Comparing CBCT to model scanner for dental model scanning. An in vitro imaging accuracy study.

OBJECTIVE: The aim of this study is to compare the accuracy of cone beam computed tomography (CBCT) for dental model scanning to the accuracy of model scanners. METHODS: Subjects from private practice were collected and scanned according to specific selection criteria. A total of 10 STL files were produced and used as reference files. They were printed with a three-dimensional (3D) printer and then scanned with CBCT and model scanner. For trueness evaluation, all models were scanned once with both equipments. Each file derived from each scan was compared with the corresponding reference model file. For the precision measurements, the physical model from the first master reference model file was scanned 10 times with each equipment and compared with the reference STL file. A reverse engineering software was used for all 3D best-fit comparisons. RESULTS: With regard to the measurement of trueness of each method, the calculated mean root mean square (RMS) value was 0.06±0.01mm for the CBCT, and 0.15±0.02mm for the model scanner. There was a significant difference between the two methods (P<0.01). For the evaluation of precision of each scanner, the mean RMS value was 0.0056±0.001mm for the CBCT, and 0.153±0.002mm for model scanner. There was a significant difference between the two methods (P<0.01). CONCLUSIONS: Cone Beam Computed Tomography seems to be an accurate method for scanning dental models. CBCT performs better than model scanners to scan dental models in terms of trueness and precision.

Three-Dimensional Digital Superimposition of Orthodontic Bracket Position by Using a Computer-Aided Transfer Jig System: An Accuracy Analysis.

Accurate bracket placement is essential for successful orthodontic treatment. An indirect bracket bonding system (IDBS) has been developed to ensure proper bracket positioning with three-dimensional computer-aided transfer jigs. The purpose of this study was to investigate the accuracy of bracket positioning by a one-body transfer jig according to the tooth type and presence/absence of a resin base. In total, 506 teeth from 20 orthodontic patients were included in this study. After initial dental models were scanned, virtual setup and bracket positioning procedures were performed with 3D software. Transfer jigs and RP models were fabricated with a 3D printer, and brackets were bonded to the RP model with or without resin base fabrication. The best-fit method of 3D digital superimposition was used to evaluate the lineal and angular accuracy of the actual bracket position compared to a virtual bracket position. Although all the measurements showed significant differences in position, they were clinically acceptable. Regarding the tooth types, premolars and molars showed higher accuracy than anterior teeth. The presence or absence of a resin base did not consistently affect the accuracy. In conclusion, the proper application of IDBS should be performed considering the errors, and resin base fabrication might not be essential in ensuring high-accuracy IDBS.

Accuracy and dimensional reproducibility by model scanning, intraoral scanning, and CBCT imaging for digital implant dentistry.

BACKGROUND: Recently, it has become possible to analyze implant placement position using the digital matching data of optical impression data of the oral cavity or plaster models with cone beam computed tomography (CBCT) data, and create a highly accurate surgical guide. It has been reported that CBCT measurements were smaller than the actual values, termed shrinkage. Matching of digital data is reliable when the plaster model or intraoral impression values show shrinkage at the same rate as the CBCT data. However, if the shrinkage rate is significantly different, the obtained digital data become unreliable. To clarify digital matching reliability, we examined dimensional reproducibility and shrinkage in measurements obtained with a model scanner, intra-oral scanner (iOS), and CBCT. MATERIALS AND METHODS: Three implants that were arranged in a triangle were fixed in an acrylic plate. The distance between each implants were measured using model scanner, iOS, and CBCT. The actual size measured by electronic caliper was regarded as control. RESULTS: All values measured with CBCT were significantly smaller than that of model scanner, iOS, and control (p<0.001). The model scanner shrinkage was 0.37-0.39%, iOS shrinkage was 0.9-1.4%, and CBCT shrinkage was 1.8-6.9%. There were statistically significant differences among the shrinkage with iOS, CBCT, and model scanner (p<0.001). CONCLUSION: Our findings showed that all measurements obtained with those modalities showed shrinkage as compared to the actual values. In addition, CBCT shrinkage was largest among three different measuring methods. They indicated that data matching between CBCT and scanner measurements requires attention in regard to the reliability of values obtained with those devices.

Comparison of reliability, validity, and accuracy of linear measurements made on pre- and posttreatment digital study models with conventional plaster study models.

