Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery

The online attention analysis on orthognathic surgery research

OBJECTIVES

Altmetrics is one of the fields of bibliometrics that seeks to assess the impact and interest of a given subject through Internet users. The aim of this study is to make an altmetric analysis of the orthognathic surgery literature.

METHODS

A literature search was conducted using Dimensions app up to December 2023. A list of the 100 most mentioned articles on the topic was compiled. A Google Trends search was performed with same strategy to visualize important data regarding internet search. Charts and tables were created using Microsoft Excel and VOSviewer software to allow bibliometric visualization.

RESULTS

There was a very poor correlation between the number of mentions and the number of citations (r = 0.0202). Most articles discussed on technical innovations associated to orthognathic surgery, majority related to virtual planning (n = 26). Other topics considered interesting to internet readers were complications (n = 18), surgical technique (n = 14), and psychological aspects/quality of life (n = 13).

CONCLUSION

Online interest in orthognathic surgery closely aligns with the level of academic interest but is also influenced by factors such as location and economic status. The internet is a powerful tool for disseminating scientific research to a broad audience, making it more accessible and engaging than traditional academic channels.

Create virtual dentoskeletal model by superimposing digital dental cast into cone-beam computed tomography scan

PURPOSE

Many artifacts and obstacles associated with cone-beam computed tomography (CBCT) scan can obscure or distort the details of the teeth and occlusal surface, like distorted teeth, streak artifacts, noise, and some malocclusion cases with excessive overlapping between jaws cause decrease the interocclusal space, which can impact diagnosis and treatment planning, and the 3D reconstruction accuracy. Optimizing dental precision by Integrating CBCT scans with other imaging modalities, supply more information to enhance CBCT accuracy, mainly in dental areas with limited clarity.

METHODS

Performing the Structure-from-Motion (SfM) photogrammetry method, using phone camera and photograph studio setup using simple hardware, to digitize the dental casts and obtain an accurate digital dental model. Using this digital dental model to enhance dental precision in the CBCT data by performing the superimposition process, using a surface-based registration method and integration process to create a virtual dentoskeletal model. Evaluate the accuracy and quality of the superimposition results using qualitative (visual inspection) and quantitative measures.

RESULTS

The differences between the virtual dentoskeletal model and the reference CBCT model are calculating by the 3D Euclidean distance, the mean ± SD are 0.212 ± 0.169 mm and 0.26 ± 0.149 mm for the maxilla and mandible, respectively. The color-coded map shows that the two surfaces are similar, but the extremist values are concentrated in the dental region due to the presence of the noise in the reference model and the gingiva in the virtual dentoskeletal model.

CONCLUSIONS

The resulting virtual dentoskeletal model can be viewed and manipulated on a computer screen, allowing for a detailed analysis of the teeth and supporting structures. The 3D model generated by the SfM photogrammetry technique did well during the superimposition process, representing a reliable method for virtual-based processing such as orthognathic surgery planning and splint design.

Single scanning of CBCT and intraoral scanning for guided implantation in terminal dentitions with multi-unit metal restorations: technical note

When anatomical landmarks are missing or obstructed by metal artefacts, it is challenging to accurately merge cone beam computed tomography (CBCT) and intraoral scanning (IOS) information, and the accuracy of the implant surgical guides would be compromised. This article describes a novel technical note using oral wound dressings and flowable resin as additional new radiopaque fiducial landmarks to design surgical guides for full-arch immediate implant placement. This technical note provided an accurate, convenient, and cost-effective option for the clinician.

The in-vitro accuracy of fiducial marker-based versus markerless registration of an intraoral scan with a cone-beam computed tomography scan in the presence of restoration artifact

OBJECTIVES

To determine the effect of restoration artifact ('metal artifact') on registration accuracy of an intraoral scan and cone-beam computed tomography (CBCT) scan, comparing fiducial marker-based registration with markerless registration.

MATERIALS AND METHODS

A maxillary model was fitted with multiple configurations of zirconia crowns to simulate various states of oral rehabilitation. Intraoral scans and CBCT scans (half and full rotation) were acquired. Registration was performed using markerless (point-based registration with surface-based refinement) and fiducial marker-based registration. Each experimental condition was repeated 10 times (n = 320). The absolute deviation was measured at the canines and first molars, and the average and maximum values were analysed using multiple linear regression.

RESULTS

R2 was 0.874 for average error and 0.858 for maximum error. For markerless registration, there were 0.041 mm (p < .001) and 0.045 mm (p < .001) increases in average and maximum error per crown, respectively. For fiducial marker-based registration, the effect of additional crowns was not statistically significant for average (p = .067) or maximum (p = .438) error. For a full arch of crowns, the regression model predicted average and maximum errors of 0.581 and 0.697 mm for the markerless technique, and 0.185 and 0.210 mm for the fiducial marker-based technique. Overall, the fiducial marker-based technique was more accurate for four or more crowns. The half rotation scan increased average error by 0.021 mm (p = .001) and maximum error by 0.029 mm (p < .001).

CONCLUSIONS

Under the present study's experimental conditions, the fiducial marker-based technique should be considered if four or more full-coverage highly radiopaque restorations are present.

The influence of metal artifact reduction on the trueness of registration of a cone-beam computed tomography scan with an intraoral scan in the presence of severe restoration artifact

PURPOSE

When planning guided implant surgery, highly radiopaque materials such as metals or zirconia produce streaking artifacts ('metal artifact') on cone-beam computed tomography scans, which can impair registration of the intraoral scan. This study aimed to determine the effect of metal artifact reduction on the trueness of registration in the presence of multiple full-coverage zirconia crowns.

MATERIALS AND METHODS

A 3D-printed maxillary study model was restored with 12 full-coverage zirconia crowns and scanned with an intraoral scanner. Cone-beam computed tomography scans of the study model were acquired, with and without activation of the metal artifact reduction algorithm. Registration of the optical scans was performed using initial point-based registration with surface-based refinement, and the deviation was measured at four pre-defined dental landmarks. Welch's t-test was used to compare the registration error for the metal artifact reduction group with the control group.

RESULTS

The average registration error was 0.519 mm (95% CI 0.507 to 0.531) with metal artifact reduction deactivated, compared to 0.478 mm (95% CI 0.460 to 0.496) without metal artifact reduction. Therefore, activation of the metal artifact reduction algorithm was associated with a 0.041 mm (95% CI 0.020 to 0.061, p < 0.001) increase in average registration error.

CONCLUSIONS

The use of the metal artifact reduction algorithm slightly reduced trueness in this in vitro study. Clinicians are advised not to rely on a metal artifact reduction (MAR) algorithm for registration of a cone-beam computed tomography scan with an intraoral scan when planning guided implant surgery in the presence of restoration artifacts.

A chairside digital radiographic guide for registering digital casts to cone beam computed tomography scans with strong metallic artifacts

Accurate registration of digital casts and cone beam computed tomography (CBCT) scans with strong metallic artifacts is essential for the accuracy of guided implant surgery. This article describes a procedure for mapping digital casts onto CBCT scans containing significant scatter artifacts in the virtual implant planning stage. The technique uses a chairside segmented occlusal wing-like radiographic guide, which is constructed of digital splints fabricated using a desktop 3-dimensional printer and composite resin spheres as markers to accurately superimpose the bimaxillary digital scans onto the CBCT scans in a single procedure. This cost-effective technique is timesaving for clinicians and patients, and the digital information for implant planning can be collected in a single visit.

