Objective: To compare the clinical effects of ProTaper rotary and root canal measuring instrument with manual K files and X file in one- visit root canal therapy of primary molars. Methods: Fifty patients in five to eight years old with chronic pulpitis of both sides mandibular second molar were elected in this study. They were randomly divided into test group A and control group B. The operating time,the degree of the pain,the quality of the root canal prepration,and the visit record after 6 h,24 h,48 h an...