title: Reliability of reference distances used in photogrammetry.
abstract: OBJECTIVE
  To determine the reliability of the reference distances used for photogrammetric assessment.
  
  
  METHODS
  The sample consisted of 100 subjects with mean ages of 22.97 +/- 2.98 years. Five lateral and four frontal parameters were measured directly on the subjects' faces. For photogrammetric assessment, two reference distances for the profile view and three reference distances for the frontal view were established. Standardized photographs were taken and all the parameters that had been measured directly on the face were measured on the photographs. The reliability of the reference distances was checked by comparing direct and indirect values of the parameters obtained from the subjects' faces and photographs. Repeated measure analysis of variance (ANOVA) and Bland-Altman analyses were used for statistical assessment.
  
  
  RESULTS
  For profile measurements, the indirect values measured were statistically different from the direct values except for Sn-Sto in male subjects and Prn-Sn and Sn-Sto in female subjects. The indirect values of Prn-Sn and Sn-Sto were reliable in both sexes. The poorest results were obtained in the indirect values of the N-Sn parameter for female subjects and the Sn-Me parameter for male subjects according to the Sa-Sba reference distance. For frontal measurements, the indirect values were statistically different from the direct values in both sexes except for one in male subjects. The indirect values measured were not statistically different from the direct values for Go-Go. The indirect values of Ch-Ch were reliable in male subjects. The poorest results were obtained according to the P-P reference distance.
  
  
  CONCLUSIONS
  For profile assessment, the T-Ex reference distance was reliable for Prn-Sn and Sn-Sto in both sexes. For frontal assessment, Ex-Ex and En-En reference distances were reliable for Ch-Ch in male subjects.
authors.affiliation: Department of Orthodontics, Hacettepe University Faculty of Dentistry, Hacettepe University, Ankara, Turkey. mugepeh@hacettepe.edu.tr
authors.forename: Muge
authors.initials: M
authors.lastname: Aksu
authors.forename: Demet
authors.initials: D
authors.lastname: Kaya
authors.forename: Ilken
authors.initials: I
authors.lastname: Kocadereli
mesh_terms: D000704:Analysis of Variance; D002508:Cephalometry / Q000592:standards; D003627:Data Interpretation, Statistical; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D010780:Photogrammetry; D010781:Photography; D012016:Reference Values; D015203:Reproducibility of Results; D012737:Sex Factors; D055815:Young Adult