Integration accuracy of craniofacial cone-beam computed tomography images with three-dimensional facial scans according to different registration areas

OBJECTIVES

To evaluate the integration accuracy of cone-beam computed tomography (CBCT) images with three-dimensional (3D) facial scans according to different registration areas.

MATERIALS AND METHODS

Twenty-five patients (14 males and 11 females), with a mean age of 19.0 ± 11.3 years, were included in this study. Each patient underwent CBCT and facial scans on the same day in an upright position. The facial scans were integrated with the corresponding soft-tissue images of CBCT scans. Three methods were used to integrate the two imaging modalities based on the facial regions scanned: R1, only the forehead and nasal bridge area were included; R2, the right and left malar area were included; and R3, the forehead, nasal bridge, and malar areas were included. The integration accuracy between the facial scans and CBCT images was evaluated by color-mapping methods and average surface distances, calculated by measuring the 3D distances between the surface points on the two superimposed images.

RESULTS

The average surface differences between facial scans and CBCT images were less than 1.0 mm in all three methods. The R3 method showed fewer differences between the facial scans and CBCT images than the other methods did.

CONCLUSIONS

Facial scans obtained using a low-cost facial scanner showed clinically acceptable performance. The integration accuracy of facial and CBCT scans can be increased by including the forehead, nasal bridge, and malar areas as registration areas.

Accuracy of markerless registration methods of DICOM and STL files used for computerized surgical guides in mandibles with metal restorations: An in vitro study

STATEMENT OF PROBLEM

Digital imaging and communications in medicine (DICOM) files together with surface scans must be accurately registered in virtual implant planning software programs to match real-life dimensions and ensure correct plan transfer through computer-aided manufactured surgical guides.

PURPOSE

The purpose of this in vitro study was to evaluate the accuracy of 3 different registration methods of DICOM data with and without metal restorations and a metal artifact reduction (MAR) tool for surface scans.

MATERIAL AND METHODS

Thirteen dentate mandibles were assigned to each group of this study (n=39). Baseplate wax was adapted to the bone surfaces of each mandible, and 5 radiopaque markers were attached. A desktop scanner was used to obtain control scans. The groups of metal-free mandibles (MFM) and mandibles with metal restorations (MRM) were scanned to obtain DICOM data without a MAR tool. Additional DICOM data for the MRM were obtained with the MAR tool (MRM-MAR). Point-based registration (PBR), best-fit registration (BFR), and automatic registration (AR) were used to align standard tessellation language (STL) and DICOM data, and 3 data sets were exported. Radiographic markers on each data set were compared with those on the control scan, and positional deviations were calculated and statistically evaluated with 1-way ANOVA followed by multiple pairwise comparisons, independent samples t test, and 2-way ANOVA (α=.05).

RESULTS

Within each group, PBR had the lowest deviation values with statistical significance in the MFM and the MRM-MAR groups (P<.001). AR showed failure in the MRM and the MRM-MAR groups. Statistically significant differences were found on comparing the average deviations among the 3 groups for PBR only (P<.001). No association was found between deviation values and the presence or absence of metal restoration, while a positive association was found with the type of registration method (P<.001).

CONCLUSIONS

PBR had the highest accuracy level compared with AR and BFR methods. An increase in the number of calculations resulted in more deviation values. The MAR tool had a positive effect on PBR in mandibles with metal restorations.

Integrating maxillary dentition and 3D facial photo using a modified CAD/CAM facebow

Background

Accurate integration of the dentitions with the face is essential in dental clinical practice. Here we introduce a noninvasive and efficient protocol to integrate the digitized maxillary dentition with the three-dimensional (3D) facial photo using a prefabricated modified computer-aided design/computer-aided manufacture (CAD/CAM) facebow.

Methods

To integrate the maxillary dentition with the 3D facial photo, the CAD/CAM facebow protocol was applied to 20 patients by taking a series of 3D facial photos in the clinic and integrating them in the laboratory. The integration accuracy of this protocol was compared with that of a valid 3D computed tomography (CT)-aided protocol concerning translational deviations of the landmarks representing maxillary incisors and maxillary first molars as well as the rotational deviation of the maxillary dentition. The intra- and inter-observer reproducibility was assessed, and the time of clinical operation and laboratory integration was recorded.

Results

This facebow-aided protocol generated 3D fused images with colored faces and high-resolution dentitions, and showed high reproducibility. Compared with the well-established CT-aided protocol, the translational deviations ranged from 0 to 1.196 mm, with mean values ranging from 0.134 to 0.444 mm, and a relatively high integration error was found in the vertical dimension (Z) with a mean ± standard deviation (SD) of 0.379 ± 0.282 mm. Meanwhile, the rotational deviations ranged from 0.020 to 0.930°, with mean values less than 1°, and the most evident deviation was seen in pitch rotation with a mean ± SD of 0.445 ± 0.262°. The workflow took 4.34 ± 0.19 min (mins) for clinical operation and 11.23 ± 0.29 min for laboratory integration.

Conclusion

The present radiation-free protocol with the modified CAD/CAM facebow provided accurate and reproducible transfer of the digitized maxillary dentition to the 3D facial photo with high efficiency.

Accuracy of a surface-based fusion method when integrating digital models and the cone beam computed tomography scans with metal artifacts

The aim of this study was to evaluate the intra- and inter-observer reliability of maxillary digital dental model integration into cone-beam computed tomography (CBCT) scans to reconstruct three-dimensional (3D) skeletodental models for orthognathic patients. This retrospective study consisted of CBCT and digital maxillary dentition images of 20 Class III orthognathic patients. After two repeated fusions of digital cast images with reconstructed CBCT images by a digital engineer and an orthodontist respectively, the 3D coordinate values of the canines, first molars, and central incisors were evaluated. The intra- and inter-observer reliability of 3D positions of maxillary teeth were compared using intraclass correlation coefficients (ICCs). Intra-observer reliability of x-, y-, and z-coordinate values of maxillary teeth showed significant and excellent agreement in an engineer (0.946 ≤ ICC ≤ 1.000) and an orthodontist (0.876 ≤ ICC ≤ 1.000). The inter-observer reliability of the y- and z-coordinates of each tooth was significantly excellent or good, but that of the x-coordinates showed insignificantly poor to moderate agreement. This study showed that the integration of maxillary digital models into CBCT scans was clinically reliable. However, considering the low inter-observer reliability on the x-coordinates of dentition, clinical experience and repeated learning are needed for accurate application of digital skeletodental model in orthognathic patients.

Evaluation of different registration methods and dental restorations on the registration duration and accuracy of cone beam computed tomography data and intraoral scans: a retrospective clinical study

OBJECTIVES

To evaluate whether the accuracy and duration of registration for cone beam computed tomography (CBCT) and intraoral scans differ according to the method of registration and ratio of dental restorations to natural teeth.

