Virtual setup: application in orthodontic practice

Comparison of dental movements in digital setups created by orthodontists and "3shape design service®" engineers: A cross-sectional study

INTRODUCTION

The demand for faster and invisible orthodontic treatments has led to the increased use of clear aligners, facilitated by advancements in digital treatment planning. This study aims to evaluate the reliability of digital orthodontic setups performed by orthodontists compared to those by 3Shape Design Service®engineers.

MATERIAL AND METHODS

A monocentric, cross-sectional observational study was conducted at Bretonneau Hospital from October 2022 to May 2023. All patients meeting the inclusion criteria and willing to participate were included in the study. Intraoral scans were used to create treatment setups using the Ortho System® software, performed by both orthodontists and 3Shape® engineers. The primary objective was to compare the dental movements (rotation, intrusion, extrusion, buccolingual inclination, tipping, mesiodistal translation and buccolingual translation) between the two groups. Secondary objectives included the number of teeth displaced, aligners needed, interproximal enamel reduction and number of attachments placed.

RESULTS

Nineteen patients with mild to moderate malocclusion were included. Statistically significant differences were found in tooth displacements between the two groups with engineers executing greater dental movements for derotation (4.9±2.6 vs. 3.7±2.3), tipping (0.79±0.69 vs. 0.26±0.44), bucco-lingual (0.40±0.26 vs. 0.08±0.11) and mesio-distal translations (0.31±0.20 vs. 0.20±0.17). Secondary measures showed no significant differences except for the number of teeth displaced (15.32±5.21 vs. 9.68±4.82), which was higher in the 3Shape group.

DISCUSSION

While digital setups by engineers showed more significant tooth movements, the practical impact on mild malocclusion treatment was minimal. This study highlights the need for precise treatment objectives and consideration of overcorrection practices.

CONCLUSION

For mild malocclusions, outsourcing setups to 3Shape engineers can be an alternative to in-office setups by orthodontists. However, further studies are needed to evaluate setup reliability for more complex malocclusions.

Evaluation of the accuracy of automated tooth segmentation of intraoral scans using artificial intelligence-based software packages

INTRODUCTION

The accuracy of tooth segmentation in intraoral scans is crucial for performing virtual setups and appliance fabrication. Hence, the objective of this study was to estimate and compare the accuracy of automated tooth segmentation generated by the artificial intelligence of dentOne software (DIORCO Co, Ltd, Yongin, South Korea) and Medit Ortho Simulation software (Medit Corp, Seoul, South Korea).

METHODS

Twelve maxillary and mandibular pretreatment dental scan sets comprising 286 teeth were collected for this investigation from the archives of the Department of Orthodontics, Faculty of Dentistry, Alexandria University. The scans were imported as standard tessellation language files into both dentOne and Medit Ortho Simulation software. Automatic segmentation was run on each software. The number of successfully segmented teeth vs failed segmentations was recorded to determine the success rate of automated segmentation of each program. Evaluation of success and/or failure was based on the software's identification of the teeth and the quality of the segmentation. The mesiodistal tooth width measurements after segmentation using both tested software programs were compared with those measured on the unsegmented scan using Meshmixer software (Autodesk, San Rafael, Calif). The unsegmented scans served as the reference standard.

RESULTS

A total of 288 teeth were examined. Successful identification rates were 99% and 98.3% for Medit and dentOne, respectively. Success rates of segmenting the lingual surfaces of incisors were significantly higher in Medit than in dentOne (93.7% vs 66.7%, respectively; P <0.001). DentOne overestimated the mesiodistal width of canines (0.11 mm, P = 0.032), premolars (0.22 mm, P < 0.001), and molars (0.14 mm, P = 0.043) compared with the reference standard, whereas Medit overestimated the mesiodistal width of premolars only (0.13 mm, P = 0.006). Bland-Altman plots showed that mesiodistal tooth width agreement limits exceeded 0.2 mm between each software and the reference standard.

CONCLUSIONS

Both artificial intelligence-segmentation software demonstrated acceptable accuracy in tooth segmentation. There is a need for improvement in segmenting incisor lingual tooth surfaces in dentOne. Both software programs tended to overestimate the mesiodistal widths of segmented teeth, particularly the premolars. Artificial intelligence-segmentation needs to be manually adjusted by the operator to ensure accuracy. However, this still does not solve the problem of proximal surface reconstruction by the software.

