Objective To compare the endotoxin levels between acute and chronic periapical periodontitiswith different clinical symptoms.Methods 10 cases of acute periapical priodontitis(Group 1) ,10 cases of chronic periapical periodontitis(group 2, the diameter of apical radiolucency area was less than 2 mm),10 cases of chronic periapical periodontitis with sinus(group 3, the diameter of apical radiolucency area was greater than 2 mm), 10 cases of chronic periapical periodontitis without sinus (group 4, the diameter of apical radiolucency area was greater than 2 mm), were included in the study. Chromogenic substrate method of limulus amebocyte lysate(LAL) test was used to measure the endotoxin level.Results Endotoxin concentrations in group 2 were significantly lower than those in group 1, group 3 and group 4(P
