Abstract: Objective: To investigate the efficacy of root canal therapy for periapical periodontitis of maxillary primary incisors accompanied by crown defects. Methods:A total of 114 children patients with periapical periodontitis of maxillary primary incisors (162) accompanied by crown defects, who were admitted for root canal therapy during January 2010 and December 2012, were allocated into the caries group(85 incisors) and the trauma group(77 incisors)according to whether they had trauma history or not.Among them, there were 75 incisors from 2-3 years group and 87 incisors from 3-4 years group. The efficacy analysis were conducted after one year root canal therapy with Vitapex calcium hydroxide paste from J. Morita Corporation. Results:The total cure rate was 62.35% during one year follow-up. The cure rate in trauma group was lower than that in the caries group, and the difference was statistically significant(P<0.01).The cure rate of 2-3 years group was lower than that of 3-4 years group, and the difference was statistically significant(P<0.05).There was no significant difference regarding cure rate among children with different genders or mobility degrees, as well as with or without sinus(P>0.05). Conclusions:The long term efficacy of root canal therapy for periapical periodontitis of maxillary primary incisors with traumatic history is inferior to that for periapical periodontitis of maxillary primary incisors caused by caries.