[Root resorption after orthodontic treatment: a study of age factor and prevalence in anterior teeth]. 
To investigate the impact of age factor on root resorption and the prevalence in anterior teeth during orthodontic treatment.  Sixty extraction cases treated with straight wire appliance were divided into adult group and child group, with 30 cases in each group. The panoramic radiographs pre-treatment and post-treatment were examined to measure the degrees of root resorption.  A total of 360 anterior teeth in each group were evaluated.  SPSS 13.0 software package was applied to perform statistical analysis.  There was significant difference in root resorption index before and after treatment(P<0.01).  The incidence of root resorption increased remarkably after orthodontic treatment.  There was significant difference in the degree of root resorption in two groups (P<0.01).  The prevalence of root resorption in anterior teeth was: upper central incisors, upper lateral incisors, lower central incisors, lower lateral incisors, upper canines and lower canines.  The root resorption in adult patients are more obvious than child patients.  The prevalence of root resorption in anterior teeth is different.  Moderate or severe root resorption is prone to happen in upper central incisors or lateral incisors in adult patients.