Accuracy of a cone beam computed tomography–guided surgical stent for orthodontic mini-implant placement

Objective:To validate the accuracy of a cone-beam computed tomography (CBCT)–guided surgical stent for orthodontic mini-implant (OMI) placement by quantitatively evaluating the difference between CBCT-prescribed and actual position of mini-implants in preoperative and postoperative CBCT images.Materials and Methods:A surgical stent was fabricated using Teflon-Perfluoroalkoxy, which has appropriate biological x-ray attenuation properties. Polyvinylsiloxane impression material was used to secure the custom-made surgical stent onto swine mandibles. CBCT scanning was done with the stent in place to virtually plan mini-implants using a three-dimensional (3D) software program. An appropriate insertion point was determined using 3D reconstruction data, and the vertical and horizontal angulations were determined using four prescribed angles. A custom-designed surveyor was used to drill a guide hole within the surgical stent as prescribed on the CBCT images for insertion of 32 OMIs. The mandibles with a surgical stent in place were rescanned with CBCT to measure the deviations between the virtual planning data and surgical results.Results:The difference between the prescribed and actual vertical angle was 1.01 ± 7.25, and the horizontal difference was 1.16 ± 6.08. The correlation coefficient confirms that there was no intrarater variability in either the horizontal (R  =  .97) or vertical (R  =  .74) vectors.Conclusions:The surgical stent in this study guides mini-implants to the prescribed position as planned in CBCT. Since the statistical difference was not significant, the surgical stent can be considered to be an accurate guide tool for mini-implant placement in clinical use.     

Accuracy of three-dimensional printed models derived from cone-beam computed tomography

ObjectivesTo determine the accuracy of three-dimensional (3D) printed models fabricated from cone-beam computed tomography (CBCT) scans of human mandibular dry skulls in comparison with models derived from intraoral scanner (IOS) data.Materials and MethodsSix human mandibular dry skulls were scanned by IOS and CBCT. Digital models (DMs) constructed from the IOS and CBCT data were fabricated physically using a 3D printer. The width and thickness of individual teeth and intercanine and molar widths were measured using a digital caliper. The accuracy of the DMs was compared between IOS and CBCT. Paired t-tests were used for intergroup comparisons.ResultsAll intraclass correlation coefficient values for the three measurements (mesial-distal, buccal-lingual, width) exceeded 0.9. For the mandibular teeth, there were significant discrepancies in model accuracy between the IOS (average discrepancies of 0.18 ± 0.08 mm and 0.16 ± 0.12 mm for width and thickness, respectively) and CBCT (0.28 ± 0.07 mm for width, 0.37 ± 0.2 mm for thickness; P < .01). Intercanine (P = .38) and molar widths (P = .41) showed no significant difference between groups.ConclusionsThere was a statistically significant difference in the accuracy of DMs obtained from CBCT and IOS; however, this did not seem to result in any important clinical difference. CBCT could be routinely used as an orthodontic diagnostic tool and for appliance construction.     

Automated landmark identification on cone-beam computed tomography: Accuracy and reliability

ObjectivesTo evaluate the accuracy and reliability of a fully automated landmark identification (ALI) system as a tool for automatic landmark location compared with human judges.Materials and MethodsA total of 100 cone-beam computed tomography (CBCT) images were collected. After the calibration procedure, two human judges identified 53 landmarks in the x, y, and z coordinate planes on CBCTs using Checkpoint Software (Stratovan Corporation, Davis, Calif). The ground truth was created by averaging landmark coordinates identified by two human judges for each landmark. To evaluate the accuracy of ALI, the mean absolute error (mm) at the x, y, and z coordinates and mean error distance (mm) between the human landmark identification and the ALI were determined, and a successful detection rate was calculated.ResultsOverall, the ALI system was as successful at landmarking as the human judges. The ALI''s mean absolute error for all coordinates was 1.57 mm on average. Across all three coordinate planes, 94% of the landmarks had a mean absolute error of less than 3 mm. The mean error distance for all 53 landmarks was 3.19 ± 2.6 mm. When applied to 53 landmarks on 100 CBCTs, the ALI system showed a 75% success rate in detecting landmarks within a 4-mm error distance range.ConclusionsOverall, ALI showed clinically acceptable mean error distances except for a few landmarks. The ALI was more precise than humans when identifying landmarks on the same image at different times. This study demonstrates the promise of ALI in aiding orthodontists with landmark identifications on CBCTs.     

