title: Structural optimization of the fibre-reinforced composite substructure in a three-unit dental bridge.
abstract: BACKGROUND
  Failures of fixed partial dentures (FPDs) made of fibre-reinforced composites (FRC) have been reported in many clinical and in vitro studies. The types of failure include debonding at the composite-tooth interface, delamination of the veneering material from the FRC substructure and fracture of the pontic. The design of the FRC substructure, i.e. the position and orientation of the fibres, will affect the fracture resistance of the FPD.
  
  
  OBJECTIVE
  The purpose of this study was to find an optimal arrangement of the FRC substructure, by means of structural optimization, which could minimize the failure-initiating stresses in a three-unit FPD.
  
  
  METHODS
  A structural optimization method mimicking biological adaptive growth was developed for orthotropic materials such as FRC and incorporated into the finite element (FE) program ABAQUS. Using the program, optimization of the fibre positions and directions in a three-unit FPD was carried out, the aim being to align the fibre directions with those of the maximum principal stresses. The optimized design was then modeled and analyzed to verify the improvements in mechanical performance of the FPD.
  
  
  RESULTS
  Results obtained from the optimization suggested that the fibres should be placed at the bottom of the pontic, forming a U-shape substructure that extended into the connectors linking the teeth and the pontic. FE analyses of the optimized design indicated stress reduction in both the veneering composite and at the interface between the veneer and the FRC substructure.
  
  
  CONCLUSIONS
  The optimized design obtained using FE-based structural optimization can potentially improve the fracture resistance of FPDs by reducing some of the failure-initiating stresses. Optimization methods can therefore be a useful tool to provide sound scientific guidelines for the design of FRC substructures in FPDs.
authors.affiliation: Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Shi
authors.forename: Alex S L
authors.initials: AS
authors.lastname: Fok
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D003801:Dental Veneers; D003779:Denture Design; D003830:Denture, Partial, Fixed; D055119:Elastic Modulus; D020342:Finite Element Analysis; D005898:Glass; D005899:Glass Ionomer Cements; D008422:Materials Testing; D033081:Shear Strength; D012823:Silicate Cement; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D005899:Glass Ionomer Cements; C111282:dental polyglass; C009753:fiberglass; D012823:Silicate Cement