title: Flexural strength and moduli of hypoallergenic denture base materials.
abstract: BACKGROUND
  Hypoallergenic denture base materials show no residual methyl methacrylate (MMA) or significantly lower residual MMA monomer content compared to polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin. There is insufficient knowledge of the mechanical properties of hypoallergenic denture base materials to warrant their use in place of PMMA-based acrylic resins for patients with allergic reaction to MMA.
  
  
  OBJECTIVE
  This in vitro study compared flexural strength and flexural modulus of 4 hypoallergenic denture base materials with flexural strength/modulus of a PMMA heat-polymerizing acrylic resin.
  
  
  METHODS
  The following denture base resins were examined: Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), Microbase (microwave-polymerized, polyurethane-based), and Paladon 65 (heat-polymerized, methacrylate, control group). Specimens of each material were tested for flexural strength and flexural modulus (MPa, n = 5) according to ISO 1567:1999. The data were analyzed with 1-way analysis of variance and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05).
  
  
  RESULTS
  Flexural strength of Microbase (67.2 +/- 5.3 MPa) was significantly lower than Paladon 65 (78.6 +/- 5.5 MPa, P <.0001). Flexural strength of Polyan (79.7 +/- 4.2 MPa, P =.599), Promysan (83.5 +/- 3.8 MPa, P =.412), and Sinomer (72.3 +/- 2.1 MPa, P =.015) did not differ significantly from the control group. Significantly lower flexural modulus was obtained from Sinomer (1720 +/- 30 MPa, P =.0007) compared to the PMMA control group (2050 +/- 40 MPa), whereas the flexural modulus of Promysan (2350 +/- 170 MPa, P =.0005) was significantly higher than the PMMA material. Microbase (2100 +/- 210 MPa, P =.373) and Polyan (2070 +/- 60 MPa, P =.577) exhibited flexural modulus similar to the PMMA material. The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). With the exception of Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding flexural modulus (>2000 MPa).
  
  
  CONCLUSIONS
  Flexural modulus of Promysan was significantly higher than the PMMA material. Microbase and Sinomer exhibited significantly lower flexural strength and flexural modulus, respectively, than PMMA. The other groups did not differ significantly from the control group.
authors.affiliation: School of Oral Medicine, University of Cologne, Germany. peter.pfeiffer@uni-koeln.de
authors.forename: Peter
authors.initials: P
authors.lastname: Pfeiffer
authors.forename: Christian
authors.initials: C
authors.lastname: Rolleke
authors.forename: Lamia
authors.initials: L
authors.lastname: Sherif
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D020366:Methylmethacrylate / Q000737:chemistry; D010795:Phthalic Acids / Q000737:chemistry; D018583:Pliability; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D000180:Acrylic Resins; D003764:Dental Materials; D008689:Methacrylates; C441199:Microbase; D010795:Phthalic Acids; D011140:Polyurethanes; C489262:polyan; C489263:promysan; C437924:sinomer; D020366:Methylmethacrylate; C024149:paladon; D019904:Polymethyl Methacrylate