Accuracy and surgical feasibility of a CBCT‐based stereolithographic surgical guide aiding autotransplantation of teeth: in vitro validation

Summary The aims of this study were to determine the accuracy of a 3D computer model and stereolithographic (STL) replica when compared to the real tooth and to develop a cone beam computed tomography (CBCT)‐based planning technique including surgical guide fabrication. A STL surgical guide and a tooth replica were fabricated using SimPlant Pro 12.1. To validate this process, tooth segmentation and replica design were prepared for comparison to an optical scan of the corresponding tooth. For surgical intervention, a dry dentate mandible was scanned using a Scanora CBCT and the donor tooth was segmented. The donor tooth was repositioned, and two guides were designed. These tooth replica and guides were used in socket preparation of the dry mandible. The 3D computer model of the segmented teeth and related STL models showed satisfactory results with an acceptable accuracy. The surfaces were within 0·25 mm distance, but in some areas up to 2·5 mm deviation were seen. The results showed that 79% of the points was between 0·25 and ?0·25 mm, 3% was overestimated (>0·25 mm) and 18% was underestimated (in vivo planning of CBCT‐based autotransplantation.     

锥形束CT对下颌前磨牙髓腔三维重建的精度分析

目的:评价锥形束CT（cone-beam CT, CBCT）对下颌前磨牙髓腔三维重建的精度。方法:选取32颗单根下颌前磨牙,分别采用显微CT(micro-CT)和CBCT进行扫描,对髓腔进行三维重建,分别提取髓腔的三维表面模型和三维体积模型。在Amira 5.0软件中对髓腔表面模型配准后,以micro-CT重建的髓腔模型为参考,检测CBCT重建模型和其相比的形态差异,进行色阶图颜色标示,记录整体形态的三维偏差值并分析2种扫描图像对髓腔体积重建的测量值差异。采用SPSS 13.0软件包对数据进行统计学分析。结果:32颗牙的三维形态偏差RSM值平均为0.27 mm,最大的形态差异分布于髓腔的根尖段和一些细小的解剖变异结构。Micro-CT和CBCT重建髓腔模型的体积测量值分别为(34.89±4.36) mm3和(27.32±4.83) mm3, 差异具有显著性（P<0.05）。结论:利用CBCT扫描图像对下颌前磨牙髓腔进行三维重建时,存在着一定程度的结构丢失,且多位于根尖段和细小的解剖变异部位。口腔临床医师在利用CBCT辅助诊疗时,应考虑到以上特点。     

3D打印铝合金种植手术导板准确度的体外评价

目的 在体外树脂模型上设计并模拟种植体植入实验，分析比较一种新型铝合金材质种植导板与传统树脂导板的准确度差异。方法 选取一名肯氏III类牙列缺损患者并制取硅橡胶印模，灌制超硬石膏模型后使用口内扫描仪扫描，设计并打印20个树脂模型。将患者的锥束计算机断层扫描（CBCT）数据导入软件（3Shape Implant Studio 2019）并规划该患者的种植方案，设计种植导板。使用3D打印机分别制作树脂与铝合金材质手术导板各一个。通过全程引导手术将种植体植入模型中，植入后拍摄术后CBCT。在软件中测量术后CBCT图像与原治疗计划图像，在近远中面和唇腭面分析种植体相对于原设计在三维线性以及角度上的准确度差异。结果 种植体在金属导板引导下的线性偏差分别为近中（0.51±0.63）mm，远中（0.49±0.58） mm，唇向（1.14±1.40） mm，腭向（1.15±1.42） mm；垂直向（2.09±0.84） mm。近远中角度和唇腭侧角度的角度偏差分别为（1.41°±0.81°）和（1.78°±1.03°）。种植体在垂直向的偏差与近远中角度、唇腭侧角度偏差与树脂导板引导下的种植体偏差有统计学...     

基于3D打印技术新型金属镂空式种植外科导板的临床应用

目的：探讨基于3D打印技术制作的新型金属镂空式种植外科导板在种植手术中的效果及其精确性。方法牙缺失患者23例,利用新型金属镂空式种植外科导板辅助植入52枚种植体,观测其种植体颈部偏移距离（植入位点）和种植体1年存活率。结果48枚种植体进入预定位置,仅4枚种植体颈部出现偏移,偏移范围在2 mm内,颈部偏移的平均距离为（1.08±0.24） mm。所有种植体均顺利修复。种植体1年存活率为100％。结论新型金属镂空式种植外科导板辅助植入技术具有操作简便、术中冷却效果良好和手术视野开阔等优点,且精确度较高。     

