title: Comparative strengths of metal framework structures for removable partial dentures.
abstract: BACKGROUND
  The framework of removable partial dentures often breaks where the metal retention for the resin denture base attaches to the clasp and major connector.
  
  
  OBJECTIVE
  To study these failure factors, various types of three-dimensional simulated denture frameworks were designed to measure their ultimate strengths and stiffnesses under static load. This study also sought to determine which could be recommended for long-term clinical service.
  
  
  METHODS
  Three groups of three-dimensional frameworks (double, T-shaped, and trussed structure) were designed, and two groups of classic framework designs (uniform and nonuniform skeleton) were used with an acrylic resin block as a control (n = 5 per group). Fatigue strength, stiffness and amount of strain, and free-end displacement under dynamic loads were measured for each framework. The fatigue strength was determined with a constant-loading fatigue test by counting the number of loading cycles required to induce catastrophic failure.
  
  
  RESULTS
  With 20 kgf of load, four T-shaped samples and three trussed structure samples failed at 30,000 to 60,000 loading cycles. No samples of double structure group failed until 100,000 loading cycles.
  
  
  CONCLUSIONS
  Three-dimensional frameworks, especially the double structure, have significant differences in fatigue strength and can provide long-term clinical service.
authors.affiliation: Department of Removable Partial Prosthodontics, Tsurumi University, School of Dental Medicine, Yokohama, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Ohkubo
authors.forename: M
authors.initials: M
authors.lastname: Abe
authors.forename: T
authors.initials: T
authors.lastname: Miyata
authors.forename: J
authors.initials: J
authors.lastname: Obana
mesh_terms: D002858:Chromium Alloys; D016734:Dental Clasps; D003799:Dental Stress Analysis; D003819:Denture Bases; D003779:Denture Design; D003832:Denture, Partial, Removable; D004548:Elasticity; D008422:Materials Testing; D013718:Tensile Strength
chemical_list: D002858:Chromium Alloys