Abstract: Objective To explore clinical effects of apexification for immature premolars with different root canal shapes. Methods Sixty-five immature premolars with apical periodontitis admitted in the Department of Pediatric Dentistry of our hospital from January 2017 to December 2019 were selected, and divided into three groups according to root canal development morphology. Group Ⅰ had 22 teeth with gathering root canal walls, Group Ⅱ had 26 teeth with parallel root canal walls, and Group Ⅲ had 17 teeth with flares on the canal wall. Vitapex was used for apexification. Time required for root induction after operation, types of root development, success rate, root length, and thickness of the root canal wall were compared. Results Time required for root apex induction in group Ⅰ was (10.59±5.02) months, which was the shortest. The time was (15.58±5.50) months in Group Ⅱ, and(18.80±4.42) months in group Ⅲ, which was the longest. Group Ⅰ and Ⅲ had statistically significant difference (P<0.05).The effective rate of three groups was 100%. The success rate of roots in Group Ⅰ continuing to develop into a or b type was 95.45%, Group Ⅱ57.69% and Group Ⅲ17.65%. Within three groups, root of some cases lengthened and root canal wall thickened, but there was no significant difference between three groups (P>0.05). Conclusion For immature premolars with gathering root canal wall, the success rate after apexificationis high and the curative effect is better. For immature premolars with parallel root canal wall, apexification has a certain curative effect. But it has poor curative effect on immature premolars with flares on the canal wall and low treatment success rate, and it is recommended to choose a treatment method with better curative effect.

Key words: immature premolar, apical periodontitis, apexification