title: An evaluation of the Pi analysis in the assessment of anteroposterior jaw relationship.
abstract: OBJECTIVE
  This study has investigated two new cephalometric variables, the Pi angle and Pi linear in the evaluation of anteroposterior skeletal discrepancy.
  
  
  METHODS
  Retrospective cross-sectional study.
  
  
  METHODS
  Manipal College of Dental Sciences, Manipal, India
  
  
  METHODS
  A sample of 155 subjects (mean age 19·7 years) were subdivided into skeletal class I, II and III groups based upon ANB angle. Descriptive data were calculated for each variable and group. Receiver operating characteristics curves were used to examine sensitivity and specificity of the Pi angle in the discrimination between different skeletal groups. Correlation coefficients were obtained for each of the parameters to compare their relationship with other parameters in the class I group. Coefficient of determination, regression coefficient, regression equation and standard error of estimate were also calculated from the parameters showing significant correlation with the Pi angle.
  
  
  RESULTS
  Mean values for the Pi angle in skeletal class I, II and III subjects were 3·40 (±2·04), 8·94 (±3·16) and -3·57 (±1·61) degrees, respectively. For the Pi linear they were 3·40 (±2·20), 8·90 (±3·56) and -3·30 (±2·30) mm for class I, II and III subjects, respectively. Receiver operating characteristic curves showed that a Pi angle greater than 5 degrees had 89% sensitivity and 82% specificity for discriminating a skeletal class II group from class I. A Pi angle of less than 1·3 degrees had 100% sensitivity and 84% specificity in discriminating skeletal class III groups from class I. The overall accuracy for discriminating class II groups from class I was 85% and for class III from class I, 90%. Thus, a cut-off point between class I and II groups could be considered a Pi angle of approximately 5 degrees and between class I and class III, approximately 1·3 degrees. There were no statistically significant correlations found between Pi angle and ANB (0·07), Beta angle (-0·04) and WITS analysis (0·19). The highest level of correlation was obtained for the Pi angle and Pi linear (0·96).
  
  
  CONCLUSIONS
  The anglar and linear components of the Pi analysis are a suitable method for assessing anteroposterior jaw discrepancy in daily clinical practice.
authors.affiliation: Manipal College of Dental Sciences, Manipal University Manipal, Karnataka, India. drsantoshortho@gmail.com
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumar
authors.forename: Ashima
authors.initials: A
authors.lastname: Valiathan
authors.forename: Pawan
authors.initials: P
authors.lastname: Gautam
authors.forename: Kalyana
authors.initials: K
authors.lastname: Chakravarthy
authors.forename: Priyanka
authors.initials: P
authors.lastname: Jayaswal
mesh_terms: D000293:Adolescent; D002508:Cephalometry / Q000379:methods* / Q000706:statistics & numerical data; D002680:Chin / Q000473:pathology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007180:Incisor / Q000473:pathology; D007574:Jaw Relation Record; D008297:Male; D008311:Malocclusion, Angle Class I / Q000175:diagnosis / Q000473:pathology; D008312:Malocclusion, Angle Class II / Q000175:diagnosis / Q000473:pathology; D008313:Malocclusion, Angle Class III / Q000175:diagnosis / Q000473:pathology; D008334:Mandible / Q000473:pathology*; D008335:Mandibular Condyle / Q000473:pathology; D008437:Maxilla / Q000473:pathology*; D008963:Molar / Q000473:pathology; D009295:Nasal Bone / Q000473:pathology; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult