口内扫描仪临床扫描精度及影响因素把控

牙体缺损修复中,通过口内扫描获取数字化印模的技术以其简单、舒适、快捷的特点越来越多地被应用于临床。数字化印模的精度(包括正确度和精密度),是影响修复体密合性和修复最终成败的关键。各种口内扫描设备扫描原理不同,扫描精度有所不同。另外,临床操作中采取的扫描方案、预备体质量和口腔环境等因素都会影响到扫描精度。了解口内扫描原理和扫描精度相关影响因素,在临床操作中采取相应的应对策略可以提高扫描精度,最终提高牙体缺损数字化修复的成功率。     

Trueness and precision of digital impressions obtained using an intraoral scanner with different head size in the partially edentulous mandible

Purpose

It remains unclear whether digital impressions obtained using an intraoral scanner are sufficiently accurate for use in fabrication of removable partial dentures. We therefore compared the trueness and precision between conventional and digital impressions in the partially edentulous mandible.

A novel reference model for dental scanning system evaluation: analysis of five intraoral scanners

PURPOSEThe aim of this in vitro study was to investigate the accuracy (trueness and precision) of five intraoral scanners (IOS) using a novel reference model for standardized performance evaluation.MATERIALS AND METHODSFive IOSs (Medit i500, Omnicam, Primescan, Trios 3, Trios 4) were used to digitize the reference model, which represented a simplified full-arch situation with four abutment teeth. Each IOS was used five times by an experienced operator, resulting in 25 STL (Standard Tessellation Language) files. STL data were imported into 3D software (Final Surface^®) and examined for inter- and intra-group analyses. Deviations in the parameter matching error were calculated. ANOVA F-test and Kruskal-Wallis test were applied for inter-group comparisons (α = .05); and the coefficient of variation (CV) was calculated for intra-group comparisons (in % ± SD).RESULTSPrimescan (matching error value: 0.015), Trios 3 (0.016), and Trios 4 (0.018) revealed comparable results with significantly higher accuracy compared to Medit i500 (0.035) and Omnicam (0.028) (P < .001). For intra-group comparison, Trios 4 demonstrated the most homogenous results (CV 15.8%).CONCLUSIONThe novel reference model investigated in this study can be used to assess the performance of dental scanning technologies in the daily routine setting and in research settings.     

口内三维扫描技术临床应用精度的研究进展

口内三维扫描技术发展迅速,精度不断提高,已被广泛应用于口腔医学领域。在单冠修复、三单位固定桥以及单枚种植体上部修复方面,口内三维扫描仪的扫描精度可满足临床要求;但在跨度过大的固定修复领域,其扫描精度仍存在不足。由于光学扫描原理的局限,目前临床难以通过口内三维扫描仪直接获取功能整塑后的软组织形态,口内三维扫描技术尚存在技术瓶颈。本文通过回顾和总结常见口内三维扫描仪对口腔软硬组织的扫描精度,分析口内三维扫描技术的临床适用性及局限性,以期为临床决策提供参考。     

全口牙列口内扫描的精确性与可重复性分析

目的:通过比较全口牙列传统石膏模型和数字化模型的线性测量数据,评估口腔扫描系统的精确性与可重复性.方法:由5位志愿者构成传统模型组(对照组)与口内扫描组(实验组).对志愿者进行传统硅橡胶取模、石膏灌制后,采用Trios Ortho口内扫描仪(3 Shape公司)对志愿者分别于8点、13点、18点进行全口牙列口内扫描,为期15 d.采用电子游标卡尺测量石膏模型,Simplant软件测量口内扫描图像.由经过专业培训的测试者分别于上午8点、13点、18点进行测量,重复15 d.采用SAS 11.0软件包中的配对t检验进行实验组与对照组组间数据的精确性比较,可重复性研究则为在实验组组间进行单因素方差分析.结果:精确性研究中,志愿者1的参数23L有显著差异(P＜0.01),5位志愿者的其他所有参数均无显著差异(P＞0.05).可重复性研究中,5位志愿者各参数之间均无显著差异(P＞0.05).结论:全口口内直接数字化扫描的精确性与可重复性较高.     

