title: [Clinical studies on the dental and occlusal conditions of molars with vertical cracking of the root].
abstract: OBJECTIVE
  To study the contributing factors inducing vertical cracking of the root of molars.
  
  
  METHODS
  The dental, periodontal, and occlusal conditions of molars with vertical root cracking were studied in 34 cases (39 teeth).
  
  
  RESULTS
  The age range of patients was 40-60 years. The crackings occurred mostly at mesial or mesio-buccal roots, their periodontal conditions were much more worse than those roots without cracking and manifested by deep pocket. The abrasion of the occlusal surfaces was more severe than those molars with no cracking, their contact areas were unstable and deviated buccallly. The direction of force during chewing was therefore horizontal, viz., mesio-distally and bucco-lingually.
  
  
  CONCLUSIONS
  The vertical root cracking of molars is associated with traumatical occlusal contact due to severe abrasion which increases the loading during chewing.
authors.affiliation: School of Stomatology, Beijing Medical University, Beijing 100081.
authors.forename: Y
authors.initials: Y
authors.lastname: Zeng
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: Zhou
mesh_terms: D000328:Adult; D000368:Aged; D003750:Dental Fissures / Q000209:etiology*; D003767:Dental Occlusion, Balanced; D003769:Dental Occlusion, Traumatic / Q000150:complications*; D006801:Humans; D008875:Middle Aged; D008963:Molar