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Volumetric contraction in some tooth-coloured restorative materials
1Faculty of Dentistry, The University of Sydney, New South Wales, Australia. bryantr@dental.wsahs.nsw.gov.au
Background:
Much of the concern about the setting contraction of tooth-coloured restorative materials has been focused on the composite resins. This study investigated setting contraction of a range of glassionomer materials and included, for comparison, products from other groups of restorative materials.
Methods:
A deflecting disk method was used to determine the volumetric contraction of three conventional (non-light cured) glass-ionomer cements (GICs), two restorative, one "lining" consistency and one adhesive/lining consistency resin-modified glass-ionomers (RMGIs), two resin adhesives, three restorative composite resins and two compomers. The influence of powder:liquid ratio on two hand-mixed materials was also examined.
Results:
The light-cured materials (including RMGIs) showed substantially greater per cent contraction at 5 minutes than did the three conventional GICs (not light cured) and a substantially greater proportion of the 30-minute contraction had occurred at 5 minutes for these light-cured materials. Their further contraction after 1 hour was generally less than 5 per cent of the 1 hour contraction.
Conclusion:
Although the conventional GICs contract more slowly in the first 5 minutes, by 30 minutes the current restorative GICs and RMGIs exhibit a volumetric setting contraction that is comparable with the composite resins and compomers and is generally in the range of 2-3 per cent.
