Abstract
Statement of Problem. Specification 25 of the American Dental Association (ADA) states that final setting
expansion measurements of improved dental stone are made 2 hours after mixing. In
a limited pilot study on selected type IV and V dental stones, measurements showed
delayed linear expansion or early contraction continuing up to 120 hours. Purpose. The objectives of this in vitro study were to measure the linear setting expansion
of 6 ADA type IV and V dental stones, to compare their expansion at 2 hours relative
to ADA Specification 25, and to characterize expansion changes up to 120 hours. Material and Methods. The improved dental stones tested in this study were Die-Keen, Jade Stone, Vel-Mix,
ResinRock, Fuji Rock, and Silky Rock. Mixing was performed in accordance with a standardized
technique and the manufacturers' instructions. The mixes were poured into an electronic
expansion-measuring device, and setting expansion values were continuously measured
and recorded for 120 hours. The collected data were subjected to a 2-way repeated-measures
multivariate analysis of variance at α=.05. Planned comparisons between the 2-hour
experimental and 2-hour manufacturer expansion values were made at the 95% confidence
interval. Results. All stones showed higher mean linear expansion values at 120 hours than at 2 hours.
Expansion was essentially complete at 96 hours for all stones except ResinRock. Die-Keen
exhibited the highest total mean setting expansion (0.35% ± 0.013%), and Silky Rock
exhibited the lowest mean linear expansion (0.14% ± 0.008%) at 120 hours. Multivariate
analysis of variance revealed significant interactions between stone and time (P<.0001). Mean expansion values at 2 hours were comparable to those stated by the manufacturer
except for Die-Keen and Jade Stone. Conclusion. Within the parameters of this study, all dental stones tested exhibited continued
expansion while setting under clinical conditions. The amount of expansion varied
significantly among the materials, with 22% to 71% of the expansion occurring after
2 hours. Die-Keen exhibited the highest total mean expansion but had the least amount
of expansion after 2 hours; both Die-Keen and Silky Rock remained stable after 72
hours. (J Prosthet Dent 2002;88:26-31.)
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Article info
Footnotes
☆This research was supported by a 1998 Tylman Research Grant and also received the first place Tylman competition award at the 49th annual scientific session of the American Academy of Fixed Prosthodontics, February 2000, Chicago, Ill. A poster abstract (no. 470) of the pilot research was presented at the 27th annual meeting of the American Association for Dental Research, March 1998, Minneapolis, Minn.
☆☆aAssistant Professor, Department of Restorative, Prosthodontics, and Endodontics, The Ohio State University College of Dentistry.
★bAssociate Professor and Director, Graduate Prosthodontics, Marquette University School of Dentistry.
★★cAdjunct Associate Professor, Division of Prosthodontics, Marquette University School of Dentistry.
♢dAssociate Professor (retired), Division of Dental Biomaterials, Marquette University School of Dentistry.
♢♢Reprint requests to: Dr William W. Nagy, Marquette University School of Dentistry 334, PO Box 1881, Milwaukee, WI 53201-1881, Fax: (414)288-6516, E-mail: [email protected]
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© 2002 Editorial Council of The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
