Vogel Annike B, Kilic Fatih, Schmidt Falko, Rübel Sebastian, Lapatki Bernd G
Department of Orthodontics and Orofacial Orthopedics, Center for Dental, Oral and Maxillary Medicine, University of Ulm Medical School, Ulm, Germany,
J Orofac Orthop. 2015 Jul;76(4):351-65. doi: 10.1007/s00056-015-0296-2.
Digital jaw models offer more extensive possibilities for analysis than casts and make it easier to share and archive relevant information. The aim of this study was to compare the dimensional accuracy of scans performed on alginate impressions and on stone models to reference scans performed on underlying resin models.
Precision spheres 5 mm in diameter were occlusally fitted to the sites of the first premolars and first molars on a pair of jaw models fabricated from resin. A structured-light scanner was used for digitization. Once the two reference models had been scanned, alginate impressions were taken and scanned after no later than 1 h. A third series of scans was performed on type III stone models derived from the impressions. All scans were analyzed by performing five repeated measurements to determine the distances between the various sphere centers.
Compared to the reference scans, the stone-model scans were larger by a mean of 73.6 µm (maxilla) or 65.2 µm (mandible). The impression scans were only larger by 7.7 µm (maxilla) or smaller by 0.7 µm (mandible). Median standard deviations over the five repeated measurements of 1.0 µm for the reference scans, 2.35 µm for the impression scans, and 2.0 µm for the stone-model scans indicate that the values measured in this study were adequately reproducible.
Alginate impressions can be suitably digitized by structured-light scanning and offer considerably better dimensional accuracy than stone models. Apparently, however, both impression scans and stone-model scans can offer adequate precision for orthodontic purposes. The main issue of impression scans (which is incomplete representation of model surfaces) is being systematically explored in a follow-up study.
数字化颌骨模型比石膏模型提供了更广泛的分析可能性，并且使相关信息的共享和存档更加容易。本研究的目的是比较在藻酸盐印模和石膏模型上进行的扫描与在下层树脂模型上进行的参考扫描的尺寸精度。
将直径5mm的精密球体咬合安装在一对由树脂制成的颌骨模型上第一前磨牙和第一磨牙的位置。使用结构光扫描仪进行数字化。在扫描了两个参考模型之后，采集藻酸盐印模并在不迟于1小时后进行扫描。对从印模得到的III型石膏模型进行了第三组扫描。通过进行五次重复测量来分析所有扫描，以确定各个球体中心之间的距离。
与参考扫描相比，石膏模型扫描的尺寸平均大73.6µm（上颌骨）或65.2µm（下颌骨）。印模扫描仅大7.7µm（上颌骨）或小0.7µm（下颌骨）。参考扫描的五次重复测量的中位标准差为1.0µm，印模扫描为2.35µm，石膏模型扫描为2.0µm，这表明本研究中测量的值具有足够的可重复性。
藻酸盐印模可以通过结构光扫描进行适当的数字化，并且尺寸精度比石膏模型好得多。然而，显然印模扫描和石膏模型扫描都可以为正畸目的提供足够的精度。印模扫描的主要问题（即模型表面的不完整表示）正在后续研究中进行系统探讨。
