title: [Measurement and estimation of the root surface of single-root teeth].
abstract: OBJECTIVE
  To evaluate the availability of the estimation method of the single-root surface area on periapical radiographs, and to compare with the measured method by 3-dimension laser scanning and reconstructed images.
  
  
  METHODS
  Ninety single-root teeth with severe periodontitis were selected, periapcal radiographs were taken before teeth extracted. Root lengths and crown lengths were measured on periapical radiographs. The ratio of crown to root of each tooth was calculated. Then the root surface areas were also estimated according to mathematics limit principle on the periapical radiographs. The image of the roots were reconstructed by using a 3D laser scanning, the root surface areas were measured with a CAD/CAM software.
  
  
  RESULTS
  No significant difference was found between the measured values of the ratio of crown to root by 3D laser scanning and the estimated values on periapical radiographs (t=0.58, P>0.05). For the lower incisors, no significant difference was found between the measured root surface areas with the 3D laser scanning and the estimated ones on periapical radiographs(t=0.46, P>0.05). The surface area of the root in each tooth was divided into three parts: the coronal 1/3, the middle 1/3 and the apical 1/3. Each part of root surface area was measured and estimated. And then the percentage of each part in total root surface area was calculated. The measured percentage was similar to the estimated one except the middle 1/3 part of the upper premolars(t=0.77, P>0.05).
  
  
  CONCLUSIONS
  No significant difference was found between the measured ratio of crown to root with 3D laser scanning and the estimated one on periapical radiographs. The evaluated method on periapical radiographs to estimate root surface areas was relatively reliable for the lower incisor.
authors.affiliation: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Tian
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Huan-xin
authors.initials: HX
authors.lastname: Meng
authors.forename: Pei-jun
authors.initials: PJ
authors.lastname: Lv
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Yi-jiao
authors.initials: YJ
authors.lastname: Zhao
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D009811:Odontometry / Q000379:methods*; D010518:Periodontitis / Q000473:pathology; D011859:Radiography; D014092:Tooth Root / Q000000981:diagnostic imaging* / Q000473:pathology