~INCE Paul Revere constructed dentures for George Washington, many techk_~ niques have been developed and used by the dental profession. While they may differ widely ill the approach to the problem, reasonably satisfactory dentnres can be produced by using ahnost any one of these techniques if the patient possesses normal edentulous ridges. However, there are conditions, brought about by resorption, which present extremely difficult problems for the prosthodontist. In many cases of extreme resorption, the construction of satisfactory mandibular dentures becomes almost an impossibility. The plight of patients with such ridges aroused my interest and sympathy, and in May, 1944, original research was begun to see if the problem could not be solved hy the use of some type of a mandibular implant denture. I felt that if such a technique could be perfected many patients should be able to wear dentures with peace and comfort, who would otherwise he condenmed Io go edentulous the remainder of their days. hnplantation is not new to the medical and dental professions. Some of the pioneers were Maggiolo of Paris in 1809, Rogers of Paris in 1845, Harrison of California in 1887, Edmunds of New York in 1889, Bonwill of New York in 1895, Paye in 1898, and more recently Greenfield ~ in 1913. These men used everything from lead to iridioplatinum. There were failures in these implants due to erosion of the metal or to the mechanics inwllved, as in the case of Greenfield. The tolerance of bone to certain metals varies greatly. The investigation of Stuck'* showed that cobalt, chromium, and molybdenum alloys were inert when implanted in bone. PROCEDURE The dentist who attempts the construction of the implant dentnre should be well experienced in the construction of full upper and lower dentures, and he should work in close cooperation with the oral surgeon. The first patient, carefully chosen, should be in good general heakh and have a good mental attitude. The mandible should be roentgenographed thoroughly to determine its physical characteristics. At the first appointment, roentgenograms are made of the following areas: the relation of the alveolar ridge and external oblique ridge to the anterior border of the ramus of the mandible (buccolingual and occtusal views