Thongthammachat Sudsukh, Moore B Keith, Barco M Thomas, Hovijitra Suteera, Brown David T, Andres Carl J
Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis, IN 46202, USA.
J Prosthodont. 2002 Jun;11(2):98-108.
This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times.
Two types of stock trays (plastic stock tray, perforated metal stock tray) and 4 types of custom tray materials (autopolymerizing acrylic resin, thermoplastic resin, and 2 types of light-polymerized acrylic resins) were used with 2 types of impression materials (addition polymerizing silicone and polyether), to make impressions of a metal master model. Each tray and impression material was used to make 5 impressions. Casts were made by multiple pourings at 30 minutes, 6 hours, 24 hours, and 30 days after impression making. Using a measuring microscope, 12 distances were calculated based on measurements of 8 reference points. The absolute value of the difference of each measurement was calculated, as was the corresponding measurement on the master model. A Bayesian model using a simple noninformative prior was used to analyze these data.
Statistical differences within 6 microm were found only with thermoplastic resin tray material for addition silicone, and for thermoplastic resin tray material and 1 type of light-polymerized acrylic resin for polyether. Neither stock trays nor custom trays contributed to the differences in accuracy of the casts. All deviations in casts made with silicone impression material were within a clinically acceptable range. For the polyether, distortions occurred that were clinically unacceptable. Impressions made from polyether distorted over time. Silicone impression material has dimensional stability up to 30 days.
Accurate casts can be made with either stock trays or custom trays. An impression made from polyether should be poured only once and within 24 hours after impression making, because of the distortion of the material over time. Silicone impression material has better dimensional stability than polyether. .
本研究评估了不同类型托盘和印模材料制作的牙科模型在不同时间多次灌注对尺寸精度的影响。
使用两种类型的成品托盘（塑料成品托盘、穿孔金属成品托盘）和4种类型的定制托盘材料（自凝丙烯酸树脂、热塑性树脂以及两种光固化丙烯酸树脂），搭配两种印模材料（加成型硅橡胶和聚醚橡胶），对金属母模进行印模制取。每种托盘和印模材料制作5个印模。在制取印模后30分钟、6小时、24小时和30天进行多次灌注制作模型。使用测量显微镜，基于8个参考点的测量计算12个距离。计算每次测量差值的绝对值以及母模上相应的测量值。使用具有简单非信息先验的贝叶斯模型分析这些数据。
仅在加成型硅橡胶的热塑性树脂托盘材料以及聚醚橡胶的热塑性树脂托盘材料和一种光固化丙烯酸树脂中发现6微米以内的统计学差异。成品托盘和定制托盘均未导致模型精度的差异。用硅橡胶印模材料制作的模型所有偏差均在临床可接受范围内。对于聚醚橡胶，出现了临床上不可接受的变形。聚醚橡胶制取的印模随时间发生变形。硅橡胶印模材料在30天内具有尺寸稳定性。
使用成品托盘或定制托盘均可制作出精确的模型。由于聚醚橡胶材料随时间会变形，用其制取的印模应仅在制取后24小时内灌注一次。硅橡胶印模材料比聚醚橡胶具有更好的尺寸稳定性。