MATERIALS AND METHODS

CBCT data and intraoral scans of eligible patients were grouped as follows according to the ratio of the number of dental restorations to the number of natural teeth (N): group 1, N = 0%; group 2, 0% < N < 50%; group 3, 50% ≤ N < 100%; and group 4, 100% ≤ N. Marker-free registration was performed with a deep learning-based platform and four implant planning software with different registration methods (two point-based, one surface-based, and one manual registration software) by a single operator, and the time consumption was recorded. Registration accuracy was evaluated by measuring the distances between the three-dimensional models of CBCT data and intraoral scans.

RESULTS

A total of 36 patients, one jaw per patient, were enrolled. Although registration accuracy was similar, the time consumed for registration significantly differed for the different methods. The deep learning-based registration method consumed the least time. Greater proportions of dental restorations significantly reduced the registration accuracy for semi-automatic and deep learning-based methods and reduced the time consumed for semi-automatic registration.

CONCLUSIONS

No superiority in registration accuracy was found. The proportion of dental restorations significantly affects the accuracy and duration of registration for CBCT data and intraoral scans.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: KCT0006710 CLINICAL RELEVANCE: Registration accuracy for virtual implant planning decreases when the proportion of dental restorations increases regardless of registration methods.

3D Printing and Virtual Surgical Planning in Oral and Maxillofacial Surgery

Compared to traditional manufacturing methods, additive manufacturing and 3D printing stand out in their ability to rapidly fabricate complex structures and precise geometries. The growing need for products with different designs, purposes and materials led to the development of 3D printing, serving as a driving force for the 4th industrial revolution and digitization of manufacturing. 3D printing has had a global impact on healthcare, with patient-customized implants now replacing generic implantable medical devices. This revolution has had a particularly significant impact on oral and maxillofacial surgery, where surgeons rely on precision medicine in everyday practice. Trauma, orthognathic surgery and total joint replacement therapy represent several examples of treatments improved by 3D technologies. The widespread and rapid implementation of 3D technologies in clinical settings has led to the development of point-of-care treatment facilities with in-house infrastructure, enabling surgical teams to participate in the 3D design and manufacturing of devices. 3D technologies have had a tremendous impact on clinical outcomes and on the way clinicians approach treatment planning. The current review offers our perspective on the implementation of 3D-based technologies in the field of oral and maxillofacial surgery, while indicating major clinical applications. Moreover, the current report outlines the 3D printing point-of-care concept in the field of oral and maxillofacial surgery.

Efficacy of Constructing Digital Hybrid Skull-Dentition Images Using an Intraoral Scanner and Cone-Beam Computed Tomography

Cone-beam computed tomography (CBCT) can distort dentition, and additional imaging is often required. A plaster model to help digitize dental images has been widely used in clinical practice, but there are some inconveniences such as complexity of the process and the risk of damage. The aim of this study was to evaluate the potential for improving dentition imaging with CBCT scans using an intraoral scanner instead of a plaster model. The study used laser model-scanned images of plaster models, imaging from two intraoral scanners, and CBCT images from 20 patients aged 12-18 years. CS 3600 (Carestream Dental, Atlanta, USA) and i700 (Medit, Seoul, Korea) were used as intraoral scanners. The full arch was scanned at once or in three sections using intraoral scanners. The segmented scans were merged to obtain full-arch images. With i700, full-arch images were additionally acquired using its "smart stich" function. The virtual skull-dentition hybrid images obtained from intraoral scanners were superimposed with images obtained using a plaster cast. The difference and distance of coordinate values at each reference point were measured. The average distances from the images obtained with the plaster cast were smaller than 0.39 mm, which is the voxel size of CBCT. Scanning the complete or partial arch using CS 3600 or i700 satisfactorily complemented the CBCT when compared to the plaster model. The virtual skull-dentition hybrid image obtained from intraoral scanners will be clinically useful, especially for patients and surgeons who have difficulty in scanning the complete arch at once.

Radiopaque fiducial markers as an aid to fabrication of an implant surgical guide for a patient with orthodontic brackets: A dental technique

Designing implant surgical guides for patients undergoing orthodontics merely by merging data imaging and communications in medicine (DICOM) files generated from cone beam computed tomography (CBCT) images and standard tessellation language (STL) files generated from surface scanners is challenging because of the inaccuracy caused by metal artifacts. The present technique describes a straightforward and effective method of fabricating a surgical guide with the aid of fiducial markers made from cotton swabs and flowable resin. The implant surgical guide is designed by using a software program after the superimposition of digital scan and CBCT data. This chairside technique provides an accurate, convenient, and cost-effective option for the clinician.

The question about the numerical value and quantitative data transfer of implant prosthodontics-orom experience guidance to digital guidance

The correct implant site design and placement are the basic clinical techniques that must be known for implant restoration. For a long time, most implants have been placed by free hands, and the choice of site is mostly dependent on the accumulation of long-term experience of the surgeon. The selection of implant site guided by this experience analogy logic is often based on the surgeon's level of experience,which often makes it very easy to produce complications related to the implant restoration of the incorrect site. In contrast, a clinical program using digital guidance and real-time measurable verification has emerged based on the restoration-oriented implantation concept, which marks the formation of an accurate, measurable and verifiable whole-process digital implant prototype. Furthermore, from the perspective of surveying, the numerical requirements that digital implant restoration relies on are actually incomplete to the four elements of measurement, which leading to the doubts about its authenticity. This article will question the numbers in implant restoration, and conduct a preliminary demonstration, and propose a new reliable actual measurement and verification method of the correct location and the numerical requirements of the restoration space and a new clinical program that relies on numbers from the perspective of the evolution of digital restoration, guided implantology and actual measurement technology. And this article further discusses the current mainstream implant restoration technology based on experience analogy which cannot effectively support the whole process of digital implant restoration and provides a new logical cognitive basis for the final realization of the entire process of digital implant restoration.

Effects of Exposure Parameters and Voxel Size for Cone-Beam Computed Tomography on the Image Matching Accuracy with an Optical Dental Scan Image: An In Vitro Study

This study is aimed at assessing the effects of exposure parameters and voxel size for cone-beam computed tomography (CBCT) on the image matching accuracy with an optical dental scan image. CBCT and optical scan images of a dry human mandible were obtained. Different CBCT settings were used: tube voltage, 60, 80, and 100 kVp; tube current, 6 and 8 mA; and voxel size, 100, 200, and 300 μm. Image matching between the CBCT and optical scan images was performed using implant planning software by dental professionals (n = 18). The image matching accuracy in each combination of CBCT settings was evaluated by assessing the linear discrepancy between the three-dimensionally reconstructed radiological image and the registered optical scan image using an image analysis software program. The Kruskal-Wallis test and a post hoc Mann–Whitney U test with Bonferroni correction were used to compare the accuracy of image registration between the groups (α = 0.05). Overall, the image matching accuracy was not significantly different between tube voltage and current settings; however, significantly higher image registration errors were found at the combination of 100 kVp tube voltage/8 mA tube current (F = 8.44, P < 0.001). Changes in voxel sizes did not significantly interfere with the image registration results. No interaction was found among voltage, current, and voxel size in terms of image registration accuracy (F = 2.022, P = 0.091). Different exposure parameter settings in tube voltage and tube current did not significantly influence the image matching accuracy between CBCT and optical dental scan images; however, a high radiation dose could be inappropriate. The image matching accuracy was not significantly affected by changing the voxel sizes of CBCT.

