title: [Effects of expansion fashion and expansion quantity on retention of cement-expanded composite screw post].
abstract: OBJECTIVE
  To study the effects of expansion fashion and expansion quantity on retention of cement-expanded composition screw post (CECSP).
  
  
  METHODS
  Ninety simulated tooth roots made of polymethylmethacrylate were divided into ten groups, each fashion induded five groups. The expanded plastic sheath of tricuspid valve was made with the special separated valve device and cemented and tightened up into root with the screw post at the same time by ZPC. Then the root and screw post-core system was tested by the speed of 10 mm/min on the INSTRON 4302 and the retention force was recorded.
  
  
  RESULTS
  It appeared that the difference between different expansion fashion and different expansion quantity were significantly (P < 0.05). The retention of expansion fashion one was significantly greater than those of fashion two. The retention was best when expansion quantity was within 10%.
  
  
  CONCLUSIONS
  During clinic operation, we should apply definite fashion and control the expansion quantity within 10%, and the screw post should tighten up to the bottom of prepared root.
authors.affiliation: Dept . of Prosthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: Xin-min
authors.initials: XM
authors.lastname: Chen
authors.forename: Nian-bin
authors.initials: NB
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Niu
authors.forename: Tao
authors.initials: T
authors.lastname: He
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.forename: Gui-ju
authors.initials: GJ
authors.lastname: Zhang
authors.forename: Xiao-hong
authors.initials: XH
authors.lastname: Wu
authors.forename: Ping-ping
authors.initials: PP
authors.lastname: Li
mesh_terms: D001863:Bone Screws; D002484:Cementation; D003188:Composite Resins; D003738:Dental Cements; D003739:Dental Cementum; D017268:Dental Prosthesis Retention; D005899:Glass Ionomer Cements; D006801:Humans; D011176:Post and Core Technique; D014092:Tooth Root
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D005899:Glass Ionomer Cements