Persson Anna S K, Odén Agneta, Andersson Matts, Sandborgh-Englund Gunilla
Institute of Odontology, Karolinska Institutet, P.O. Box 4064, SE-141 04 Huddinge, Sweden.
Dent Mater. 2009 Jul;25(7):929-36. doi: 10.1016/j.dental.2009.01.100. Epub 2009 Mar 4.
To compare the exactness of simulated clinical impressions and stone replicas of crown preparations, using digitization and virtual three-dimensional analysis.
Three master dies (mandibular incisor, canine and molar) were prepared for full crowns, mounted in full dental arches in a plane line articulator. Eight impressions were taken using an experimental monophase vinyl polysiloxane-based material. 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) and the impressions in a laser scanner (D250, 3Shape A/S), to create virtual models. The resulting point-clouds from the digitization of the master dies were used as CAD-Reference-Models (CRM). Discrepancies between the points in the pointclouds and the corresponding CRM were measured by a matching-software (CopyCAD 6.504 SP2; Delcam Plc). The distribution of the discrepancies was analyzed and depicted on color-difference maps.
The discrepancies of the digitized impressions and the stone replicas compared to the CRM were of similar size with a mean+/-SD within 40microm, with the exception of two of the digitized molar impressions. The precision of the digitized impressions and stone replicas did not differ significantly (F=4.2; p=0.053). However, the shape affected the digitization (F=5.4; p=0.013) and the interaction effect of shape and digitization source (impression or stone replica) was pronounced (F=28; p<0.0001). The reliability was high for both digitization methods, evaluated by repeated digitizations.
The exactness of the digitized impressions varied with shape. Both impressions and stone replicas can be digitized repeatedly with a high reliability.
运用数字化和虚拟三维分析，比较全冠预备体模拟临床印模与石膏模型的精确性。
制备三个用于全冠修复的主模型（下颌切牙、尖牙和磨牙），安装在平面架的全牙弓上。使用一种基于实验性单相乙烯基聚硅氧烷的材料制取八个印模。用IV型石膏（Vel-Mix Stone； Kerr公司）灌注石膏模型。主模型和石膏模型在接触式探针扫描仪（Procera Forte；诺贝尔生物保健公司）中进行数字化处理，印模则在激光扫描仪（D250，3Shape A/S公司）中进行数字化处理，以创建虚拟模型。主模型数字化后生成的点云用作CAD参考模型（CRM）。通过匹配软件（CopyCAD 6.504 SP2；Delcam Plc公司）测量点云中的点与相应CRM之间的差异。分析差异分布并在色差图上进行描绘。
与CRM相比，数字化印模和石膏模型的差异大小相似，平均±标准差在40微米以内，但有两个数字化磨牙印模除外。数字化印模和石膏模型的精度差异不显著（F = 4.2；p = 0.053）。然而，外形影响数字化（F = 5.4；p = 0.013），外形与数字化来源（印模或石膏模型）的交互作用显著（F = 28；p < 0.0001）。通过重复数字化评估，两种数字化方法的可靠性都很高。
数字化印模的精确性随外形而异。印模和石膏模型均可反复进行数字化处理，且可靠性高。
