Dugal Ramandeep, Railkar Bhargavi, Musani Smita
Department of Prosthodontics, M A Rangoonwala College of Dental Sciences & Research Centre, Pune, Maharashtra, India.
J Int Oral Health. 2013 Oct;5(5):85-94. Epub 2013 Oct 26.
Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. The purpose of this in vitro study was to compare the dimensional accuracy of the casts obtained from one step double mix, two step double mix polyvinyl siloxane putty- wash impression techniques using three different spacer thicknesses (0.5mm, 1mm and 1.5mm), in order to determine the impression technique that displays the maximum linear dimensional accuracy.
MATERIALS & METHODS: A Mild steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Express, 3M ESPE) and customarily made perforated metal trays. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 0.5-mm, 1mm and 1.5mm-thick metal-prefabricated spacer caps. The accuracy of the 4 different impression techniques was assessed by measuring 7 dimensions (intra- and inter abutment) (20-μm accuracy) on stone casts poured from the impressions of the mild steel model. The data were analyzed by one sample't' test.
The stone dies obtained with all the techniques had significantly larger or smaller dimensions as compared to those of the mild steel model (P<0.05). The order for highest to lowest deviation from the mild steel model was: single step putty/light body, 2-step putty/light body with 0.5mm spacer thickness, 2-step putty/light body1.5mm spacer thickness, and 2-step putty/light body with 1mm spacer thickness. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their standard deviations from the master model (P<0.05), were noted.
The 2-step putty/light-body impression technique with 1mm spacer thickness was most dimensionally accurate impression methods in terms of resultant casts. How to cite this article: Dugal R, Railkar B, Musani S. Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. J Int Oral Health 2013;5(5):85-94.
制取印模时的尺寸精度对于固定义齿修复治疗的质量至关重要，而印模技术是影响这一精度的关键因素。本体外研究的目的是比较采用三种不同间隔厚度（0.5毫米、1毫米和1.5毫米）的一步双混法、两步双混法聚醚橡胶印模膏-冲洗式印模技术所获得模型的尺寸精度，以确定能展现最大线性尺寸精度的印模技术。
制作一个带有2个基牙预备体的软钢模型，每种技术制取印模15次。所有印模均采用加成型硅橡胶印模材料（Express，3M ESPE）和定制的带孔金属托盘制取。一步法印模膏/轻体印模同时使用印模膏和轻体材料制取。两步法印模膏/轻体印模采用厚度为0.5毫米、1毫米和1.5毫米的金属预制间隔帽制取。通过测量从软钢模型印模灌注的石膏模型上的7个尺寸（基牙内和基牙间）（精度为20微米）来评估4种不同印模技术的精度。数据采用单样本t检验进行分析。
与软钢模型相比，所有技术所获得的石膏代型尺寸均显著偏大或偏小（P<0.05）。与软钢模型偏差从高到低的顺序为：一步法印模膏/轻体，两步法印模膏/轻体（间隔厚度0.5毫米），两步法印模膏/轻体（间隔厚度1.5毫米），两步法印模膏/轻体（间隔厚度1毫米）。所有组之间在石膏代型的绝对尺寸及其与母模的标准偏差方面均存在显著差异（P<0.05）。
就最终模型而言，间隔厚度为1毫米的两步法印模膏/轻体印模技术是尺寸精度最高的印模方法。如何引用本文：Dugal R, Railkar B, Musani S.制取印模时的尺寸精度对于固定义齿修复治疗的质量至关重要，而印模技术是影响这一精度的关键因素。《国际口腔健康杂志》2013；5(5):85 - 94。