Orthognathic Surgery: A Bibliometric Analysis of the Top 100 Cited Articles

PURPOSE

An increasing number of articles on orthognathic surgery are published every year. This paper aims to provide a list of the top 100 cited articles on orthognathic surgery to help any professional level with interest in this topic and to map the trends of orthognathic surgery publications over time.

METHODS

A bibliographic search (retrospective study) following STROBE guidelines was performed on Google Scholar (GS) and Dimensions with the term "orthognathic surgery" in the title, abstract, and keywords. The number of citations, citations per year, authors, and publication year were evaluated. A ranking was created in GS citations order with the top 100 cited articles and variables discussed individually. A graphical illustration of keywords was created using VOSviewer. These steps are fundamental in creating this list and relating it to all published articles on the topic.

RESULTS

A helpful list of the top 100 articles was developed to help professionals in entirely different manners. Virtual planning and complications in orthognathic surgery were the most cited topics, with a 95% confidence interval (P < .05). Some curiosities are discussed, such as increasing interest in surgery first and the relation between airway/obstructive sleep apnea and orthognathic surgery.

CONCLUSIONS

Bibliometric and altmetric analysis for free using Google Scholar and Dimensions is laborious but possible. Bibliometrics is a powerful tool to become actualized at any health professional level, from students to academics; and could save considerable effort and time for parties interested in the topic. Appropriate keywords are a crucial step to wider article dissemination.

Accuracy of digital model generated from CT data with metal artifact reduction algorithm

This study investigated whether metal artifact reduction (MAR) applied computed tomography (CT) scans could be used to generate precise digital models and explored possible correlations between the amount of metal artifact and model accuracy. Thirty maxillofacial CT scans were randomly selected and a MAR algorithm was applied. By subtracting the original and MAR-applied CT images, the amount of metal artifact was quantified. Digital models were generated from the original and the MAR-applied CT data. Paired digital models were superimposed and shape deviation in planar surface was measured at 10 points in 4 planes. Statistical analyses were performed to compare deviations and to assess correlations between the amount of artifact and deviation. The MAR algorithm reduced metal artifact in all cases. The overall mean deviation of the MAR-applied models was 0.0868 mm, with no significant difference according to the reference plane. The amount of artifact did not significantly influence the accuracy of the digital models. MAR-applied CT is a convenient source for digital modeling with clinically acceptable accuracy. The MAR algorithm can be used regardless of the amount of metal artifact, which are generated by dental prostheses, for the quick and convenient manipulation of dental digital models.

Prosthetically-Driven Full-Mouth Implant-Supported Prostheses Using Guided Surgical Implant Planning with Composite Resin Markers: A Case Report

This report describes a prosthetically-driven implant planning method, guided by the alignment procedures between the cone beam computed tomography, intraoral digital scans, and digitized maxillary and mandibular interim complete dentures using intraoral composite resin markers as a common reference. The markers were attached to the keratinized oral mucosa of the edentulous ridges using cyanoacrylate and kept in place during the digitizing procedures. The technique provides a simpler and more economical alternative to conventional prosthetically-driven static implant planning methods.

Fusion of intra-oral scans in cone-beam computed tomography scans

PURPOSE

The purpose of this study was to evaluate the clinical accuracy of the fusion of intra-oral scans in cone-beam computed tomography (CBCT) scans using two commercially available software packages.

MATERIALS AND METHODS

Ten dry human skulls were subjected to structured light scanning, CBCT scanning, and intra-oral scanning. Two commercially available software packages were used to perform fusion of the intra-oral scans in the CBCT scan to create an accurate virtual head model: IPS CaseDesigner® and OrthoAnalyzer™. The structured light scanner was used as a gold standard and was superimposed on the virtual head models, created by IPS CaseDesigner® and OrthoAnalyzer™, using an Iterative Closest Point algorithm. Differences between the positions of the intra-oral scans obtained with the software packages were recorded and expressed in six degrees of freedom as well as the inter- and intra-observer intra-class correlation coefficient.

RESULTS

The tested software packages, IPS CaseDesigner® and OrthoAnalyzer™, showed a high level of accuracy compared to the gold standard. The accuracy was calculated for all six degrees of freedom. It was noticeable that the accuracy in the cranial/caudal direction was the lowest for IPS CaseDesigner® and OrthoAnalyzer™ in both the maxilla and mandible. The inter- and intra-observer intra-class correlation coefficient showed a high level of agreement between the observers.

CLINICAL RELEVANCE

IPS CaseDesigner® and OrthoAnalyzer™ are reliable software packages providing an accurate fusion of the intra-oral scan in the CBCT. Both software packages can be used as an accurate fusion tool of the intra-oral scan in the CBCT which provides an accurate basis for 3D virtual planning.

[Method and accuracy of determining the jaw position of repositioning splint with the aid of digital technique]

OBJECTIVE

To establish the workflow of determining the jaw position of repositioning splint with the aid of digital technique, and to evaluate the accuracy of this workflow and compare the accuracy of raising different vertical dimensions in vitro.

METHODS

A volunteer was recruited. The data of full-arch scans, cone beam computed tomography (CBCT) image and ultrasonic jaw motion tracking of the volunteer were acquired. The full-arch scans were merged with the CBCT image, which were then matched to the jaw motion tracking reference system. The jaw position of repositioning splint was determined when the anterior teeth opening was 3 mm and the condyle was in centric relation of the fossa in the sagittal plane. A digital repositioning splint was designed in the software based on virtual articulator and fabricated with additive manufacturing technique. After the splint was tried in, another CBCT image was taken and a qualitative analysis was conducted to compare the position of condyle between these two CBCT images. In the in vitro study, standard dental plaster casts with resin ball markers attached to the base were mounted onto a fully adjustable articulator in the intercuspal position. The dental casts were scanned by an extraoral scanner to establish digital models. The ultrasonic jaw motion tracking device was used to obtain simulated jaw movements on the articulator, which was repeated for three times. The digital models and data of jaw movements were merged in one coordination with the aid of bite forks. The jaw position of repositioning splint was determined by adjusting data of jaw movements, each of which was used to determine three vertical jaw positions 4 mm, 5 mm, and 6 mm with the horizontal jaw position of protrusion 2 mm. The virtual articulators with differently adjusted jaw movements were applied in designing repositioning splints, and the final repositioning splints and virtual jaw relationships were exported in STL format. Then the repositioning splints were fabricated with additive manufacturing technique and tried in plaster casts on the mechanical articulator, which were scanned and the jaw relationships on the mechanical articulator were exported later. The virtual jaw relationships and scanned jaw relationships were registered according to lower models and displacement of upper models was calculated. Ball markers were fit to acquire the coordinates of centers and absolute difference values of centers along three coordinating axes X, Y, and Z were calculated. One-way analysis of variance was conducted using SPSS 18.0 software to compare deviations of the three different vertical jaw relationships in two-side test and the significance level was 0.05.

