title: Evaluation of periapical changes following endodontic therapy: digital subtraction technique compared with computerized morphometric analysis.
abstract: OBJECTIVE
  The aim of this study was to compare two methods for the evaluation of periapical lesion changes following endodontic therapy (digital subtraction technique and morphometric analysis) by outlining the radiolucent area.
  
  
  METHODS
  13 human anterior teeth with pulp necrosis and chronic periapical lesions were used. Periapical radiographs were taken immediately after endodontic therapy (0) and then 2 months, 4 months and 6 months post treatment, using an intraoral radiographic film holder stabilized with impression material. The films were processed in a standard manner and the digitized images were submitted to digital subtraction using Adobe Photoshop 6.0. New bone formation or bone resorption areas were then measured. In the morphometric analysis, the periapical lesions were outlined using VixWin 2000 and the area (in square millimetres) was recorded. The obtained data were submitted to agreement analysis for comparison of the two techniques.
  
  
  RESULTS
  There was no correlation between the areas of radiographic changes detected by digital subtraction and periapical lesion outline (r = 0.02-0.45). The new bone formation areas observed by digital subtraction presented higher values, with bone changes being especially evident in the 2 month follow-up radiographs, which suggests a higher sensitivity for this method.
  
  
  CONCLUSIONS
  Both methods are suitable for the evaluation of periapical lesion changes, but the digital subtraction technique is more sensitive for detecting radiographic periapical changes.
authors.affiliation: Department of Restorative Dentistry, São Paulo State University, UNESP, Araraquara, Brazil.
authors.forename: F B
authors.initials: FB
authors.lastname: Carvalho
authors.forename: M
authors.initials: M
authors.lastname: Gonçalves
authors.forename: J M
authors.initials: JM
authors.lastname: Guerreiro-Tanomaru
authors.forename: M
authors.initials: M
authors.lastname: Tanomaru-Filho
mesh_terms: D002908:Chronic Disease; D003790:Dental Pulp Necrosis / Q000000981:diagnostic imaging*; D005500:Follow-Up Studies; D006801:Humans; D010483:Periapical Diseases / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods*; D012390:Root Canal Therapy; D012984:Software; D013382:Subtraction Technique; D014584:User-Computer Interface