Digital setup accuracy for moderate crowding correction with fixed orthodontic appliances: a prospective study

OBJECTIVES

To evaluate the accuracy of a semi-automatic 3D digital setup process in predicting the orthodontic treatment outcome achieved by labial fixed appliances.

SUBJECTS AND METHODS

Twenty-five adult patients (18 to 24 years old) with class I malocclusion and moderate crowding were prospectively enrolled and received treatment on both jaws through the straight-wire technique. Prior to treatment commencement, a semi-automatic digital setup simulating the predicted treatment outcome was performed for each patient through Orthoanalyzer software (3Shape®, Copenhagen, Denmark) to obtain the prediction model. This was compared to the final outcome model through 3D superimposition methods. Metric variables and inspection of color-coded distance maps were used to detect how accurately the digital setup predicts the actual treatment outcome.

RESULTS

The mean absolute distances (MAD) between the superimposed dental arches of the predicted and the final models were: 0.77 ± 0.13 mm following superimposition on the palate, 0.52 ± 0.06 mm following superimposition on the maxillary dental arch, and 0.55 ± 0.15 mm following superimposition on the mandibular dental arch. The MAD at the palatal reference area was 0.09 ± 0.04 mm. Visualization of color-coded distance maps indicated that the digital setup accurately predicted the final teeth position in a few cases. Almost half of the cases had posteriorly wider upper and lower dental arches and palatally/lingually positioned or inclined anterior teeth, whereas the rest still showed errors within 2-3 mm, distributed over the entire dental arches with no distinct pattern.

CONCLUSIONS

The accuracy of semi-automatic prediction of the labial fixed appliance treatment outcome in Class I cases with moderate crowding is not yet sufficient. While average measures showed deviations less than 1 mm, examination of individual color-coded distance maps revealed significant disparities between the simulated and the actual results.

Contributions of Digital Simulation to Orthodontic Therapeutic Decision-Making: A Case Report

Adult orthodontics aims to achieve optimal functional and aesthetic corrections. However, for several reasons, some patients will wish to benefit from a limited treatment where only certain aspects of a malocclusion will be corrected. In these clinical situations, the therapeutic objectives must be adjusted to the individual needs of the patient insofar as they can bring them real benefits. The use of digital technology makes it possible to study the therapeutic possibilities better and visualize the occlusal results before choosing the best therapeutic approach, especially in cases requiring customization. The aim of this clinical case report is to illustrate the orthodontic compromise made after the analysis of the digital setup in an adult patient who presented with a class III malocclusion but refused orthodontic-surgical therapy and requested an alternative treatment.

Deep learning driven segmentation of maxillary impacted canine on cone beam computed tomography images

The process of creating virtual models of dentomaxillofacial structures through three-dimensional segmentation is a crucial component of most digital dental workflows. This process is typically performed using manual or semi-automated approaches, which can be time-consuming and subject to observer bias. The aim of this study was to train and assess the performance of a convolutional neural network (CNN)-based online cloud platform for automated segmentation of maxillary impacted canine on CBCT image. A total of 100 CBCT images with maxillary canine impactions were randomly allocated into two groups: a training set (n = 50) and a testing set (n = 50). The training set was used to train the CNN model and the testing set was employed to evaluate the model performance. Both tasks were performed on an online cloud-based platform, 'Virtual patient creator' (Relu, Leuven, Belgium). The performance was assessed using voxel- and surface-based comparison between automated and semi-automated ground truth segmentations. In addition, the time required for segmentation was also calculated. The automated tool showed high performance for segmenting impacted canines with a dice similarity coefficient of 0.99 ± 0.02. Moreover, it was 24 times faster than semi-automated approach. The proposed CNN model achieved fast, consistent, and precise segmentation of maxillary impacted canines.

Biomechanical model registration for monitoring and simulating large orthodontic tooth movements in the maxilla and mandible

PURPOSE

Superimposition of digital dental-arch models allows quantification of orthodontic tooth movements (OTM). Currently, this procedure requires stable reference surfaces usually only present in the maxilla. This study aimed to investigate the accuracy of a novel superimposition approach based on biomechanical principles of OTM and the equilibrium of forces and moments (EFM)-applicable in both jaws-for monitoring and simulating large OTM.

