title: KPG index versus OPG measurements: a comparison between 3D and 2D methods in predicting treatment duration and difficulty level for patients with impacted maxillary canines.
abstract: OBJECTIVE
  The aim of this study was to test the agreement between orthopantomography (OPG) based 2D measurements and the KPG index, a new index based on 3D Cone Beam Computed Tomography (CBCT) images, in predicting orthodontic treatment duration and difficulty level of impacted maxillary canines.
  
  
  METHODS
  OPG and CBCT images of 105 impacted canines were independently scored by three orthodontists at t 0 and after 1 month (t 1), using the KPG index and the following 2D methods: distance from cusp tip and occlusal plane, cusp tip position in relation to the lateral incisor, and canine inclination. Pearson's coefficients were used to evaluate the degree of agreement and the χ(2) with Yates correction test was used to assess the independence between them.
  
  
  RESULTS
  Inter- and intrarater reliability were higher with KPG compared to 2D methods. Pearson's coefficients showed a statistically significant association between all the indexes, while the χ(2) with Yates correction test resulted in a statistically significant rejection of independency only for one 2D index.
  
  
  CONCLUSIONS
  2D indexes for predicting impacted maxillary canines treatment duration and difficulty sometimes are discordant; a 3D index like the KPG index could be useful in solving these conflicts.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy ; Department of Medical, Surgical and Health Sciences, School of Dentistry, University of Trieste, Piazza Ospitale 1, 34129 Trieste, Italy.
authors.forename: Domenico
authors.identifier: 0000-0002-9020-7843
authors.initials: D
authors.lastname: Dalessandri
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy.
authors.forename: Marco
authors.identifier: 0000-0001-8671-3025
authors.initials: M
authors.lastname: Migliorati
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Visconti
authors.affiliation: Department of Medical, Surgical and Health Sciences, School of Dentistry, University of Trieste, Piazza Ospitale 1, 34129 Trieste, Italy.
authors.forename: Luca
authors.identifier: 0000-0001-9274-9470
authors.initials: L
authors.lastname: Contardo
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Alabama, Birmingham, AL 35233, USA.
authors.forename: Chung How
authors.identifier: 0000-0002-4606-9551
authors.initials: CH
authors.lastname: Kau
authors.affiliation: Department of Stomatology IV, School of Dentistry, Complutense University of Madrid, Plaza Ramòn Cajal s/n, 28040 Madrid, Spain.
authors.forename: Conchita
authors.identifier: 0000-0003-3997-6900
authors.initials: C
authors.lastname: Martin
mesh_terms: D000818:Animals; D054893:Cone-Beam Computed Tomography; D003481:Cuspid / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008437:Maxilla / Q000000981:diagnostic imaging* / Q000473:pathology; D019647:Oral Surgical Procedures; D014095:Tooth, Impacted / Q000000981:diagnostic imaging* / Q000473:pathology