RESULTS

With the aid of multi-source data fusion and individualized jaw motion, the clinical workflow of determining jaw position of repositioning splint was preliminarily established. The designed jaw position was realized on the right and the condyle was more inferior than the designed position on the left. Both displacement of the upper models and absolute difference values of centers showed no significant differences (P>0.05) in different vertical jaw dimensions. The displacement of the upper models was (0.25±0.04) mm. The absolute difference values of centers along the three coordinating axes X, Y, and Z were respectively (0.08±0.01) mm, (0.30±0.02) mm, and (0.21±0.04) mm.

CONCLUSION

A novel method of determining the jaw position of repositioning splint with the aid of digital technique is established. It is proved to be feasible by try-in after multi-data fusion, computer-aided design and computer-aided manufacturing. As is shown in vitro, it is accurate to apply this method in adjusting jaw position. Further clinical trial will be designed to evaluate its clinical effect.

A dual scan approach to creating an accurate dental surface for virtual implant planning: A dental technique

Artifacts from metal restorations can make it challenging or impossible to accurately orient a digital dental cast to cone beam computed tomography (CBCT) scan data for virtual implant planning. A dual scan technique is described that uses an alginate impression with fiducial markers in a stock tray to create a digital dental cast that is precisely oriented to the scan in the same patient coordinate system for surgical guide design.

Effect of artifact area on cone beam computed tomography scans when integrated with intraoral scans

OBJECTIVE

The aim of this study was to examine whether integration accuracy increases upon removing artifacts from the registration area when integrating maxillofacial cone beam computed tomography (CBCT) scans and intraoral scans.

STUDY DESIGN

Three methods were implemented according to the region of interest (ROI): R0, all teeth included as the registration area (artifacts included); R1, anterior teeth included as the registration area (artifacts in premolars and molars not included); and R2, anterior teeth and second molars included as the registration area (artifacts in premolars and first molars not included). Discrepancies between the 2 images were evaluated by using color-mapping methods. The average surface distance was calculated by measuring the shell/shell deviations for overall discrepancies and 3-dimensional distances between the surface points on the 2 images for registration discrepancies.

RESULTS

The R1 method showed more discrepancies between the CBCT and intraoral scans compared with the other 2 methods. The R2 method showed smaller overall discrepancy values compared with the R1 method. Most CBCT artifacts were located in the posterior area. Registration discrepancies were greatest in the x-dimension.

CONCLUSIONS

The results suggest that intraoral and CBCT scans might be integrated by using a registration method that involves exclusion of artifacts and inclusion of the second molar on both sides.

Impacts of Thresholds of Gray Value for Cone-Beam Computed Tomography 3D Reconstruction on the Accuracy of Image Matching with Optical Scan

In cone-beam computed tomography (CBCT), the minimum threshold of the gray value of segmentation is set to convert the CBCT images to the 3D mesh reconstruction model. This study aimed to assess the accuracy of image registration of optical scans to 3D CBCT reconstructions created by different thresholds of grey values of segmentation in partial edentulous jaw conditions. CBCT of a dentate jaw was reconstructed to 3D mesh models using three different thresholds of gray value (-500, 500, and 1500), and three partially edentulous models with different numbers of remaining teeth (4, 8, and 12) were made from each 3D reconstruction model. To merge CBCT and optical scan data, optical scan images were registered to respective 3D reconstruction CBCT images using a point-based best-fit algorithm. The accuracy of image registration was assessed by measuring the positional deviation between the matched 3D images. The Kruskal-Wallis test and a post hoc Mann-Whitney U test with Bonferroni correction were used to compare the results between groups (α = 0.05). The correlations between the experimental factors were calculated using the two-way analysis of variance test. The positional deviations were lowest with the threshold of 500, followed by the threshold of 1500, and then -500. A significant interaction was found between the threshold of gray values and the number of remaining teeth on the registration accuracy. The most significant deviation was observed in the arch model with four teeth reconstructed with a gray-value threshold of -500. The threshold for the gray value of CBCT segmentation affects the accuracy of image registration of optical scans to the 3D reconstruction model of CBCT. The appropriate gray value that can visualize the anatomical structure should be set, especially when few teeth remain in the dental arch.

Registration of digital dental models and cone-beam computed tomography images using 3-dimensional planning software: Comparison of the accuracy according to scanning methods and software

INTRODUCTION

The registration of cone-beam computed tomography (CBCT) images and digital dental models is required for the design and manufacturing of dental devices such as implant guides and surgical wafers. This study aims to register intraoral scan (IS) models and cast scan (CS) models onto CBCT images using 3-dimensional (3D) planning software and evaluate the registration accuracy according to scanning methods and 3D planning software.

METHODS

The CBCT image of an artificial skull model with reference markers was taken. The CS model and the IS model were obtained from the same skull model, registered onto the CBCT image using 3D planning software packages providing manual registration (MR) function and point-based registration (PR) functions, and set as the experimental groups. After registration, shell to shell deviations and positional differences between the reference model and the experimental models were evaluated.

RESULTS

The shell to shell deviations ranged from 0.03 to 0.18 mm. Deviations in both the maxilla and mandible were significantly different according to scanning methods and software packages. In the anteroposterior direction, the IS-MR and CS-MR groups showed significantly different positions. In the superoinferior direction, the MR and PR groups showed significantly different positions.

CONCLUSIONS

The registration using the PR function of the 3D planning software packages was significantly more accurate than the registration using the MR function. There was no significant difference between the registrations using the IS model and the CS model when using the PR functions.

Design and manufacture of dental-supported surgical guide for genioplasty

Background/purpose

Genioplasty were used widely to correct chin deformities. The purpose of this study was to design and manufacture a dental-supported surgical guide for genioplasty surgery and assess for surgical accuracy.

Materials and methods

eleven patients with chin deformities were treated in this study. The computed tomography (CT) data of the patient's skull and the digital dental models of stone dental models were acquired preoperatively. For each patient, a virtual three-dimensional (3D) model of the skull was constructed and enhanced with digital dental models. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on clinical examination and 3D cephalometry. The surgery was simulated preoperatively which allowed the design of a cutting guide and a dental-supported repositioning guide for genioplasty, which was then 3D-printed and used during operation after disinfection. After surgery, the outcome was evaluated by superimposing the postoperative CT model onto the preoperative model, recording the linear and angular deviation of landmarks and plane, then measuring the differences between the planned and actual outcomes.

Results

The osteotomy and repositioning were successfully performed as planned using surgical guides. No inferior alveolar nerve damage was seen in this study. The dental-supported surgical guide showed excellent accuracy, with the largest differences between the planned and the postoperative chin segment being 0.9 mm and 3.2°.

Conclusion

The dental-supported surgical guide designed preoperatively provided a reliable method of transfer genioplasty planning. This can assist surgeons in accurately performing osteotomy and repositioning bone segments during a genioplasty.

Comparison of the Accuracy of Image Registration Methods for Merging Optical Scan and Radiographic Data in Edentulous Jaws

PURPOSE

The image registration of optical scans to radiographic images is essential for performing computer-guided implant surgery. This study aimed to evaluate the effect of different image matching conditions on the accuracy of image registration for computer-guided implant surgery in completely edentulous jaws.

