An expansion of Shearhashub Spooner's 32-page dissertation, An inaugural dissertation on the pysiology [sic] and diseases of the teeth. Submitted to the examination of John Augustus Smith, M.D, president, and the trustees and professors of the College of Physicians and Surgeons of the University of the State of New York; and publicly defended for the degree of doctor of medicine, April 6th, 1835. New York: J.& W. Sandford, printers, 1835.  

John Roach Spooner (1794-1838) an American dentist living in Montreal, was the first to use arsenous acid to devitalize the pulp. This discovery was first published in the above work by his brother. Digital facsimile of the 1836 work from the U.S. National Library of Medicine at this link.