Research Associate, Clinical Affairs, Glidewell Dental, Newport Beach, Calif.
Vice President, Clinical Affairs, Glidewell Dental, Newport Beach, Calif.
J Prosthet Dent. 2019 May;121(5):797-802. doi: 10.1016/j.prosdent.2018.08.010. Epub 2019 Jan 5.
Accuracy in impression making may be enhanced by digitizing the physical impression directly and thereby be unhampered by errors introduced by gypsum casts.
The purpose of this in vitro study was to compare the dimensional accuracy of microcomputed tomography (micro-CT) scans of impressions with that of optical scans of impressions and gypsum casts.
A titanium maxillary cast with 3 metrology-grade ruby spheres in place of 3 teeth was used as a reference. Sphere 1 (S1) to sphere 2 (S2) distance (S1-S2) was 25.036 mm, and sphere 1 (S1) to sphere 3 (S3) distance (S1-S3) was 41.846 mm. Half-arch impressions were made of the titanium cast using polyvinyl siloxane impression material with a 1-step 2-phase technique. The polyvinyl siloxane impressions were then micro-CT scanned and optically scanned, and the resulting stone casts were also optically scanned. Scans from the 3 groups-CT scanning of impressions (CT), optical scanning of impressions (OP), and optical scanning of stone casts (SC)-were used to measure the distances between the 3 ruby spheres and were compared with the reference titanium model. The Wilcoxon signed-rank test for matched pairs was used to compare the groups (α=.01).
For the distance of 25.036 mm, S1-S2 distance, CT scans of impressions (CT) showed an error of 20 ±20 μm, whereas optical scans of stone casts (SC) showed an error of 0 ±20 μm. At a distance of 41.846 mm, S1-S3 distance, CT showed an error of 0 ±40 μm, whereas SC showed an error of -40 ±40 μm. The difference in error between measurements at both distances was statistically significant (P<.01). The group of optical scans of impressions (OP) had to be excluded because of missing data and deformed features on the scan.
Although optically scanned stone models are more dimensionally accurate than micro-CT scanned impressions at a 25.036-mm distance, at a distance of 41.846 mm, micro-CT scanned impressions showed less error than optically scanned stone models. Micro-CT scanning of half-arch impressions is a viable method of digitizing a physical impression of dental structures and capturing data about the patient's oral structures. A digital image obtained by micro-CT scanning is more accurate than that obtained by optical scans of stone casts for long-span restorations.
通过直接数字化物理印模，准确性可能会提高，从而避免石膏模型引入的误差。
本体外研究的目的是比较微计算机断层扫描（micro-CT）印模扫描、光学印模扫描和石膏模型扫描的尺寸精度。
使用一个带有 3 个计量级红宝石球的钛上颌模型作为参考。球 1（S1）到球 2（S2）的距离（S1-S2）为 25.036mm，球 1（S1）到球 3（S3）的距离（S1-S3）为 41.846mm。使用一步两阶段技术的聚硅氧烷印模材料对钛模型进行半口印模。然后对聚硅氧烷印模进行 micro-CT 扫描和光学扫描，并对所得的石膏模型进行光学扫描。来自 3 组的扫描——印模的 CT 扫描（CT）、印模的光学扫描（OP）和石膏模型的光学扫描（SC）——用于测量 3 个红宝石球之间的距离，并与参考钛模型进行比较。使用配对符号秩检验对匹配的组（α=.01）进行比较。
对于 25.036mm 的 S1-S2 距离，CT 扫描的印模（CT）显示误差为 20±20μm，而光学扫描的石膏模型（SC）显示误差为 0±20μm。在 41.846mm 的 S1-S3 距离处，CT 显示误差为 0±40μm，而 SC 显示误差为-40±40μm。两个距离处测量的误差差异具有统计学意义（P<.01）。由于扫描中存在缺失数据和变形特征，光学扫描的印模（OP）组不得不被排除在外。
虽然在 25.036mm 的距离处，光学扫描的石膏模型比 micro-CT 扫描的印模更具尺寸精度，但在 41.846mm 的距离处，micro-CT 扫描的印模比光学扫描的石膏模型误差更小。半口印模的 micro-CT 扫描是数字化牙齿结构物理印模并获取患者口腔结构数据的一种可行方法。micro-CT 扫描获得的数字图像比光学扫描的石膏模型更适合长跨度修复体。
