title: Poly(acrylic acid) grafted montmorillonite as novel fillers for dental adhesives: synthesis, characterization and properties of the adhesive.
abstract: OBJECTIVE
  This work investigates the graft polymerization of acrylic acid onto nanoclay platelets to be utilized as reinforcing fillers in an experimental dental adhesive. Physical and mechanical properties of the adhesive and its shear bond strength to dentin are studied. The effect of the modification on the stability of the nanoparticle dispersion in the dilute adhesive is also investigated.
  
  
  METHODS
  Poly(acrylic acid) (PAA) was grafted onto the pristine Na-MMT nanoclay (Cloisite(®) Na(+)) through the free radical polymerization of acylic acid in an aqueous media. The resulting PAA-g-nanoclay was characterized using FTIR, TGA and X-ray diffraction (XRD). The modified nanoclays were added to an experimental dental adhesive in different concentrations and the morphology of the nanoclay layers in the photocured adhesive matrix was studied using TEM and XRD. Shear bond strength of the adhesives containing different filler contents was tested on the human premolar teeth. The stability of nanoclay dispersion in the dilute adhesive was also studied using a separation analyzer. The results were then statistically analyzed and compared.
  
  
  RESULTS
  The results confirmed the grafting reaction and revealed a partially exfoliated structure for the PAA-g-nanoclay. Incorporation of 0.2 wt.% of the modified nanoclay into the experimental adhesive provided higher shear bond strength. The dispersion stability of the modified nanoparticles in the dilute adhesive was also enhanced more than 25 times.
  
  
  CONCLUSIONS
  Incorporation of the modified particles as reinforcing fillers into the adhesive resulted in higher mechanical properties. The nanofiller containing bonding agent also showed higher shear bond strength due to the probable interaction of the carboxylic acid functional groups on the surface of the modified particles with hydroxyapatite of dentin.
authors.affiliation: Iran Polymer and Petrochemical Institute (IPPI), Tehran, Iran.
authors.forename: Laleh
authors.initials: L
authors.lastname: Solhi
authors.forename: Mohammad
authors.initials: M
authors.lastname: Atai
authors.forename: Azizollah
authors.initials: A
authors.lastname: Nodehi
authors.forename: Mohammad
authors.initials: M
authors.lastname: Imani
authors.forename: Azadeh
authors.initials: A
authors.lastname: Ghaemi
authors.forename: Kazem
authors.initials: K
authors.lastname: Khosravi
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000268:Adhesiveness; D000704:Analysis of Variance; D001546:Bentonite / Q000737:chemistry*; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents / Q000138:chemical synthesis / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D053758:Nanoparticles; D058105:Polymerization; D019279:Resin Cements / Q000138:chemical synthesis / Q000737:chemistry*; D033081:Shear Strength; D017550:Spectroscopy, Fourier Transform Infrared; D018709:Statistics, Nonparametric; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; D001546:Bentonite; C006903:carbopol 940; D017886:Durapatite