title: Optimization of Fracture Resistance and Stiffness of Heat-Polymerized High Impact Acrylic Resin with Localized E-Glass FiBER FORCE® Reinforcement at Different Stress Points.
abstract: OBJECTIVE
  Dentures are subject to fracture through flexural stresses during masticatory function. Distribution of stresses under flexural loading varies from compressive to tensile stress along the thickness of the denture cross section. The goal of this investigation was to evaluate the effect of reinforcing compressive, tensile, and no stress regions of flexurally loaded rectangular bars of heat-cured denture base acrylic resin reinforced with tough E-Glass FiBER FORCE (GFF) on their fracture resistance under flexural loading.
  
  
  METHODS
  Forty rectangular specimens (65 mm long × 10 mm wide × 2.5 mm thick) were prepared and divided into four groups (n = 10). Group FN had no fiber reinforcement, group FM had fiber in the middle at the no-stress neutral axis, group FC had fiber close to the surface on the compressive stress side, and group FT had the fiber close to the surface on the tensile stress side. The effect of GFF reinforcement on flexural strength (FS), flexural toughness (TG), and flexural modulus of elasticity (MOE) was evaluated.
  
  
  RESULTS
  The mean and (SD) of the FS, TG, and MOE varied as follows. FS (MPa): group FN: 91.49 (7.88); group FM: 102.83 (13.5); group FC: 107.68 (11.21); group FT: 141.46 (14.77). TG (mJ/mm3): group FN: 0.171 (0.026); group FM: 0.236 (0.033); group FC: 0.156 (0.032); group FT: 0.347 (0.010). MOE (MPa): group FN: 2682 (761); group FM: 2601 (417); group FC: 4188 (1012); group FT: 4215 (674). Statistical analysis showed that reinforcement on the tensile side of the neutral axis yielded improvement in all properties evaluated.
  
  
  CONCLUSIONS
  Placement of the GFF close to the tensile stress side surface of the bar increased the resistance to elastic deformation (i.e., higher MOE or stiffness) and the stress level needed for flexural fracture (i.e., higher FS). In addition, more energy was absorbed by reinforced specimens before fracture occurred (i.e., higher toughness). Localized reinforcement targeting tensile stress centers is thus a practical way to improve clinical durability of dentures against intra- and extraoral fracture.
authors.affiliation: Department of Restorative Clinical Science, University of Missouri-Kansas City, Kansas City, MO.
authors.forename: Haitham
authors.initials: H
authors.lastname: Agha
authors.affiliation: Department of Restorative Dentistry, Rutgers School of Dental Medicine, Newark, NJ.
authors.forename: Robert
authors.initials: R
authors.lastname: Flinton
authors.affiliation: Department of Restorative Dentistry, Rutgers School of Dental Medicine, Newark, NJ.
authors.forename: Tritala
authors.initials: T
authors.lastname: Vaidyanathan
mesh_terms: D000180:Acrylic Resins; D003799:Dental Stress Analysis; D003819:Denture Bases; D005898:Glass; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D013314:Stress, Mechanical
chemical_list: D000180:Acrylic Resins; C009753:fiberglass
keywords: FiBER FORCE; Reinforcement; compressive surface; denture base; flexural strength; modulus of elasticity; tensile surface; toughness