Determination of Mouth Width for Facial Reconstruction Based on Statistical Regression Model.

INTRODUCTION: It is important to generate predictable statistical models by increasing the number of variables on the human skeletal and soft tissue structures on the face to increase the accuracy of human facial reconstructions. The purpose of this study was to determine mouth width 3-dimensionally based on statistical regression model. MATERIAL AND METHODS: Cone-beam computed tomography scan data from 130 individuals were used to measure the horizontal and vertical dimensions of orbital and nasal structures and intercanine width. The correlation between these hard tissue variables and the mouth width was evaluated using the statistical regression model. RESULTS: Orbital width, nasal width, and intercanine width were found to be strong predictors of the mouth width determination and were used to generate the regression formulae to find the most approximate position of the mouth. CONCLUSION: These specific variables may contribute to improving the accuracy of mouth width determination for oral and maxillofacial reconstructions.

Deep Learning-based Assessment of Facial Asymmetry Using U-Net Deep Convolutional Neural Network Algorithm.

OBJECTIVES: This study aimed to evaluate the diagnostic performance of a deep convolutional neural network (DCNN)-based computer-assisted diagnosis (CAD) system to detect facial asymmetry on posteroanterior (PA) cephalograms and compare the results of the DCNN with those made by the orthodontist. MATERIALS AND METHODS: PA cephalograms of 1020 patients with orthodontics were used to train the DCNN-based CAD systems for autoassessment of facial asymmetry, the degree of menton deviation, and the coordinates of its regarding landmarks. Twenty-five PA cephalograms were used to test the performance of the DCNN in analyzing facial asymmetry. The diagnostic performance of the DCNN-based CAD system was assessed using independent t -tests and Bland-Altman plots. RESULTS: Comparison between the DCNN-based CAD system and conventional analysis confirmed no significant differences. Bland-Altman plots showed good agreement for all the measurements. CONCLUSIONS: The DCNN-based CAD system might offer a clinically acceptable diagnostic evaluation of facial asymmetry on PA cephalograms.

Digital application of three-dimensional diagnosis and treatment with a virtual articulator.

OBJECTIVE: The purpose of this article was to introduce a method for the digital application of three-dimensional (3D) diagnosis and treatment with a virtual articulator and 3D data. CLINICAL CONSIDERATION: With the use of cone-beam computed tomography (CBCT) and intraoral and facial scans, we can create a virtual articulator and evaluate the mandibular position in maximum intercuspation and centric-related occlusion for the patient with an unstable occlusion and temporomandibular disorders (TMD). Based on this, we treated a case using a digital mandibular position indicator (MPI) and fabricated a stabilization splint using a 3D printer. This approach eliminates the traditional impression or model mounting process and the analog face bow transfer. Furthermore, the design of the stabilization splint is accomplished using software. CONCLUSIONS: The approach outlined in this article offers the potential for a digital diagnosis and treatment process by seamlessly integrating CBCT, intraoral scans, and facial scans with a high degree of accuracy. This may enhance precision in diagnosis and treatment planning, especially for patients with complicated TMD, in addition to facilitating effective communication with orthodontic patients who require thorough attention. CLINICAL SIGNIFICANCE: Utilizing a virtual articulator and digital MPI for the occlusal evaluation of patients with TMD and unstable occlusion makes it possible to diagnose and analyze the occlusal condition accurately. This approach also allows for precision and efficiency in treatment.

Long-term evaluation of the upper airway following mandibular setback surgery in the patients with mandibular prognathism.