Effects of inter-implant distance on the accuracy of intraoral scanner: An in vitro study

PURPOSESeveral studies focused on the accuracy of intra-oral scanners in implant dentistry, but the data of inter-implant distances were not widely mentioned. Therefore, this study aimed to evaluate the effect of distance between two implants on the surface distortion of scanned models generated by intra-oral scanners.MATERIALS AND METHODSThree models with the distances between two fixed scan bodies of 7, 14, and 21 mm were fabricated and scanned with a highly precise D900L dental laboratory scanner as reference models. Fifteen scans were performed with TRIOS3 and CEREC Omnicam intra-oral scanners. Trueness, precision, and angle deviation of the test models were analyzed (α=.05).RESULTSThere was a significant difference among inter-implant distances in both intraoral scanners (P <.001). The error of trueness and precision increased with the increasing inter-implant length, while the angle deviation did not show the same trend. A significant difference in the angle deviation was found among the inter-implant distance. The greatest angle deviation was reported in the 14-mm group of both scanners (P <.05). In contrast, the lowest angle deviation in the 21-mm group of the TR scanner and the 7-mm of the CR scanner was reported (P <.001).CONCLUSIONThe inter-implant distance affected the accuracy of intra-oral scanner. The error of trueness and precision increased along with the increasing distance between two implants. However, the distortions were not clinically significant. Regarding angle deviation, the clinically significant angle deviation may be possible when using intra-oral scanners in the partially edentulous arch.     

Accuracy of intraoral scans of edentulous jaws with different generations of intraoral scanners compared to laboratory scans

PURPOSEPurpose of this in vitro study was to determine the accuracy of different intraoral scans versus laboratory scans of impressions and casts for the digitization of an edentulous maxilla.MATERIALS AND METHODSA PEEK model of an edentulous maxilla, featuring four hemispheres on the alveolar ridges in region 13, 17, 23 and 27, was industrially digitized to obtain a reference dataset (REF). Intraoral scans using Cerec Primescan AC (PRI) and Cerec AC Omnicam (OMN), as well as conventional impressions (scannable polyvinyl siloxane) were carried out (n = 25). Conventional impressions (E5I) and referring plaster casts were scanned with the inEOS X5 (E5M). All datasets were exported in STL and analyzed (Geomagic Qualify). Linear and angular differences were evaluated by virtually constructed measurement points in the centers of the hemispheres (P13, P17, P23, P27) and lines between the points (P17–P13, P17–P23, P17–P27). Kolmogorov-Smirnov test and Shapiro-Wilk test were performed to test for normal distribution, Kruskal-Wallis-H test, and Mann-Whitney-U test to detect significant differences in trueness, followed by 2-sample Kolmogorov-Smirnov test to detect significant differences in precision (P < .008).RESULTSGroup PRI showed the highest trueness in linear and angular parameters (P < .001), while group E5I showed the highest precision (P < .001).CONCLUSIONIntraoral scan data obtained using Primescan showed the highest trueness while the indirect digitization of impressions showed the highest precision. To enhance the workflow, indirect digitization of the impression itself appears to be a reasonable technique, as it combines fast access to the digital workflow with the possibility of functional impression of mucosal areas.     

Impact of scanning strategy on the accuracy of complete-arch intraoral scans: a preliminary study on segmental scans and merge methods

PURPOSEThis study investigated the accuracy of full-arch intraoral scans obtained by various scan strategies with the segmental scan and merge methods.MATERIALS AND METHODSSeventy intraoral scans (seven scans per group) were performed using 10 scan strategies that differed in the segmental scan (1, 2, or 3 segments) and the scanning motion (straight, zigzag, or combined). The three-dimensional (3D) geometric accuracy of scan images was evaluated by comparison with a reference image in an image analysis software program, in terms of the arch shape discrepancies. Measurement parameters were the intermolar distance, interpremolar distance, anteroposterior distance, and global surface deviation. One-way analysis of variance and Tukey honestly significance difference post hoc tests were carried out to compare differences among the scan strategy groups (α = .05).RESULTSThe linear discrepancy values of intraoral scans were not different among scan strategies performed with the single scan and segmental scan methods. In general, differences in the scan motion did not show different accuracies, except for the intermolar distance measured under the scan conditions of a 3-segmental scan and zigzag motion. The global surface deviations were not different among all scan strategies.CONCLUSIONThe segmental scan and merge methods using two scan parts appear to be reliable as an alternative to the single scan method for full-arch intraoral scans. When three segmental scans are involved, the accuracy of complete arch scan can be negatively affected.     

Comparison of intraoral scanning and conventional impression techniques using 3-dimensional superimposition

PURPOSE

The aim of this study is to evaluate the appropriate impression technique by analyzing the superimposition of 3D digital model for evaluating accuracy of conventional impression technique and digital impression.