METHODS

The study included 7 patients who had undergone extraction of the first (PM1-Ex) or second (PM2-Ex) premolar in each quadrant. Digital models taken at start and end of the T‑Loop treatment phase were superimposed by applying 3 EFM variants differing in the number of teeth used for registration. Maxillary OTM results for EFM were validated against those for a conventional surface registration method (SRM). In an additional case study, OTM were simulated for PM1-Ex, PM2-Ex and non-extraction treatment strategies.

RESULTS

The EFM variant that included all teeth of the dental arch achieved the highest accuracy, with median translational and rotational OTM deviations from SRM of only 0.37 mm and 0.56°, respectively. On average, retracted canines and first premolars were distalized by 3.0 mm, accompanied by 6.2° distal crown tipping and 12.2° distorotation. The share of space closure by molar mesialization was 19.4% for PM1-Ex quadrants and 34.5% for PM2-Ex quadrants.

CONCLUSION

EFM allows accurate OTM quantification relative to the maxillary and mandibular bases even in challenging situations involving large OTM. Superimposition of malocclusion and setup models enables realistic simulation of final tooth positions. This may greatly enhance the value of digital setups for decision-making in orthodontic treatment planning.

Quantifying maxillary anterior tooth movement in digital orthodontics: Does the choice of the superimposition software matter?

BACKGROUND

To compare the agreement between predetermined angular and linear tooth movement measurements processed with three digital model registration software packages.

METHODS

Twenty maxillary intraoral pretreatment scans of patients undergoing clear aligner therapy were randomly selected. Digital setups were generated using OrthoAnalyzer Clear Aligner Studio software to serve as the reference standard. Both pretreatment scans and setups were converted to STL files and exported to Geomagic, OrthoAnalyzer-Model Set Compare, and Compare model registration software packages. The amount of tooth movement of the maxillary incisors and canines was calculated in six degrees of freedom.

RESULTS

Statistical significance of the obtained results was expressed at P < 0.01 to account for multiple comparisons. The maxillary central incisors showed the highest agreement for torque and rotation as measured by all software programs. Lateral incisors showed the least agreement in linear movements as measured by Geomagic and Compare, and for tip as measured by Geomagic and OrthoAnalyzer. Maxillary canines had the highest agreement for all linear movements as measured by Geomagic and Compare, and tip as measured by Geomagic and OrthoAnalyzer. Geomagic showed excellent agreement for all measurements except for torque, whereas Compare showed excellent agreement only for rotation and linear measurements. OrthoAnalyzer showed moderate agreement for all measurements except for rotation, which showed good agreement.

CONCLUSIONS

Maxillary central incisor measurements showed higher agreement compared with measurements of the maxillary lateral incisors and canines. Although none of the software showed poor agreement, Geomagic seemed to have the highest accuracy.

The accuracy of virtual setup in simulating treatment outcomes in orthodontic practice: a systematic review

OBJECTIVES

To evaluate the accuracy of virtual orthodontic setup in simulating treatment outcomes and to determine whether virtual setup should be used in orthodontic practice and education.

MATERIALS AND METHODS

A systematic search was performed in five electronic databases: PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar from January 2000 to November 2022 to identify all potentially relevant evidence. The reference lists of identified articles were also screened for relevant literature. The last search was conducted on 30 November 2022.

RESULTS

This systematic review included twenty-one articles, where all of them were assessed as moderate risk of bias. The extracted data were categorized into three groups, which were: (1) Virtual setup and manual setup; (2) Virtual setup and actual outcomes in clear aligner treatment; (3) Virtual setup and actual outcomes in fixed appliance treatment. There appeared to be statistically significant differences between virtual setups and actual treatment outcomes, however the discrepancies were clinically acceptable.

CONCLUSION

This systematic review supports the use of orthodontic virtual setups, and therefore they should be implemented in orthodontic practice and education with clinically acceptable accuracy. However, high-quality research should be required to confirm the accuracy of virtual setups in simulating treatment outcomes.

Comparing virtual setup software programs for clear aligner treatment

BACKGROUND

The aim of this study was to compare the outcomes of the same amount of tooth movement among four different virtual setup software programs.

