Dimensional changes of resin/ionomer restoratives in aqueous and neutral media

D. C. Watts, B. K. Kisumbi, G. K. Toworfe

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Objectives: The aim was to study dimensional time-dependence of resin/ionomer formulations from 5 min age to one month and to separate out the intrinsic setting shrinkage and hygroscopic expansion effects, by using non-aqueous and aqueous storage media, respectively. Methods: Materials studied included: A: resin-, B: metal- and C: polyphosphonate-modified glass-ionomer cements [GICs]; and controls of D: poly-acid modified composite [compomer]; and E: resin-composite. Separate specimen groups (n = 5) were stored in different storage-media: (i) silicone fluid; (ii) de-ionized water. Experiments were repeated at 23 and 37°C. Volumetric changes of specimens (4 mm diameter × 6 mm height) were obtained via accurate mass measurements (to 10-4 g), using Archimedes principle, with silicone or water also used as the Archimedean fluid. These measurements were made periodically over a 30 day period, post fabrication. Results: In silicone at 23°C, all materials underwent further gradual intrinsic shrinkage (after 5 min from mix). This was highly significant (p <0.05) for the RM-GIC (A). At 37°C, however the RM-GIC expanded, indicating that its cure is temperature-sensitive. In water, at 23 and 37°C, the shrinkage was either partially offset (materials C, D, E), or replaced by appreciable expansions (materials A and B). Differences between RM-GIC (A) and MM-GIC (B) were significant (p <0.05). Significance: The deployment of dual storage media made an important contribution to the separate analysis of the volumetric changes due to the on-going setting chemistry in these systems and the time-dependent effects of an aqueous environment. © 2000 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.
    Original languageEnglish
    Pages (from-to)89-96
    Number of pages7
    JournalDental Materials
    Volume16
    Issue number2
    Publication statusPublished - Mar 2000

    Keywords

    • Compomer
    • Dental materials
    • Dimensional change
    • Glass ionomer
    • Hygroscopic expansion
    • Shrinkage

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