Vitti Rafael Pino, da Silva Marcos Aurélio Bomfim, Consani Rafael Leonardo Xediek, Sinhoreti Mário Alexandre Coelho
Department of Restorative Dentistry, Piracicaba School of Dentistry, University of Campinas, PiracicabaSP, Brazil.
Department of Restorative Dentistry and Dental Materials, School of Dentistry, Federal University of Alagoas, MaceióAL, Brazil.
Braz Dent J. 2013 Sep-Oct;24(5):498-502. doi: 10.1590/0103-6440201302334.
The aim of this study was to measure and compare the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two condensation silicones, two addition silicones and three impression techniques (1-step putty/light-body, 2-step putty/light-body and monophase technique). A partially edentulous standard stainless steel mandibular arch cast was obtained with reference points on the permanent mandibular right and left canines, and permanent mandibular right and left second molars. The anteroposterior distances (between the mandibular left canine and second molar and between the mandibular right canine and second molar) and transverse distances (between the mandibular left and right canines and between the mandibular left and right second molars) of stainless steel cast were measured by a microscope at 30× magnification and 0.5 µm accuracy. All impressions were made with condensation or addition silicones. The 1- and 2-step putty/light-body impressions were accomplished with putty and light-body materials and the monophase impressions with light-body material only. After the impression procedures, accuracy of each material and technique was assessed measuring the stone casts poured (n=5) from the impressions, by the same microscope. The differences between the values of stone cast and stainless steel cast were calculated, presented as percentages and analyzed statistically by two-way ANOVA and the means compared by Tukey's test (α=0.05). All distances measured on stone casts showed altered dimensions with significantly negative linear changes (shrinkage) as compared to those of the stainless steel cast. The stone casts made from the addition silicones were dimensionally more accurate. No differences were found among the impression techniques.
本研究的目的是测量并比较由两种缩合型硅橡胶、两种加成型硅橡胶以及三种印模技术（一步法双重印模、两步法双重印模和单相印模技术）制作的部分无牙下颌牙弓石膏模型的尺寸精度。通过在永久性下颌左右尖牙以及永久性下颌左右第二磨牙上设置参考点，获得了一个部分无牙的标准不锈钢下颌牙弓模型。使用显微镜在30倍放大倍率和0.5 µm精度下测量不锈钢模型的前后距离（下颌左尖牙与第二磨牙之间以及下颌右尖牙与第二磨牙之间）和横向距离（下颌左右尖牙之间以及下颌左右第二磨牙之间）。所有印模均使用缩合型或加成型硅橡胶制作。一步法和两步法双重印模使用了重体和轻体材料，单相印模仅使用轻体材料。在印模操作完成后，使用同一台显微镜测量从印模灌注的石膏模型（n = 5），评估每种材料和技术的精度。计算石膏模型与不锈钢模型数值之间的差异，以百分比表示，并通过双向方差分析进行统计分析，均值比较采用Tukey检验（α = 0.05）。与不锈钢模型相比，在石膏模型上测量的所有距离均显示尺寸改变，呈显著的负线性变化（收缩）。由加成型硅橡胶制作的石膏模型尺寸精度更高。在印模技术之间未发现差异。