METHODS

This retrospective study included 32 patients who underwent Invisalign treatment. Patients' initial stereolithography (STL) files were imported to three different software programs (SureSmile Aligner [Dentsply Sirona, Charlotte, NC], Ortho Insight 3D [Motion View software, Chattanooga, TN], and Ortho Analyzer [3Shape, Copenhagen, Denmark]). After virtually moving teeth based on the numbers from ClinCheck Pro (Align Technology, Inc., Santa Clara, CA) tooth movement tables, final STL files were exported from all four software programs. ClinCheck Pro final STL files were used as references, while final STL files from the other software programs were used as targets. Superimpositions were performed between references and target STL files using Geomagic Control X software (3D Systems, Rock Hill, SC), and color-coded maps were obtained to illustrate potential differences.

RESULTS

Intraclass correlation coefficient showed a high degree of reliability for repeated methodology (0.995-0.997). The differences among absolute averages (Abs Avg.), averages of positive values (+Avg.), and negative values (-Avg.) for both upper and lower models were significant among all software programs (ClinCheck Pro, SureSmile Aligner, Ortho Insight 3D, and Ortho Analyzer), for both upper and lower STL files, the smallest difference was found between ClinCheck Pro and SureSmile Aligner with a median of (0.03, 0.31, -0.19) mm for upper and (0.02, 0.29, -0.17) mm for lower STL files (Abs Avg., +Avg. and -Avg.), respectively. The biggest difference was found to be between ClinCheck Pro and Ortho Analyzer with a median of (0.05, 0.46, -0.45) mm for upper and (0.06, 0.48, -0.40) mm for lower STL files. There were no significant differences in the number of aligners per patient.

CONCLUSIONS

Final outcomes of the same amount of tooth movement in four different software programs differed significantly. The number of aligners per patient remained unchanged.

The Prediction Accuracy of Digital Orthodontic Setups for the Orthodontic Phase before Orthognathic Surgery

The purpose of this study was to verify whether pre-treatment digital setups can accurately predict the tooth positions after presurgical orthodontic treatment has been performed in a 3-dimensional way. Twenty-six patients who underwent a combined orthodontic-orthognathic surgical treatment were included. Pre-treatment digital dental models were merged with cone beam computed tomography (CBCT) scans. One operator fabricated virtual setups to simulate the tooth movements of the presurgical orthodontic treatment. Prior to surgery, digital dental models were merged with the CBCT scans. Differences between de virtual setups and the presurgical dental models were calculated using linear mixed model analyses. Differences in tooth displacements exceeding the boundaries of clinical acceptance (>2 degrees for rotations and >0.6 mm for translations) were found in 75% of the rotational and 52% of translational mean differences in the maxilla and in 74% of the rotational mean differences and 44% of the translational mean differences in the mandible. Significant differences were found for all tooth types and in all tooth displacement directions with significant effects of extractions and surgically assisted rapid maxillary expansion (SARME) procedures. The accuracy of the digital setup is still too limited to correctly simulate the presurgical orthodontic treatment.

The Potential of Digital Impression in Orthodontics

Background: Over the past 20 years, there have been many innovations in orthodontic diagnosis and therapy. Among the innovations, there is the taking of dental impressions (DIs). Dental impressions are the negative imprint of hard and soft tissues of one or both arches, and they allow a plaster model to be formed, i.e., a positive reproduction. Traditional dental impressions can be made of different materials, such as alginate, while digital impression is captured by an intra-oral scanner. Digital impression, despite the evident advantages, has not yet replaced the conventional impression. The aim of this study is to evaluate which dental impressions are the most used by dentists. For this purpose, we considered 120 questionnaires sent electronically to patients of different dental private practices from different countries, where the dentists can use both techniques. The results highlighted that the kind of impression adopted is very much influenced by the type of therapy and orthodontic devices used in the treatment. We can conclude that, despite the advent of digital technology, conventional impressions are still used for fixed devices, while digital impressions are more adopted for orthodontic customized devices and therapies with clear aligners, that are very widespread among adult patients.

Precision medicine using patient-specific modelling: state of the art and perspectives in dental practice

The dental practice has largely evolved in the last 50 years following a better understanding of the biomechanical behaviour of teeth and its supporting structures, as well as developments in the fields of imaging and biomaterials. However, many patients still encounter treatment failures; this is related to the complex nature of evaluating the biomechanical aspects of each clinical situation due to the numerous patient-specific parameters, such as occlusion and root anatomy. In parallel, the advent of cone beam computed tomography enabled researchers in the field of odontology as well as clinicians to gather and model patient data with sufficient accuracy using image processing and finite element technologies. These developments gave rise to a new precision medicine concept that proposes to individually assess anatomical and biomechanical characteristics and adapt treatment options accordingly. While this approach is already applied in maxillofacial surgery, its implementation in dentistry is still restricted. However, recent advancements in artificial intelligence make it possible to automate several parts of the laborious modelling task, bringing such user-assisted decision-support tools closer to both clinicians and researchers. Therefore, the present narrative review aimed to present and discuss the current literature investigating patient-specific modelling in dentistry, its state-of-the-art applications, and research perspectives.

