title: Flexural strengths of denture base resin repaired with autopolymerizing resin and reinforcements after thermocycle stressing.
abstract: OBJECTIVE
  Fracture of an acrylic denture base is a common problem in prosthodontic practice. Although various reinforcement methods have been used, when a fractured denture base is repaired with autopolymerizing resin recurrent fractures frequently occur at the repairing interface or adjacent areas. The purpose of this study was to evaluate the maximum flexural load of denture base resin repaired with autopolymerizing resin and several reinforcement systems after thermocycle stressing.
  
  
  METHODS
  Rectangular (10 x 70 x 3 mm) flexural specimens were fabricated by repairing a pair of heat-cured denture base resin specimens using autopolymerizing resin and a series of reinforcement materials. The materials included 4 metal wires and a woven glass fiber. Each reinforcement was embedded in the center of the specimens. Flexural specimens repaired without reinforcement were prepared as controls. Specimens were subjected to 50,000 thermocycles (4 approximately 60 degrees C, 1-minute dwell time). A 3-point flexural test was carried out by loading the center of the repaired site at 5 mm/minute crosshead speed with 50 mm span jig supports. The load necessary to cause fracture was recorded for each specimen. All data were statistically analyzed using ANOVA and the Bonferroni/Dunn test (alpha < 0.05).
  
  
  RESULTS
  The average load to fracture of specimens repaired with nonreinforced autopolymerizing resin was 68.4 N after 50,000 thermocycles. Specimens reinforced with 1.2 mm diameter stainless steel wire exhibited the highest value (89.8 N). The value for specimens reinforced with 1.2 mm diameter Co-Cr-Ni wire was 86.6 N. These fracture loads were significantly higher than those for specimens without reinforcement (p < 0.05). Low elasticity reinforcement, such as pure titanium wires, woven metal wire, and woven glass fiber were not effective in increasing the load to fracture values of flexural specimens.
  
  
  CONCLUSIONS
  Specimens reinforced with 1.2 mm diameter stainless steel wires or Co-Cr-Ni wires resulted in significantly higher loads to fracture as compared to specimens without reinforcement. The use of pure titanium wire, woven metal wire, and woven glass fiber did not improve the fracture loads.
authors.affiliation: Department of Prosthodontics, Kagoshima University, Kagoshima, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Minami
authors.forename: Shiro
authors.initials: S
authors.lastname: Suzuki
authors.forename: Hisanori
authors.initials: H
authors.lastname: Kurashige
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Minesaki
authors.forename: Takuo
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000180:Acrylic Resins; D003188:Composite Resins; D003722:Dental Alloys; D003799:Dental Stress Analysis; D003819:Denture Bases; D003780:Denture Repair; D004548:Elasticity; D005898:Glass; D008422:Materials Testing; D018583:Pliability
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D003722:Dental Alloys; C009753:fiberglass