title: Physical properties of an acrylic resin after incorporation of an antimicrobial monomer.
abstract: OBJECTIVE
  This study evaluated the effect of the incorporation of the antimicrobial monomer methacryloyloxyundecylpyridinium bromide (MUPB) on the hardness, roughness, flexural strength, and color stability of a denture base material.
  
  
  METHODS
  Ninety-six disk-shaped (14-mm diameter × 4-mm thick) and 30 rectangular (65 × 10 × 3.3 mm(3) ) heat-polymerized acrylic resin specimens were divided into three groups according to the concentration of MUPB (w/w): (A) 0%, (B) 0.3%, (C) 0.6%. Hardness was assessed by a hardness tester equipped with a Vickers diamond penetrator. Flexural strength and surface roughness were tested on a universal testing machine and a surface roughness tester, respectively. Color alterations (ΔE) were measured by a portable spectrophotometer after 12 and 36 days of immersion in water, coffee, or wine. Variables were analyzed by ANOVA/Tukey HSD test (α= 0.05).
  
  
  RESULTS
  The following mean results (±SD) were obtained for hardness (A: 15.6 ± 0.6, B: 14.6 ± 1.7, C: 14.8 ± 0.8 VHN; ANOVA: p= 0.061), flexural strength (A: 111 ± 17, B: 105 ± 12, C: 88 ± 12 MPa; ANOVA: p= 0.008), and roughness (A: 0.20 ± 0.11, B: 0.20 ± 0.11, C: 0.24 ± 0.08 μm; ANOVA: p= 0.829). Color changes of immersed specimens were significantly influenced by solutions and time (A: 9.1 ± 3.1, B: 14.8 ± 7.5, C: 13.3 ± 6.1 ΔE; ANOVA: p < 0.05).
  
  
  CONCLUSIONS
  The incorporation of MUPB affects the mechanical properties of a denture base acrylic resin; however, the only significant change was observed for flexural strength and may not be critical. Color changes were slightly higher when resin containing MUPB was immersed in wine for a prolonged time; however, the difference has debatable clinical relevance.
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Rômulo Rocha
authors.initials: RR
authors.lastname: Regis
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Zanini
authors.forename: Maria P
authors.initials: MP
authors.lastname: Della Vecchia
authors.forename: Cláudia Helena
authors.initials: CH
authors.lastname: Silva-Lovato
authors.forename: Helena Freitas
authors.initials: HF
authors.lastname: Oliveira Paranhos
authors.forename: Raphael Freitas
authors.initials: RF
authors.lastname: de Souza
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000890:Anti-Infective Agents / Q000737:chemistry*; D055598:Chemical Phenomena; D003069:Coffee; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003819:Denture Bases; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011726:Pyridinium Compounds / Q000737:chemistry*; D013053:Spectrophotometry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry; D014920:Wine
chemical_list: D000180:Acrylic Resins; D000890:Anti-Infective Agents; D003069:Coffee; D003764:Dental Materials; D008689:Methacrylates; D011726:Pyridinium Compounds; D014867:Water; C060243:1-undecylpyridinium