Expansion of contaminated amalgams assessed by photoelastic resin.
OBJECTIVE
Eight amalgam alloys, 6 high-copper and 2 low-copper, were assessed for expansion via photoelastic resin.


METHODS
The photoelastic resin sheet was sectioned into 20 x 25-mm blocks, and two 4 x 8-mm holes were drilled into the resin. The amalgam alloys were hand condensed into the prepared holes. Test conditions for each alloy were (1) uncontaminated, (2) contaminated with 5 microL of Ringer's solution, and (3) contaminated with 5 microL of cell culture medium.


RESULTS
Contaminated high-copper amalgam alloys may exhibit expansion to varying degrees but do not show the classic delayed expansion. One spherical, nonzinc high-copper alloy showed no expansion, whether it was uncontaminated or contaminated, and 3 high-copper alloys with different amounts of zinc (0% to 1%) showed slight expansion when contaminated. One low-copper alloy displayed delayed expansion; within 17 days after initial expansion in the photoelastic resin, it had exceeded the greatest stress observed in any contaminated, high-copper zinc-containing alloy at 3 months.


CONCLUSIONS
Contamination of dental amalgam is to be avoided, but a zinc-containing high-copper amalgam will not exhibit classic delayed expansion even if contaminated.
Osborne
J W
JW
Department of Restorative Dentistry, University of Colorado Health Science Center, Denver 80262, USA. john.osborne@uchsc.edu
D001718:Birefringence; D003300:Copper; D003470:Culture Media; D003723:Dental Amalgam / Q000737:chemistry*; D003799:Dental Stress Analysis; D004853:Epoxy Resins; D004866:Equipment Contamination; D007552:Isotonic Solutions; D000077331:Ringer's Solution; D018709:Statistics, Nonparametric; D015032:Zinc
D003470:Culture Media; D004853:Epoxy Resins; D007552:Isotonic Solutions; D003300:Copper; D000077331:Ringer's Solution; D003723:Dental Amalgam; D015032:Zinc