A Cone Beam Computed Tomography Analysis Of The Dentition Change Before And After En Masse Retraction In Customized Lingual Orthodontics Therapy

Purpose In this study,we measured the dentition change before and after en masse retraction in customized lingual orthodontics therapy by cone beam computed tomography(CBCT)in order to observe how clinical approaches managed the negative effects under en masse retraction in customized lingual orthodontics.Methods 10 adult patients with alveolar protrusion(Shen’s Classification)were involved(age24.77±3.24 years old;2 males and 8 females).Each of them was planned to extracted four first premolars and treated with customized lingual orthodontics appliances.The customized bracket slots of the maxillary incisors were designed to be vertical and applied 13 degree positive torque,and the slots of the canines were designed to be horizontal.Micro-implant was used during en masse retraction,meanwhile,reverse-curve and horizontal abduction-curve on the maxillary arch wire together with light and elastic force were applied to retract the anterior teeth.Oral and maxillofacial CBCT data of the patients before and after the en masse retraction were collected.Simplant pro 11.04 software were used to measure the arch width,arch flatness,the mesio-distal inclination of the maxillary canines and the torque of the anterior teeth.All the data were analyzed by SPSS v19.0 software package.Paired-samples t test was used to analyze dentition differences between before and after en masse retraction in customized lingual orthodontics therapy.Results 1.Changes in arch width: The arch width between the crowns: between second premolars,first molars and second molars,decreases were noticeable as follows : 2.23 mm,1.16 mm,2.96 mm,and there was no significant change between the canines(P>0.05).The arch width between the apexes: between second premolars decrease was noticeable as 1.84 mm.There was no significant change between canines,first molars and second molars(P>0.05).2.Changes in arch flatness: There was no significant change in arch flatness(P>0.05).3.Changes in the mesio-distal inclination of the maxillary canines: There was no significant change in the mesio-distal inclination of the maxillary canines,the degree decreased by 0.76°(P>0.05).4.Changes in the torque of the maxillary anterior teeth: There was no significant change in the torque of the maxillary central incisors,lateral incisors and canines,the decreases were2.66°,2.69°,4.08°(P>0.05).Conclusions 1.CBCT combined with Simplant pro software can be used for orthodontic analysis.2.By adopting vertical slot customized lingual brackets applied with additional positive torque on maxillary incisors,together with reverse-curve on the maxillary arch wire during the retraction phase,vertical “bowing effect” can be prevented.3.By using micro-implant as anchorage and applying horizontal abduction-curve on the maxillary arch wire during the retraction phase,horizontal “bowing effect” can be prevented.4.The width of the maxillary posterior arch decreased after retraction in customized lingual orthodontic treatment,while the width between maxillary canines remain the same.5.By adopting horizontal slot customized lingual brackets on maxillary canines,together with tight ligation,posterior inclination of maxillary canines can be prevented...