Modeling and Simulating an Orthodontic System Using Virtual Methods

Cone beam computed tomography (CBCT) is a modern imaging technique that uses X-rays to investigate the structures of the dento-maxillary apparatus and obtain detailed images of those structures. The aim of this study was to determine a functional mathematical model able to evaluate the elastic force intensity on each bracket and tube type element and the ways in which those components act on the orthodontic system being used. To analyze a real orthodontic system, we studied the case of a 13-year-old female patient. To transfer geometric information from tomographic images, we used the InVesalius software. This software can generate three-dimensional reconstructions based on sequences and files in the DICOM format and was purchased from CBCT equipment. We analyzed and processed the geometries of the converted tissues in InVesalius using the Geomagic software. After using the Geomagic software, we exported the resulting model to the SolidWorks software used in computer-aided design. In this software, the model is transformed into a virtual solid. After making the geometric model, we analyzed the model using the Ansys Workbench software, which incorporates finite element analysis techniques. Following the simulations, we obtained result maps, which showed the complete mechanical behavior of the analyzed structures.

Digital model superimpositions: are different software algorithms equally accurate in quantifying linear tooth movements?

Background

To evaluate the accuracy of three different 3D digital model registration software packages for linear tooth movement measurements, with reference to a 3D digital virtual setup (DS).

Methods

Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital Setups were generated from pre-treatment scans using OrthoAnalyzer software. Both the pretreatment digital scans (T1) and Digital Setups (T2) were converted to STL files to be imported to the three studied software packages: Geomagic, OrthoAnalyzer and Compare. Linear changes in tooth positions were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the Digital Setups. Continuous data was expressed as mean and standard deviation. Intraclass Correlation Coefficients for agreements between Digital Simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intraclass Correlation Coefficients. Significance of the obtained results was expressed at p ≤ 0.01. Geomagic software showed agreements > 0.90 for maxillary linear tooth movements and between 0.75 and 0.90 for mandibular measurements. OrthoAnalyzer software showed agreements between 0.50 and < 0.75 for maxillary and mandibular measurements. Compare software showed agreements > 0.90 for maxillary and mandibular linear tooth movements, indicating the best consistency.

Conclusions

Compare and Geomagic software packages consistently showed maximum accuracy in measuring the amount of tooth movement in the maxillary arch compared to the reference standard. Compare software showed the highest agreements in the mandibular arch. None of the three studied software packages showed poor agreement with the Digital Setup across all tooth movement measurements. Buccolingual tooth movements showed the highest agreements amongst linear measurements.

TIP, TORQUE & ROTATIONS: How accurately do digital superimposition software packages quantify tooth movement?

Background

To investigate the accuracy of three different 3D digital model registration software for tip, torque and rotation measurements, with reference to a 3D digital virtual setup. Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital setups were generated from pre-treatment scans using a tooth movement software. Both the pretreatment digital scans (T1) and digital setups (T2) were converted to STL files to be exported to the 3 studied software that employed: (1) Semiautomatic best fit registration (S-BF), (2) Interactive surface-based registration (I-SB), and (3) Automatic best fit registration (A-BF) respectively. Changes in tip, torque and rotation were calculated for all the registered pairs.

Results

The change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the digital setups. Continuous data was expressed as mean and standard deviation. Intra Class Correlation Coefficient for agreement between digital simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intra Class Correlation Coefficient. Significance of the obtained results was expressed at p ≤ 0.01. Semiautomatic best fit registration software showed excellent agreement (> 0.90) for all tooth movements, except for good agreement for torque (0.808). Interactive surface-based registration software showed moderate agreement for all measurements (0.50 and < 0.75), except for good agreement for rotation (0.783). Automatic best fit registration software demonstrated excellent agreement (> 0.90) for rotation, good agreement for tip (0.890) and moderate agreement for torque (0.740).

