Heshmati Reza H, Nagy William W, Wirth Carl G, Dhuru Virendra B
College of Dentistry, The Ohio State University, Columbus, Ohio, USA.
J Prosthet Dent. 2002 Jul;88(1):26-31.
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.
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.
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 alpha=.05. Planned comparisons between the 2-hour experimental and 2-hour manufacturer expansion values were made at the 95% confidence interval.
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.
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.
美国牙科协会（ADA）规范25指出，改良牙科石膏的最终凝固膨胀测量应在调拌后2小时进行。在一项针对选定的IV型和V型牙科石膏的有限初步研究中，测量结果显示线性膨胀延迟或早期收缩持续至120小时。
本体外研究的目的是测量6种ADA IV型和V型牙科石膏的线性凝固膨胀，比较它们在2小时时相对于ADA规范25的膨胀情况，并描述直至120小时的膨胀变化。
本研究中测试的改良牙科石膏有Die-Keen、Jade Stone、Vel-Mix、ResinRock、Fuji Rock和Silky Rock。按照标准化技术和制造商说明进行调拌。将调拌物倒入电子膨胀测量装置中，连续测量并记录120小时的凝固膨胀值。对收集的数据进行α = 0.05的双向重复测量多因素方差分析。在95%置信区间对2小时实验膨胀值和2小时制造商膨胀值进行计划比较。
所有石膏在120小时时的平均线性膨胀值均高于2小时时。除ResinRock外，所有石膏在96小时时膨胀基本完成。Die-Keen在120小时时表现出最高的总平均凝固膨胀（0.35% ± 0.013%），Silky Rock表现出最低的平均线性膨胀（0.14% ± 0.008%）。多因素方差分析显示石膏和时间之间存在显著交互作用（P <.0001）。除Die-Keen和Jade Stone外，2小时时的平均膨胀值与制造商所述值相当。
在本研究参数范围内，所有测试的牙科石膏在临床条件下凝固时均表现出持续膨胀。不同材料的膨胀量差异显著，22%至71%的膨胀发生在2小时之后。Die-Keen表现出最高的总平均膨胀，但2小时后膨胀量最少；Die-Keen和Silky Rock在72小时后均保持稳定。
