title: [Effects of post diameter on retention of post-core crown system].
abstract: OBJECTIVE
  To access the effects of post's diameter on the retention of post-core restorations.
  
  
  METHODS
  Thirty-three simulant roots with same length,taper and different diameter (1.305 mm, 1.830 mm, 2.175 mm and 2.700 mm respectively) were made of polymethylmethacrylate and were divided into 4 groups. The wax patterns of post-cores were manufactured and cast. The post-cores were cemented. After that, the adhesion, frictional force and restriction of the post-core restorations were measured.
  
  
  RESULTS
  When the proportion of length and diameter was smaller than 4.372, the linear regression between the post's diameter and the retention of post-core crown system was F = 107.98 + 72.08D. The linear regression between the post's diameter and the adhesion was P = 9.60 + 2.22D. The linear regression between the post's diameter and the frictional force and restriction was Q = 98.37 + 69.87D. The statistical analysis of the results indicated significant difference (P < 0.05). When the proportion of length and diameter was lager than 4.372, the retention of post-core crown system increased although the post's diameter decreased.
  
  
  CONCLUSIONS
  When the proportion of length and diameter was smaller than 4.372, the retention of post-core crown system increased with the decrease of the post's diameter. While the proportion was lager than a certain value, this rule did not exist.
authors.affiliation: Dept. of Prosthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Wu
authors.forename: Xin-Min
authors.initials: XM
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.forename: Lin
authors.initials: L
authors.lastname: Niu
authors.forename: Wei
authors.initials: W
authors.lastname: Yao
mesh_terms: D003442:Crowns; D003799:Dental Stress Analysis; D006801:Humans; D011176:Post and Core Technique