Conclusions

Overall, semiautomatic best fit registration software consistently showed excellent agreement in superimpositions compared to other software types. Automatic best fit registration software consistently demonstrated better agreement for mandibular superimpositions, compared to others. Accuracy of digital model superimpositions for tooth movements studied in superimposition studies, can be attributed to the algorithm employed for quantification.

Operator Performance of the Digital Setup Fabrication for Orthodontic–Orthognathic Treatment: An Explorative Study

The purpose of this study was to explore the operator performance of the fabrication of digital orthodontic setups integrated into cone beam computed tomography (CBCT) scans. Fifteen patients who underwent a combined orthodontic–orthognathic surgical treatment were included. The pre-treatment digital dental models and CBCT scans were fused, and four operators made virtual setups twice for all patients. Differences between the virtual setups were calculated by recording tooth crown movement from the pre-treatment model to the virtual setup. To examine performance, Pearson’s correlation coefficients, duplicate measurement errors, and inter-operator differences were calculated. For intra-operator performance, correlation values varied among tooth types, with mean correlation values from 0.66 to 0.83 for the maxilla and 0.70 to 0.83 for the mandible. For inter-operator performance, mean correlation values varied from 0.40 to 0.87 for the maxilla and from 0.44 to 0.80 for the mandible. Rotational mean differences exceeded the range of clinical acceptance (>2 degrees) at 18% for the maxilla and 20.8% for the mandible, and translational mean differences exceeded the range of clinical acceptance (0.6 mm) at 9.7% and 26% for the maxilla and mandible, respectively. The intra- and inter-operator performance of digital orthodontic setup construction for virtual three-dimensional orthognathic planning shows significant errors.

Orthodontic digital workflow: devices and clinical applications

Introduction:

The digital technology has contributed to improve and simplify diagnosis, treatment planning and execution in Orthodontics. Among CAD/CAM system (Computer-Aided Design / Computer-Aided Manufacturing) applications in Orthodontics, we highlight the installation and removal of fixed appliance, clear aligners, customized appliances, and retainers fabricated in digital environment. This approach has several advantages for practitioner and patient, as it enhances appliances precision, directly interferes in treatment time and predictability. Even with all the benefits arising from the digital workflow, few orthodontists have adopted this technique in their clinical practice, most due to high cost and lack of technical preparation for proper execution.

Objectives:

Thus, given the importance of digital technology to improve specialty performance and the still incipient incorporation of digital flow in Orthodontics, the purpose of this article is to describe the available resources and clinical applications of the CAD/CAM technology in Orthodontics.

The influence of the model superimposition method on the assessment of accuracy and predictability of setup models

INTRODUCTION

The aim of this study was to evaluate the influence of different superimposition methods on the accuracy and predictability of conventional and virtual diagnostic setups.

MATERIALS AND METHODS

Ten finished cases were used to make a conventional setup and a virtual setup. Second molars were not moved in the two setup situations to allow a reference for superimposition. Conventional and virtual setups were superimposed and compared by second molar registration and the whole surface best fit method (WSBF). Conventional and virtual setups were compared to the posttreatment models with WSBF and palatal rugae best fit (PRBF). Anterior, intermediate, and posterior regions of the dental arches were compared. The paired t-test was used to compare the mean differences between conventional and virtual setups, posttreatment models and both conventional and virtual setups by the WSBF method, and between maxillary posttreatment and virtual setup models using the WSBF and PRBF methods.

RESULTS

Conventional and virtual setups differed depending on the two superimposition methods used. Superimposition of the posttreatment models and both setups using WSBF presented no statistically significant differences. There were statistically significant differences between posttreatment and virtual setup models using WSBF and PRBF superimposition methods.

CONCLUSIONS

The model superimposition method influenced the assessment of accuracy and predictability of setup models. There were statistically significant differences between the maxillary posttreatment and virtual setup models using the WSBF and the PRBF superimposition methods. It is important to establish stable structures to evaluate the accuracy and predictability of setup models.

Lower incisor extraction therapy in a complex case with an ankylosed tooth in an adult patient: A case report

This case report describes a successful orthodontic therapy of an adult female treated by mandibular central incisor extraction and vestibular fixed appliances. The patient presented a skeletal Class I with normodivergent facial pattern, Class II subdivision dental relationship, extremely deep Curve of Spee and severe overbite. Moreover, during the treatment, the upper left first molar does not respond to orthodontic forces due to tooth ankylosis, augmenting the difficulty of this case. Despite this, a good occlusal relationship on both sites and an optimal extraoral outcome have been achieved after a 26-months therapy. To our knowledge no case report with such entity of Curve of Spee with contemporary tooth ankylosis has been presented.

