全口义齿牙列基托分体数字控制加工后装配粘接精度的定量评价

目的：定量评价全口义齿牙列基托分体数字控制加工后的装配粘接精度，为临床应用提供参考。方法：用Activity 880牙颌模型三维扫描仪获取标准无牙颌石膏模型及牙合托三维数据，用本课题组自主研发的全口义齿计算机辅助设计（computer aided design，CAD）软件设计上颌总义齿CAD数据Data1。用Imageware 10.0、13.2软件（西门子，德国）及Geomagic Studio软件将基托与牙列结合部设计为无倒凹固位钉形态，设定固位钉端面处基托与牙列间隙为0 mm，其余部分预留0.05 mm粘接剂间隙，得到牙列、基托CAD数据Data2和Data3。用Zenotec T1 5自由度切削机及其配套的聚甲基丙烯酸甲酯（polymethyl methacrylate，PMMA）可切削树脂盘分别加工牙列和基托，其中牙列分为双侧后牙区段和前牙区段3个部分进行加工，在基托对应区域就位后用沪鸽自凝树脂分别粘接。扫描获得义齿整体三维表面数据Data4，用多点对齐和注册器命令将Data2、Data3分别对齐于Data4获得Data5，提取出Data5中Data2、Data3结合部形态中原本设计牙合龈方向上间隙为0 mm的部分数据，用3D偏差分析工具检测该部分间隙量的大小，获得牙列、基托装配后的平均间隙量，定量评价装配粘接精度。结果：Data2和Data3的平均间隙量为：左后牙区段(0.44±0.04) mm，最大偏差值0.52 mm，最小偏差值0.29 mm；右后牙区段(0.52±0.07) mm，最大偏差值0.64 mm，最小偏差值0.28 mm；前牙区段(0.60±0.10) mm，最大偏差0.81 mm，最小偏差0.40 mm；牙列与基托整体平均粘接装配精度为(0.52±0.10) mm。结论：将全口义齿牙列基托结合部设计为无倒凹固位钉形态并将牙列分为3个区段时，可将分体数字控制加工的牙列与基托之间的装配粘接误差控制在0.5 mm量级，探索了全口义齿计算机数字控制加工路线，虽然精度在咬合方向上还有进一步改进的空间，但证明了拥有个性化咬合的全口义齿数字加工技术路线可行。

Quantitative evaluation of fabricating complete denture by computer numerical con-trol in manufacturing dentition and baseplate separately plus adhesive molding

Objective:To quantitatively evaluate the assembly precision of fabricating complete denture by computer numerical control (CNC)in manufacturing dentition and baseplate separately plus adhesive molding.Methods:The 3D surface data of a standard edentulous maxilla plaster cast model and the tem-porary base-plate were obtained using an Activity 880 3D scanner.The data (data1)of a complete den-ture were designed using a set of computer aided design (CAD)software developed by the research group of this study.The pins without undercut were designed as 3D shape of the joining area of the dentition and the baseplate by using the software of Imageware 13.2 and Geomagic Studio 2013.Zero in the top and 0.05 mm in the rest surfaces of the retention pins were set for adhesive clearance.Zenotec T1 (5-axis milling machine)was employed to manufacture polymethyl methacrylate (PMMA)dentition and baseplate.Double sides posterior and one anterior “union teeth”were got.The teeth were inserted into the retention pins in the baseplate and cemented with self-curing resin (Huge Dental Material Co., Ltd).The denture was scanned with the 3D scanner to obtain dataset Data4.Data2 and Data3 registra-tion was set in Data4,Data2 and Data3 were united to gain Data 5.The adhesive clearance on the top of the retentional pins was measured,which was originally designed into 0 mm,and the assembly precision of dentition and baseplate obtained.Results:The average clearance measurements between the dentition and the baseplate:left molar teeth (0.44 ±0.04)mm,max 0.52 mm,min 0.29 mm;right molar teeth (0.52 ±0.07)mm,max 0.64 mm,min 0.28 mm;anterior teeth (0.60 ±0.10)mm,max 0.81 mm, min 0.40 mm;total average clearance (0.52 ±0.10)mm.Conclusion:The adhesive clearance can be controlled to the level of 0.5 mm when the joining part of the artificial teeth and the base was designed in-to the shape of retentional pins and the artificial dentition divided into 3 parts.We succeeded in using the CAD /computer aided manufacturing (CAM)technology to fabricate the complete denture.Although the assembly precision of the dentition and the baseplate is not perfect,the results have proved that the tech-nical routes are workable.