ANALYSIS OF REACTIONS IN GLASS-POLYALKENOATE RESIN SYSTEMS BY DIELECTRIC IMPEDANCE SPECTROSCOPY/

The principles of impedance spectroscopy are surveyed, with considerat ion of both low and high impedance dielectric biomaterials where the r esponse mechanisms are dominated, respectively, by dipolar relaxation and ionic charge migration. The situation of dental biomaterials is co nsidered with special reference to glass-ionomer polyelectrolyte syste ms and to the impedance changes that may arise in consequence of setti ng mechanisms. Measurements have been conducted using both static and frequency-dependent potentials; where appropriate, with a high impedan ce interface and frequency-response analyser. Data are presented for t he control situation of poly(methyl methacrylate) (PMMA) and for a ser ies of glass-ionomer and resin-modified glass-ionomer biomaterials. It is observed that in the glass-polyalkenoate (G-PA) materials, ionic c onduction and polarization are the dominant factors contributing to th e impedance. This contrasts with the dipolar relaxation characteristic of PMMA. It is concluded that a more extended programme of data-acqui sition is required, where possible from a 'homologous' series of formu lations, to lay a firm foundation of mechanistic interpretation. (C) 1 998 Published by Elsevier Science Ltd. All rights reserved.