OBJECTIVE: The aim of this study was to evaluate the changes in the upper airway following mandibular setback surgery. METHODS: The patients underwent mandibular setback surgery and cone-beam computed tomography scan data obtained at four time points: before surgery, immediately after surgery, short- and long-term follow-up. Upper airway geometries were segmented and extracted at each time point. Time-averaged airflow through the upper airway was evaluated at each time point. The measurements of airway volume and minimum cross-sectional areas were obtained at four time points. RESULTS: The airway volume and cross-sectional areas of airway significantly decreased immediately after surgery (p = 0.013 for airway volume and 0.016 for cross-sectional area). At short-term follow-up, the decreased airway volume and cross-sectional areas still showed statistically significant difference to original dimension (p = 0.017 for airway volume and 0.006 for cross-sectional area). At long-term follow-up, although there were no statistical significances (p = 0.859 for airway volume and 0.721 for cross-sectional area), the airway volume and cross-sectional areas had increased slightly compared to those at short-term follow-up. CONCLUSIONS: Although the airflow and dimensional parameters of the upper airway worsened following mandibular setback surgery, there was a tendency to gradually recover during long-term follow-up.

Survival rates of mandibular fixed retainers: comparison of a tube-type retainer and conventional multistrand retainers : A prospective randomized clinical trial.

OBJECTIVE: The purposes of this study were to evaluate the survival rate of a tube-type mandibular fixed retainer and compare it to conventional multistrand retainers. MATERIALS AND METHODS: In all, 66 patients who had completed their orthodontic treatment were enrolled in this study. They were allocated randomly to a tube-type retainer group or a 0.020 multistrand fixed retainer group. In case of the tube-type retainer, a thermoactive 0.012 NiTi was placed into 6 mini-tubes passively bonded to the anterior teeth. The patients were recalled at 1, 3, 6, 12, and 24 months after retainer placement. During the 2­year follow-up period, any first-time failure of retainers was recorded. Kaplan-Meier survival analysis and log-rank tests were used to compare the failure rates between the two types of retainers. RESULTS: Of the 34 patients, 14 (41.2%) showed failure in the multistrand retainer group, whereas only 2 of 32 (6.3%) reported failure in the tube-type retainer group. There was a statistically significant difference in failure between the multistrand retainer and the tube-type retainer (log-rank test, P = 0.001). The hazard ratio was 11.937 (95% confidence interval 2.708-52.620; P = 0.005). CONCLUSION: The tube-type retainer can be used with fewer concerns about recurrent retainer detachments during orthodontic retention.

Anthropometric Comparison of 3-Dimensional Facial Scan Taken With a Low-Cost Facial Scanner With Cone-Beam Computed Tomography Scan.

OBJECTIVE: The aim of this study was to evaluate the accuracy of 3-dimensional (3D) facial scans taken with a low-cost facial scanner compared with cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Twenty-five patients had their CBCT scan and 3D facial scan taken on the same day. Facial scans were taken with a low-cost facial scanner (Bellus3D, ARC-1 scanner) in an upright position. The facial scans were imported into Invivo5 software and were integrated with the corresponding CBCT scans. Then, 16 soft tissue landmarks were identified on the CBCT scans and the 3D-integrated facial scans. The 6 vertical, 7 horizontal, 10 oblique linear, and 11 angular anthropometric measurements were obtained and compared between the CBCT scans and 3D-integrated facial scans using paired t test and Bland-Altman plots. RESULTS: The differences between CBCT scans and 3D-integrated facial scans showed no statistical significance except for 2 vertical measurements. Bland-Altman plots showed that all anthropometric measurements were within the limit of agreement. The differences between CBCT scans and 3D-integrated facial scans were <1.5 mm or 1.5 degrees except for 2 vertical measurements. CONCLUSIONS: Three-dimensional facial scans taken with facial scanner showed a clinical acceptance when compared with CBCT scans.

Consideration of root position in virtual tooth setup for extraction treatment: A comparative study of simulated and actual treatment results.

