title: A study of parallelism of the occlusal plane and ala-tragus line.
abstract: OBJECTIVE
  Orientation of the occlusal plane is one of the most important clinical procedures in prostho-dontic rehabilitation of edentulous patients. The aim of this study was to define the best posterior reference point of ala-tragus line for orientation of occlusal plane for complete denture fabrication.
  
  
  METHODS
  Fifty-three dental students (27 females and 26 males) with complete natural dentition and Angel's Class I occlusal relationship were selected. The subjects were photographed in natural head position while clenching on a Fox plane. After tracing the photographs, the angles between the following lines were measured: the occlusal plane (Fox plane) and the superior border of ala-tragus, the occlusal plane (Fox plane) and the middle of ala-tragus as well as the occlusal plane (Fox plane) and the inferior border of ala-tragus. Descriptive statistics, one sample t-test and independent t-test were used. P value less than 0.05 was considered significant.
  
  
  RESULTS
  There was no parallelism between the occlusal plane and ala-tragus line with three different posterior ends and one sample t-test showed that the angles between them were significantly different from zero (p<0.05). However, the supe-rior border of ala-tragus line had the lowest mean angle, 1.80° (3.12) and was almost parallel to the occlusal plane.
  
  
  CONCLUSIONS
  The superior border of the tragus is suggested as the posterior reference for ala-tragus line.
authors.affiliation: Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Tabriz University of Medical science, Tabriz, Iran.
authors.forename: Katayoun
authors.initials: K
authors.lastname: Sadr
authors.forename: Makan
authors.initials: M
authors.lastname: Sadr