MATERIALS AND METHODS

Twenty-four patients who had no periodontitis or temporomandibular joint disease were selected for analysis. As a reference model, digital impressions with a digital impression system were performed. As a test models, for conventional impression dual-arch and full-arch, impression techniques utilizing addition type polyvinylsiloxane for fabrication of cast were applied. 3D laser scanner is used for scanning the cast. Each 3 pairs for 25 STL datasets were imported into the inspection software. The three-dimensional differences were illustrated in a color-coded map. For three-dimensional quantitative analysis, 4 specified contact locations(buccal and lingual cusps of second premolar and molar) were established. For twodimensional quantitative analysis, the sectioning from buccal cusp to lingual cusp of second premolar and molar were acquired depending on the tooth axis.

RESULTS

In color-coded map, the biggest difference between intraoral scanning and dual-arch impression was seen (P<.05). In three-dimensional analysis, the biggest difference was seen between intraoral scanning and dual-arch impression and the smallest difference was seen between dual-arch and full-arch impression.

CONCLUSION

The two- and three-dimensional deviations between intraoral scanner and dual-arch impression was bigger than full-arch and dual-arch impression (P<.05). The second premolar showed significantly bigger three-dimensional deviations than the second molar in the three-dimensional deviations (P>.05).     

硅橡胶印模与口内扫描印模在口腔临床教学中的比较

目的：通过本科实习医师制取硅橡胶印模及数字化口内扫描印模的教学实践,对比2种取模方式的操作时间、学习的难易程度和患者的接受程度等。方法：6名本科实习医师分别作为医师和患者进行取模练习,由专人记录操作时间,并用视觉模拟量表（VAS）记录患者满意度。采用SPSS 23.0软件包对数据进行统计学分析。结果：在取模时间、学习总时间、总体舒适度方面,硅橡胶印模优于口内扫描印模,两者之间有显著差异(P<0.05)。结论：采用硅橡胶取模,患者的就诊体验更好。采用口内扫描印模技术,需要医师具有更熟练的操作技能。应用角色扮演的方式,实习医师可以更好地学习到不同取模方式的操作要点及注意事项。     

不同扫描范围下3种口内扫描系统的咬合匹配精度对比研究

目的 探究不同颊侧咬合扫描范围下3种口内扫描仪之间咬合匹配精度的差异。方法 采用3种类型的口内扫描仪（Medit i500、iTero element flex、3 Shape Trios3）对安装于半可调架上的标准石膏模型进行4种不同范围的颊侧咬合扫描。扫描范围分组为Group1：双侧1-3牙位、Group2：双侧4-5牙位、Group3：双侧4-6牙位、Group4：双侧4-7牙位,每组重复扫描10次。对照组采用台式扫描仪获取咬合关系。将实验组与对照组上颌模型进行最佳拟合对齐,下颌模型通过矩阵变换保持初始咬合位置不变。通过三维偏差分析技术分析不同扫描范围对咬合匹配精度的影响。结果 同一扫描系统下,i500和Trios3前牙组Group1咬合匹配精密度显著低于3个后牙组Group2、Group3、Group4(P<0.05),且后牙组两两之间差异无统计学意义;同一扫描范围下,咬合匹配正确度在3个口内扫描仪间表现出了相同的趋势：前牙组Group1显著低于后牙组（P<0.05）,在后牙组中,随着扫描范围的增大,咬合匹配的偏差减小,正确度提高;使用iTero进行咬合匹配时整体正...     

Use of measuring gauges for in vivo accuracy analysis of intraoral scanners: a pilot study

PURPOSEThe purpose of this study is to present a methodology to evaluate the accuracy of intraoral scanners (IOS) used in vivo.MATERIALS AND METHODSA specific feature-based gauge was designed, manufactured, and measured in a coordinate measuring machine (CMM), obtaining reference distances and angles. Then, 10 scans were taken by an IOS with the gauge in the patient''s mouth and from the obtained stereolithography (STL) files, a total of 40 distances and 150 angles were measured and compared with the gauge''s reference values. In order to provide a comparison, there were defined distance and angle groups in accordance with the increasing scanning area: from a short span area to a complete-arch scanning extension. Data was analyzed using software for statistical analysis.RESULTSDeviations in measured distances showed that accuracy worsened as the scanning area increased: trueness varied from 0.018 ± 0.021 mm in a distance equivalent to the space spanning a four-unit bridge to 0.106 ± 0.08 mm in a space equivalent to a complete arch. Precision ranged from 0.015 ± 0.03 mm to 0.077 ± 0.073 mm in the same two areas. When analyzing angles, deviations did not show such a worsening pattern. In addition, deviations in angle measurement values were low and there were no calculated significant differences among angle groups.CONCLUSIONCurrently, there is no standardized procedure to assess the accuracy of IOS in vivo, and the results show that the proposed methodology can contribute to this purpose. The deviations measured in the study show a worsening accuracy when increasing the length of the scanning area.     