Objective: The purpose of the present study was to compare the root positions in virtual tooth setups using only crowns in a simulated treatment with those achieved in the actual treatment. Methods: Pre- and post-treatment intraoral and corresponding cone beam computed tomography (CBCT) scans were obtained from 15 patients who underwent orthodontic treatment with premolar extraction. A conventional virtual tooth setup was used for the treatment simulation. Pre- and post-treatment three-dimensional digital tooth models were fabricated by integrating the patients' intraoral and CBCT scans. The simulated root positions in the virtual setup were obtained by merging the crown in the virtual setup and root in the pre-treatment tooth model. The root positions of the simulated and actual post-treatment tooth models were compared. Results: Differences in root positions between the simulated and actual models were > 1 mm in all teeth, and statistically significant differences were observed (p < 0.05), except for the maxillary lateral incisors. The differences in the inter-root angulation were > 1° in all teeth, and statistically significant differences were observed in the maxillary and mandibular canines. Conclusions: The virtual tooth setup using only crown data showed errors over the clinical limits. The clinical application of a virtual setup using crowns and roots is necessary for accurate and precise treatment simulation, particularly in extraction treatment.

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.

Evaluation of alveolar bone changes around mandibular incisors during surgical orthodontic treatment of patients with mandibular prognathism: Surgery-first approach vs conventional orthognathic surgery.

INTRODUCTION: This retrospective study aimed to investigate the alveolar bone changes around mandibular incisors in patients with skeletal Class III malocclusion treated with surgery-first orthognathic approach (SFA) and conventional orthognathic surgery (COS) using cone-beam computed tomography scans. METHODS: Sixty-four patients were divided into 2 groups according to the inclusion of presurgical orthodontic treatment; the SFA group included 32 patients treated without presurgical orthodontic treatment, and the COS group included 32 patients treated with presurgical orthodontic treatment. Cone-beam computed tomography scans were obtained before treatment, after presurgical orthodontic treatment, and after treatment for the COS group and were obtained before and after treatment for the SFA group. The measurements of vertical alveolar bone height and horizontal bone thickness at 4 levels and the alveolar bone area surrounding the mandibular incisors were compared according to the treatment progress and groups. RESULTS: The vertical bone levels and horizontal bone thickness of the labial and lingual sides and the area of the alveolar bone around the mandibular incisors were reduced after treatment in both SFA and COS groups. Vertical bone loss was more prominent than horizontal bone loss after treatment in both groups, and alveolar bone loss was greater on the lingual side than on the labial side. There were no significant differences in alveolar bone changes around the mandibular incisor between the SFA and COS groups. However, the alveolar bone was reduced more in the COS group than in the SFA group. CONCLUSIONS: The results indicate that SFA and COS may trigger degeneration of the alveolar bone around the mandibular incisors after treatment in patients with mandibular prognathism. Careful consideration is needed to avoid iatrogenic degeneration of the periodontal support around the incisors, particularly during presurgical orthodontic treatment.

Creation of Digital Virtual Patient by Integrating CBCT, Intraoral Scan, 3D Facial Scan: An Approach to Methodology for Integration Accuracy.

ABSTRACT: The purpose of this paper was to introduce a method for creating a digital virtual patient by combining cone-beam computed tomography (CBCT), intraoral scan, and facial scan with a high accuracy of integration. CBCT scan, facial scan, and intraoral scan were obtained from initial visit. The virtual patient was created using the integration of these imaging modalities. Once the virtual patient was generated, digital workflow could be applied to initial patient consultation, diagnosis, treatment planning, virtual tooth setup, virtual treatment simulation, and post-treatment evaluation. integration of digital technology allows clinicians to improve diagnosis and treatment outcome. in addition, it allows for favorable patient communication. This technique eliminates the traditional impression process and complicated laboratory procedures for evaluating patient's occlusion during smile and habitual resting position. Based on this protocol, it is possible to create a digital virtual patient using CBCT, intraoral scan, and facial scan with a high accuracy of integration. it would be helpful for precision diagnosis and accurate treatment as well as favorable communication with patient.

Three-Dimensional Visualization of Postsurgical Airway Changes Using 3D Printing Technology in a Patient With Mandibular Prognathism: A 5-Year Follow-up Study.

