title: Effects of polymerization shrinkage on the interfacial stress at resin-metal joint in denture-base: a non-linear FE stress analysis.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effects of polymerization shrinkage on stress at the interface between resin and metal in removable dentures.
  
  
  METHODS
  Three-dimensional finite element models of a denture-base were studied, which consisted of acrylic occlusal rims with different heights and metal frameworks. A relaxation modulus of 1.5 GPa for the resin and a Young's modulus of 220 GPa for the metal were used as the material properties. Each model was constrained at the edge of the framework on the palatal vault. Surface-to-surface contact elements were used to calculate the interfacial stress in a direction perpendicular to the bond surface under a linear shrinkage ranging from 0.41 to 0.65%. The principal stress within the resin was also calculated.
  
  
  RESULTS
  The maximum interfacial and principal stresses within the denture-base increased with resin shrinkage. Under the lowest linear shrinkage, the mean area percentages in the resin-metal joint that showed interfacial tensile stresses over 10 and 20 MPa were 63.4 and 0%, respectively. While under the highest linear shrinkage, these mean area percentages were 98.8 and 38.1%, respectively. Negligible differences in the stresses were shown by occlusal heights.
  
  
  CONCLUSIONS
  The polymerization shrinkage level has a significant influence on the residual stress at the resin-metal interface. Enhancement of the bond strength on the interface can reduce the failure probability at a resin-metal joint.
authors.affiliation: Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113-8549, Japan. t.ikeda.rpro@tmd.ac.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ikeda
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Wakabayashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ona
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohyama
mesh_terms: D000180:Acrylic Resins; D003722:Dental Alloys; D003799:Dental Stress Analysis / Q000379:methods; D003819:Denture Bases; D003827:Denture, Complete, Upper; D004548:Elasticity; D020342:Finite Element Analysis; D044367:Phase Transition; D013718:Tensile Strength; D014783:Viscosity
chemical_list: D000180:Acrylic Resins; D003722:Dental Alloys