Rajapur Anand, Dixit Santosh, Hoshing Chetan, Raikar Sonal P
Department of Prosthodontics and Implantology, Vyas Dental College and Hospital, Jodhpur 342001, Rajasthan, India.
J Contemp Dent Pract. 2012 Nov 1;13(6):824-9. doi: 10.5005/jp-journals-10024-1236.
While literature demonstrates that the optimum accuracy is obtained with the custom trays, the use of stock trays for elastomeric impressions appears to be popular in general practice. The aim of the study was to evaluate the effect of thickness of impression material on the dimensional accuracy of impressions made from monophasic polyvinylsiloxane impression material. This study also studies the dimensional stability of the impressions poured at different time intervals.
A metal model simulating two abutment teeth was fabricated along with reference lines inscribed on them. Custom impression trays were fabricated with spacer thickness of 2, 4 and 6 mm. impressions were made using monophasic polyvinyl siloxane impression material. The impressions were poured and stone models were obtained. The dimensional accuracy of the impressions were determined indirectly by measuring the dimensional changes of the recovered stone models. The dimensional stability was also evaluated by pouring the impressions at time intervals of 1 hour, 24 hours and 7 days. The obtained data was statistically analyzed.
The results of the study indicated that the impressions made from 2 and 4 mm tray space produced more accurate stone models when compared to 6 mm tray space. There was no significant deviation in the mesiodistal and buccolingual dimensions when impressions were made using impression trays with 2, 4 and 6 mm tray spacers. There was a significant decrease in interabutment distance (p = 0.001) and height of the abutment (p = 0.024) when impressions were made using impression trays with a tray space of 6 mm. There were no significant differences found among the stone models obtained from 1 hour, 24 hours and 1 week pour times.
The mesiodistal and buccolingual dimensions of the abutments were not affected by the variations in thickness of impression material. There was a decrease in the height of the abutment which was clinically not significant. As the thickness of the impression material increased, the interabutment space decreased, which is a factor of concern when impressions are made for fixed partial dentures.
When monophasic polyvinylsiloxane is used as the impression material, stock trays can be used for making impressions for individual castings.
虽然文献表明定制托盘能获得最佳精度，但在一般临床实践中，使用成品托盘制取弹性印模似乎很普遍。本研究的目的是评估印模材料厚度对单相聚乙烯基硅氧烷印模材料制取印模尺寸精度的影响。本研究还探讨了在不同时间间隔灌注的印模的尺寸稳定性。
制作一个模拟两颗基牙的金属模型，并在其上刻有参考线。制作了间隔厚度为2、4和6mm的定制印模托盘。使用单相聚乙烯基硅氧烷印模材料制取印模。灌注印模并获得石膏模型。通过测量回收石膏模型的尺寸变化间接确定印模的尺寸精度。还通过在1小时、24小时和7天的时间间隔灌注印模来评估尺寸稳定性。对获得的数据进行统计分析。
研究结果表明，与6mm托盘间隔相比，2mm和4mm托盘间隔制取的印模能产生更精确的石膏模型。使用2mm、4mm和6mm托盘间隔的印模托盘制取印模时，近远中尺寸和颊舌尺寸无显著偏差。使用托盘间隔为6mm的印模托盘制取印模时，基牙间距离（p = 0.001）和基牙高度（p = 0.024）显著减小。在1小时、24小时和1周灌注时间获得的石膏模型之间未发现显著差异。
基牙的近远中尺寸和颊舌尺寸不受印模材料厚度变化的影响。基牙高度有所降低，但在临床上不显著。随着印模材料厚度增加，基牙间间隙减小，这在制作固定局部义齿印模时是一个需要关注的因素。
当使用单相聚乙烯基硅氧烷作为印模材料时，成品托盘可用于制取单个铸件的印模。