MATERIALS AND METHODS

The optical scan image of a completely edentulous study model was registered to the respective cone-beam computed tomography data using three different image matching conditions: small point (SP), large point (LP), and entire surface (ES). For the SP and LP groups, gutta-percha markers (1.0 and 3.0 mm in diameter) were attached to a base template, and a radiopaque impression material was relined on the intaglio surface of template in the ES group. Image registration was performed by 20 operators in the images obtained from each group at an interval of 2 weeks (n = 20 in each group), and the registration accuracy was assessed by calculating the aligned position of the edentulous arch image. One-way analysis of variance with Tukey post hoc tests was used to compare the results among the groups (α = 0.05).

RESULTS

The mean registration error was significantly larger in the SP group (0.52 ± 0.19 mm) than in the LP group (0.29 ± 0.08 mm) and ES group (0.27 ±0.06 mm) (F = 24.689, p < 0.001). No difference was found between the LP and ES groups. The image matching discrepancy was more homogeneously distributed on the arch in the ES group than in the other groups.

CONCLUSION

The accuracy of image registration is affected by the size of the congruent area shown in the optical scan and radiographic images. The entire surface-based matching method is more accurate as compared to the small point-based matching method in the image registration for implant planning in full edentulous jaws.

Virtual implant planning and fully guided implant surgery using magnetic resonance imaging-Proof of principle

OBJECTIVES

To present a workflow of virtual implant planning and guided implant surgery with magnetic resonance imaging (MRI) and virtual dental models without the use of ionizing radiation.

METHODS

Five patients scheduled for implant placement underwent an MR examination at three Tesla using individualized 2D and 3D turbo spin-echo (TSE) sequences and dedicated head coils. The MRI data and virtual dental models derived from either optical model scans or intraoral scans were imported to a virtual implant planning software (coDiagnostiX, Dental Wings, Montreal, Canada). Virtual prosthetic planning and implant planning were performed regarding the hard and soft tissue anatomy. A drill guide was designed on the virtual dental model using computer-aided design (CAD) and manufactured in-house, using a 3D printer (Eden 260V, Stratasys, Eden Prairie, MN, USA).

RESULTS

The MRI displayed all relevant anatomical structures for dental implant planning such as cortical and cancellous bone, floor of the nasal and maxillary sinus, inferior alveolar nerve and neighboring teeth. The manual alignment of virtual dental models with the MRI was possible using anatomical landmarks. Dental implant planning, CAD/CAM of a drill guide and fully guided implant placement were successfully performed.

CONCLUSIONS

Guided implant surgery is feasible with MRI without ionizing radiation. Further studies will have to be conducted to study the accuracy of the presented protocol and compare it to the current workflow of guided surgery using CBCT.

Registration accuracy between intraoral-scanned and cone-beam computed tomography-scanned crowns in various registration methods

INTRODUCTION

The purpose of this study was to investigate the registration accuracy between intraoral-scanned crowns and cone-beam computed tomography (CBCT)-scanned crowns in various registration methods.

METHODS

The samples consisted of 18 Korean adult patients, whose pretreatment intraoral scans and CBCT images were available. A 3-dimensional (3D) dental model was fabricated using a TRIOS intraoral scanner (3Shape, Copenhagen, Denmark) and the OrthoAnalyzer program (version 1.7.1.4; 3Shape). After the CBCT image was taken, 3D volume rendering was performed to fabricate a 3D dental model using InVivo5 software (version 5.1; Anatomage, San Jose, Calif). Registration of the 3D dental crowns made from intraoral- and CBCT-scanned images was performed with Rapidform 2006 software (Inus Technology, Seoul, Korea) by a single operator. According to registration methods, 3 groups were established: individual-arch-total-registration group, individual-arch-segment-registration group, and bimaxillary-arch-centric-occlusion-registration group (n = 18 per group). After the amounts of shell/shell deviation were obtained, the mixed model analysis of variance and Bonferroni correction were performed.

RESULTS

Although there was no significant difference in the registration accuracy between the individual-arch-total-registration group and individual-arch-segment-registration group, the bimaxillary-arch-centric-occlusion-registration group exhibited the lowest registration accuracy (maxillary and mandibular teeth, all 0.21 mm in the individual-arch-total-registration group; all 0.20 mm in the individual-arch-segment-registration group vs 0.26 mm and 0.25 mm in the bimaxillary-arch-centric-occlusion-registration group; P <0.001). Color-coded visualization charts exhibited that most red spots were localized on the occlusal surface of the posterior teeth in all 3 groups.

CONCLUSIONS

When considering the registration accuracy and convenience of the process, the individual-arch-total-registration method can be regarded as an efficient tool when integrating CBCT-scanned crown and intraoral-scanned crown.

A technique for registering digital dental casts onto cone beam computed tomography scans with excessive metallic artifacts

This article describes a method of integrating digital dental casts into cone beam computed tomography (CBCT) scans in virtual implant planning in situations with an excessive number of metal artifacts. This technique requires the use of a prefabricated registration tray to provide a common landmark; is noninvasive, minimally time-consuming, and cost-effective; and requires only a single registration and minimal exposure to radiation.

Automatic matching of computed tomography and stereolithography data

BACKGROUND AND OBJECTIVE

Computed tomography (CT) is one of the most frequently used medical imaging methods. An important application area of CT is dental implants, which require precise inspection and analysis of oral structures. Since CT provides a precise 3D model of the teeth, bones and nerves, it can be used as a surgical guide for dental implants. Along with CT, optical 3D images called stereolithography (STL) have also been widely used. STL images obtained from optical 3D images can be used to show the 3D surfaces of oral structures. Since CT data and STL data deploy different technologies to obtain dental information, we can obtain more accurate dental implants by combining the two datasets. Since the two datasets are acquired by using different sensors, the datasets need to be registered.

METHODS

An automatic matching algorithm is proposed for CT and STL image registration, which is based on depth maps and maximum intensity projection. Then, fine tuning was performed based on volume matching.

RESULTS

When applied to real-world databases, the proposed method provided an average matching error of 2.7 mm for the upper jaw and 2.3 mm for the lower jaw with an average processing time of about 19 s.

CONCLUSIONS

The proposed method performs accurate registration of CT and STL.

Impact of number of registration points on the positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan by surface scan registration: An in vitro study

OBJECTIVES

To evaluate the accuracy of a prosthetic treatment plan incorporation into a cone beam computed tomography (CBCT) scan using point-based registration with three registration points selected and to evaluate the impact of number of registration points on prosthetic plan accuracy.

MATERIAL AND METHODS

A CBCT scan of a completely dentate master model with removable teeth was exposed after removing the mandibular left first premolar, second premolar, and first molar. A digital scan of the master model with all teeth present was made by scanning a stone replica using a laboratory scanner. The digital model was registered onto the three-dimensional (3D) volume rendering of the CBCT scan using implant planning software. The point-based registration was repeated using three, four, five, six, seven, eight, nine, and 10 reference points. Metrology software was used to measure the 3D deviation of the registered models for each reference point group on standard tessellation language (STL) files obtained from the CBCT scans. An STL file of the master model with all teeth present obtained from another CBCT scan was used as reference.

