Objective:To investigate the clinical effects of modified pendulum appliance and modified Jones on distalization of maxillary first molars.Methods:Twenty-two moderate anterior crowding of class Ⅱ malocclusion patients

between extraction and non-extraction treatment were chosen.The 22 patients were divided into two equal groups randomly.This study measured the changes in distance

velocity and position of maxillary first molars.The effects were evaluated by cephalometric radiographs and dental models analysis before and after distalization treatment.SPSS was used to determine if there were any significant differences.Results:Two effects of distal movement were obvious.However

there were significant differences between group A and group B in the travel speed

molar central fossa width

overbite

the inclination of maxillary second premolar and first molar.Conclusion:The results indicate that both modified pendulum appliance and modified Jones candistalize maxillary molars effectively.But the molars of Modified Jones Group have less distal tilting

and with short treatment time

faster movement

and consume lower anterior teeth anchorage.