Objective: To study the influence of implant depth and scanning rod lengths on the accuracy of digital impression for single-tooth implant restoration of the mandibular posterior teeth.
Methods: Five standard dental cast models with missing right mandibular first molar (46) were prepared with the subgingival implant depths of 0, 1, 3, 5 and 7 mm. ITI RC and ITI RC H11 scanning rods were connected to the replacement body and placed into the seating tract for scanning. The reference data were obtained using a 3D dental scanner, and the experimental data were obtained by 10 scans of each model using a digitized intraoral scanner. Geomagic Wrap 2021 was used to analyze the model data to test the trueness and precision of the models.
Results: The trueness did not differ significantly among the groups (P > 0.05). The implant depth of 1 mm achieved the highest impression precision (66.81±2.45 μm), and the depth of 0 mm resulted in a significantly lower precision (95.60±3.04 μm) than the depth of 1 and 3 mm. Starting from the subgingival depth of 1 mm, the precision of the scan decreased progressively with the increase of the implant depth. At the subgingival implant depth of 5 or 7 mm, the use of an extended rod significantly improved the scan precision.
Conclusion: For single-tooth implant restoration of the mandibular posterior teeth, the implant depth can substantially affect the accuracy of digital impression, which decreases as the implant depth increases. For a deep implant, the use of a longer scanning rod can improve the scanning accuracy.
目的: 体外研究不同植入深度的种植体以及相同植入深度下，不同长度扫描杆的使用对口内数字化印模精度的影响。
方法: 将右下颌第1磨牙（46）缺失的5个标准牙列石膏模型制备出植入深度分别为龈下0、1、3、5、7 mm的就位道，将ITI RC及ITI RC H11型号的扫描杆与替代体连接后置入就位道进行扫描。使用三维牙齿扫描仪获得参考数据，使用数字化口内扫描仪对每种模型进行10次扫描，获得实验数据。通过3D分析软件Geomagic Wrap 2021进行模型数据的对比分析，测试相应模型的精密度与准确度。对植入深度不同的5组数据进行单因素方差分析，并采用LSD检验进行成对比较；对植入深度相同扫描杆长度不同的两对数据进行配对t检验。
结果: 各组间精密度差异无统计学意义（P>0.05）。不同植入深度下的印模准确度：龈下1 mm组准确度为66.81±2.45 μm，表现最佳，高于其他组（P<0.05）。龈下0 mm组准确度为95.60±3.04 μm，低于龈下1和3 mm组（P<0.05）。从龈下1 mm开始，扫描的准确度随深度的加深逐渐降低（P<0.05）。相同植入深度不同扫描杆长度的印模准确度：在龈下5和7 mm组使用延长的扫描杆后，扫描准确度均有所提高（P<0.05）。
结论: 种植体植入深度对数字化口内扫描精度具有影响，大体趋势为随植入深度的增加扫描精度逐渐降低，在植入深度较深时，可通过使用长度更长的扫描杆以提升扫描精度。
Keywords: Digital impression technology; Impression accuracy; Oral implants; implantation depth; scanning rod.