This case-report described the 3-dimensional (3D) evaluation of airway changes using 3D printing technology in a patient with mandibular prognathism, treated via mandibular setback surgery with maxillary posterior impaction. The airway dimensions, following orthognathic surgery, were printed using 3D printing technology and the sequential airway changes were visualized. The patient underwent orthognathic surgery for the correction of mandibular prognathism. Five years later, the airway changes were visualized and evaluated using rapid prototyping. The 3D visualization of the airway changes following surgery alerted clinicians of patients with mandibular prognathism and facilitated effective communication with their patients. This case-report documented the long-term evaluation and visualization of the postoperative airway changes in patients with mandibular prognathism using cone-beam computed tomography and 3D printing technology.

Accuracy of deep learning-based integrated tooth models by merging intraoral scans and CBCT scans for 3D evaluation of root position during orthodontic treatment.

OBJECTIVE: This study aimed to evaluate the accuracy of deep learning-based integrated tooth models (ITMs) by merging intraoral scans and cone-beam computed tomography (CBCT) scans for three-dimensional (3D) evaluation of root position during orthodontic treatment and to compare the fabrication process of integrated tooth models (ITMs) with manual method. MATERIAL AND METHODS: Intraoral scans and corresponding CBCT scans before and after treatment were obtained from 15 patients who completed orthodontic treatment with premolar extraction. A total of 600 ITMs were generated using deep learning technology and manual methods by merging the intraoral scans and CBCT scans at pretreatment. Posttreatment intraoral scans were integrated into the tooth model, and the resulting estimated root positions were compared with the actual root position at posttreatment CBCT. Discrepancies between the estimated and actual root position including average surface differences, arch widths, inter-root distances, and root axis angles were obtained in both the deep learning and manual method, and these measurements were compared between the two methods. RESULTS: The average surface differences of estimated and actual ITMs in the manual method were 0.02 mm and 0.03 mm for the maxillary and mandibular arches, respectively. In the deep learning method, the discrepancies were 0.07 mm and 0.08 mm for the maxillary and mandibular arches, respectively. For the measurements of arch widths, inter-root distances, and root axis angles, there were no significant differences between estimated and actual models both in the manual and in the deep learning methods, except for some measurements. Comparing the two methods, only three measurements showed significant differences. The procedure times taken to obtain the measurements were longer in the manual method than in the deep learning method. CONCLUSION: Both deep learning and manual methods showed similar accuracy in the integration of intraoral scans and CBCT images. Considering time and efficiency, the deep learning automatic method for ITMs is highly recommended for clinical practice.

A Digital Approach to Evaluating Tooth Root Position Without Repeated Cone-beam Computed Tomography Scans.

ABSTRACT: The purpose of this report is to introduce a digital approach to evaluating three-dimensional root position without radiation using virtual tooth model which is composed of intraoral-scanned crown and cone-beam computed tomography (CBCT)-scanned root. Successful treatment depends not only on the formulation of a proper initial diagnosis, but also on an accurate assessment of treatment progress, which should include the monitoring and evaluation of tooth and root movements. Although CBCT allows the visualization of the true root position and angulation in three-dimensions, the obtaining of serial CBCT scans for this purpose is associated with concerns regarding radiation exposure. This report introduces a method for monitoring three-dimensional root position following tooth movement during treatment that does not require repeated CBCT scans. This method uses an individual virtual tooth model composed of intraoral-scanned crowns and CBCT-scanned roots. When an evaluation of root positions is needed during treatment, only additional intraoral scan is needed and is integrated into the tooth model; this allows root positions to be estimated without the need for another CBCT scan. The use of a virtual tooth model can potentially allow clinicians to accurately monitor tooth position in routine clinical practice, without the hazards of increased radiation exposure.

Effects of the Nasal Cavity Complexity on the Pharyngeal Airway Fluid Mechanics: A Computational Study.