OBJECTIVES: To compare the accuracy of the linear measurements made on pre- and posttreatment three-dimensional (3D) scanned digital models with conventional plaster study models. MATERIALS AND METHODS: The study was conducted on pre- and posttreatment study models of 132 patients. A 3D model scanner was used to scan the plaster models to form 3D digital models. The measurements were made on the plaster models using digital Vernier calipers, and the 3D digital models were assessed for similar measurement using a software of the model scanner. The intraclass correlation for intraoperator error showed good correlations between the measurements made on conventional plaster models and digital models. RESULTS: Although the comparison of the linear measurements made by conventional and digital methods on both pre- and posttreatment study models using intraclass coefficient showed a good correlation, analysis of variance showed significant mean differences in the measurements of multiple variables in both the groups. The number of variables showing significant differences was more in the pretreatment group. The measurements obtained by Vernier calipers were generally higher than those of scanned pre- and posttreatment study models. CONCLUSION: The linear measurements made by conventional and digital methods showed statistically significant mean differences. The accuracy of recording can be affected by the severity of pretreatment malocclusion, but the deviations were not large enough to contradict the use of the digital models for orthodontic records.

Comparison of marginal and internal discrepancies of zirconia crowns fabricated by various digital scan methods / 대한치과재료학회지

In this study, marginal and internal discrepancies of zirconia crowns fabricated with the CAD/CAM (computer aided design

Effect of abutment superimposition process of dental model scanner on final virtual model / 대한치과보철학회지

PURPOSE: The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner. MATERIALS AND METHODS: A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (α=.05). RESULTS: The RMS mean abutment for single full crown preparation was 10.93 µm and the RMS average abutment for 3 unit bridge preparation was 6.9 µm. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged 9.83 µm, −6.79 µm and 3-units bridge abutment 6.22 µm, −3.3 µm, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001). CONCLUSION: Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.

Three-Dimensional Static Articulation Accuracy of Virtual Models-Part II: Effect of Model Scanner-CAD Systems and Articulation Method.

PURPOSE: Accurate maxillomandibular relationship transfer is important for CAD/CAM prostheses. This study compared the 3D-accuracy of virtual model static articulation in three laboratory scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using two virtual articulation methods: mounted models (MO), interocclusal record (IR). MATERIALS AND METHODS: The master model simulated a single crown opposing a 3-unit fixed partial denture. Reference values were obtained by measuring interarch and interocclusal reference features with a coordinate measuring machine (CMM). MO group stone casts were articulator-mounted with acrylic resin bite registrations while IR group casts were hand-articulated with poly(vinyl siloxane) bite registrations. Five test model sets were scanned and articulated virtually with each system (6 test groups, 15 data sets). STL files of the virtual models were measured with CMM software. dRR , dRC , and dRL , represented interarch global distortions at right, central, and left sides, respectively, while dRM , dXM , dYM , and dZM represented interocclusal global and linear distortions between preparations. RESULTS: Mean interarch 3D distortion ranged from -348.7 to 192.2 µm for dRR , -86.3 to 44.1 µm for dRC , and -168.1 to 4.4 µm for dRL . Mean interocclusal distortion ranged from -257.2 to -85.2 µm for dRM , -285.7 to 183.9 µm for dXM , -100.5 to 114.8 µm for dYM , and -269.1 to -50.6 µm for dZM . ANOVA showed that articulation method had significant effect on dRR and dXM , while system had a significant effect on dRR , dRC , dRL , dRM , and dZM . There were significant differences between 6 test groups for dRR, dRL dXM , and dZM . dRR and dXM were significantly greater in AG-IR, and this was significantly different from SIR-IR, ZKN-IR, and all MO groups. CONCLUSIONS: Interarch and interocclusal distances increased in MO groups, while they decreased in IR groups. AG-IR had the greatest interarch distortion as well as interocclusal superior-inferior distortion. The other groups performed similarly to each other, and the overall interarch distortion did not exceed 0.7%. In these systems and articulation methods, interocclusal distortions may result in hyper- or infra-occluded prostheses.

Three-Dimensional Static Articulation Accuracy of Virtual Models - Part I: System Trueness and Precision.

