title: Volumetric measurement of root resorption following molar mini-screw implant intrusion using cone beam computed tomography.
abstract: OBJECTIVE
  Molar intrusion by mini-screw implantation can cause different degrees of root resorption. However, most methods (2-D and 3-D) used for evaluating root resorption have focused on the root length without considering 3-D resorption. The purpose of this study was to volumetrically evaluate root resorption using cone beam computed tomography(CBCT) after mini-screw implant intrusion.
  
  
  METHODS
  1. The volumes of 32 teeth were measured using CBCT and laser scanning to verify the accuracy of CBCT. 2. Twelve overerupted molars from adult patients were investigated in this study. After mini-screw implants were inserted into the buccal and palatal alveolar bones, 150 g of force was applied to the mini-screw implants on each side to intrude the molars. CBCT images of all patients were taken immediately prior to intrusion and after intrusion. The volumes of the roots were calculated using the Mimics software program. The differences between the pre-intrusion and post-intrusion root volumes were statistically evaluated with a paired-samples t-test. In addition, the losses of the roots were statistically compared with each other using one-way analysis of variance at the P<0.05 level.
  
  
  RESULTS
  No statistically significant volume differences were observed between the physical (laser scanning) and CBCT measurements (P>0.05). The overerupted molars were significantly intruded (P<0.05), and the average intrusion was 3.30±1.60 mm. The differences between the pre-intrusion and post-intrusion root volumes were statistically significant for all of the roots investigated (P<0.05). The roots were sorted by volume loss in descending order as follows: mesiobuccal, palatal, and distobuccal. Statistical significance was achieved among the three roots. The average total resorption for each tooth was 58.39±1.54 mm(3).
  
  
  CONCLUSIONS
  Volume measurement using CBCT was able to effectively evaluate root resorption caused by mini-screw intrusion. The highest volume loss was observed in the mesiobuccal root among the three roots of the investigated first molar teeth.
authors.affiliation: Department of Orthodontics, School of Stomatology affiliated to Medical College, Zhejiang University, Hangzhou City, Zhejiang Province, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Fei
authors.initials: F
authors.lastname: Chen
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Wanghui
authors.initials: W
authors.lastname: Ding
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Ye
authors.forename: Jiejun
authors.initials: J
authors.lastname: Shi
authors.forename: Baiping
authors.initials: B
authors.lastname: Fu
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D054893:Cone-Beam Computed Tomography; D019250:Dental Implants, Single-Tooth; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D008963:Molar / Q000000981:diagnostic imaging* / Q000601:surgery; D052280:Orthodontic Anchorage Procedures; D012391:Root Resorption / Q000000981:diagnostic imaging* / Q000601:surgery; D014087:Tooth Movement Techniques; D014092:Tooth Root / Q000000981:diagnostic imaging* / Q000601:surgery