title: A cusp supporting framework design can decrease critical stresses in veneered molar crowns.
abstract: OBJECTIVE
  Veneered zirconia restorations predominately fail due to veneering fractures. It is hypothesized that a cusp-supporting framework design can prevent these catastrophic failures in all-ceramic restorations. Therefore, we investigated the influence of framework design and framework material on the stress distribution in a single tooth restoration using the numerical finite element method.
  
  
  METHODS
  A three-dimensional model of a veneered lower molar (36) crown with constant outer shape was used. The framework design was either cusp supporting or with a constant framework thickness. Zirconia, alumina, and a gold alloy were used as framework material. A glass ceramic material was used as veneering material for both cases. Two different load cases were simulated: terminal occlusion with load distributed over the occlusal surface of the tooth and a fairly extreme load case with all force concentrated on one cusp.
  
  
  RESULTS
  Maximum tensile stresses in the glass ceramic veneering material concentrated in the fissure region for all models. A cusp supporting framework design decreased the maximum tensile stresses significantly up to 30.5%. The distolingual load case resulted in an approximately fourfold higher stress level compared to the terminal occlusion load case.
  
  
  CONCLUSIONS
  A cusp supporting framework design can significantly decrease the maximum tensile stresses in the veneering material of single crowns. Based on the numerical results of this study it can be expected that such a design could decrease the risk of veneering failure in vivo.
authors.affiliation: Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital, Germany. Electronic address: akirsten@ukaachen.de.
authors.forename: Armin
authors.initials: A
authors.lastname: Kirsten
authors.affiliation: Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Parkot
authors.affiliation: Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Raith
authors.affiliation: Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital, Germany.
authors.forename: Horst
authors.initials: H
authors.lastname: Fischer
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D020342:Finite Element Analysis; D006046:Gold; D066298:In Vitro Techniques; D003765:Models, Dental; D008963:Molar; D013718:Tensile Strength; D015040:Zirconium
chemical_list: D003722:Dental Alloys; D006046:Gold; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide
keywords: All-ceramic restorations; Chipping; Cusp supporting design; Finite element analysis; Framework design; Framework material; Stress distribution; Veneering failure