Abstract: Abstract: Objective To evaluate the incidence of pain and inflammation after treating acute apical periodontitis of deciduous teeth using pulp open or cover treatment at the first time.Methods 100 patients with acute apical periodontitis were randomly allocated to two groups. One was pulp open group, and the other was cover treatment group, 50 cases in each group. In the pulp open group, the dental cavity was conventionally opened, the dental pulp was extracted using H file, the pulp chamber and infected sloughs in the root canal were cleaned, then the root canal was douched, the occlusion was lowered, and the dental cavity was open with cotton ball in. In the cover treatment group, the dental cavity was conventionally opened, inflected sloughs were eliminated, K file was used for root canal preparation to No.35, then the root canal was douched, and was covered with CP (camphor phenol) cotton ball after the exudation became low. The relief of pain at 24th h and of inflammation on 7th d were observed. Results There were obviously difference between two groups about pain and on the changes of inflammation.Conclusions The treatment by opened can reduce the pain in a short time, but the cover treatment can effectively prevent to develope into chronic periodontitis during root canal therapy on acute apical periodo ntitis.

Key words: deciduous teeth, acute apical periodontitis, pulp open, pulp covered