title: New regression equations for mixed dentition space analysis in an Iranian population.
abstract: OBJECTIVE
  Prediction of the mesiodistal crown width of unerupted canines and premolars is an important aspect of mixed dentition analysis. The accuracy of Tanaka-Johnston equations, the most commonly method, is questionable when it is applied to different ethnic groups. In this study, we aimed to develop a new regression equation for this prediction in an Iranian population.
  
  
  METHODS
  The dental casts of 120 Iranian subjects with complete permanent dentition were selected. Mesiodistal crown widths of teeth were measured with digital caliper. In the first part of the study, the correlation and linear regression equations between four mandibular incisors and the canine-premolars segments of both arches were developed (modified Tanaka-Johnston equation). In the second part, as a new method, correlation and linear regression equations were developed between the sum of mandibular central incisors-maxillary first molars and the canine-premolars segments.
  
  
  RESULTS
  It was found that the correlation coefficients between the sum of mandibular central incisors-maxillary first molars and the maxillary and mandibular canine-premolars segments were higher (r = 0.66, 0.68 respectively) than the one between the four mandibular incisors and the canine-premolars segments (r = 0.58. 0.64).
  
  
  CONCLUSIONS
  New linear regression equations were derived. In this study, the sum of mandibular central incisors and maxillary first molars was better predictor for unerupted canines and premolars. This novel approach allows the prediction of width of unerupted canines and premolars to take place at earlier age.
  
  
  CONCLUSIONS
  Using the new method, orthodontists could take advantage of mixed dentition analysis at earlier age. Moreover, to test the derived equations on a larger sample size and in other ethnicities is highly recommended.
authors.affiliation: Assistant Professor, Department of Orthodontics, Faculty of Dentistry Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Toodehzaeim
authors.affiliation: Assistant Professor, Department of Orthodontics, Faculty of Dentistry Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Aghili
authors.affiliation: Dentist, Faculty of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Elham
authors.initials: E
authors.lastname: Shariatifar
authors.affiliation: Assistant Professor, Dental Research Center, Department of Orthodontics, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran, Phone: +98 (511) 8829501, Fax: +98 (511) 8829500, e-mail: dehghanimm@mums.ac.ir.
authors.forename: Mahboobe
authors.initials: M
authors.lastname: Dehghani
mesh_terms: D000293:Adolescent; D000328:Adult; D001641:Bicuspid / Q000033:anatomy & histology*; D002508:Cephalometry / Q000706:statistics & numerical data; D003481:Cuspid / Q000033:anatomy & histology*; D003724:Dental Arch / Q000033:anatomy & histology; D003818:Dentition, Mixed; D005260:Female; D005544:Forecasting; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D007492:Iran; D008297:Male; D008334:Mandible / Q000033:anatomy & histology; D008437:Maxilla / Q000033:anatomy & histology; D008963:Molar / Q000033:anatomy & histology; D009811:Odontometry / Q000706:statistics & numerical data*; D012044:Regression Analysis; D019228:Tooth Crown / Q000033:anatomy & histology*; D014097:Tooth, Unerupted / Q000033:anatomy & histology*; D055815:Young Adult