title: Influence of substructure design and occlusal reduction on the stress distribution in metal ceramic complete crowns: 3D finite element analysis.
abstract: OBJECTIVE
  Occlusal reduction is considered a fundamental step for providing adequate and uniform space for the ceramic prosthesis; however, a flat occlusal surface is usually found. The prosthesis design influences the resistance to deformation and the stress state within the ceramic. This finite element (FE) study analyzes the influence of changing the substructure design on the stress distribution of a metal-ceramic crown in a premolar tooth with three types of occlusal reduction.
  
  
  METHODS
  Each part of three-dimensional metal ceramic complete crown models was designed according to the space provided by different levels of occlusal reduction and the same external morphology of the tooth. Three models were designed: (1) correct occlusal reduction with a uniform thickness of the substructure (0.3 mm) and the veneering porcelain (1.5 mm); (2) flat occlusal reduction with different thicknesses of veneering porcelain to produce a uniform substructure; and (3) a flat occlusal reduction with different thicknesses of substructure for a uniform thickness of veneering porcelain.
  
  
  RESULTS
  Stress distributions were very similar in the three models. The highest tensile stresses were concentrated immediately below the midline fissure in both the veneering porcelain and the metal alloy substructure. Although models with flat occlusal reduction had lower stress values, this preparation results from a reduction that removes a greater amount of sound tissue, which may increase the probability of dental pulp injury.
  
  
  CONCLUSIONS
  Occlusal reduction must be anatomic; however, when a flat occlusal reduction already exists, the substructure must reproduce the correct anatomic form to allow a uniform thickness of the veneering porcelain.
authors.affiliation: Department of Mechanical Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Andréa Barreira
authors.initials: AB
authors.lastname: Motta
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Pereira
authors.forename: Fernando Pereira
authors.initials: FP
authors.lastname: Duda
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Anusavice
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D001641:Bicuspid / Q000033:anatomy & histology; D001696:Biomechanical Phenomena; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D003804:Dentin / Q000033:anatomy & histology; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar; D015036:Zinc Phosphate Cement
keywords: Finite element analysis; complete crown; occlusal reduction; stress distribution; substructure