Attending, Department of Oral Implantology, School and Hospital of Stomatology, Peking University, Beijing, China; National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & NHC Research Center of Engineering and Technology for Computerized Dentistry, Beijing, China.
Chairman, Clinic of Reconstructive Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
J Dent. 2024 Nov;150:105303. doi: 10.1016/j.jdent.2024.105303. Epub 2024 Aug 10.
This in vitro study was formulated to clarify how mandibular partial edentulous distal extension involving three missing teeth affects the virtual occlusal record (VOR) accuracy, in terms of both trueness and precision, when using two different intraoral scanners (IOSs) - the Primescan (PS) and Trios 4 (TR) scanners.
A typodont model missing the left mandibular second premolar, first molar, and second molar as well as the right mandibular first molar was mounted on a semi-adjustable articulator. Four implants were placed at the sites of the missing mandibular teeth. Six pairs of stainless steel markers (diameter: 0.5 mm) were affixed to the maxillary and mandibular casts in the buccal gingiva adjacent to the implants and on the facial surfaces of teeth as reference positions for measurements. The model was digitized with an inEox X5 laboratory scanner to create a reference dataset. Intraoral scans were performed with the PS and TR scanners, with each scan duplicated 10 times to generate 20 paired IOS files. Automatic VOR generation followed the bilateral buccal scan protocol, divided into PS and TR groups (n = 10). Six subgroups of linear distances between interarch markers were assessed with Geomagic Control software, comparing deviations from the reference scan. Data normality was confirmed with the Shapiro-Wilk test. Trueness was evaluated with two-way ANOVAs and pairwise comparisons performed with Tukey's test, whereas precision was assessed with the Levene test (α=0.05).
The mean linear deviation (Δd) and standard deviation (SD) of VOR were both significantly affected by marker position (P < 0.001), and a significant position × scanner interaction was detected (P < 0.001). Negative mean deviations were observed for the distally extended edentulous areas in both groups. PS scans exhibited trueness that was significantly better than that for TR scans in the D16-46, D13-43, D23-33, and D27-37 subgroups (P < 0.05), whereas there were no significant differences in the D25-35 or D26-36 subgroups. PS scanning was associated with significantly better precision than TR scanning (P < 0.001), and worse precision was observed at D27-37 for both tested IOSs.
Mandibular partial edentulous distal extension can significantly affect VOR accuracy. The type of IOS could also affect VOR accuracy depending on the area being scanned, with better overall performance observed for the Primescan device as compared to the Trios 4 scanner. Both of these IOSs tended to underestimate VOR occlusal dimensions in mandibular distally extended edentulous areas.
Mandibular distal edentulous areas can contribute to occlusal dimensions that are underestimated in digital workflows, which may result in infraocclusal discrepancies that arise when performing restorations. IOSs and VOR scanning protocols should thus be carefully considered in order to minimize these risks.
本体外研究旨在阐明下颌部分缺牙远中游离端涉及三颗缺失牙时，使用两种不同的口内扫描仪（IOS）——Primescan（PS）和Trios 4（TR）扫描仪，对虚拟咬合记录（VOR）准确性的准确性和精密度有何影响。
在一个半可调式关节架上安装一个缺少左下颌第二前磨牙、第一磨牙和第二磨牙以及右下颌第一磨牙的牙模型。在缺失下颌牙齿的部位放置四颗种植体。将六对不锈钢标记物（直径：0.5 毫米）固定在上颌和下颌模型的颊侧牙龈上，紧邻种植体，并固定在牙齿的颊面作为测量的参考位置。使用 inEox X5 实验室扫描仪对模型进行数字化，以创建参考数据集。使用 PS 和 TR 扫描仪进行口内扫描，每个扫描重复 10 次，生成 20 对 IOS 文件。根据双侧颊侧扫描协议，自动生成 VOR，分为 PS 和 TR 组（n=10）。使用 Geomagic Control 软件评估 6 组标记物之间的线性距离，比较与参考扫描的偏差。使用 Shapiro-Wilk 检验确认数据正态性。使用双向方差分析评估准确性，并使用 Tukey 检验进行两两比较，使用 Levene 检验评估精度（α=0.05）。
VOR 的平均线性偏差（Δd）和标准偏差（SD）均受标记物位置的显著影响（P<0.001），并且检测到位置×扫描仪的显著交互作用（P<0.001）。两组中游离端缺牙区的负平均偏差。PS 扫描的准确性明显优于 TR 扫描，在 D16-46、D13-43、D23-33 和 D27-37 亚组中（P<0.05），而在 D25-35 或 D26-36 亚组中没有显著差异。PS 扫描的精度明显优于 TR 扫描（P<0.001），并且在两种测试的 IOS 中，D27-37 的精度都较差。
下颌部分缺牙远中游离端可显著影响 VOR 准确性。IOS 的类型也可能影响 VOR 的准确性，具体取决于扫描的区域，与 Trios 4 扫描仪相比，Primescan 设备的整体性能更好。这两种 IOS 都倾向于低估下颌远中游离端缺牙区的 VOR 咬合尺寸。
下颌远中游离端缺牙区可能导致数字化工作流程中低估咬合尺寸，这可能导致在进行修复时出现低于咬合的差异。因此，在进行修复时，应仔细考虑 IOS 和 VOR 扫描协议，以尽量减少这些风险。
