title: Mechanical properties and characteristics of developmental copolymers incorporating catechin or chlorhexidine.
abstract: OBJECTIVE
  This study evaluated catechin and chlorhexidine release from copolymers based on bis-GMA diluted with TEGDMA (R1), propoxylated bis-GMA-CH(3)bis-GMA (R2) or fluorinated bis-GMA-CF(3)bis-GMA (R3). Mechanical properties, degree of conversion, water sorption and solubility were also tested.
  
  
  METHODS
  Experimental comonomers (R1, R2, R3) were prepared combining bis-GMA with the diluents (70/30 mol%). Each comonomer had either catechin or chlorhexidine incorporated in the following ratios: 0, 0.2, 1.0, 2.0 wt%. The degree of conversion (%DC) of resins was evaluated by FT-IR spectrophotometry (n=3). Flexural strength and elastic modulus were tested on a universal testing machine at a crosshead speed of 0.5mm/min (n=6). Resin disks (7 mm in diameter × 2 mm high) were immersed in deionized water and mass changes recorded daily. Spectral measurements were made to follow any changes in optical densities of deionized water in order to examine catechin and chlorhexidine release rates (n=6). After a 28-day period, water sorption and solubility were calculated using appropriate equations (n=6). Data within the tests were evaluated by one- and three-way ANOVA and Tukey-Kramer's test (α=0.05).
  
  
  RESULTS
  Except for R1 with 2.0% drug none of the groups had changes in degree of conversion and water sorption. Solubility increased with increased drug ratios. Changes in flexural strength and elastic modulus were shown to be variable and material-dependent. All resins presented a ∼24 h burst of drug release. Release rates were drug-ratio dependent and significantly higher for chlorhexidine than for catechin.
  
  
  CONCLUSIONS
  Monomer type, %DC, drug ratio and type lead to different interactions between resins and chlorhexidine/catechin drug particles. It should be possible to develop different resins based on clinical needs.
authors.affiliation: Restorative Department, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Smiley
authors.initials: S
authors.lastname: Pallan
authors.forename: Michel Victor
authors.initials: MV
authors.lastname: Furtado Araujo
authors.forename: Renato
authors.initials: R
authors.lastname: Cilli
authors.forename: Anuradha
authors.initials: A
authors.lastname: Prakki
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry*; D002710:Chlorhexidine / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003188:Composite Resins; D011108:Polymers; D017438:Bisphenol A-Glycidyl Methacrylate; D002392:Catechin; D002710:Chlorhexidine