title: Apical root resorption due to mandibular first molar mesialization: A split-mouth study.
abstract: BACKGROUND
  Our aim was to evaluate the risk of external apical root resorption (EARR) in mesialized mandibular molars due to space closure in patients with unilateral second premolar agenesis. The contralateral side served as the control.
  
  
  METHODS
  After application of eligibility criteria, 25 retrospectively selected subjects (median age, 14.9 years; range, 12.0-31.9 years) were analyzed. Space closure (approximately 10 mm) was performed using skeletal anchorage. EARR was measured at the mandibular permanent canines, first premolars, and first molars in the pretreatment and posttreatment orthopantomograms. Measurements were performed by 2 examiners independently and were corrected for distortion and magnification of radiographs, which were assessed in a pilot study. Multivariate analysis of covariance and pairwise comparisons were performed.
  
  
  RESULTS
  The mean enlargement factor of the panoramic machine was 29% ± 0.3%. Distortion exceeded 5% only in cases of large positioning errors (>20°). Intraclass correlation coefficients showed strong to almost perfect agreement (mean, 0.80 mm; 95% CI, 0.75-0.85) of the two examiners. Multivariate analysis of covariance resulted in no difference in EARR between the canines and premolars of the space closure and control sides. On the contrary, there was a statistically significant difference between mesialized and nonmezialized molars (0.73 mm; 95% confidence interval, 0.19-1.27). The mean total EARR in each tooth type did not exceed 1 mm.
  
  
  CONCLUSIONS
  Space closure through extensive tooth movement in the mandible was identified as a risk factor for EARR. However, the amount of EARR attributed to space closure and the total EARR were not considered clinically significant.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Bern, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Winkler
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Bern, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Göllner
authors.affiliation: Private practice, Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Göllner
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Bern, Switzerland.
authors.forename: Pawel
authors.initials: P
authors.lastname: Pazera
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Bern, Switzerland. Electronic address: nikosgant@yahoo.gr.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Gkantidis
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008963:Molar; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D012391:Root Resorption / Q000000981:diagnostic imaging / Q000209:etiology*; D019227:Tooth Apex; D014087:Tooth Movement Techniques / Q000009:adverse effects*; D055815:Young Adult