基于两种不同设计理论的数字化牙冠外形精度的比较

Comparison of the morphological accuracy of the digital crowns generated by two different design concepts with 3Shape Dental System

目的通过比较基于3Shape计算机设计软件的两种设计方法自主设计牙冠精度的差异以探索最优牙冠设计方法用于指导临床工作。方法收集10副健康志愿者的上下颌石膏模型并扫描获得数字印模,记录原始牙齿形态的开放格式数据-STL格式;对左下颌第一磨牙进行标准全瓷冠预备,口内扫描仪扫描模型;分别利用预制备体模式和数据库模式进行自主牙冠设计,获得自动设计冠的STL数据,将数据分别记为复制组和个性化设计组。再将各组自动设计冠数据交由技师调整,获得各组调整冠的STL数据;利用Geomagic qualify 2012软件对上述数据进行三维拟合比较,曼-惠特尼秩和检验分析两种设计模式间的自动设计牙冠与原始形态的差异及技师调整量差异,检验水平α=0.05。结果复制组和个性化设计组的自动设计冠与原始牙冠形态间的差异有统计学意义(P<0.05);复制组与个性化设计组间技师调整量差异有统计学意义(P<0.05)。结论在原始牙冠形态可获取且患者适应良好的情况下,建议选择预制备体模式即复制法进行全冠设计。

Objective To compare the morphological accuracy of full crowns generated by two different design methods of the 3 Shape CAD software for better guiding clinicians choose the appropriate design strategies. Methods Maxillary and mandibular casts of ten volunteers were collected and digital impressions of each cast were recorded as a stereolithography(STL) format. The left mandibular first molars of the models were prepared according to the standard of all-ceramic full crown, and the models were scanned by an intraoral scanner. Correlation mode and library mode were used to generate virtual full crowns, and these STL data were recorded as copy group and individual design group. One experienced technician was requested to modify the auto-generated crowns according to the clinical criteria, and the data of modified crowns were also recorded. The discrepancy between original teeth and autogenerated crowns and the discrepancy between the modified crowns and the autogenerated crowns were evaluated by the Geomagic Qualify software. The diffe-rences between the two modes were statistically analyzed by Mann-Whitney U test(α=0.05). Results The discrepancies between the autogenerated crowns and the original teeth in copy group were significantly smaller than those in individual design group(P<0.05), and the differences between the auto-generated crowns and the modified crowns in copy group were significantly smaller than those in individual design group(P<0.05). Conclusion It is recommended to choose the correlation method for full crown design when the morphology of the original tooth could be obtained and patients adapt well.