New 3-dimensional cephalometric analysis for orthognathic surgery

Advancements in computer-assisted orthognathic surgery: A comprehensive review and clinical application in South Korea

OBJECTIVES

Orthognathic surgery (OS) has evolved with technological advancements, notably through the implementation of computer-assisted orthognathic surgery (CAOS). This article aims to elucidate various types of CAOS and their efficiency and accuracy, supplemented by a thorough literature review focusing on their clinical applications in South Korea.

STUDY SELECTION, DATA, AND SOURCES

A comprehensive search strategy was employed, including systematic reviews, meta-analyses, randomized controlled trials, and observational studies published until December 2023 in the PubMed, MEDLINE, and Google Scholar databases. The literature search was limited to articles written in English.

RESULTS

Static CAOS demonstrated high precision, reduced operative time, and high accuracy, suggesting its potential reliability in orthognathic procedures. Dynamic CAOS presented a promising avenue for exploration, showing an accuracy comparable to that of traditional methods. The critical considerations for CAOS include accuracy, time efficiency, and cost-effectiveness. Recent studies have indicated advancements in the time efficiency of static CAOS. Static CAOS requires less equipment and is more cost-effective than dynamic CAOS.

CONCLUSIONS

CAOS offers clear advantages over conventional OS in terms of surgical convenience and accuracy in implementing the surgical plan. To achieve recognition as the gold standard method for maxillofacial deformity treatment, CAOS must overcome its limitations and undergo continuous verification via well-designed studies.

CLINICAL SIGNIFICANCE

The introduction of CAOS, mainly static CAOS with high precision and reduced surgical time, signifies a notable advancement in OS. However, rigorous studies are warranted to validate CAOS as the gold standard for treating maxillofacial deformities.

Deep learning for 3D cephalometric landmarking with heterogeneous multi-center CBCT dataset

Cephalometric analysis is critically important and common procedure prior to orthodontic treatment and orthognathic surgery. Recently, deep learning approaches have been proposed for automatic 3D cephalometric analysis based on landmarking from CBCT scans. However, these approaches have relied on uniform datasets from a single center or imaging device but without considering patient ethnicity. In addition, previous works have considered a limited number of clinically relevant cephalometric landmarks and the approaches were computationally infeasible, both impairing integration into clinical workflow. Here our aim is to analyze the clinical applicability of a light-weight deep learning neural network for fast localization of 46 clinically significant cephalometric landmarks with multi-center, multi-ethnic, and multi-device data consisting of 309 CBCT scans from Finnish and Thai patients. The localization performance of our approach resulted in the mean distance of 1.99 ± 1.55 mm for the Finnish cohort and 1.96 ± 1.25 mm for the Thai cohort. This performance turned out to be clinically significant i.e., ≤ 2 mm with 61.7% and 64.3% of the landmarks with Finnish and Thai cohorts, respectively. Furthermore, the estimated landmarks were used to measure cephalometric characteristics successfully i.e., with ≤ 2 mm or ≤ 2° error, on 85.9% of the Finnish and 74.4% of the Thai cases. Between the two patient cohorts, 33 of the landmarks and all cephalometric characteristics had no statistically significant difference (p < 0.05) measured by the Mann-Whitney U test with Benjamini-Hochberg correction. Moreover, our method is found to be computationally light, i.e., providing the predictions with the mean duration of 0.77 s and 2.27 s with single machine GPU and CPU computing, respectively. Our findings advocate for the inclusion of this method into clinical settings based on its technical feasibility and robustness across varied clinical datasets.

Classification and characterization of facial asymmetry in adult patients with skeletal Class III malocclusion using cluster analysis

INTRODUCTION

This study aimed to analyze the comprehensive maxillofacial features of patients with skeletal Class III malocclusion and facial asymmetry to develop a classification system for diagnosis and surgical planning.

METHODS

A total of 161 adult patients were included, with 121 patients in the asymmetry group (menton deviation >2 mm) and 40 patients in the symmetry group (menton deviation ≤2 mm). Twenty-eight variables were determined, including transverse translation, roll and yaw of each facial unit, transverse width, mandibular morphology, and transverse dental compensation. Principal component (PC) analysis was conducted to extract PCs, and cluster analysis was performed using these components to classify the asymmetry group. A decision tree was constructed on the basis of the clustering results.

RESULTS

Six PCs were extracted, explaining 80.622% of the data variability. The asymmetry group was classified into 4 subgroups: (1) atypical type (15.7%) showed an opposite roll direction of maxillary dentition than of menton deviation; (2) compound type (34.71%) demonstrated significant ramus height differences, maxillary roll, and mandibular roll and yaw; (3) mandibular yaw type (44.63%) showed slight mandibular yaw without mandibular morphology asymmetry; and (4) maxillary-shift type (4.96%) shared similarities with the compound type but showed significant maxillary translation. The classification and regression tree model achieved a prediction accuracy of up to 85.11%.

CONCLUSIONS

This study identified 4 distinct phenotypes using cluster analysis and proposed tailored treatment recommendations on the basis of their specific characteristics. The classification results emphasized the importance of spatial displacement features, especially mandibular yaw, in diagnosing facial asymmetry. The established classification and regression tree model enables clinicians to identify patients conveniently.

Orthognathic surgery improves compromised natural head position and pharyngeal airway in patients with Skeletal Class II or III malocclusion

BACKGROUND

Natural head position (NHP), pharyngeal airway and maxillofacial growth pattern are correlated. The author's previous studies proved that following surgical correction of Skeletal Class II malocclusion, the over-extended NHP returned upright, and the pharyngeal airway space (PAS) dimension expanded.

