title: An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers.
abstract: BACKGROUND
  Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties.
  
  
  OBJECTIVE
  This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens.
  
  
  METHODS
  The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test.
  
  
  RESULTS
  Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization.
  
  
  CONCLUSIONS
  Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.
authors.affiliation: Department of Prosthodontics, Kalinga Institute of Dental Sciences, Bhubaneswar, Odisha, India.
authors.forename: Anjana
authors.initials: A
authors.lastname: Raut
authors.forename: Polsani Laxman
authors.initials: PL
authors.lastname: Rao
authors.forename: B V J
authors.initials: BV
authors.lastname: Vikas
authors.forename: T
authors.initials: T
authors.lastname: Ravindranath
authors.forename: Archana
authors.initials: A
authors.lastname: Paradkar
authors.forename: G
authors.initials: G
authors.lastname: Malakondaiah
mesh_terms: D019245:Compressive Strength; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis; D003819:Denture Bases; D006358:Hot Temperature; D066298:In Vitro Techniques; D008422:Materials Testing; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011312:Pressure; D013499:Surface Properties
chemical_list: D003764:Dental Materials; D011108:Polymers; D019904:Polymethyl Methacrylate