title: Effect of the addition of poly(methyl methacrylate) beads on some properties of acrylic resin.
abstract: OBJECTIVE
  There have been numerous attempts to improve the mechanical properties of acrylic resin. However, the fracture of dentures is still an unresolved problem. The potential advantage of self-reinforcement should be improved mechanical properties over the amorphous random polymer. This study investigated the addition of poly(methyl methacrylate) (PMMA) beads in a variety of percentages on a range of mechanical properties of PMMA denture base acrylic resin.
  
  
  METHODS
  The transverse and impact strengths and hardness of acrylic resin specimens stored in water for periods of 1 week and 6 months prior to testing were investigated.
  
  
  RESULTS
  The results showed that for specimens stored for 1 week, the addition of up to 25% beads produced a significant increase in the modulus of elasticity. Addition of 5% beads produced a slight but nonsignificant increase in the modulus of rupture, although additions of increasing percentages produced a decrease in the modulus of rupture. The impact strength was increased for 5% to 25% beads and decreased for 40% beads. The hardness showed only small changes. For specimens stored in water for 6 months, the modulus of rupture decreased with increasing percentages of beads. The addition of beads up to 10% significantly increased the modulus of elasticity. There was no significant increase in impact strength but a significant increase in hardness for 5% beads.
  
  
  CONCLUSIONS
  The addition of PMMA beads to acrylic resin did not produce a substantial improvement in the mechanical properties and cannot be recommended as a method of reinforcement in its present form.
authors.affiliation: Department of Oral and Dental Science, Division of Restorative Dentistry (Prosthodontics), Bristol Dental School and Hospital, Lower Maudlin Street, Bristol BSI 2LY, United Kingdom. D.C.Jagger@bris.ac.uk
authors.forename: D C
authors.initials: DC
authors.lastname: Jagger
authors.forename: A
authors.initials: A
authors.lastname: Harrison
authors.forename: K
authors.initials: K
authors.lastname: al-Marzoug
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000704:Analysis of Variance; D003819:Denture Bases; D004548:Elasticity; D019544:Equipment Failure Analysis; D006244:Hardness; D008422:Materials Testing; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D013314:Stress, Mechanical
chemical_list: D000180:Acrylic Resins; D019904:Polymethyl Methacrylate