The relationship between the indications for the surgical removal of impacted third molars and the incidence of alveolar osteitis.
 Six hundred forty-two impacted third molars were surgically removed in 412 patients.
 Before surgery, each patient was assessed clinically and radiographically, and the reason for the removal of each tooth was specifically recorded.
 One hundred eighty-two of the impacted teeth were removed for prophylactic reasons and 460 for therapeutic reasons.
 As much as possible, standardization of the operating procedure and environment, and of the preoperative and postoperative regimens was observed.
 After surgery, each case was followed to determine the absence or presence of signs and symptoms of alveolar osteitis.
 It was found that several factors seem to contribute to the development of alveolar osteitis; however, the most significant related finding was that the reason for the extraction, that is, whether the extraction was undertaken for therapeutic or prophylactic reasons.