Titanium dioxide-based scanning powder can modulate cell activity of oral soft tissue - Insights from in vitro studies with L929 cells and periodontal fibroblasts

PurposeTo reveal the impact of titanium dioxide-based scanning powder for intraoral digital impression on the biological activity of oral fibroblasts.MethodsMurine L929 cells and human periodontal ligament (PDLF) and gingival fibroblasts (GF) were treated with ten-fold serial dilutions of scanning powder and the corresponding conditioned medium (filtrate of overnight incubation of powder in medium) starting with 30 mg/ml. Bicinchoninic acid protein assay, formazan- and resazurin-based toxicity assays, live/dead and annexin V/propidium iodide (PI) staining and immunoassays for interleukin (IL)-6 and IL-8 were performed. Powder composition was analyzed using energy dispersive X-ray spectroscopy (EDS).ResultsFormazan and resazurin conversion was lesser in L929 cells than PDLF and GF in the presence of scanning powder. Induction of cell death was caused by 30 mg/ml of powder in L929 cells but not in PDLF and GF. No pronounced impact of the conditioned medium was seen in cytotoxicity assays or live/dead-, and annexin V/PI staining. In PDLF and GF IL-6 expression was increased by the powder, while there was a decrease in IL-8. Powder particles did not deplete protein from medium. EDS showed a heterogeneous mixture consisting predominantly of titanium dioxide.ConclusionsScanning powder decreased cell activity and induced cell death in L929 cells at high concentrations. Human oral fibroblasts showed an increase in IL-6 levels but more resistance to the cytotoxicity of the powder. Within the limitations of an in vitro study our results suggest that proper cleaning after scanning is of clinical relevance to avoid potential unwanted effects of the powder.     

Local accuracy of actual intraoral scanning systems for single-tooth preparations in vitro

BackgroundThe authors evaluated the local accuracy of intraoral scanning (IOS) systems for single-tooth preparation impressions with an in vitro setup.MethodsThe authors digitized a mandibular complete-arch model with 2 full-contour crowns and 2 multisurface inlay preparations with a highly accurate reference scanner. Teeth were made from zirconia-reinforced glass ceramic material to simulate toothlike optical behavior. Impressions were obtained either conventionally (PRESIDENT, Coltène) or digitally using the IOS systems TRIOS 3 and TRIOS 3 using insane scan speed mode (3Shape), Medit i500, Version 1.2.1 (Medit), iTero Element 2, Version 1.7 (Align Technology), CS 3600, Version 3.1.0 (Carestream Dental), CEREC Omnicam, Version 4.6.1, CEREC Omnicam, Version 5.0.0, and Primescan (Dentsply Sirona). Impressions were repeated 10 times per test group. Conventional (CO) impressions were poured with type IV gypsum and digitized with a laboratory scanner. The authors evaluated trueness and precision for preparation margin (MA) and preparation surface (SU) using 3-dimensional superimposition and 3-dimensional difference analysis method using (95% – 5%) / 2 percentile values. Statistical analysis was performed using Kruskal-Wallis test. Results were presented as median (interquartile range) values in micrometers.ResultsThe authors found statistically significant differences for MA and SU among different test groups for both trueness and precision (P < .05). Median (interquartile range) trueness values ranged from 11.8 (2.0) μm (CO) up to 40.5 (10.9) μm (CEREC Omnicam, Version 5.0.0) for SU parameter and from 17.7 (2.6) μm (CO) up to 55.9 (15.5) μm (CEREC Omnicam, Version 5.0.0) for MA parameter.ConclusionsIOS systems differ in terms of local accuracy. Preparation MA had higher deviations compared with preparation SU for all test groups.Practical implicationsTrueness and precision values for both MA and SU of single-unit preparations are equal or close to CO impression for several IOS systems.