title: [Evaluation of the remaining periodontal ligament from attachment level].
abstract: OBJECTIVE
  To estimate the total periodontal ligament areas and the remaining periodontal ligament areas from different attachment level of each tooth type, and to determine the relationship between the attachment loss and the prognosis of periodontal diseases.
  
  
  METHODS
  Four hundred and twenty extracted teeth (30 of each tooth type of one side of both arches,except for the third molar) were collected.The root surface of each tooth was coated with polyvinyl alcohol to produce a membrane after cleaning. The membrane was peeled off after guidelines were drawn on to simulate various attachment levels. The root surface area of each simulated attachment level was measured using image analysis software Photoshop cs 9.0 and Scion Image 4.0.3. SAS 6.12 software package was used for statistical analysis.
  
  
  RESULTS
  The correlation and significance of the linear function for each tooth type were significant(P<0.001);Based on the regression beeline, the mean total periodontal ligament area of the teeth was reduced to about 50% when the attachment loss was more than 5.37mm.
  
  
  CONCLUSIONS
  The linear function provides an appropriate fit for estimation of the remaining area of periodontal ligament from the attachment level measurement.The remaining periodontal ligament of teeth whose attachment loss is more than 5.37mm could not supply half of the original support force. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality(Grant No.08DZ2271100).
authors.affiliation: Department of Periodontology, Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai 200011, China. happyrain01@163.com
authors.forename: Zhong-kai
authors.initials: ZK
authors.lastname: Wu
authors.forename: Yuan-zheng
authors.initials: YZ
authors.lastname: Yin
mesh_terms: D006801:Humans; D010510:Periodontal Diseases; D010513:Periodontal Ligament; D014070:Tooth; D014081:Tooth Extraction; D014092:Tooth Root