title: Effect of treated filler loading on the photopolymerization inhibition and shrinkage of a dimethacrylate matrix.
abstract: This study shows how treated filler loading influences the photopolymerization of a dimethacrylate comonomer mixture, regarding, in particular, shrinkage and inhibition under atmospheric oxygen, present in oral environment. Bis-GMA/TEGDMA (75/25 wt.%) resins were loaded with hybrid filler (Ba aluminosilicate glass and pyrogenic silica), treated with gamma-methacryloxy(propyl)trimethoxysilane, at 0-50 wt.% and light cured over a total of 30 s (45 mW/cm2). Degree of double-bond conversion (DC), obtained using FTIR, decreased with filler content. 1H MAS spectra (293-340 K) and STRAFI images (293 K) were obtained as a function of irradiation time and filler concentration. 1H signals of unreacted methacrylate groups were more intense for higher loaded resins and resonances from -CH2SiO2(OH) (T2) and -CH2SiO3- (T3) units, also observed by 29Si NMR, were resolved and suggest the presence of T2-resin bonds. 1D images show a reduction on polymerization contraction and reaction inhibition at the composite resin surface with filler loading. 2D resin images present a highly mobile surface layer, hence with lower DC.
authors.affiliation: Departamento de Engenharia de Materiais/IST, Univ. Técnica de Lisboa, Av.Rovisco Pais 1, Lisboa, 1049-001, Portugal. Teresa.Nunes@ist.utl.pt
authors.forename: T G
authors.initials: TG
authors.lastname: Nunes
authors.forename: S G
authors.initials: SG
authors.lastname: Pereira
authors.forename: S
authors.initials: S
authors.lastname: Kalachandra
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D008027:Light; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011109:Polymethacrylic Acids; D012821:Silanes; C020946:triethylene glycol dimethacrylate; C017492:methacryloxypropyltrimethoxysilane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D010100:Oxygen