title: Finite element analysis of the principles and loosening force of the conical telescopic crown: a computer-based study.
abstract: OBJECTIVE
  The primary goal of the present finite element (FE) analysis of a special removable prosthesis, the conical telescopic crown (CTC), was to validate established results based on a rigid model of the CTC and to analyze its characteristic features as a function of the essential material and geometric parameters. Furthermore, the effectiveness of a new element, the composite stop (CS), was investigated.
  
  
  METHODS
  The study used an axisymmetric FE model containing the inner and outer crown including resin or ceramic veneer, the CS, the cement layer between the interior crown and the tooth, and the upper part of the tooth itself.
  
  
  RESULTS
  For a convergence angle (half-cone angle) α = 4 degrees and a moderate chewing force F = 150 N the loosening force decreased from - 50 N without to - 10 N with CS. Increasing α values yielded a decrease of the loosening force. Adherence between the inner (IC) and outer crown (OC) was achieved for all configurations (α = 2 degrees, 4 degrees, and 6 degrees), except for zirconium crowns with α = 6 degrees. In systems without CS, the maximum tensile stress in the veneer increased proportionally to F, but remained limited in those with CS.
  
  
  CONCLUSIONS
  The angle a and the coefficient of static friction μ0 emerged as the decisive parameters of the CTC. The computed fitting/loosening behavior agreed well with results of a simple rigid-body model and experiments. The incorporation of a CS allows ceramic veneering of the outer crown.
  
  
  CONCLUSIONS
  The optimal angle α of the CTC is ascribed to a number of customary material combinations for IC and OC. The CS limits the loosening forces of the CTC to values which guarantee non-traumatic removal of the prosthesis.
authors.affiliation: Universitätklinikum Heidelberg.
authors.forename: C
authors.initials: C
authors.lastname: Fingerhut
authors.forename: H J
authors.initials: HJ
authors.lastname: Schindler
authors.forename: K
authors.initials: K
authors.lastname: Schweizerhof
authors.forename: B
authors.initials: B
authors.lastname: Kordass
authors.forename: J
authors.initials: J
authors.lastname: Lenz
mesh_terms: D001696:Biomechanical Phenomena; D002516:Ceramics / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003198:Computer Simulation; D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003801:Dental Veneers; D003828:Denture, Overlay; D020342:Finite Element Analysis; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008409:Mastication / Q000502:physiology; D008954:Models, Biological; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003188:Composite Resins; D003722:Dental Alloys; D003764:Dental Materials; D006047:Gold Alloys; D015036:Zinc Phosphate Cement; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide