Setting Reaction of Polyacid Modified Composite Resins or Compomers

J.L.R Arrondo*, 1, M.I Collado1, Soler I2, R Triana2, J Ellacuria2
1 Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Spain
2 Departamento de Estomatología, Facultad de Medicina y Odontología, Universidad del País Vasco, Spain

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© Arrondo et al.; Licensee Bentham Open.

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* Address correspondence to this author at the Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU). Bº Sarriena s/n, Leioa, Vizcaya, Spain; Tel: +34 946 012 485; Fax: + 34 946 013 360; E-mail:


The hardening of modified polyacid composite resins (compomers) and glass-ionomers have been studied using infrared spectroscopy. The acid-base reaction in Ketac-fil, a glass ionomer, was followed by the ratio between the COOH band located around 1715 cm-1 and that corresponding to COO- located around 1570 cm-1. The combination of infrared analysis and band narrowing treatments enable us to propose in the glass-ionomer two maturation steps. First, a very rapid equilibrium acid-base related, and second the cross-linking of polycarboxylate with the metal ions present in the cement. In compomers, a new reaction has been described involving polymerization induced by free radicals besides the two steps associated with the acid-base reaction. Using infrared spectroscopy and band narrowing techniques, it is shown that water is essential to complete the hardening process but no acid-base reaction is produced since the COO- band does not appear. The reaction associated with free radicals could be described as a polymerization of methacrylate monomers together with an aqueous dilution of the filling particles releasing different metal cations that would chelate with the polymer molecules to form a macromolecular structure.