Lo Russo Lucio, Sorrentino Roberto, Esperouz Fariba, Zarone Fernando, Ercoli Carlo, Guida Laura
Professor of Prosthodontics, Department of Clinical and Experimental Medicine, School of Dentistry, University of Foggia, Foggia, Italy.
Professor of Prosthodontics, Department of Neurosciences, Reproductive and Odontostomatological Sciences, Scientific Unit of Digital Dentistry, University "Federico II" of Naples, Naples, Italy.
J Prosthet Dent. 2025 Jul;134(1):151-159. doi: 10.1016/j.prosdent.2023.09.029. Epub 2023 Nov 4.
Manufacturers of several intraoral scanners have recommended a 2-step strategy for scanning the edentulous mandible. The 2-step technique requires scanning one side first and then moving to the other side. However, whether inconsistency in stitching occurs that results in loss of accuracy or distortion is unclear.
The purpose of this clinical study was to measure the potential distortion of intraoral scans of edentulous mandibular arches made with a 2-step scanning strategy and to assess their differences with conventional impressions.
Twenty mandibular edentulous arches were scanned by 1 investigator with an intraoral scanner using a 2-step scanning strategy, and a corresponding polysulfide conventional impression was obtained. The conventional impression was then immediately scanned with the same intraoral scanner. The obtained standard tessellation language (STL) files were superimposed with a surface-matching software program. After a preliminary alignment, the STL meshes were trimmed and reoriented; then, the final alignment was carried out and meshes moved to a metrology software program where their mean distance was measured. In addition, a surface curve (SIOS) was traced on the intraoral scan from the right to left retromolar pad along the residual ridge and automatically projected onto to the conventional impression scan to obtain a new curve (SC). The mean distance between SIOS and SC was measured and recorded as an indicator of the distortion by considering the X-, Y-, and Z-axes and the overall 3-dimensional (3D) deviation. The analysis was performed for the full curve length and after dividing it into 6 regions of interest. Univariate and multivariate statistical analyses were used to investigate the significance of the extent of the mean 3D distance, as well as the effects of measurement positions (side and region) between and within patients on differences along the X-, Y-, and Z-axes (α=.05).
The mean (-0.08 mm; standard error: 0.025) 3D distance between the intraoral scan and conventional impression was significantly different from zero (P=.003). No significant effect of the factor "side" was found by using generalized estimated equation models for the X-, Y-, and Z-axes, and global 3D deviations between SIOS and SC (P>.05), which appeared to exclude distortion. Conversely, a significant effect was found for the factor "region" (P<.05), with no significant differences (P>.05) between corresponding regions on the 2 sides.
Intraoral scans of the edentulous mandibular arch made in a 2-step procedure did not exhibit significant distortion in comparison with conventional impressions.
几种口腔内扫描仪的制造商推荐了一种用于扫描无牙下颌骨的两步策略。两步技术要求先扫描一侧，然后再扫描另一侧。然而，拼接过程中是否会出现不一致，从而导致精度损失或变形尚不清楚。
本临床研究的目的是测量采用两步扫描策略对无牙下颌牙弓进行口腔内扫描时的潜在变形，并评估其与传统印模的差异。
由一名研究人员使用口腔内扫描仪采用两步扫描策略对20个下颌无牙牙弓进行扫描，并获取相应的多硫化物传统印模。然后立即使用同一台口腔内扫描仪对传统印模进行扫描。将获得的标准镶嵌语言（STL）文件与一个表面匹配软件程序进行叠加。经过初步对齐后，对STL网格进行修剪和重新定向；然后进行最终对齐，并将网格移动到一个计量软件程序中，在该程序中测量它们的平均距离。此外，沿着剩余牙槽嵴从右侧向后磨牙垫向左在口腔内扫描上绘制一条表面曲线（SIOS），并自动投影到传统印模扫描上以获得一条新曲线（SC）。通过考虑X、Y和Z轴以及整体三维（3D）偏差，测量并记录SIOS和SC之间的平均距离，作为变形的指标。对整条曲线长度以及将其划分为6个感兴趣区域后进行分析。使用单变量和多变量统计分析来研究平均3D距离范围的显著性，以及患者之间和患者内部测量位置（侧和区域）对沿X、Y和Z轴差异的影响（α = 0.05）。
口腔内扫描与传统印模之间的平均3D距离（-0.08 mm；标准误差：0.025）显著不同于零（P = 0.003）。对于X、Y和Z轴以及SIOS和SC之间的整体3D偏差，使用广义估计方程模型未发现“侧”因素的显著影响（P>0.05），这似乎排除了变形。相反，发现“区域”因素有显著影响（P<0.05），两侧相应区域之间无显著差异（P>0.05）。
与传统印模相比，采用两步法对无牙下颌牙弓进行的口腔内扫描未表现出明显变形。
