Ortorp Anders, Jemt Torsten, Bäck Tomas
The Brånemark Clinic, Göteborg, Sweden.
Clin Implant Dent Relat Res. 2005;7(1):43-50. doi: 10.1111/j.1708-8208.2005.tb00046.x.
The development of digitized techniques for manufacturing implant frameworks has made possible alternative "impression" techniques for recording implant positions.
The objective of the present study was to test the precision and accuracy of a three-dimensional photogrammetric technique to record implant positions in vitro and to compare casts made with this technique with conventional casts fabricated with two conventional impression techniques.
Twenty casts were fabricated from 10 polyether (Impregum, ESPE Dental AG, Seefeld, Germany) impressions and 10 plaster (Kühns Abdrucksgips, Ernst Hirnischs GmbH, Goslar, Germany) impressions of one master model. The casts were measured in a coordinate measuring machine (Zeiss Prismo VAST, Oberkochen, Germany) and compared with the master model. Six separate three-dimensional photographs of the master model were taken with a special camera. After the photographs were measured with an analytic plotter, results were analyzed and compared to the coordinates of the original model and casts.
A systematic pattern of distortion in the x-axis was found for the two impression techniques. Expansion of the implant arch at the terminal implants (p < .01) averaged 22 microm and 94 microm on photographs and plaster casts, respectively. Polyether casts contracted an average of 52 microm when compared with the master (p < .01). In absolute figures, photogrammetry and the polyether technique reproduced the x-axis and three-dimensional parameters more accurately than the plaster technique did when cylinder center point distortion was compared (p < .05 to p < .001). However, angular cylinder distortion in absolute figures was greater with the photographic technique than with either of the impression techniques (p < .05-p < .001).
Photogrammetry is a valid option for recording implant positions and has a precision comparable to that of conventional impression techniques. At present, however, it is limited to framework fabrication techniques that are based on digital platforms.
用于制造种植体支架的数字化技术的发展使得记录种植体位置的替代“印模”技术成为可能。
本研究的目的是测试一种三维摄影测量技术在体外记录种植体位置的精度和准确性，并将用该技术制作的模型与用两种传统印模技术制作的传统模型进行比较。
从一个主模型的10个聚醚（Impregum，ESPE Dental AG，德国塞费尔德）印模和10个石膏（Kühns Abdrucksgips，Ernst Hirnischs GmbH，德国戈斯拉尔）印模制作20个模型。在坐标测量机（蔡司Prismo VAST，德国奥伯科亨）中测量模型，并与主模型进行比较。用一台特殊相机拍摄主模型的六张独立的三维照片。在用解析绘图仪测量照片后，分析结果并与原始模型和模型的坐标进行比较。
两种印模技术在x轴上均发现了系统性的变形模式。在照片和石膏模型上，末端种植体处种植体弓的扩展（p <.01）分别平均为22微米和94微米。与主模型相比，聚醚模型平均收缩52微米（p <.01）。在比较圆柱体中心点变形时，就绝对值而言，摄影测量法和聚醚技术在x轴和三维参数方面比石膏技术更准确地再现（p <.05至p <.001）。然而，就绝对值而言，摄影技术的圆柱体角度变形比任何一种印模技术都大（p <.05 - p <.001）。
摄影测量法是记录种植体位置的一种有效选择，其精度与传统印模技术相当。然而，目前它仅限于基于数字平台的支架制造技术。