The crucial role of imaging in digital dentistry

One of the recent trends in dentistry - and this in every field from the restorative to the orthodontic one- is the introduction of simplified completely digital workflows. Digital dentistry is supposed to allow dentists to work more efficiently, and this at higher precision, and with the possibility of all-in-one sessions using in-house computerized techniques. In this workflow, one of the major tools for simulating and transferring dental treatments is imaging. Both 3D low dose radiographic as well as optical imaging are playing crucial roles and have been overwhelming the market. Novel design platforms, compact and extremely fast milling and printing units are now also plentiful and rapidly being adopted in practice. Nevertheless, many of the steps in this digital dentistry process, no matter how simplified, present risks that can contribute to reduced precision and clinical difficulties. It is therefore the purpose of the article to briefly describe the role of imaging in this digital workflow, and where the pitfalls can be found that may lead to errors and imprecision.

Current status of surgery-first approach (part III): the use of 3D technology and the implication in obstructive sleep apnea

Considering psychosocial needs of patients, it is not surprising that surgery-first approach (SFA) is becoming more popular than ever. Although the concept of SFA was introduced a few decades ago, the limitation of analysis method based on two-dimensional images makes surgeons reluctant to choose SFA. Recently, the advancement of three-dimensional technology allows us to perform SFA even without minimal pre-surgical orthodontic treatment, and the prediction of surgical outcome became more accurate, especially in obstructive sleep apnea (OSA) patients to whom the advantages of SFA should be more significant. Here, we describe the current trend of SFA and its implication in OSA patients.

Virtual setup in orthodontics: planning and evaluation

OBJECTIVES

The purpose of this study was to evaluate the clinical accuracy of virtual orthodontic setups by using a new CBCT-based approach.

MATERIALS AND METHODS

Ten patients who underwent pre-surgical orthodontics were included in this study. Pre-treatment and pre-surgical cone-beam CT (CBCT) scans and digital dental models were available. The pre-treatment digital dental model was used to create an orthodontic virtual setup. The digital dental models were fused with the corresponding CBCT scans, and the two CBCT scans were aligned using voxel-based matching. Moving each individual tooth from the virtual setup to the final outcome allows the calculation of the accuracy of the virtual setup by using an iterative closest point algorithm. Differences between virtual setup and final outcome were recorded as well as the ICC between two observers.

RESULTS

The inter-observer variability showed a high level of agreement between the observers. The largest mean difference between observers was found in the cranial/caudal direction (0.36 ± 0.30 mm) and the roll rotation (1.54 ± 0.98°). Differences between the virtual setup and final outcome were small in the translational direction (0.45 ± 0.48 mm). Rotational mean differences were larger with the pitch of the incisors (0.00 ± 7.97°) and molars (0.01 ± 10.26°) as largest difference. Excessive extrusion of all upper teeth and more anterior movement than planned were seen for both upper and lower arch. Lower molars showed less extrusion.

CLINICAL RELEVANCE

The data of this study can be used to obtain more insight in the accuracy and achievability of orthodontic virtual setup. Tooth movement can now be studied in more details which can lead to new insights.

Assessing the accuracy of two posterior tooth-size discrepancy prediction methods based on virtual occlusal setups

OBJECTIVE

To assess accuracy of the Bolton and Johnson/Bailey (JB) analyses in identifying clinically significant posterior tooth-size discrepancies using virtually constructed occlusal setups.

MATERIALS AND METHODS

Virtual models and cone-beam computed tomography data sets from 30 patients were utilized to construct 60 (two per patient) virtual posterior occlusal setups. Observed discrepancies in cusp-embrasure relationships were compared to estimated posterior interarch tooth-size discrepancies (ITSDs) calculated via Bolton and JB posterior analyses. Clinical significance for discrepancies was established at >1 mm from ideal cusp-embrasure relationships in accordance with current American Board of Orthodontics methodology. Data within groups were normally distributed, thus comparisons were completed via paired t-tests. Paired nominal data were analyzed utilizing McNemar's test, and simple linear regression was used to model the relationship of predicted to observed discrepancies.

