The periapical lesions, granuloma and cyst, are being dealt with in modern scientific articles. The ethiology, whether it be infectious, traumatic, physical or chemical, is reviewed and mention is made of the fact that pulpal necrosis or gangrene is a prerequisite for these chronic proliferous lesions. According to epidemiological studies, the granuloma is observed more often than the cyst and the cyst more often in the upper jaw bone. Furthermore, certain teeth show a particular susceptibility to one or the other of these lesions. An x-ray is not sufficient to assure the appropriate clinical diagnosis. Electrophoresis and histopathology does, however, allow one to do the same. Acting as an immunological entity, the granuloma is less of an immunological irritation than a local defense protective barrier.