基于CBCT图像构建下颌第一前磨牙三维有限元模型

目的：探索基于CBCT扫描图像快速建立下颌第一前磨牙三维有限元模型的方法。方法：选用经测量基本符合中国人牙尺寸平均值的成人下颌第一前磨牙,表面处理,石蜡包埋,应用CBCT扫描技术获取层厚为0．1mm的205张离体牙断层影像,导入Mimics10．01软件获得轮廓线点云,结合Magics9．9图像处理软件,HyPerMesh网格自动划分软件,通过特定Abaqus6．10软件建立下颌第一前磨牙三维有限元模型,并对模型进行力学加载。结果：准确地建市了下颌第一前磨牙三维有限元模型,共生成8725个单元和1874个节点,所得模型具有良好的几何相似性与生物力学相似性。从应力分布来看垂直载荷下牙体出现两个应力集中区,即加载区和牙颈部,牙颈部应力值明显小于加载区。结论：采用CBCT技术与Mimics、Anesys软件相结合建模的方法快速可行,为以后进行三维有限元分析提供了精确的模利。     

Accuracy of a non-contact 3D measuring system for dental model analysis

PurposeThis study aimed to assess the accuracy of digital dental models obtained using a new non-contact 3D measuring system compared to direct measurements made on plaster models as the gold standard.MethodsThree examiners independently examined the sizes of various teeth and the intercanine and intermolar arch width on plaster casts and digital models. Each parameter was measured 10 times on each model under uniform conditions. The order of measurements was changed each time.ResultsThe means of the 10 parameters were different between the 2 methods, and the absolute differences ranged between 0.07 and 0.23 mm; some of which were statistically significant (P < 0.05). However, all these differences were less than 0.3 mm, so are not considered clinically significant. The ratios of standard deviation and coefficient of variation were larger than 1 in 7 of 10 parameters, suggesting that the reproducibility of the 3D scanner was slightly less reproducible than the direct measurements, but still clinically acceptable.ConclusionOur non-contact 3D measuring system showed high reliability on repeated measurement of study models, suggesting that the accuracy of model analysis by 3D scanner is equivalent to that of direct measurement of plaster models by digital caliper.     

Accuracy of contacts calculated from 3D images of occlusal surfaces

OBJECTIVES: Compare occlusal contacts calculated from 3D virtual models created from clinical records to contacts identified clinically using shimstock and transillumination. METHODS: Upper and lower full arch alginate impressions and vinyl polysiloxane centric interocclusal records were made of 12 subjects. Stone casts made from the alginate impressions and the interocclusal records were optically scanned. Three-dimensional virtual models of the dental arches and interocclusal records were constructed using the Virtual Dental Patient Software. Contacts calculated from the virtual interocclusal records and from the aligned upper and lower virtual arch models were compared to those identified clinically using 0.01mm shimstock and transillumination of the interocclusal record. Virtual contacts and transillumination contacts were compared by anatomical region and by contacting tooth pairs to shimstock contacts. Because there is no accepted standard for identifying occlusal contacts, methods were compared in pairs with one labeled "standard" and the second labeled "test". Accuracy was defined as the number of contacts and non-contacts of the "test" that were in agreement with the "standard" divided by the total number of contacts and non-contacts of the "standard". RESULTS: Accuracy of occlusal contacts calculated from virtual interocclusal records and aligned virtual casts compared to transillumination were: 0.87+/-0.05 and 0.84+/-0.06 by region and 0.95+/-0.07 and 0.95+/-0.05 by tooth, respectively. Comparisons with shimstock were: 0.85+/-0.15 (record), 0.84+/-0.14 (casts), and 81+/-17 (transillumination). CONCLUSIONS: The virtual record, aligned virtual arches, and transillumination methods of identifying contacts are equivalent, and show better agreement with each other than with the shimstock method.     

基于CT的三维正颌手术仿真模拟平台的建立

目的:建立基于CT的三维正颌手术仿真模拟平台,通过计算机定性定量模拟畸形矫治,并精确设计手术方案。方法:取医学实验用成年男性尸体,进行头颅螺旋CT扫描并完成三维图像重建;解读标准DICOM3.OCT数据库,采用VisualC 6.0语言、VTK工具包在PC机上编制出三维显示、交互式操作模拟手术仿真平台。结果:实现了在颌骨三维模型上以人机交互方式任意切割并按要求定量移动或旋转骨的目标,可模拟畸形矫治过程。结论:借助专用软件和计算机图形学方法,基于CT的三维手术仿真模拟平台,使外科医生能应用逼真的三维可视图像进行诊断分析、术前模拟预测和术后评价,从而使正颌外科手术更为精确。     

