title: Effects of quaternary ammonium-methacrylates on the mechanical properties of unfilled resins.
abstract: OBJECTIVE
  Adding antimicrobial/anti-MMP quaternary ammonium methacrylates (QAMs) to comonomer blends should not weaken the mechanical properties of dental resins. This work evaluated the degree conversion and mechanical properties of BisGMA/TEGDMA/HEMA (60:30:10) containing 0-15 mass% QAMs A-E (A: 2-acryloxyethyltrimethyl ammonium chloride; B: [3-(methacryloylamino)propyl]trimethylammonium chloride; C: [2-(methacryloxy)ethyl] trimethyl ammonium chloride; D: diallyldimethyl ammonium chloride; E: 2-(methacryloyloxy) ethyltrimethyl ammonium methyl sulfate.
  
  
  METHODS
  Unfilled resins with and without QAM were placed on ATR-FTIR and light-polymerized for 20s in a thin film at 30°C. Unfilled resin beams were casted from square hollow glass tubings. Half of the beams were tested after 3 days of drying (control); the other half were tested wet after 3 days of water storage.
  
  
  RESULTS
  Addition of QAMs in control resins significantly increased conversion 600 s after light termination, with the exception of 5% MAPTAC (p<0.05). Increase of QAM content within a formulation significantly increased conversion. Control beams gave dry Young's moduli of ∼700 MPa. Addition of 5, 10 or 15 mass% QAMs produced significant reductions in dry Young's moduli except for 5% B or C. 15 mass% A, B and C lowered the wet Young's moduli of the resin beams by more than 30%. The ultimate tensile stress (UTS) of control dry resin was 89±11 MPa. Addition of 5-10 mass% QAMs had no adverse effect on the dry UTS. After water storage, the UTS of all resin blends fell significantly (p<0.05), especially when 15 wt% QAMs was added. Control dry beams gave fracture toughness (KIC) values of 0.88±0.1 MPa m(1/2). Wet values were significantly higher at 1.02±0.06 (p<0.05). KIC of dry beams varied from 0.85±0.08 at 5% QAMs to 0.49±0.05 at 15% QAMs. Wet beams gave KIC values of 1.02±0.06 MPa m(1/2) that fell to 0.23±0.01 at 15% QAMs.
  
  
  CONCLUSIONS
  Addition of 10% QAMs increased the degree of conversion of unfilled resins, but lowered wet toughness and UTS; addition of 15% QAMs lowered the mechanical properties of wet resins below acceptable levels.
authors.affiliation: Department of Operative Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hoshika
authors.affiliation: Department of Operative Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nishitani
authors.affiliation: Department of Operative Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshiyama
authors.affiliation: Department of Oral Biology, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA.
authors.forename: William O
authors.initials: WO
authors.lastname: Key
authors.affiliation: Department of Oral Biology, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA.
authors.forename: William
authors.initials: W
authors.lastname: Brantley
authors.affiliation: Department of Oral Biology, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA.
authors.forename: Kelli A
authors.initials: KA
authors.lastname: Agee
authors.affiliation: Department of Biomedicine, University of Trieste and IGM-CNR, Unit of Bologna, c/o IOR, Bologna, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Breschi
authors.affiliation: Department of Biomedicine, Unit of Dental Sciences and Biomaterials, University of Trieste, Trieste, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Cadenaro
authors.affiliation: Department of Endodontics, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA.
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.affiliation: Department of Oral Biology, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA.
authors.forename: Frederick
authors.initials: F
authors.lastname: Rueggeberg
authors.affiliation: Department of Oral Biology, Georgia Regents University, College of Dental Medicine, Augusta, GA, USA. Electronic address: dpashley@gru.edu.
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
mesh_terms: D003188:Composite Resins; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D000644:Quaternary Ammonium Compounds
keywords: Dry-testing; Fracture toughness; Percent-conversion; Quaternary ammonium methacrylates; TPO; Ultimate tensile strength; Wet-testing; Young's modulus