RESULTS

Using three registration points, the registered prosthetic plan had a mean absolute deviation of 17.63 µm from the reference. Increasing the number of registration points failed to demonstrate statistically significant effects on the deviation (p > 0.05).

CONCLUSIONS

For this clinical scenario, three registration points provided adequate accuracy for prosthetic plan incorporation into CBCT scans. Increasing the number of registration points had no significant impact on the prosthetic plan accuracy in this study.

Digital setting of postoperative planned occlusion using occlusal contact points on a dental cast model in digital maxillofacial surgery

OBJECTIVES

This study analyzed the accuracy of digital occlusion settings for maxillofacial surgery simulation using occlusal contact points obtained from dental cast models.

METHODS

Twenty-nine paired dental cast models of patients were used. The orthodontist set the dental cast for postoperative planned occlusion in the articulator. In the experimental group, a digital dental cast was placed in the occlusion state between the maxillary cast and the mandibular cast by the paired points matching method according to the more than four paired occlusal contact points. In the control group, the obtained digital dental cast data and occlusal lateral surface scan data were used to create maxillary and mandibular digital occlusions of the dental cast.

RESULTS

Significantly greater error occurred when occlusion was set based on paired points matched by occlusal contact points than when direct intraoral scanning was used.

CONCLUSIONS

This paired points matching method may be considered an alternative in cases in which superimposition using occlusal surfaces or the external surface of dental cast models is difficult in the clinical setting. However, the occlusal surface-based method for digital dental casts is recommended for digital planned occlusion in maxillofacial simulation.

Real-time augmented model guidance for mandibular proximal segment repositioning in orthognathic surgery, using electromagnetic tracking

It is essential to reposition the mandibular proximal segment (MPS) as close to its original position as possible during orthognathic surgery. Conventional methods cannot pinpoint the exact position of the condyle in the fossa in real time during repositioning. In this study, based on an improved registration method and a separable electromagnetic tracking tool, we developed a real-time, augmented, model-guided method for MPS surgery to reposition the condyle into its original position more accurately. After virtual surgery planning, using a complex maxillomandibular model, the final position of the virtual MPS model was simulated via 3D rotations. The displacements resulting from the MPS simulation were applied to the MPS landmarks to indicate their final postoperative positions. We designed a new registration body with 24 fiducial points for registration, and determined the optimal point group on the registration body through a phantom study. The registration between the patient's CT image and physical spaces was performed preoperatively using the optimal points. We also developed a separable frame for installing the electromagnetic tracking tool on the patient's MPS. During MPS surgery, the electromagnetic tracking tool was repeatedly attached to, and separated from, the MPS using the separable frame. The MPS movement resulting from the surgeon's manipulation was tracked by the electromagnetic tracking system. The augmented condyle model and its landmarks were visualized continuously in real time with respect to the simulated model and landmarks. Our method also provides augmented 3D coronal and sagittal views of the fossa and condyle, to allow the surgeon to examine the 3D condyle-fossa positional relationship more accurately. The root mean square differences between the simulated and intraoperative MPS models, and between the simulated and postoperative CT models, were 1.71 ± 0.63 mm and 1.89 ± 0.22 mm respectively at three condylar landmarks. Thus, the surgeons could perform MPS repositioning conveniently and accurately based on real-time augmented model guidance on the 3D condyle positional relationship with respect to the glenoid fossa, using augmented and simulated models and landmarks.

Assessing the Correlation between Skeletal and Corresponding Soft-Tissue Equivalents to Determine the Relationship between CBCT Skeletal/Dental Dimensions and 3D Radiographic Soft-Tissue Equivalents

Objective

Compare measurements of skeletal and dental areas on the CBCT to the corresponding soft-tissue measures taken from a 3D Facial Scanner.

Methods

30 patients with CBCT and 3D Facial scanner photos were selected from the orthodontic program database. 30 different distance measurements were obtained from CBCT and facial scan. OrthoInsight software was used to obtain the measurements from the facial scan images, and AVIZO software was used for corresponding CBCT landmarks. The Euclidean distance formula was used to determine the distances for the corresponding x, y, and z coordinates of the CBCT. Reliability for CBCT and Facial Scanner was completed by calculating 30 distances for 10 patients, 3 times. Once reliability was determined, all 30 distances were calculated once for CBCT and facial scanner on each patient and descriptive statistics and paired t-test were applied.

Results

All distances measured presented excellent reliability, the lowest one being the left eye width for the facial scanner (ICC 0.847). The landmark with the highest mean error on the CBCT was 2.0 ± 1.6 mm on the z-axis for the spinal level landmark. The Facial Scanner's largest mean measurement error was 1.5 ± 0.9 mm for the distance of the left corner of the mouth to gonion. All data except width between outer eye corners were statistically significant (p < 0.05). The average differences between facial scan and CBCT measurements ranged between 0.77 mm (left canine to cheekbone) to 26.94 mm (left subnasale to gonion) and are thus comparable. All measurements show a reasonable standard deviation between 2.57 mm (left eye width) to 9.91 mm (left gnathion to EAM).

Conclusion

Distances obtained from CBCT and facial scan present mild differences giving the perspective of a relationship between them. Understanding this difference and relationship can make it plausible to expect certain underlying skeletal distances under soft-tissue structures.

Accuracy of the match between cone beam computed tomography and model scan data in template-guided implant planning: A prospective controlled clinical study

BACKGROUND

Template-guided implant placement is a method for optimal implant positioning from a prosthetic and surgical viewpoint. The treatment planning is based on three-dimensional X-ray data and model scan data, as well as on prosthetic planning (set-up). These data are matched (superimposed) with the aid of an X-ray template or by manual matching without special referencing.

PURPOSE

The objective of this prospective controlled clinical study was to determine and compare the accuracy of the match with and without an additional X-ray template.

MATERIALS AND METHODS

The DICOM data of the cone beam computed tomography (CBCT) were converted into surface data sets and then superimposed on model scan data using three different methods (manually, based on an X-ray template, or semi-automatically with computer assistance). The mean deviations between these results of these matching methods were investigated.

RESULTS

The procedures achieved a matching accuracy of 0.2 mm on average. This corresponds to the resolution of the CBCT (0.2 voxels). Further studies are necessary to verify the procedure even for patients with few (0-4) residual teeth.

CONCLUSION

In the presence of a sufficient number of residual teeth, the manual matching of model scan data with CBCT data is sufficiently accurate for implant planning and template-guided implementation. The results of the present study suggest that X-ray templates can be dispensed with saving the patient a substantial amount of time and money.

Registration area and accuracy when integrating laser-scanned and maxillofacial cone-beam computed tomography images

INTRODUCTION

The purpose of this study was to examine changes in registration accuracy after including occlusal surface and incisal edge areas in addition to the buccal surface when integrating laser-scanned and maxillofacial cone-beam computed tomography (CBCT) dental images.

METHODS

CBCT scans and maxillary dental casts were obtained from 30 patients. Three methods were used to integrate the images: R1, only the buccal and labial surfaces were used; R2, the incisal edges of the anterior teeth and the buccal and distal marginal ridges of the second molars were used; and R3, labial surfaces, including incisal edges of anterior teeth, and buccal surfaces, including buccal and distal marginal ridges of the second molars, were used. Differences between the 2 images were evaluated by color-mapping methods and average surface distances by measuring the 3-dimensional Euclidean distances between the surface points on the 2 images.

