Periapical processes, often found to be the pathologic result in dental patients, are the cause of many problems, and can be very dangerous in advanced stages. They usually happen when vital and nonvital irritants pass from the infected root canals towards apical, causing damage to the tissue and infection. The infection itself has not been entirely explained yet, but numerous substances are considered to be mediators in the process. Clinical periapical processes can be divided into symptomatic and asymptomatic ones (acute apical periodontitis, chronic apical periodontitis, condensing osteitis, acute apical abscess, chronic apical abscess). In order to make a diagnosis, anamnestic as well as clinical and radiological diagnostic procedures are usually carried out. After making a diagnosis, endodontic therapy is carried out using manual techniques or instruments to mechanically and chemically clean and widen the root canal, and fill it by using cold or warm techniques, in order to completely close the endodontic area and stop any possible reinfection. If abscess is present or the process is of cellulitic character, incision and drenage, as well as adequate antibiotic therapy, are needed besides endodontic instrumentation. In advanced stages hospitalization of the patient is necessary. It is considered that a six month period is needed in order to estimate the success of the healing of the periapical lesion. Healing can be complete (restitutio ad integrum), with a scar or it can not occur, which is considered a failure of the endodontic therapy.This can be caused by numerous reasons. Should the conservative endodontic therapy fail, and there is no contraindication, one of the surgical procedures is carried out.