title: Incisal Apical Root Resorption Evaluation after Low-Friction Orthodontic Treatment Using Two-Dimensional Radiographic Imaging and Trigonometric Correction.
abstract: BACKGROUND
  Root resorption shall be taken into consideration during every orthodontic treatment, and it can be effected by the use of different techniques, such as the application of low friction mechanics. However, its routinely assessment on orthopantomography has limitations related to distortions and changes in dental inclination.
  
  
  OBJECTIVE
  The aim of this investigation was to evaluate the severity of apical root resorption of maxillary and mandibular incisors after low-friction orthodontic treatment, using the combination of panoramic and lateral radiographs, and applying a trigonometric correction.
  
  
  METHODS
  A hospital based Retrospective study at the orthodontic Department (Dental School, University of Brescia, Spedali Civili di Brescia, Brescia, Italy).
  
  
  METHODS
  Ninety-three subjects (53 females and 40 males; mean age, 14 years) with mild teeth crowding were treated without extractions by the same operator using a low-friction fixed appliance following an integrated straight wire (ISW) protocol. The pre- and post-treatment tooth lengths of the maxillary and mandibular incisors were measured on panoramic radiographs. A trigonometric factor of correction for the pre-treatment length was calculated based on the difference between the pre and post-treatment incisal inclination on lateral cephalograms.
  
  
  METHODS
  The changes in lengths were investigated using the Student's t-test for paired values (p<0.05).
  
  
  RESULTS
  Maxillary central incisors showed no changes (0.3%, 0.6%), maxillary lateral incisors showed a small increase (1.4%, 1.8%) that was attributed to the completion of root development in younger patients, mandibular central and lateral incisors underwent slight resorption (-3.1%, -3.4%). A statistically significant difference was found for the mandibular incisors but not for the maxillary ones.
  
  
  CONCLUSIONS
  In patients with mild crowding and consequent low amount of root movement, a low-friction orthodontic treatment can lead to slight apical root resorption, mainly involving lower incisors. The use of a trigonometric correction in the panoramic radiograph analysis may reduce the limitations of this 2D evaluation.
authors.affiliation: Postgraduate Student, Department of Orthodontics, Dental School, University of Brescia , Brescia, Italy .
authors.forename: Fabio
authors.initials: F
authors.lastname: Savoldi
authors.affiliation: Assistant Professor, Department of Orthodontics, Dental School, University of Brescia , Brescia, Italy .
authors.forename: Stefano
authors.initials: S
authors.lastname: Bonetti
authors.affiliation: Adjunct Assistant Professor, Department of Orthodontics, Dental School, University of Brescia , Brescia, Italy .
authors.forename: Domenico
authors.initials: D
authors.lastname: Dalessandri
authors.affiliation: Adjunct Assistant Professor, Department of Orthodontics, Dental School, University of Brescia , Brescia, Italy .
authors.forename: Gualtiero
authors.initials: G
authors.lastname: Mandelli
authors.affiliation: Professor and Director, Department of Orthodontics, Dental School, University of Brescia , Brescia, Italy .
authors.forename: Corrado
authors.initials: C
authors.lastname: Paganelli
keywords: Lateral cephalogram; Orthopantomography; Root shortening; Self-ligating