RESULTS

The R1 method showed more discrepancies between the laser-scanned and CBCT images than did the other methods. The R2 method did not show a significant difference in registration accuracy compared with the R3 method.

CONCLUSIONS

The results of this study indicate that accuracy when integrating laser-scanned dental images into maxillofacial CBCT images can be increased by including occlusal surface and incisal edge areas as registration areas.

Accuracy of Three-dimensional Cone Beam Computed Tomography Digital Model Measurements Compared with Plaster Study Casts

Purpose

The purpose of this study was to assess the accuracy of three-dimensional (3D) cone beam computed tomography (CBCT) study casts by comparing with direct measurements taken from plaster study casts.

Materials and Methods

The dental arches of 30 patient subjects were imaged with a Kodak 9300 3D CBCT devise; Anatomodels were created and in vivo 5 imaging software was used to measure 10 dental arch variables which were compared to measurements of plaster study casts.

Results:

Three of the 10 variables, i.e., overbite, maxillary intermolar width, and arch length, were found significantly smaller (P < 0.05) using the Anatomodels following nonparametric Wilcoxon signed-rank testing. None of the differences found in the study averaged <0.5 mm.

Conclusions

3D CBCT imaging provided clinically acceptable accuracy for dental arch analysis. 3D CBCT imaging tended to underestimate the actual measurement compared to plaster study casts.

Integration of digital dental casts in cone beam computed tomography scans-a clinical validation study

OBJECTIVES

Images derived from cone beam computed tomography (CBCT) scans lack detailed information on the dentition and interocclusal relationships needed for proper surgical planning and production of surgical splints. To get a proper representation of the dentition, integration of a digital dental model into the CBCT scan is necessary. The aim of this study was to validate a simplified protocol to integrate digital dental models into CBCT scans using only one scan.

MATERIALS AND METHODS

Conventional protocol A used one combined upper and lower impression and two CBCT scans. The new protocol B included placement of ten markers on the gingiva, one CBCT scan, and two separate impressions of the upper and lower dentition. Twenty consecutive patients, scheduled for mandibular advancement surgery, were included. To validate protocol B, 3-dimensional reconstructions were made, which were compared by calculating the mean intersurface distances obtained with both protocols.

RESULTS

The mean distance for all patients for the upper jaw is 0.39 mm and for the lower jaw is 0.30 mm. For ten out of 20 patients, all distances were less than 1 mm. For the other ten patients, all distances were less than 2 mm.

CONCLUSIONS

Mean distances of 0.39 and 0.30 mm are clinically acceptable and comparable to other studies; therefore, this new protocol is clinically accurate.

CLINICAL RELEVANCE

This new protocol seems to be clinically accurate. It is less time consuming, gives less radiation exposure for the patient, and has a lower risk for positional errors of the impressions compared to other integration protocols.

Systematic three-dimensional analysis of wafer-based maxillary repositioning procedures in orthognathic surgery

PURPOSE

Little is known about the three-dimensional (3D) transfer accuracy in maxillary repositioning procedures based on conventionally manufactured dental-mounted wafers. The purpose of the present study was a systematic 3D analysis for wafer-based maxillary positioning in orthognathic surgery.

MATERIALS AND METHODS

A total of 92 patients underwent Le Fort I in addition to mandibular bilateral sagittal split osteotomies (BSSO). Alignment of the pre- and postsurgical CBCT data sets allowed measuring maxillary position changes in axial, sagittal and transversal directions.

RESULTS

The highest achieved absolute transfer inaccuracies were 1.37 mm, ±0.84 in the sagittal direction, followed by 1.15 mm, ±0.69 in the axial, as well as 1.05 mm, ±0.79 in the transversal direction. The largest relative deviations could be found for repositions in the transversal plane (109.4%, ±4.5), followed by the axial (66.2%, ±51.5) and sagittal plane (49.3%, ±2.2). Significant transfer accuracy differences of repositioning procedures in the sagittal direction, mainly advancement procedures, could be detected if performed with (1.75 mm, ±0.90) or without (1.18 mm, ±0.78) additional rotational correction component. No significant differences were found between unidirectional and multidirectional maxillary correction procedures.

CONCLUSION

The present study for the first time delivers systematic 3D accuracy data of wafer-based maxillary positioning procedures, attesting to its feasibility but also further encouraging the search for improvement strategies.

Registration of cone beam computed tomography data and intraoral surface scans - A prerequisite for guided implant surgery with CAD/CAM drilling guides

OBJECTIVES

Guided implant surgery (GIS) is performed with drilling guides that are produced on the virtual tooth model using CAD/CAM technology. The prerequisite for this workflow is the alignment of patients cone beam computed tomography CBCT and surface scan (registration). Dental restorations may cause deteriorating imaging artifacts in CBCT data, which in turn can have an impact on the registration process. The influence of the user and the preprocessing of data and of image artifacts on the registration accuracy were examined.

MATERIAL AND METHODS

CBCT data and intraoral surface scans of 36 patients were used for virtual implant planning in coDiagnostiX (Dentalwings, Montreal, Canada). CBCT data were reconstructed to a three-dimensional anatomical model with the default settings provided by the software and also manually by four different examiners. Subsequently, the CBCT and intraoral surface models were registered by each examiner with the help of anatomical landmarks. Patients' data were subdivided into four groups (A-D) according to the number of metallic restorations: A = 0-2 restorations, B = 3-5 restorations, C = 6-8 restorations and D > 8 restorations. After registration, the distances between CBCT and dental surface models were measured. Linear regression models were used to assess the influence of the segmentation, the examiner and to the number of restorations (P < 0.05).

RESULTS

The deviations between surface scan and CBCT models accounted to 0.54 mm (mean). The mean deviations were 0.69 mm (max. 24.8 mm) and 0.4 mm (max. 9.1 mm) for default and manual segmentation, respectively. Mean deviations of 0.36 mm (Group A), 0.43 mm (Group B), 0.67 mm (Group C) and 1.01 mm (Group D) were recorded. The segmentation (P = 0.000), the user (P = 0.0052) and the number of restorations (P = 0.0337) had a significant influence on the registration accuracy.

CONCLUSIONS

The deviation between CBCT and surface scan model resulting from inaccurate registration is transferred to the surgical field and results in a deviation between the planned and actual implant position. The registration accuracy in commercial virtual implant planning software is significantly influenced by the preprocessing of imported data, by the user and by the number of restorations resulting in clinically non-acceptable deviations encoded in drilling guides.

Novel CBCT and optical scanner-based implant treatment planning using a stereolithographic surgical guide: a multipronged diagnostic approach

This report describes the use of the combination of 2 technologies (Cone-beam computed tomography and Optical 3-dimensional scan) to maximize accuracy of implant placement in an area where previous implants failed and had to be removed. This report also stresses the increased efficiency of combining technologies to fabricate stereolithographic surgical guide which, when used intraoperatively, can improve precision of placement.