Multivariate Analysis Of Inclination Change During Extraction-treatment

Objective:To investigate the factors affecting incisal inclination during extraction treatment.Methods:From 892 orthodontic cases of Yantai Stomatological hospital,126 samples with symmetric premolar-extracted were selected according to the inclusion and exclusion criteria.The relationship between incisal inclination change and 15 potential influencing factors (from cepholometric analysis, model analysis and treatment records) were analyzed by Multiple stepwise regression.Results:Among the 15 potential influencing factors(including crowding,the position of the extracted teeth,the sagittal skeletal type,SN-OP, the angle between SN and maxilla or mandibular,the angle between incisor and maxilla or mandibular,the angle between incisor and OP,the change of the anterior and median arch width,the change of the anterior and median arch depth,the ending arch wire,weather the rolling wire was used,the elastic type and the elastic time), only two factors(crowding,the angle between the incisor and the maxilla or mandibular)affected the incisal inclination,crowding had a greater impact than the angle between the incisal and the maxillary or mandibular.The change of the incisal inclination increases companied with the increasing crowding and decreasing angle between the incisal and the maxillary or mandibular.Only one factor (the change of anterior arch depth) affected the position of the rotation center of the incisor.The more the anterior arch depth changed,the closer the rotation center is to the uncontrolled rotation center of the tipping tooth movement.Conclusions:Crowding and the angle between the incisal and the maxillary or mandibular play great roles in incisal inclination during extraction treatment.