title: The effect of polymerization mode on monomer conversion, free radical entrapment, and interaction with hydroxyapatite of commercial self-adhesive cements.
abstract: OBJECTIVE
  This study evaluated the degree of conversion, the free radical entrapment, and the chemical interaction of self-adhesive resin cements mixed with pure hydroxyapatite, as a function of the polymerization activation mode among a variety of commercial self-adhesive cements.
  
  
  METHODS
  Four cements (Embrace WetBond, MaxCem Elite, Bifix SE, and RelyX U200) were mixed, combined with hydroxyapatite, dispensed into molds, and distributed into three groups, according to polymerization protocols: IP (photoactivation for 40s); DP (delayed photoactivation, 10 min self-curing plus 40s light-activated); and CA (chemical activation, no light exposure). Infrared (IR) spectra were obtained and monomer conversion (%) was calculated by comparing the aliphatic-to-aromatic IR absorption peak ratio before and after polymerization (n=10). The free radical entrapment values of the resin cements were characterized using Electron Paramagnetic Resonance (EPR) and the concentration of spins (number of spins/mass) calculated (n=3). Values were compared using two-way ANOVA and Tukey's post-hoc test (α=5%). X-ray diffraction (XRD) characterized the crystallinity of hydroxyapatite as a function of the chemical interactions with the resin cements.
  
  
  RESULTS
  The tested parameters varied as a function of resin cement and polymerization protocol. Embrace WetBond and RelyX U200 demonstrated dependence on photoactivation (immediate or delayed), whereas MaxCem Elite exhibited dependence on the chemical activation mode. Bifix SE presented the best balance based on the parameters analyzed, irrespective of the activation protocol.
  
  
  CONCLUSIONS
  Choice of polymerization protocol affects the degree of conversion, free radical entrapment, and the chemical interaction between hydroxyapatite and self-adhesive resin cement mixtures.
authors.affiliation: Biomaterials Research Group, School of Dentistry, UNIAN/SP-Universidade Anhanguera de São Paulo, São Paulo, SP, Brazil. Electronic address: paulodalpino@yahoo.com.
authors.forename: Paulo Henrique Perlatti
authors.initials: PH
authors.lastname: D'Alpino
authors.affiliation: Biomaterials Research Group, School of Dentistry, UNIAN/SP-Universidade Anhanguera de São Paulo, São Paulo, SP, Brazil.
authors.forename: Marília Santos
authors.initials: MS
authors.lastname: Silva
authors.affiliation: DF-FC, UNESP-Universidade Estadual Paulista, POSMAT-Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Bauru, SP, Brazil.
authors.forename: Marcus Vinícius Gonçalves
authors.initials: MV
authors.lastname: Vismara
authors.affiliation: Biomaterials Research Group, School of Dentistry, UNIAN/SP-Universidade Anhanguera de São Paulo, São Paulo, SP, Brazil.
authors.forename: Vinicius
authors.initials: V
authors.lastname: Di Hipólito
authors.affiliation: Biomaterials Research Group, School of Dentistry, UNIAN/SP-Universidade Anhanguera de São Paulo, São Paulo, SP, Brazil.
authors.forename: Alejandra Hortencia
authors.initials: AH
authors.lastname: Miranda González
authors.affiliation: DF-FC, UNESP-Universidade Estadual Paulista, POSMAT-Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Bauru, SP, Brazil.
authors.forename: Carlos Frederico
authors.initials: CF
authors.lastname: de Oliveira Graeff
mesh_terms: D017886:Durapatite / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D019279:Resin Cements; C095998:Adhesive cement; D017886:Durapatite
keywords: Chemical interaction; EPR; FT-IR; Hydroxyapatite; Self-adhesive resin cement; X-ray diffraction