title: Measure of microhardness, fracture toughness and flexural strength of N-vinylcaprolactam (NVC)-containing glass-ionomer dental cements.
abstract: OBJECTIVE
  To investigate the effects of N-vinylcaprolactam (NVC)-containing terpolymers on the fracture toughness, microhardness, and flexural strength of conventional glass-ionomer cements (GIC).
  
  
  METHODS
  The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with 8:1:1 (AA:IA:NVC) molar ratio was synthesized by free radical polymerization and characterized using (1)H NMR and FTIR. Experimental GIC samples were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Plane strain fracture toughness (K(Ic)) was measured in accordance with ASTM Standard 399-05. Vickers hardness was determined using a microhardness tester. Flexural strength was measured using samples with dimensions of 2 mm×2 mm×20 mm. For all mechanical property tests, specimens were first conditioned in distilled water at 37°C for 1 day or 1 week. Fracture toughness and flexural strength tests were conducted on a screw-driven universal testing machine using a crosshead speed of 0.5mm/min. Values of mechanical properties for the experimental GIC were compared with the control group (Fuji IX GIC), using one-way ANOVA and the Tukey multiple range test at α=0.05.
  
  
  RESULTS
  The NVC-modified GIC exhibited significantly higher fracture toughness compared to the commercially available Fuji IX GIC, along with higher mean values of flexural strength and Vickers hardness, which were not significantly different.
  
  
  CONCLUSIONS
  It was concluded that NVC-containing polymers are capable of enhancing clinically relevant properties for GICs. This new modified glass-ionomer is a promising restorative dental material.
authors.affiliation: Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA.
authors.forename: Alireza
authors.initials: A
authors.lastname: Moshaverinia
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Winston W L
authors.initials: WW
authors.lastname: Chee
authors.forename: Nima
authors.initials: N
authors.lastname: Rohpour
authors.forename: Sahar
authors.initials: S
authors.lastname: Ansari
authors.forename: Fengyuan
authors.initials: F
authors.lastname: Zheng
authors.forename: Reza H
authors.initials: RH
authors.lastname: Heshmati
authors.forename: Jawwad A
authors.initials: JA
authors.lastname: Darr
authors.forename: Scott R
authors.initials: SR
authors.lastname: Schricker
authors.forename: Ihtesham U
authors.initials: IU
authors.lastname: Rehman
mesh_terms: D002209:Caprolactam / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry; D019245:Compressive Strength; D003799:Dental Stress Analysis; D004548:Elasticity; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D008422:Materials Testing; D018583:Pliability; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D013718:Tensile Strength
chemical_list: D005899:Glass Ionomer Cements; D011108:Polymers; C110713:fuji IX; C086861:poly-N-vinylcaprolactam; D002209:Caprolactam