PURPOSE: To evaluate the 3D static articulation accuracy of 3 model scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using a coordinate measuring machine (CMM). Trueness and precision for each system will be reported in Part I. MATERIALS AND METHODS: The master model simulated a single crown opposing a 3-unit fixed dental prosthesis. Five mounted stone cast sets were prepared, and one set was randomly selected. Reference values were obtained by measuring interarch and interocclusal reference features with the CMM. The stone cast set was scanned 5 times consecutively and articulated virtually with each system (3 test groups, n = 5). STL files of the virtual models were measured with CMM software. dRR , dRC , and dRL , represented interarch global distortions at right, central, and left sides, respectively, while dRM , dXM , dYM , and dZM represented interocclusal global and linear distortions between preparations. RESULTS: For trueness values, mean interarch global distortions ranged from 13.1 to 40.3 µm for dRR , -199.0 to -48.1 µm for dRC , and -114.1 to -47.7 µm for dRL . Mean percentage error of interarch distortion did not exceed 0.6%. Mean interocclusal distortions ranged from 16.0 to 117.0 µm for dRM , -33.1 to 101.3 µm for dXM , 32.9 to 49.9 µm for dYM and -32.0 to 133.1 µm for dZM. ANOVA of trueness found statistically significant differences for dRC , dRL , dRM , dXM , and dZM . For precision values, absolute mean difference between the 10 superimposition combinations ranged from 25.3 to 91.0 µm for dRR , 21.5 to 85.5 µm for dRC , 24.8 to 70.0 µm for dRL . Absolute mean difference ranged from 49.9 to 66.1 µm for dRM , 20.7 to 92.1 µm for dXM , 86.8 to 96.0 µm for dYM , and 36.5 to 100.0 µm for dZM . ANOVA of precision of all test groups found statistically significant differences for dRR , dRC , dRL , dXM and dZM , and the SIR group was the least precise. CONCLUSION: The overall interarch global distortion of all three model scanner-CAD systems was low and did not exceed 0.6%. Variations in scanner technology, virtual articulation algorithm, and use of physical articulators contributed to the differences in distortion observed among all three groups.

Comparison of Three-Dimensional Accuracy between Digital Models Obtained from Impression Scan and Model Scan / 대한치과재료학회지

The purpose of the study is to compare and analyze the accuracy of digital images obtained from impression and stone model with model scanner and to find out clinical effectiveness. A mandibular left first molar composite resin tooth was made for abutment. Digital models were obtained with a same model scanner(Ceramill Map 400, Amann Girrbach, Austria); (1) Fabricated resin model was scanned(Group C). (2) 10 impressions were taken with putty and polyvinyl siloxane, then were scanned (Group I). (3) Type IV stone was poured in each impressions made in step(2) and 10 stone models were scanned(Group S). 3 dimensional super-impositional program (Geomagic control X, 3D Systems, USA) was used to analyze the STL files. Stone model scan(Group S) showed lower deviation than impression scan(Group I) compared to the control group(P < 0.001). Both Group I and Group S showed signs of expansion in the occlusion surface and margin surface while showing contraction in the axial surface. The deviations were smaller in order of occlusal plane, horizontal plane of margin and axial plane. Within the limited boundary of this study, the digital model obtained from stone model scan showed smaller deviation than the digital model obtained from impression scan.

Comparative study on quality of scanned images from varying materials and surface conditions of standardized model for dental scanner evaluation

PURPOSE: The purpose of this study is to evaluate the image acquisition ability of intraoral scanners by analyzing the comprehensiveness of scanned images from standardized model, and to identify problems of the model. MATERIALS AND METHODS: Cast models and 3D-printed models were prepared according to international standards set by ISO12836 and ANSI/ADA no. 132, which were then scanned by model scanner and two different intraoral scanners (TRIOS3 and CS3500). The image acquisition performance of the scanners was classified into three grades, and the study was repeated with varying surface conditions of the models. RESULTS: Model scanner produced the most accurate images in all models. Meanwhile, CS3500 showed good image reproducibility for angled structures and TRIOS3 showed good image reproducibility for rounded structures. As for model ingredients, improved plaster model best reproduced scan images regardless of the type of scanner used. When limited to 3D-printed model, powdered surface condition resulted in higher image quality. CONCLUSION: When scanning structures beyond FOV (field of view) in standardized models (following ISO12836 and ANSI/ADA 132), lack of reference points to help distinguish different faces confuses the scanning and matching process, resulting in inaccurate display of images. These results imply the need to develop a new standard model not confined to simple pattern repetition and symmetric structure.