title: [Application research of cone beam CT in dowel preparation for the mandibular first molar].
abstract: OBJECTIVE
  To measure the root anatomic topography of mandibular first molar using cone beam CT (CBCT), calculate the proper space for dowel preparation.
  
  
  METHODS
  The roots of 121 mandibular first molars from 71 patients were scanned by CBCT, the images from cross section, sagittal plane, and coronal plane were got respectively. The dowel preparation spaces according to established three dimensional images and dowel preparation requirements were analyzed.
  
  
  RESULTS
  Three dowels could be prepared. The dowel length for distal-root was (7.19 +/- 0.91) mm, dowel diameter was (0.80 +/- 0.12) mm on the level of 4mm above root apex. The dowel length for mesio-root was (6.92 +/- 1.02) mm, and dowel diameter was (0.71 +/- 0.08) mm on the lever of 4 mm above root apex for buccal side and (0.71 +/- 0.07) mm for lingual side. Dowel should be prepared cone-shaped.
  
  
  CONCLUSIONS
  Many factors affect dowel preparation, individualized design is needed. CBCT can provide reliable radiographic evidence.
authors.affiliation: Dept. of Stomatology, Shangyu Second People's Hospital, Shangyu 312365, China.
authors.forename: Jiangshan
authors.initials: J
authors.lastname: Zhang
authors.forename: Xueyan
authors.initials: X
authors.lastname: Li
authors.forename: Yanzhen
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D054893:Cone-Beam Computed Tomography; D003786:Dental Pulp Cavity; D006801:Humans; D008334:Mandible; D008963:Molar; D014092:Tooth Root