The impact of the human nasal airway complexity on the pharyngeal airway fluid mechanics is investigated at inspiration. It is the aim to find a suitable degree of geometrical reduction that allows for an efficient segmentation of the human airways from cone-beam computed tomography images. The flow physics is simulated by a lattice Boltzmann method on high-performance computers. For two patients, the flow field through the complete upper airway is compared to results obtained from three surface variants with continuously decreasing complexity. The most complex reduced airway model includes the middle and inferior turbinates, while the moderate model only features the inferior turbinates. In the simplest model, a pipe-like artificial structure is attached to the airway. For each model, the averaged pressure is computed at different cross sections. Furthermore, the flow fields are investigated by means of averaged velocity magnitudes, in-plane velocity vectors, and streamlines. By analyzing the averaged pressure loss from the nostrils to each cross section, it is found that only the most complex reduced models are capable of approximating the pressure distribution from the original geometries. In the moderate models, the geometry reductions lead to overpredictions of the pressure loss in the pharynx. Attaching a pipe-like structure leads to a higher deceleration of the incoming flow and underpredicted pressure losses and velocities, especially in the upper part of the pharynx. Dean-like vortices are observed in the moderate and pipe-like models, since their shape comes close to a [Formula: see text]-bend elbow pipe.

Sequential Changes in Pharyngeal Airway Dimensions After Mandibular Setback Surgery and Its Correlation With Postsurgical Stability in Patients With Mandibular Prognathism.

PURPOSE: This study aimed to evaluate the sequential changes in the pharyngeal airway dimensions after mandibular setback surgery and to verify its correlation with postsurgical mandibular stability in patients with mandibular prognathism. PATIENTS AND METHODS: This retrospective study included 28 patients with mandibular prognathism who underwent surgical orthodontic treatment and isolated mandibular setback surgery. Patients who had cone-beam computed tomography before surgery, immediately after surgery, at short-term follow-up (11.8 ± 5.1 months), and long-term follow-up (43.0 ± 13.1 months) were included. Airway dimensions, including distance, minimum cross-sectional area, and airway volume, were measured to evaluate the changes following mandibular setback surgery. With the measurements of postsurgical mandibular relapse, the relationship between sequential changes in airway dimensions and the mandible was verified using correlation analysis. RESULTS: Airway dimensions decreased immediately after mandibular setback surgery. The decreased airway dimensions recovered during short-term follow-up and maintained to the long-term follow-up. The mandible was set back 7.7 ± 5.1 mm at pogonion immediately after surgery. Postsurgical skeletal relapse was 1.1 mm at pogonion during short-term follow-up. During long-term follow-up, the mandible moved 0.4 mm anteriorly, which was about 50% of the changes during short-term follow-up. Statistically significant correlations were found between the sequential changes in airway dimensions and the postsurgical skeletal relapse. CONCLUSION: The decreased airway dimensions following mandibular setback surgery recovered during short-term follow-up and maintained to the long-term follow-up. Dimensional recovery of the pharyngeal airway was correlated with postsurgical skeletal relapse during the 1-year follow-up period.

Comparison of cephalometric measurements between conventional and automatic cephalometric analysis using convolutional neural network.

OBJECTIVE: The rapid development of artificial intelligence technologies for medical imaging has recently enabled automatic identification of anatomical landmarks on radiographs. The purpose of this study was to compare the results of an automatic cephalometric analysis using convolutional neural network with those obtained by a conventional cephalometric approach. MATERIAL AND METHODS: Cephalometric measurements of lateral cephalograms from 35 patients were obtained using an automatic program and a conventional program. Fifteen skeletal cephalometric measurements, nine dental cephalometric measurements, and two soft tissue cephalometric measurements obtained by the two methods were compared using paired t test and Bland-Altman plots. RESULTS: A comparison between the measurements from the automatic and conventional cephalometric analyses in terms of the paired t test confirmed that the saddle angle, linear measurements of maxillary incisor to NA line, and mandibular incisor to NB line showed statistically significant differences. All measurements were within the limits of agreement based on the Bland-Altman plots. The widths of limits of agreement were wider in dental measurements than those in the skeletal measurements. CONCLUSIONS: Automatic cephalometric analyses based on convolutional neural network may offer clinically acceptable diagnostic performance. Careful consideration and additional manual adjustment are needed for dental measurements regarding tooth structures for higher accuracy and better performance.

