title: [Clinical analysis of 255 dental crown fracture].
abstract: OBJECTIVE
  To analyse dental crown fracture occurrence situation in the long-term mastication process, and discuss the correlation factor of crown fracture occurrence.
  
  
  METHODS
  From December, 2005 to December, 2007, 255 crown fracture teeth were chosen as the object of study. The sex, age, teeth position, fracture position and occlusal state of patients were analyzed.
  
  
  RESULTS
  In 255 teeth, 1) 76 teeth (29.8%) were maxillary first molars, 45 teeth (17.6%) were mandibular first molars, 41 teeth (16.1%) were maxillary second molars, 37 teeth (14.5%) were mandibular second molars, 32 teeth (12.5%) were maxillary second premolars, 15 teeth (5.9%) were maxillary first premolars, 9 teeth (3.5%) were mandibular second premolars. 2) The fracture position of 158 teeth (62.0%) overlapped with pit and fissure. The fracture position of 97 teeth (38.0%) occurred in dental inclined surface. 3) The occlusal state of 85 patients (33.3%) was normal. The occlusal surface shape of 55 patients (21.6%) was unnormal. The occlusal shape of 115 patients (45.1%) was unnormal.
  
  
  CONCLUSIONS
  The teeth position and occlusal state has certain relations with occurrence of dental crown fracture. Occlusal force was the basic factor for dental crown fracture, but it was not the only one.
authors.affiliation: Dept. of Stomatology, The First People's Hospital of Lanzhou City, Lanzhou 730050, China.
authors.forename: Jing-Fan
authors.initials: JF
authors.lastname: Zhao
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Xie