title: [A positioning device for oral paralleling technique].
abstract: OBJECTIVE
  To design a reliable method for standardized paralelling dental projection, for comparison of the tiny variations of alveolar bone during the treatment of the periodontal disease.
  
  
  METHODS
  Periapical radiographs in 29 pairs of films with this device and 14 pairs of films with traditional method on dried skulls were comparatively analysed by digital subtraction. Standard deviations and angle variations of subtracted image were studied comparatively between this method and traditional paralleling technique.
  
  
  RESULTS
  Significant difference of reproducibility between two groups was showed. The reproducibility of the successive pictures was apparently increased when projected with positioning device.
authors.affiliation: School of Stomatology, Beijing Medical University.
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Ma
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D011861:Radiography, Dental / Q000295:instrumentation*; D019227:Tooth Apex / Q000000981:diagnostic imaging