental Medicine, with a four-year course of instruction equally divided between medicine and clinical dentistry – a realization of his long-cherished dream that dentistry be regarded as a branch of medicine.
At the age of eighty-five, Howe died of a cerebral hemorrhage at his home in Belmont, Massachussets. He was buried in the Belmont Cemetery.
Among the honors that came to Howe were the presidency of the American Dental Association (1929 - 1930) – maverick though he had been – and election as a fellow in dental surgery of the Royal College of Surgeons in England (1948).
A man of stocky build, with a firm set to his jaw, Howe had great courage, and no opposition could dissuade him from what he believed to be the better course. Yet he was warm and sympathetic in his relations with his associates and with the child patients at the Forsyth.
On December 21, 1891, Howe married Rose Alma Hilton, a college classmate. They had two sons, James Albert and John Farwell. His wife died after a marriage of fifty years, and on August 18, 1943, he married Ruth Loring White, a nutritionist who had long been his assistant.
