Resident Doctor, Department of Oral Implantology, Peking University School and Hospital of Stomatology, Beijing, PR China.
Professor and Chairman, Department of Oral Implantology, Peking University School and Hospital of Stomatology, Beijing, PR China.
J Prosthet Dent. 2022 Nov;128(5):1017-1023. doi: 10.1016/j.prosdent.2021.01.016. Epub 2021 Feb 25.
Intraoral scanning has benefits over conventional impression making, but whether scanning is sufficiently accurate for multiple implants is unclear.
The purpose of this in vitro study was to compare the trueness of digital scans acquired by using intraoral scanners from a small range to a complete arch with the conventional impression technique and to determine the influence of 2 different evaluation methods (best-fit algorithm versus absolute linear deviation) on the outcomes of accuracy assessment.
A mandibular model with 8 implants (A-H) around an edentulous arch was used as the master model. Open-format standard tessellation language (STL) data sets (1 reference file from a highly accurate dental laboratory scanner, 10 files from an intraoral scanner, and 10 files from digitized conventional impressions at room temperature) were imported to a metrology software program, and 5 groups of scanning ranges (AB, FGH, CDEF, BCDEFG, and ABCDEFGH) were identified simulating different clinical situations. Two evaluation methods-root mean square values calculated from the best-fit algorithm and average value of linear discrepancies from absolute linear deviation-were used to describe the trueness values. The impacts of different scanning or impression methods, ranges, and evaluation methods were tested by using a 3-way ANOVA. The effect of the scanning range on accuracy was further identified with 1-way ANOVA. The paired-sample t test was used to determine the differences of trueness values between the 2 methods in different groups.
The trueness values of the implant impressions were significantly affected by different scanning or impression methods (P<.001), evaluation methods (P<.001), and scanning ranges (P<.001) as independent variables. With use of the best-fit algorithm, deviations from the digital scans were significantly greater than those from the conventional impressions in cross-arch situations (groups CDEF, BCDEFG, and ABCDEFGH). With use of the absolute linear deviation method, statistically significant lower accuracy was found when larger areas were encountered (groups BCDEFG and ABCDEFGH). Use of the absolute linear deviation method resulted in a higher mean score of inaccuracy than that from the best-fit algorithm method in most situations.
Scanning or impression methods, ranges, and evaluation methods affected the dimensional accuracy (trueness) of scans or impressions with multiple implants. Digital scans had worse trueness values compared with those made with the conventional splinting open-tray technique when cross-arch implant impressions were acquired.
与传统印模相比，口内扫描具有优势，但扫描是否足以精确用于多个种植体尚不清楚。
本体外研究的目的是比较使用口内扫描仪从小范围到全弓获得的数字扫描与传统印模技术的准确性，并确定两种不同评估方法（最佳拟合算法与绝对线性偏差）对准确性评估结果的影响。
使用无牙弓周围 8 个种植体（A-H）的下颌模型作为主模型。将开放式标准 tessellation language (STL) 数据集（来自高精度牙科实验室扫描仪的 1 个参考文件、10 个来自口内扫描仪的文件和 10 个室温下数字化的常规印象文件）导入计量软件程序，并识别模拟不同临床情况的 5 组扫描范围（AB、FGH、CDEF、BCDEFG 和 ABCDEFGH）。使用两种评估方法（从最佳拟合算法计算的均方根值和绝对线性偏差的平均线性差异）来描述准确性值。使用三因素方差分析测试不同扫描或印象方法、范围和评估方法的影响。使用单向方差分析进一步确定扫描范围对准确性的影响。使用配对样本 t 检验确定两种方法在不同组中的准确性值之间的差异。
种植体印象的准确性值受不同的扫描或印象方法（P<.001）、评估方法（P<.001）和扫描范围（P<.001）的影响。使用最佳拟合算法时，在跨弓情况下，数字扫描的偏差明显大于常规印象的偏差（组 CDEF、BCDEFG 和 ABCDEFGH）。使用绝对线性偏差法时，当遇到更大的区域时，准确性会显著降低（组 BCDEFG 和 ABCDEFGH）。在大多数情况下，使用绝对线性偏差法会导致不准确的平均值高于最佳拟合算法方法。
扫描或印象方法、范围和评估方法会影响具有多个种植体的扫描或印象的尺寸准确性（准确性）。与使用传统开口托盘技术获得跨弓种植体印象相比，数字扫描的准确性值较差。
