Walker Mary P, Ries Dave, Borello Blake
Departments of Restorative Dentistry and Oral Biology, University of Missouri-Kansas City School of Dentistry, Kansas City, Missouri 64108, USA.
Int J Oral Maxillofac Implants. 2008 Jul-Aug;23(4):669-74.
The aim of this study was to compare implant cast accuracy as a function of impression technique, closed tray impressions using indirect, metal impression copings at the implant level or direct, plastic impression caps at the abutment level, and impression material viscosity combinations.
A stainless steel master model with three implant replicas was utilized to produce Type IV stone casts. Master model impressions were made using closed trays at the implant level with screw-on metal impression copings (indirect/implant level) or at the abutment level with snap-on plastic impression caps (direct/abutment level). With both techniques, either medium-body or heavy-body polyether impression material was syringed around the implant impression coping or abutment impression cap with medium body material in a custom tray. Twenty casts were produced with 5 casts in each test group. A measuring microscope (0.001 mm accuracy) was used to measure cast inter-implant or inter-abutment distances. Cast accuracy was calculated based on the percent difference of the measurements as compared to the master model.
A repeated measures 2-factor ANOVA (alpha = .05) indicated no significant difference in cast accuracy as a function of impression viscosity. However, cast accuracy was significantly different between casts made with indirect/implant level versus direct/abutment level impressions. With the plastic impression caps, the cast inter-abutment distances were larger than the master model, with mean percent differences of 0.19% to 0.24% across the 3 measurement sites. In contrast, with the metal impression coping impressions, the cast inter-implant distances were almost equal to or slightly smaller than the master model, with mean percent differences -0.06% to 0.02%.
Impression material viscosity does not appear to be a critical factor for implant cast accuracy. However, casts made with indirect, metal impression copings might be more accurate than casts made with direct, plastic impression caps. This could be an especially important factor with casts used to fabricate multiple-implant restorations.
本研究旨在比较种植体模型的铸造精度，该精度是印模技术、在种植体水平使用间接金属印模帽的封闭托盘印模或在基台水平使用直接塑料印模帽以及印模材料粘度组合的函数。
使用带有三个种植体复制体的不锈钢母模制作IV型石膏模型。母模印模在种植体水平使用拧上式金属印模帽（间接/种植体水平）或在基台水平使用卡上式塑料印模帽（直接/基台水平）通过封闭托盘制作。对于这两种技术，均将中稠度或高稠度聚醚印模材料用中稠度材料注入定制托盘中种植体印模帽或基台印模帽周围。共制作了20个模型，每个测试组5个模型。使用测量显微镜（精度为0.001毫米）测量模型种植体间或基台间距离。根据测量值与母模的百分比差异计算模型精度。
重复测量双因素方差分析（α = 0.05）表明，模型精度作为印模粘度的函数无显著差异。然而，间接/种植体水平印模与直接/基台水平印模制作的模型之间，模型精度存在显著差异。使用塑料印模帽时，模型基台间距离大于母模，在3个测量部位平均百分比差异为0.19%至0.24%。相比之下，使用金属印模帽印模时，模型种植体间距离几乎等于或略小于母模，平均百分比差异为-0.06%至0.02%。
印模材料粘度似乎不是种植体模型精度的关键因素。然而，使用间接金属印模帽制作的模型可能比使用直接塑料印模帽制作的模型更精确。对于用于制作多颗种植体修复体的模型而言，这可能是一个尤为重要的因素。
