转移牙合架固定法三维重建牙尖交错牙合的精度评价

目的:评价转移牙合架固定法三维扫描重建牙列石膏模型牙尖交错牙合的精度,为临床应用提供参考。方法:标准全牙列石膏模型底座分别粘贴直径6.0 mm树脂切削圆柱,于牙尖交错牙合(intercuspal occlusion,ICO)上平均值牙合架。以100 μm红色马蹄形咬合纸记录后牙区咬合接触点,以咬合记录硅橡胶记录ICO咬合接触,统计咬合纸及咬合记录硅橡胶重叠的咬合接触点数目N_A。以模型扫描仪配套转移牙合架分别固定上颌、下颌及位于ICO的上下颌并扫描,利用扫描仪内置配准软件重建模型牙尖交错牙合,保存位于ICO的上下颌模型数据为STL格式。利用Geomagic Studio 2013软件偏差分析功能分析三维模型的咬合接触点数目N_S。将N_A作为参考值,N_S作为测量值,评价模型扫描仪重现咬合接触的阳性预测值、灵敏度,即真阳性率。采用三坐标测量系统Faro Edge获取上下颌模型相对应圆柱底面圆心之间的距离D_R作为参考值,构建三维模型圆柱底面圆心并测量其相对应圆心之间的距离D_M作为测量值,计算圆心距离偏差。结果:模型扫描仪重现咬合接触点的阳性预测值是0.76、灵敏度是0.81,重建牙尖交错牙合的上下颌特征点之间的距离测量误差是(0.232±0.089) mm,经单样本t检验,特征点对5-5’差异没有统计学意义,其他特征点对之间的差异有统计学意义(P<0.05)。结论:转移牙合架固定法较好地再现了咬合接触点的个数和位置,满足临床需求,但该方法重建ICO的特征点距离大于参考值,以此进行修复体制作会导致咬合增高,需要进行临床调磨。

Accuracy of intercuspal occlusion in 3D reconstruction with the dental articulator position method

Objective: To evaluate the three-dimensional (3D) reconstruction accuracy of the intercuspal occlusion (ICO) of the dental casts, by the dental articulator position method, and provide a refe-rence for clinical application. Methods: The standard dental casts in ICO were mounted on average values articulator, and five pairs of milling resin cylinders were respectively attached to the base of both the casts. 100 μm articulating paper and occlusal record silicone rubber were used to detect the occlusal contact number between the posterior teeth of casts mounted on articulator in ICO. The occlusal contact numbers N_A detected by the two methods were calculated simultaneously, as the reference. After the upper and lower casts were scanned separately, and the buccal data of casts in ICO were scanned with the aid of the dental articulator position, registration was carried out utilizing the registration software. Then the digital casts mounted in ICO as well as the buccal occlusal data were saved in standard tessellation language (STL) format. Geomagic Studio 2013 software was used to analyze the contact number N_S between digital upper and lower casts by the “deviation analysis” function. The differences were compared between N_S and N_A, to evaluate the sensitivity and positive predict value (PPV) of the model scanner to reproduce the occlusal contact with the aid of dental articulator position. The distance D_R between the centers of the circles at the top surface of the upper and lower corresponding cylinders was obtained by the three-coordinate measuring system Faro Edge, as the reference value. The Geomagic Studio 2013 software was used to construct the cylinders of digital casts and the distance D_M between the centers of the circles at the top surface of the corresponding cylinders were measured, as the test value. The one-sample T test was used to analyze the variable differences between D_M and D_R. Results: The PPV of reproducing the occlusal contact point was 0.76 and sensitivity was 0.81. The distance error of the opposite cylinder was (0.232±0.089) mm. There was no statistical difference between the feature points 5-5’, while there were statistical differences between the other feature points. Conclusion: By the dental articulator position method, the model scanner reproduces the occlusal contact point with high sensitivity and PPV, and that meets clinical needs. Meanwhile, the distance between the feature points is greater than the reference value, which will lead to occlusal disturbance, and require clinical grinding.