Holst Stefan, Karl Matthias, Wichmann Manfred, Matta Ragai-Edward T
University Clinic Erlangen, Dental Clinic 2-Prosthodontics, Glückstr 11, 91054 Erlangen, Germany.
Quintessence Int. 2011 Sep;42(8):651-7.
Assessing the level of precision entailed by the virtual fit of dental restorations is a very challenging issue. A cement space between an abutment tooth and a dental restoration is a clinical requisite that precludes the application of conventional best-fit registration protocols routinely applied in industrial precision measurements. Since two-dimensional fit assessment techniques currently used in dentistry miss important information about the third dimension, a new protocol was developed to provide three-dimensional information for the virtual registration of the digitized restoration with respect to the abutment.
CAD/CAM was used to produce 10 titanium single crown copings for five gypsum master casts each, representing a molar prepared for a full crown. An industrial noncontact scanner was used for digitizing the components. Registration of surface data sets was achieved by a new triple-scan protocol. For statistical analysis and repeatability testing of the triple-scan protocol, mean distances of the cement space of all copings on their respective abutments were measured three times.
The validity of the approach is verified by intraclass correlation coefficients that revealed an almost perfect coefficient for repeatability (ICC = 0.981, P < .001) with a 95% confidence range between 0.970 and 0.989.
The triple-scan protocol represents a reliable registration approach for surface data sets in dental applications and eliminates the limitations of conventional best-fit registration protocols when a cement space or gap is present between a restoration and its underlying abutment. Future fit assessment investigations can implement this approach of obtaining detailed information of component precision in all spatial orientation.
评估牙科修复体虚拟拟合所需的精度水平是一个极具挑战性的问题。基牙与牙科修复体之间的粘结剂间隙是临床必需的，这使得工业精密测量中常规应用的传统最佳拟合配准协议无法适用。由于目前牙科中使用的二维拟合评估技术会遗漏有关第三维度的重要信息，因此开发了一种新协议，以提供数字化修复体相对于基牙的虚拟配准的三维信息。
使用计算机辅助设计/计算机辅助制造（CAD/CAM）为五个石膏母模各制作10个钛单冠内冠，每个母模代表一个准备进行全冠修复的磨牙。使用工业非接触式扫描仪对部件进行数字化处理。通过一种新的三次扫描协议实现表面数据集的配准。为了对三次扫描协议进行统计分析和重复性测试，对所有内冠在其各自基牙上的粘结剂间隙的平均距离进行了三次测量。
组内相关系数验证了该方法的有效性，该系数显示重复性系数几乎完美（ICC = 0.981，P <.001），95%置信区间在0.970至0.989之间。
三次扫描协议是牙科应用中表面数据集的可靠配准方法，当修复体与其下方的基牙之间存在粘结剂间隙或缝隙时，消除了传统最佳拟合配准协议的局限性。未来的拟合评估研究可以采用这种方法来获取所有空间方向上部件精度的详细信息。
