title: Digital subtraction radiography evaluation of the bone repair process of chronic apical periodontitis after root canal treatment.
abstract: OBJECTIVE
  To monitor radiographically the progress of bone repair within chronic periapical lesions after root canal treatment using digital subtraction radiography (DSR).
  
  
  METHODS
  Twelve patients with 17 single-rooted teeth with chronic apical periodontitis associated with an infected necrotic pulp were selected for root canal treatment. Periapical radiographs were taken before treatment (baseline) and immediately post-treatment, 45, 90, 135 and 180 days after treatment. The radiographic protocol included the use of individualized film holders with silicone bite blocks. The six radiographic images were digitized and submitted to digital subtraction using DSR software, resulting in five subtracted images (SI). Quantitative analysis of these SI was performed using Image Tool software to assess pixel value changes, considering a step-wedge as the gold standard and a cut-off value of 128 pixels. The aim was to identify any increase or decrease in mineral density in the region of the periapical lesion.
  
  
  RESULTS
  A minor decrease in mineral density at the canal filling session and a significant progressive mineral gain in the following evaluations (P < 0.001) occurred. Pairwise comparison of pixel grey values revealed that only the 180-day follow-up differed significantly from the previous SI.
  
  
  CONCLUSIONS
  Digital subtraction radiography is a useful method for evaluating the progress of bone repair after root canal treatment. Noticeable mineral gain was observed approximately 90 days after root canal filling and definite bone repair after 180 days.
authors.affiliation: Department of Oral Medicine, School of Dentistry, Federal University of Goiás, Goiânia, Brazil.
authors.forename: J
authors.initials: J
authors.lastname: Benfica e Silva
authors.forename: C R
authors.initials: CR
authors.lastname: Leles
authors.forename: A H G
authors.initials: AH
authors.lastname: Alencar
authors.forename: C A B C M
authors.initials: CA
authors.lastname: Nunes
authors.forename: E F
authors.initials: EF
authors.lastname: Mendonça
mesh_terms: D000293:Adolescent; D000328:Adult; D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001861:Bone Regeneration / Q000502:physiology*; D055113:Chronic Periodontitis / Q000000981:diagnostic imaging / Q000503:physiopathology; D003790:Dental Pulp Necrosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D010485:Periapical Periodontitis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D019252:Radiography, Dental, Digital / Q000379:methods*; D012390:Root Canal Therapy; D013382:Subtraction Technique; D055815:Young Adult