Investigation Of The Factors Related To Premolar Root Resorption During Orthodontic Treatment

Objective: The purpose of this study was to observation the change law ofcrown-to-root ratio of the premolar by compared to pre-treatment and post-treatment panoramic radiograph. According to the change of crown-to-rootratio, analysis the influence factors relating to premolar root resorptionduring orthodontic treatment. In order to control and reduce root resorptionduring orthodontic treatment provide advices.Methods: Sixty patients treated with MBT fixed orthodontic applianceswere selected in The Affiliated Stomatology Hospital, Chongqing MedicalUniversity between2009-2011. Age began treatment13-16years. Therewere divided into two groups according to whether extraction secondpremolar: experimental group and control group. With the first premolar asthe research object, the change of crown–to–root ratio of184firstpremolars were measured before and after orthodontic treatment bypanoramic radiograph. The changes of root length were reflected thechanges of the crown–to–root ratio of first premolar before and afterorthodontic treatment. Results: The crown–to–root ratio increase of first premolar before andafter the treatment, control group were0.033±0.021,among them themaxillary were0.033±0.023,the mandible were0.032±0.019,the male were0.032±0.016,the female were0.034±0.026, experimental group were0.048±0.023,among them the maxillary were0.050±0.019,the mandiblewere0.047±0.027,the male were0.047±0.025,the female were0.049±0.021.The results showed that there was significant difference in crown–to–rootratio of first premolar before and after the treatment (P<0.05).There wassignificant difference in change of crown–to–root ratio of first premolarbefore and after the treatment between experimental group and controlgroup (P<0.05).There was no significant difference between differentgenders and different teeth locations (P>0.05).Conclusion: Movement distance of teeth will influence premolar rootresorption. There is no significant difference in amount of root resorptionof premolar of the different gender and tooth location.