摘要目的:探讨采用激光选区熔化（selective laser melting，SLM）技术制作纯钛及钴铬合金下颌全牙弓种植固定义齿上部结构支架和上颌可摘局部义齿支架的精度，为SLM纯钛支架的临床应用提供参考。方法:选择下颌无牙颌模型1个，于双侧尖牙和第一磨牙处制作螺丝固位的基台替代体，作为下颌全牙弓种植修复用牙颌模型；同时选用上颌Kennedy第一类牙列缺损牙颌模型1个；扫描牙颌模型获得数字化模型，并用扫描仪配套软件设计下颌全牙弓种植固定义齿上部结构金属支架和上颌可摘局部义齿金属支架（设计模型）。通过改良的双激光金属打印机分别制作钴铬合金组和纯钛组下颌支架各12个（每组6个进行热处理，其余6个不进行热处理），以及钴铬合金组和纯钛组上颌支架各7个，扫描获得数字化模型，借助逆向工程软件Geomagic重叠数字化模型与设计模型。以牙颌模型矢状轴为X轴，牙颌模型冠状轴为Y轴，打印粉末堆积方向为Z轴，分析下颌支架数字化模型基台替代体接口中心点在X、Y、Z轴方向上与设计模型的偏差，作为下颌支架的正确度，偏差数据越大，正确度越差。分析上颌支架整体和7个测量点（腭板中心点和双侧 支托、I杆、邻面板）与设计模型的均方根，作为上颌支架的适合度，均方根数据越大，适合度越差。比较每组下颌支架热处理前后正确度差异以及下颌支架正确度和上颌支架适合度的组间差异。 结果:钴铬合金组下颌支架热处理前X、Y、Z轴方向上的正确度［（96.3±12.1）、（86.3±11.4）、（61.2±13.2） μm］与纯钛组［（82.3±11.2）、（72.2±10.2）、（51.2±11.6） μm］的差异均无统计学意义（ P>0.05）；热处理能减小两组支架的变形，热处理后纯钛组下颌支架在X、Y、Z轴方向上的正确度［（62.4±11.3）、（55.2±13.2）、（41.3±10.8） μm］均显著优于钴铬合金组［（84.5±10.5）、（72.3±11.2）、（54.2±11.6） μm］（ P<0.05）。纯钛组上颌支架的整体适合度［（121.3±17.0） μm］显著好于钴铬合金组［（174.0±18.3） μm］（ P<0.05）。 结论:SLM纯钛支架可满足全牙弓种植修复和可摘局部义齿纯钛大跨度支架的制作要求，且相应热处理后下颌纯钛支架的正确度优于钴铬合金支架。

abstractsObjective:To investigate the accuracy of pure titanium and cobalt-chromium alloy frameworks fabricated using the additive manufacturing (AM) of selective laser melting technology (SLM) for the mandibular implant-supported fixed prostheses and the maxillary removable partial denture (RPD), and to provide a reference for clinical application of SLM pure titanium frameworks.Methods:One edentulous mandibular model with implants and screw fixed abutments at bilateral canines and the first molars was selected and used as the mandibular full arch implant-supported model. At the same time, a Kennedy class Ⅰ maxillary dentition defect model was selected. The digital models were obtained by scanning the dental models, and the metal frameworks of the mandibular full arch implant-supported denture and the maxillary RPD (design model) were designed using the 3 Shape software. Meanwhile, 12 mandibular frameworks in the cobalt-chromium alloy and the pure titanium (6 in each group were treated with heat treatment, while the other 6 were not treated), and 7 maxillary frameworks in the cobalt-chromium alloy and the pure titanium were respectively made by SLM with the improved dual-laser metal printer. The axial direction of the printing powder accumulation was taken as the Z-axis. During the design process, the software (3Shape Dental System 2018) automatically generated the X-axis and Y-axis, X axis was the sagittal axis of the dental model and Y axis was the coronal axis of the dental model. The deviation of the interface center of the abutment of the digital model of the mandibular frameworks from the design model in the X, Y and Z axes was analyzed. As for the trueness of the mandibular framework, the larger the deviation data was, the worse the trueness was. The deviation of the whole maxillary framework and 7 measuring points (palatal plate center point and bilateral occlusal rests, I bars, proximal plates) were analyzed. The fitness of the whole maxillary framework to the design model was expressed by root mean square (RMS) of the deviation data, and the fitness of measuring points was expressed by the mean±standard deviation of the data. The trueness differences of each group before and after heat treatment of the mandibular framework and the fitness of the maxillary framework were compared.Results:The cobalt-chromium alloy frameworks showed lower trueness on the X, Y, Z-axes [(96.3±12.1), (86.3±11.4), (61.2±13.2) μm] than did the pure Ti frameworks [(82.3±11.2), (72.2±10.2), (51.2±11.6) μm] by SLM, and the heat treatment could reduce the discrepancy between the SLM frameworks and STL models, for pure titanium frameworks [(62.4±11.3), (55.2±13.2), (41.3±10.8) μm] and for cobalt-chromium alloy [(84.5±10.5), (72.3±11.2), (54.2±11.6) μm]. For the thin RPD major frameworks, pure titanium had better fitness [(121.3±17.0) μm] than cobalt-chromium alloy [(174.0±18.3) μm] by SLM, and the difference was statistically significant ( P<0.05). Conclusions:Pure titanium frameworks fabricated by SLM additive manufacturing technology exhibited better fitness and trueness than did the Co-Cr frameworks after heat treatment respectively, and this satisfied the requirements of implant-supported fixed prostheses and RPD major metal frameworks.