Application of the Digital Articulator in Surgery-First Approach.

ABSTRACT: Orthognathic surgery with surgery-first concept inevitably leads to an increase in posterior vertical dimension and anterior mandibular movement, causing a relapse. This case report introduces a digital technique for predictable surgical outcome in mandibular setback with the surgery-first orthognathic concept using digital articulator. Intraoral scans and a digital articulator were used to simulate the mandibular position after surgery and to predict postoperative increase in vertical dimension and its expecting forward movement of mandibile. This was incorporated in surgical planning. Sequential cone-beam computed tomography evaluation showed stable condylar position at 3 and 6 months after surgery. Thus, a digital articulator can be used to simulate the surgical outcome and to predict postsurgical increase in vertical dimension for better treatment planning.

Accuracy of virtual 3-dimensional cephalometric images constructed with 2-dimensional cephalograms using the biplanar radiography principle.

PURPOSE: The purpose of this study was to evaluate the accuracy of virtual 3-dimensional (3D) cephalograms constructed using the principle of biplanar radiography by comparing them with cone-beam computed tomography(CBCT) images. MATERIALS AND METHODS: Thirty orthodontic patients were enrolled in this study. Frontal and lateral cephalograms were obtained with the use of a head posture aligner and reconstructed into 3D cephalograms using biplanar radiography software. Thirty-four measurements representing the height, width, depth, and oblique distance were computed in 3 dimensions, and compared with the measurements from the 3D images obtained by CBCT, using the paired t-test and Bland-Altman analysis. RESULTS: Comparison of height, width, depth, and oblique measurements showed no statistically significant differences between the measurements obtained from 3D cephalograms and those from CBCT images (P>0.05). Bland-Altman plots also showed high agreement between the 3D cephalograms and CBCT images. CONCLUSION: Accurate 3D cephalograms can be constructed using the principle of biplanar radiography if frontal and lateral cephalograms can be obtained with a head posture aligner. Three-dimensional cephalograms generated using biplanar radiography can replace CBCT images taken for diagnostic purposes.

Effect of the presence of orthodontic brackets on intraoral scans.

OBJECTIVES: The need for intraoral scanning in the presence of brackets has increased for monitoring tooth movement during orthodontic treatment. The purpose of this study was to evaluate the effect of orthodontic brackets bonded to tooth surfaces on intraoral scans. MATERIALS AND METHODS: Intraoral scans were performed in 30 patients using both iTero and Trios scanners before and after bonding of the brackets. The two sets of intraoral scans of each patient and intraoral scans with and without brackets were superimposed using a best-fit algorithm, and three-dimensional (3D) surface analysis was performed. In each superimposition, discrepancies in the 3D axes and arch-width measurements in the incisor and molar regions were compared. In addition, the range of distortion around the brackets was evaluated on the cross sections of each superimposition. RESULTS: The overall discrepancies between the intraoral scans with and without brackets were within 0.30 mm. The arch-width discrepancies in the molar region were greater than those in the incisor region, but the differences were not statistically significant (P = .972 for iTero; P = .960 for Trios). The cross sections of the superimposed intraoral scans with and without brackets showed that the deviations were within 0.40 mm in the horizontal section and within 0.35 mm in the vertical section around the brackets. CONCLUSIONS: The results of this study indicate that the accuracy of intraoral scans, even in the presence of brackets, is clinically acceptable, and the regions beyond 0.50 mm around the brackets should be used for superimposition on images without brackets.