Toward a higher accuracy in orthognathic surgery by using intraoperative computer navigation, 3D surgical guides,and/or customized osteosynthesis plates: A systematic review

The aim of this study was to systematically review the accuracy of intraoperative computer navigation, three-dimensional surgical guides and customized osteosynthesis plates for the transfer of the virtual surgical plan to the patient in orthognathic surgery. A systematic review of the currently available publications was performed in databases MEDLINE, Embase, and Cochrane Library, using a PICOS search strategy, and reported according to PRISMA. The initial search yielded 3050 articles. In total, 16 studies were included for final quantitative analyses. The results of individual studies demonstrated a comparable accuracy in the transfer of planned surgical displacement of the jaws. A large variability was found with regard to the method of accuracy assessment and reported outcomes. The findings of this review show that these modern techniques have the potential to replace interocclusal splints in routine clinical practice in the future. We recommend that authors presenting new data on the accuracy of a technique should choose the method of accuracy assessment meticulously, acquiring postoperative imaging as soon as possible after surgery. They should report as much as possible, summarizing values or, ideally, even the raw data of the accuracy assessment in order to allow comparison with other techniques in a meta-analysis.     

3D打印导板在上前牙种植中的精度评价

目的:评价3D打印导板在上前牙种植的精确度,探讨其临床效果。方法:选取2017年6月—2018年6月在青岛大学附属医院口腔种植科行上前牙区种植手术的60例患者,采用随机数字表法随机分为G组（导板组）和R组（常规组）,每组30例,均在术前拍摄锥形束CT（CBCT）,应用“Dentiq Guide种植导板软件”进行设计。G组制作3D打印导板辅助种植手术,R组行常规种植手术。术后即刻拍摄CBCT,应用“Dentiq Guide种植导板软件”将术前、术后CT重叠,测量术前设计与种植体实际位置差异,采用SPSS 24.0软件包对所得数据进行统计分析。结果:G组共植入46颗种植体,测量偏差角度(2.34±1.03)°,顶部(0.63±0.38)mm,根尖部(0.71±0.38)mm,深度(0.41±0.40)mm;R组共植入43颗种植体,测量偏差角度(6.72±3.65)°,顶部(1.59±0.35)mm,根尖部(2.05±0.92)mm,深度(0.77±0.63)mm。2组在角度、顶部、根尖部、深度的差异均有统计学意义（P<0.05）。结论:应用3D打印导板辅助上前牙种植手术,可提高手术精确度,满足种植修复需要,践行以修复为导向的精确种植理念。     

Integration of digital maxillary dental casts with 3D facial images in orthodontic patients:: A three-dimensional validation study

ObjectiveTo evaluate three-dimensional (3D) accuracy and reliability of nonradiographic dentofacial images integrated with a two-step method.Methods3D facial images, cone-beam computed tomography (CBCT) images and digital maxillary dental casts were obtained from 20 pre-orthodontic subjects. Digital dental casts were integrated into 3D facial images using a two-step method based on the anterior tooth area. 3D coordinate values of five dental landmarks were identified in both dentofacial images and CBCT images. The accuracy of the integration method was assessed with paired t-tests between dentofacial images and CBCT-based reference standards. Intraclass correlation coefficients (ICCs) were assessed for the reliability of dentofacial images and CBCT-based images. Analysis of variance and Kruskal-Wallis tests evaluated the accuracy of the method in different dimensions.ResultsThere was no statistical difference between dentofacial images and CBCT reference standards in both translational and rotational dimensions (P > .05). Translational mean absolute errors for full dentitions were within 0.42 mm and ICCs were over 0.998 in x, y, and z directions. Rotational mean absolute errors for full dentitions were within 0.92° and ICCs over 0.734 in pitch, yaw, and roll orientations. Integration errors were significantly greater in the first molar, z-translation, and pitch rotation (P < .05).ConclusionsIntegrating 3D dentofacial images with the two-step method is precise and acceptable for clinical diagnostics and scientific purposes. Errors were greater in the molar region, z-translation, and pitch rotation.     

Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision

PURPOSE

This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types.

MATERIALS AND METHODS

To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10°-20° and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (α=.05).

RESULTS

Precision discrepancies for the canine, premolar, and molar were 3.7 µm, 3.2 µm, and 7.3 µm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 µm, 11.2 µm, and 21.8 µm, respectively, indicating the poorest trueness for the molar (P=.007).

CONCLUSION

In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall.