title: Free radical entrapment and crystallinity of resin composites after accelerated aging as a function of the expiration date.
abstract: This study evaluated the spin concentration and the crystallinity in different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to the factors: composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The magnetic properties of the composites were characterized using Electron Paramagnetic Resonance (EPR) and the concentration of spins (number of spins/mass) was calculated. The crystallinity of the composites tested was characterized with X-ray diffraction (XRD). Filtek P60 and Filtek Z250 presented similarities in terms of spin concentration and crystallinity, irrespective of the material condition. The aging protocol influenced the composite Filtek Z350XT that exhibited a significant increase in the spin concentration. Besides, lower intensity peaks of the organic matrix and amorphous silica were also observed for both aged and expired Filtek Z350XT. Although a significant lower spin concentration was observed for the silorane composite in comparison to that of the methacrylates, a decrease in the relative intensity of peaks of the amorphous region related to the organic components in the diffractograms was observed. The material conditions tested influence the crystallinity and the magnetic properties of the composites evaluated.
authors.affiliation: Biomaterials Research Group, School of Dentistry, Anhanguera University of São Paulo - UNIAN SP, São Paulo, SP, Brazil.
authors.forename: Paulo Henrique Perlatti
authors.initials: PH
authors.lastname: D'Alpino
authors.affiliation: DF-FC, UNESP - Universidade Estadual Paulista, POSMAT - Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Bauru, SP, Brazil.
authors.forename: Marcos Vinícius Gonçalves
authors.initials: MV
authors.lastname: Vismara
authors.affiliation: Biomaterials Research Group, School of Dentistry, Anhanguera University of São Paulo - UNIAN SP, São Paulo, SP, Brazil.
authors.forename: Alejandra Hortencia Miranda
authors.initials: AH
authors.lastname: González
authors.affiliation: DF-FC, UNESP - Universidade Estadual Paulista, POSMAT - Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Bauru, SP, Brazil. Electronic address: graeff@fc.unesp.br.
authors.forename: Carlos Frederico de Oliveira
authors.initials: CF
authors.lastname: Graeff
mesh_terms: D000465:Algorithms; D003188:Composite Resins / Q000032:analysis* / Q000737:chemistry*; D003198:Computer Simulation; D004355:Drug Stability; D005609:Free Radicals / Q000032:analysis* / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods*; D008956:Models, Chemical; D008968:Molecular Conformation; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D005609:Free Radicals
keywords: Aging; Composite resins; EPR; Methacrylate; Silorane; Storage temperature; X-ray diffraction