Persson Anna S K, Andersson Matts, Odén Agneta, Sandborgh-Englund Gunilla
Institute of Odontology, Karolinska Institutet, Huddinge, Sweden.
Dent Mater. 2008 Aug;24(8):1123-30. doi: 10.1016/j.dental.2008.01.008. Epub 2008 Mar 11.
To determine the reproducibility of digitized dental stone replicas compared to the master model and the reliability of the computer aided analysis.
Four master dies, prepared for complete crowns were fabricated in presintered yttria-stabilized tetragonal zirconia (Y-TZP). Eight vinyl polysiloxane impressions (PROVIL novo; Heraeus Kulzer) were taken of each die and stone replicas were poured in type IV stone (Vel-Mix Stone; Kerr). The master dies and the stone replicas were digitized in a touch-probe scanner (Procera Forte; Nobel Biocare AB), to create triangulated surface-models. The point-cloud from the first of the repeated digitizations of each master die was used as CAD-reference-models (CRM). Discrepancies between the points in the triangulated surface-models and the corresponding CRM were measured by a matching-software (CopyCAD 6.504 SP2; Delcam Plc). The distribution of the discrepancies was analyzed and presented in color-difference-maps.
The precision of the measuring method, presented as the repeatability coefficient, ranged between 7 and 16 microm (entire surface), whereas the analysis of the stone replicas revealed a precision (repeatability coefficient) ranging from 19 to 26 microm. The accuracy of the replica to master (the mean discrepancy) ranged from 0.5 to 2.0 microm (95% confidence interval 1.5-2.9 microm).
The greatest precision of the measurement was seen in the jacket surface of the die. The size of the stone replicas varied and the repeatability coefficient was on average 15 microm (2-25 microm) greater for the replica-to-master alignment than the repeated digitizations of the master.
确定数字化牙科石膏模型相对于原始模型的可重复性以及计算机辅助分析的可靠性。
用预烧结的钇稳定四方氧化锆（Y-TZP）制作四个用于全冠修复的原始代型。对每个代型取八副乙烯基聚硅氧烷印模（PROVIL novo；贺利氏古莎公司），并灌注IV型石膏（Vel-Mix Stone； Kerr公司）制作石膏模型。使用接触式探针扫描仪（Procera Forte；诺贝尔生物保健公司）对原始代型和石膏模型进行数字化处理，以创建三角化表面模型。将每个原始代型首次重复数字化得到的点云用作计算机辅助设计参考模型（CRM）。通过匹配软件（CopyCAD 6.504 SP2； Delcam Plc公司）测量三角化表面模型中的点与相应CRM之间的差异。分析差异的分布情况并以色差图的形式呈现。
测量方法的精度以重复性系数表示，在整个表面上范围为7至16微米，而对石膏模型的分析显示精度（重复性系数）范围为19至26微米。模型与原始代型的准确性（平均差异）范围为0.5至2.0微米（95%置信区间1.5 - 2.9微米）。
在代型的冠套表面观察到测量的最大精度。石膏模型的尺寸各不相同，模型与原始代型对齐的重复性系数平均比对原始代型的重复数字化大15微米（2 - 25微米）。
