Objective: To comparatively evaluate the scan time and the accuracy of maxillary full-arch scans using four intraoral scanners (IOS) on conditions of the intraoral head-simulator and the hand-held model, and to evaluate the influence of different scanning conditions on digital scan. Methods: A upper dental arch model with melamine-formaldehyde resin teeth and silica gel gingiva that could be fixed on a head simulator was scanned with an optical scanner (ATOS Core) in order to obtain the standard tessellation language dataset as reference. Intraoral scans were performed on the model fixed on the head simulator by three researchers with four IOS [A: TRIOS 3; B: CS 3600; C: CEREC Omnicam; D: iTero]. For each scanner and each researcher, six scans were performed, to obtain the datasets as the head simulator group. And another six scans with each of the four intraoral scanners were performed by each researcher on the hand-held model to obtain the STL datasets as the hand-held group. The scan time were recorded for each scan. In the Geomagic Wrap software, the digital models were trimmed with only the teeth information retained and supreimposed by best fit alignment function and compared to obtain the root mean square (RMS) values of the discrepancies by three-dimensional compare function. The test datasets of each group were compared with the reference dataset for trueness. The six test scanning datasets with the same scanner of the same researcher were cross compared for precision. Mann Whitney U test was used to statistically analyze the difference values of the scan time, trueness and precision of the same intraoral scanner between head simulator group and hand-held group. Results: Compared to the hand-held group, the scan time of A [142(82) s] and D [119(52) s], which two IOS both with handle, were longer in head simulator group [A: 98(28) s; D: 85(22) s] (P<0.01). However there were no significant differences between the two groups for scan time of IOS B and C (P>0.05). For full-arch scan accuracy (trueness and precision), there were no significant differences between the two groups of IOS A and B (P>0.05), while the trueness of C (P<0.05) and the precision of D (P<0.01) were better in head simulator group [C: 112(38) μm; D: 43(13) μm] compared to hand-held group [C: 135(47) μm; D: 53(18) μm]. However, there were no significant differences for the precision of C (P>0.05) and the trueness of D (P>0.05). Conclusions: The scan time and the accuracy of full-arch digital scans with different IOS may be effected by the scan conditions. For in vitro study of intraoral scanning, head-simulator can simulate the intraoral environment of the real patient to some extent. Meanwhile, the position of the dentist and the patient, and also the limited intraoral space during intraoral scanning are also simulated.
目的： 通过比较仿真头颅模型口内和手持牙颌模型条件下4种口内扫描仪全牙弓扫描的扫描时间及扫描精度，评估不同扫描条件对数字化扫描的影响。 方法： 选择1个可固定于仿真头颅模型口内的上颌牙颌模型，使用光学扫描仪（ATOS Core）扫描全牙弓，获取“.stl”格式数据作为参考数据。将上颌模型固定于仿真头颅模型口内，3名研究者均使用4种口内扫描仪［A（TRIOS 3）、 B（CS 3600）、C（CEREC Omnicam）、D（iTero）］分别扫描6次，获得“.stl”格式数据（头模组）；采用手持牙颌模型的方式，3名研究者再使用上述4种口内扫描仪分别扫描6次，获得“.stl”格式数据（手持组）；记录扫描时间。通过Geomagic Wrap软件修剪数字化模型，仅保留牙列数据，通过最佳拟合功能配准和三维偏差分析比较各组扫描数据与参考数据，获得扫描正确度；通过最佳拟合功能配准和三维偏差分析对每名研究者使用同一扫描仪获得的6次扫描数据进行两两比较，获得扫描精密度。结果数据均以“中位数（四分位数间距）”的形式表达。使用Mann Whitney U检验比较同一扫描仪扫描时间、正确度和精密度的组间差异。 结果： 对于带有手柄的口内扫描仪A和D，头模组扫描时间［分别为142（82）和119（52） s］均显著大于手持组［分别为98（28）和85（22） s］（P<0.01）；口内扫描仪B和C的两组扫描时间差异均无统计学意义（P>0.05）。对于口内扫描仪A和B，两组扫描正确度和精密度差异均无统计学意义（P>0.05）；对于口内扫描仪C，头模组正确度［112（38） μm］显著优于手持组［135（47） μm］（P<0.05），两组精密度差异无统计学意义（P>0.05）；对于口内扫描仪D，头模组精密度［43（13） μm］显著优于手持组［53（18） μm］（P<0.01），两组正确度差异无统计学意义（P>0.05）。 结论： 不同口内扫描仪全牙弓数字化扫描的扫描时间和扫描精度可受扫描条件影响。口内扫描仪体外研究时仿真头颅模型口内环境可模拟临床扫描中医师和患者的体位及患者有限的口内空间。.