title: Surface properties and bond strength measurements of N-vinylcaprolactam (NVC)-containing glass-ionomer cements.
abstract: BACKGROUND
  N-vinylcaprolactam (NVC)-containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical characteristics of these types of modified glass ionomers, especially their surface properties. Understanding the surface characteristics and behavior of glass ionomers is important for understanding their clinical behavior and predictability as dental restorative materials.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effect of NVC-containing terpolymers on the surface properties and bond strength to dentin of GIC (glass-ionomer cement), and to evaluate the effect of NVC-containing terpolymer as a dentin conditioner.
  
  
  METHODS
  The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with a molar ratio of 8:1:1 (AA:IA:NVC) was synthesized by free radical polymerization and characterized using nuclear magnetic resonance ((1)H-NMR) and Fourier transform infrared spectroscopy (FTIR). The synthesized terpolymer was used in glass-ionomer cement formulations (Fuji IX GP). Ten disc-shaped specimens (12 × 1 mm) were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces were also determined. The effect of NVC-modified polyacid on the bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to t test and 2-way ANOVA (α=.05).
  
  
  RESULTS
  NVC-modified glass-ionomer cements showed significantly (P<.05) lower contact angles (46 degrees) and higher work of adhesion (W(A)=60.33 erg/cm(2)) in comparison to commercially available Fuji IX GP (57 degrees and W(A)=53.01 erg/cm(2)). The wettability of dentin surfaces conditioned with NVC-containing terpolymer was significantly higher (P<.05) (22 degrees, WA=73.77 erg/cm(2)) than dentin conditioned with GC dentin conditioner (29 degrees, W(A)=70.52 erg/cm(2)). The experimental cement also showed significantly higher values for shear bond strength to dentin (8.7 ±0.15 MPa after 1 month) when compared to the control group (8.4 ±0.13 MPa after 1 month).
  
  
  CONCLUSIONS
  NVC-containing terpolymers may enhance the surface properties of GICs and increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are better dentin conditioners than a commercially available dentin conditioner (GC dentin conditioner).
authors.affiliation: Advanced Prosthodontics, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90089, USA. moshaver@usc.edu
authors.forename: Alireza
authors.initials: A
authors.lastname: Moshaverinia
authors.forename: Winston W
authors.initials: WW
authors.lastname: Chee
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Scott R
authors.initials: SR
authors.lastname: Schricker
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000268:Adhesiveness; D002209:Caprolactam / Q000737:chemistry*; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008970:Molecular Weight; D058105:Polymerization; D011108:Polymers / Q000737:chemistry; D033081:Shear Strength; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014753:Vinyl Compounds / Q000737:chemistry*; D014783:Viscosity; D017155:Wettability
chemical_list: D000180:Acrylic Resins; D017220:Dentin-Bonding Agents; D005609:Free Radicals; C439808:Fuji IX GP Fast; D005899:Glass Ionomer Cements; D011108:Polymers; D014753:Vinyl Compounds; C008219:itaconic-acrylic acid copolymer; C006903:carbopol 940; D002209:Caprolactam