RESULTS

McNemar's test revealed significant differences (P ≤ .05) between the Bolton and JB groups' frequencies in matching the virtual setups correctly. JB predictions matched 100% (right) and 97% (left) setups; whereas, Bolton predictions matched only 23% (right and left) setups. A positive correlation was observed between JB predictions and cusp-embrasure discrepancies, demonstrating that average posterior discrepancy values increased 0.28 mm for every 1 mm predicted via the JB analysis.

CONCLUSIONS

The JB analysis correctly characterized, but overestimated, the degree of posterior ITSDs corresponding to a clinically significant discrepancy in the virtual setups. Algebraically calculated posterior ITSDs based on the Overall and Anterior Bolton ratios were not accurate predictors of discrepancies observed in the virtual setups. Both Bolton and JB demonstrated weaknesses that limit precise identification of clinically significant ITSDs.

Reproducibility of digital indirect bonding technique using three-dimensional (3D) models and 3D-printed transfer trays

OBJECTIVE

To evaluate the reproducibility of digital tray transfer fit on digital indirect bonding by analyzing the differences in bracket positions.

MATERIALS AND METHODS

Digital indirect bonding was performed by positioning brackets on digital models superimposed by tomography using Ortho Analyzer (3Shape) software. Thirty-three orthodontists performed indirect bonding on prototyped models of the same malocclusion using prototyped transfer trays for two types of brackets (MiniSprint Roth and BioQuick self-ligating). The models with brackets were scanned using an intraoral scanner (Trios, 3Shape). Superimpositions were made between the digital models obtained after indirect bonding and those from the original virtual setup. To analyze the differences in bracket positions, three planes were examined for each bracket: vertical, horizontal, and angulation. Three orthodontists repeated indirect bonding after 15 days, and Bland-Altman plots and intraclass correlation coefficients were used to evaluate inter- and intraevaluator reproducibility and reliability, respectively. Repeated-measures analysis of variance (ANOVA) was used to analyze the differences between bracket positions, and multivariate ANOVA was used to evaluate the influence of orthodontists' experience on the results.

RESULTS

Differences between bracket positions were not statistically significant, except mesial-distal discrepancies in the BioQuick group (P = .016). However, differences were not clinically significant (horizontal varied from 0.04 to 0.13 mm; angulation, 0.45° to 2.03°). There was no significant influence of orthodontist experience and years of clinical practice on bracket positions (P = .314 and P = .158). The reproducibility among orthodontists was confirmed.

CONCLUSIONS

The reproducibility of digital indirect bonding was confirmed in terms of bracket positions using three-dimensional printed transfer trays.

Debonding force and shear bond strength of an array of CAD/CAM-based customized orthodontic brackets, placed by indirect bonding- An In Vitro study

Based on three-dimensional scanning and computer-aided design and computer-aided manufacturing (CAD/CAM) techniques, customized bracket systems are increasingly used. However, data remain limited regarding customized bracket design, characteristics, and stability. This study was undertaken to evaluate the design, bond strength, and residual adhesives of four different CAD/CAM customized brackets that were attached to human tooth specimens by indirect bonding. Thirty extracted human upper premolars were divided into five groups: Group 1, preadjusted self-ligating labial metal bracket; Group 2, lingual self-ligating metal injection molding customized bracket; Group 3, gold-casted lingual customized bracket; Group 4, labial self-ligating milled customized bracket; Group 5, labial customized resin base bracket. Except in Group 1, premolar specimens were scanned via model scanner, and the images were sent to each manufacturing company to fabricate customized brackets and transfer trays/jigs. Debonding force (DF; N) was measured by Instron universal testing machine and shear bond strength (SBS; MPa) was calculated via dividing DF by bonding area. Adhesive remnants were analyzed via stereo microscopic images. Group 2 (196.90±82.75 N) exhibited significantly higher DF than Group 1 (62.77±12.65 N); other groups exhibited similar DFs, compared with Group 1. No customized bracket groups exhibited significant differences in SBS, relative to Group 1 (6.73±1.36 MPa). However, SBS in Group 5 (11.46±7.22 MPa) was significantly higher than in Group 3 (3.58±2.14 MPa). Group 3 had significantly lower ARI scores than other groups (P<0.05). Customized brackets exhibited large deviations in DF and SBS; all customized bracket systems exhibited DF that was equivalent or superior to that of preadjusted brackets, even when placed by indirect bonding.