Department of Prosthetic Dentistry, Heidelberg University Hospital, University of Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.
Institute of Medical Biometry, Heidelberg University Hospital, University of Heidelberg, Heidelberg, Germany.
Clin Oral Investig. 2022 Nov;26(11):6491-6502. doi: 10.1007/s00784-022-04598-4. Epub 2022 Jul 1.
This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS).
CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans.
For DI, the largest deviations (176 µm for OC and 122 µm for PS) occurred over the cross-arch. For CI, the largest deviation (118 µm) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001).
The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values.
In contrast to conventional impressions, digital impressions lead to comparable or better results concerning scans up to a quadrant. Consequently, for larger scan volumes, several smaller scans should be performed or, if restoration-related not possible, it is recommended to take conventional impressions.
本体外研究比较了上颌部分缺牙患者常规印模（CI）和数字印模（DI）的尺寸精度。DI 由两种口内扫描仪 Omnicam（OC）和 Primescan（PS）制作。
使用 CI 和两种口内扫描仪对两个相同的参考模型进行 30 次印模。CI 用 4 型石膏浇铸，对锯切模型进行数字化。参考模型模拟了一个上颌，有六颗预备牙，容纳了一个跨弓固定局部义齿。使用五个精密球的中心点和每个预备牙的边缘水平的中心点来检测参考模型和扫描之间的尺寸和牙轴变化。
对于 DI，最大偏差（OC 为 176μm，PS 为 122μm）发生在跨弓上。对于 CI，最大偏差（118μm）发生在前部。对于短距离（至一个象限），DI 优于 CI。对于较长的扫描距离，DI 与 CI 相当（2 个六分仪和前部）或不如 CI（跨弓）。CI 的垂直和牙轴偏差明显小于 DI（p<0.001）。
印模方法对上颌有预备牙的部分缺牙患者的印模精度有影响。建议在扫描至一个象限时使用 DI。由于准确性值的较大离散度，更大的扫描体积目前还不适合制作固定局部义齿。
与传统印模相比，数字印模在扫描至一个象限时可以获得类似或更好的结果。因此，对于更大的扫描体积，应该进行几次较小的扫描，或者如果修复相关不可行，则建议进行传统印模。
