Journal of Dental Research, Vol 75, 1613-1619, Copyright © 1996 by International & American Associations for Dental Research Online Journals

ARTICLES

Early and long-term wear of conventional and resin-modified glass ionomers

A. J. de Gee, R. N. van Duinen, A. Werner and C. L. Davidson
Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam ACTA, The Netherlands.

Various studies have shown that glass ionomers are susceptible to brittle fracture and acid conditions and that they undergo long-term changes in their mechanical properties. Little information is available on how brittleness, acid susceptibility, and long-term changes are reflected in the wear characteristics of glass ionomers. The purpose of this study was to evaluate long-term changes in conventional glass ionomers, metal-reinforced glass ionomers (including a cermet), and (light-curing) resinmodified glass ionomers by wear experiments simulating the wear process in occlusal contact-free areas. The wear tests were conducted periodically over a period of one year. In addition, wear was determined after one year at a pH of 5 or 6, for assessment of acid susceptibility, and at a condition as found in the occlusal contact areas. All materials showed high early-wear rates which decreased significantly during the one-year test period. This long-term process may be related to a slow progression of the acid-base reaction extending over several months. At each stage, the resinmodified glass ionomers wore significantly faster than the acid-base setting glass ionomers. Most of these materials were not affected at a pH of 6.0, while at a pH of 5.0 only the conventional and the metal-reinforced glass ionomers showed increased wear. Direct contacts with the antagonist led to a significant increase in wear in comparison with contact-free wear, probably as a result of sub-surface fatigue phenomena. In view of the unfavorable wear characteristics of the resin-modified glass ionomers and the high early wear of the conventional glass ionomers, including the metal-reinforced glass ionomers, it was concluded that none of these materials can yet be recommended for use in high-stress-bearing situations.

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