Implant and preprosthetic surgeries aim to restore normal anatomic contours, function, comfort, aesthetics, and oral health. As such, they are not life-saving procedures. The prime concern must therefore be to not undermine the patient's overall health and safety. It is then that every step must be taken to select the appropriate treatment plan and maximize the longevity of the implanted system, including the overlying prostheses. One important category into which a number of possible complications may fall is the inadequate systemic screening of patients prior to implant and biomaterial insertion. Without wishing to enter into the whole human pathology, it is no longer appropriate to limit the general contraindications of implantology to the traditionally considered malfunctions of the pancreas, liver or hematopoietic system and to ignore the devastating long-term effect of smoking or inadequate dietary habits. There are, in fact, a number of systemic problems that may create major risk factors. On the other hand, modern standards of care should not systematically exclude the use of implant surgery on patients with relative or marginal health conditions without exploring the possibilities of improving and stabilizing those conditions. As newer techniques of general anesthesia and intravenous sedation are more frequently used on an ambulatory basis, allowing implant surgeons to take their patients into various degrees of consciousness or deep sedation, the patient screening should also take into consideration factors related to this form of management. An arbitrary guideline for patient selection may be based on the classification of the American Society of Anesthesiology. This guideline restricts (with very few exceptions) intraosseous implants and implant-related graft surgeries on patients who fall into ASA1 or ASA2 categories of the classification. In the domain of subperiosteal implants for treatment of advanced atrophy of the mandible, the body response seems to be much less dramatic than to endosseous devices or to grafted sites. The cortical histoarchitecture and metabolism are, by far, less affected by organ disorders than are endosseous structures. This article presents a number of absolute contraindications and analyzes a series of relative contraindications for which the doctor's judgment remains the decisive factor. In this latter case, it proposes treatment patterns that could optimize certain marginal health conditions or stabilize unbalanced biological functions prior to or at the time of surgery. As life expectancy in the industrial countries is continuously increasing, a greater number of elderly patients are equipped with implant-supported prosthetics. The effort must therefore be focused on keeping a regular and watchful eye on their general health and screening for possible geriatric conditions responsible for long-term implant failure. Will a minimum knowledge of internal medicine be a prerequisite for future academic implant education?