title: Effects of differing thickness and mechanical properties of cement on the stress levels and distributions in a three-unit zirconia fixed prosthesis by FEA.
abstract: OBJECTIVE
  This study analyzed the impact of cement layer thickness (CLT) and Young's modulus of the cement on the stress distribution in a three-unit zirconia fixed dental prosthesis (FDP) and in the bonding interfaces by means of finite element method.
  
  
  METHODS
  A 3D finite element model was created from a stylized three-unit FDP-cement-tooth/socket system. The pulp and the periodontal ligament were not modeled. Two CLTs (50 and 150 μm) and two values of Young's modulus of the cement (4.9 for simulation of resin cement, 20.1 GPa for glass ionomer cement) were evaluated. A 500 N static vertical load was applied at the central fossa of the pontic to calculate maximum displacement in the framework and maximum principal stresses in both framework and bonding interfaces.
  
  
  RESULTS
  The simulated results showed that the Young's modulus affected stress occurrence only in the cement interface. Lower moduli were associated with less stress. The thickness of the cement layer influenced the maximum principal stress in both the FDP and in the cement layer itself. Thicker cement layers led to higher stresses in the framework but lower stresses in the cement layer. Maximum displacement was less dependent of the investigated variables. During all trials, the location of the maximum principal stress did not change. Maximum stress concentrations were observed at the lower embrasures of the connector areas and in the bonding layer at the cervical margin of the preparation.
  
  
  CONCLUSIONS
  Choosing cements with a preferably low Young's modulus in combination with a CLT as small as possible might increase the clinical survival rate.
authors.affiliation: Department of Prosthodontics, Ludwig-Maximilians University, Munich Dental School, Munich, Germany.
authors.forename: Timea
authors.initials: T
authors.lastname: Wimmer
authors.forename: Kurt-Jürgen
authors.initials: KJ
authors.lastname: Erdelt
authors.forename: Stefan
authors.initials: S
authors.lastname: Raith
authors.forename: Jörg Markus
authors.initials: JM
authors.lastname: Schneider
authors.forename: Bogna
authors.initials: B
authors.lastname: Stawarczyk
authors.forename: Florian
authors.initials: F
authors.lastname: Beuer
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003198:Computer Simulation; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003830:Denture, Partial, Fixed; D055119:Elastic Modulus; D020342:Finite Element Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008277:Magnesium Oxide / Q000737:chemistry; D008422:Materials Testing; D008953:Models, Anatomic; D011076:Polycarboxylate Cement / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014584:User-Computer Interface; D015019:Yttrium / Q000737:chemistry; D015034:Zinc Oxide / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003738:Dental Cements; D003764:Dental Materials; D005899:Glass Ionomer Cements; D011076:Polycarboxylate Cement; C483701:Rely X Unicem; D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D008277:Magnesium Oxide; D015019:Yttrium; C040235:Ketac-cem; D015040:Zirconium; C028541:zirconium oxide; D015034:Zinc Oxide
keywords: Finite element analysis; Young's modulus; cement; cement layer thickness; zirconia