Potran Michal, Štrbac Branko, Puškar Tatjana, Hadžistević Miodrag, Hodolič Janko, Trifković Branka
Vojnosanit Pregl. 2016 Oct;73(10):895-903. doi: 10.2298/VSP150105089P.
BACKGROUND/AIM: Dental impressions present a negative imprint of intraoral tissues of a patient which is, by pouring in gypsum, transferred extraorally on the working cast. Casting an accurate and precise working cast presents the first and very important step, since each of the following stages contributes to the overall error of the production process, which can lead to inadequately fitting dental restorations. The aim of this study was to promote and test a new model and technique for in vitro evaluation of the dental impression accuracy, as well as to asses the dimensional stability of impression material depending on the material bulk, and its effect on the accuracy of working casts.
Impressions were made by the monophasic technique using the experimental master model. Custom trays with spacing of 1, 2 and 3 mm were constructed by rapid prototyping. The overall of 10 impressions were made with each custom tray. Working casts were made with gypsum type IV. Measurement of working casts was done 24 h later using a co-ordinate measuring machine.
The obtained results show that the working casts of all the three custom trays were in most cases significantly different in the transversal and sagittal planes in relation to the master model. The height of abutments was mainly unaffected. The degree of convergence showed certain significance in all the three custom trays, most pronounced in the tray with 3 mm spacing.
The impression material bulk of 1–3 mm could provide accurate working casts when using the monophasic impression technique. The increase of the distance between abutment teeth influences the accuracy of working casts depending on the material bulk. [Projekat Ministarstva nauke Republike Srbije, br. TR 35020: Research and development of modelling methods and approaches in manufacturing of dental recoveries with the application of modern technologies and computer aided systems]
背景/目的：牙印模呈现患者口腔内组织的阴模，通过灌注石膏，将其在口外转移到工作模型上。制作精确准确的工作模型是第一步且非常重要，因为后续每个阶段都会导致制作过程的整体误差，进而可能导致牙修复体贴合不佳。本研究的目的是推广并测试一种用于体外评估牙印模准确性的新模型和技术，以及评估印模材料的尺寸稳定性（取决于材料厚度）及其对工作模型准确性的影响。
使用实验性主模型通过单相技术制取印模。通过快速成型制作间距为1、2和3毫米的定制托盘。每个定制托盘制作总共10个印模。使用IV型石膏制作工作模型。24小时后使用坐标测量机对工作模型进行测量。
所得结果表明，所有三个定制托盘的工作模型在横向和矢状面与主模型相比，在大多数情况下均存在显著差异。基牙高度主要未受影响。在所有三个定制托盘中，聚合度均显示出一定的显著性，在间距为3毫米的托盘中最为明显。
当使用单相印模技术时，1 - 3毫米的印模材料厚度可提供准确的工作模型。基牙间距离的增加会根据材料厚度影响工作模型的准确性。[塞尔维亚共和国科学部项目，编号TR 35020：应用现代技术和计算机辅助系统进行牙修复体制造的建模方法和途径的研究与开发]
