Once it has been explained and defined what a prosthesis and what the masticatory apparatus and its function are, the author defines the three principles of a prosthetic restauration: --Any prosthetic restauration should be conceived and realized only after a complete study of the odontostomatognathic system. --Any prosthetic restauration must reestablish the health of the masticatory apparatus. --Any prosthetic restauration must assist in the conservation of the remaining teeth. Six corollaries are deduced from those principles and are equally defined and analysed. The indication of a prosthetic restauration comes from those principles and their corollaries. A possible fixed restauration is to be studied first, then comes the possibility of a semifixed construction. When both those solutions are impossible, the planning of a removable prosthesis, even simple, must be studied with method. This prosthesis must be composed of a cast metallic framework. If the planned prosthetic restauration can not be beneficial to the whole masticatory apparatus, it is better to renounce to do it.