If the necrotic pulp is not infected by microbes, periapical lesion will not develop (see etiology). This is particular frequently the case in ischemic necrosis. Thus, in theory the treatment of necrosis could be completed in one appointment. However, in practice the presence or absence of microbes in the root canal is difficult or impossible to determine with certainty. That is why sometimes the treatment follows the principles of apical periodontitis.