OBJECTIVE

The present study compares the post-operative change in NHP and PAS after orthognathic surgery in Skeletal Class II and III malocclusion patients.

METHODS

Patients receiving orthognathic procedures to correct Skeletal Class II or III malocclusions were reviewed in this retrospective study. Pre-operative and 6-week post-operative cone-beam computed tomography datasets were collected. Variables representing the craniofacial pattern, the NHP and the PAS were measured three-dimensionally. Post-operative variables were compared with their pre-operative counterparts using either repeat-measure 2-way analysis of variance or Wilcoxon matched-pairs signed rank test.

RESULTS

Thirty cases of Skeletal Class II malocclusion and 13 cases of Skeletal Class III malocclusion were collected. Preoperatively, the inter-group differences were significant in craniofacial pattern (68.14 ± 3.552 degree vs. 79.63 ± 2.497 degree, p < .0001) and the NHP (68.77 ± 11.02 degree vs. 82.83 ± 7.738 degree, p = .0002) while not significant in PAS; after surgery, the intergroup differences in craniofacial pattern and the NHP between groups decreased, and the PAS increased in both groups.

CONCLUSION

Orthognathic surgery may improve compromised NHP and increase PAS in Skeletal Class II and III malocclusion patients.

Deep learning for automatic detection of cephalometric landmarks on lateral cephalometric radiographs using the Mask Region-based Convolutional Neural Network: a pilot study

OBJECTIVE

We examined the effectiveness and feasibility of the Mask Region-based Convolutional Neural Network (Mask R-CNN) for automatic detection of cephalometric landmarks on lateral cephalometric radiographs (LCRs).

STUDY DESIGN

In total, 400 LCRs, each with 19 manually identified landmarks, were collected. Of this total, 320 images were randomly selected as the training dataset for Mask R-CNN, and the remaining 80 images were used for testing the automatic detection of the 19 cephalometric landmarks, for a total of 1520 landmarks. Detection rate, average error, and detection accuracy rate were calculated to assess Mask R-CNN performance.

RESULTS

Of the 1520 landmarks, 1494 were detected, for a detection rate of 98.29%. The average error, or linear deviation distance between the detected points and the originally marked points of each detected landmark, ranged from 0.56 to 9.51 mm, with an average of 2.19 mm. For detection accuracy rate, 649 landmarks (43.44%) had a linear deviation distance less than 1 mm, 1020 (68.27%) less than 2 mm, and 1281 (85.74%) less than 4 mm in deviation from the manually marked point. The average detection time was 1.48 seconds per image.

CONCLUSIONS

Deep learning Mask R-CNN shows promise in enhancing cephalometric analysis by automating landmark detection on LCRs, addressing the limitations of manual analysis, and demonstrating effectiveness and feasibility.

Three-dimensional mandibular characteristics in skeletal malocclusion : A cross-sectional study

PURPOSE

We aimed to comprehensively analyse a possible correlation between skeletal malocclusions, gender and mandibular characteristics in all three dimensions in adults and to identify mandibular characteristics that are typical for extreme skeletal patterns.

METHODS

A 3D model of the skull was calculated in 111 adult patients (mean age = 27.0 ± 10.2 years; 49 women, 62 men) from available computed tomography or cone beam computed tomography scans of their heads. Based on the 3D models, the skeletal patterns were examined in (a) the transversal dimension regarding asymmetry according to menton deviation, (b) the sagittal dimension according to the Wits appraisal and (c) the vertical dimension according to the maxillomandibular plane angle. The mandibular characteristics assessed were linear (ramus height and width, body length), angular (ramus, gonial and body angle) and volumetric (ramus/mandibular volume, body/mandibular volume) parameters.

RESULTS

No correlation between transversal skeletal asymmetry and mandibular characteristics were found, while sagittal (F(16, 174) = 3.32, p < 0.001, η2 = 0.23) and vertical (F(16, 174) = 3.18, p < 0.001, η2 = 0.23) skeletal patterns were shown to have a significant effect on the mandible. Gender correlated with mandibular characteristics independently from the skeletal pattern. Discriminant analysis revealed that class II and III patients differed in ramus and body angle with class II patients showing higher angles (ramus angle: class II = 89.8 ± 3.9° vs. class III = 84.4 ± 4.8°; body angle: class II = 87.7 ± 4.8° vs. class III = 82.1 ± 5.2°). Hypo- and hyperdivergent patients were discriminated by gonial angle, body angle and body/mandibular volume with hyperdivergent patients having a greater gonial and body angle and body/mandibular volume (gonial angle: hypodivergent = 114 ± 9.3° vs. hyperdivergent = 126.4 ± 8.6°; body angle: hypodivergent = 82.9 ± 4.4° vs. hyperdivergent = 87.7 ± 6.5°; body/mandibular volume: hypodivergent = 72.4 ± 2.7% vs. hyperdivergent = 76.2 ± 2.6%).

CONCLUSION

When analysing 3D data for treatment planning of adult patients, the orthodontist should pay attention to angular and volumetric characteristics of the mandible to identify extreme skeletal sagittal or vertical malocclusions.

Applications of Cone Beam Computed Tomography Scans in Dental Medicine and Potential Medicolegal Issues

A cone beam central tomography (CBCT) scan produces images in orthogonal and non-orthogonal with great spatial resolution. When a dental health care practitioner (DHP) orders a CBCT scan, they should consider if it is truly indicated, as CBCT scans carry up to four times the dosage of radiation compared to panoramic radiographs. Any diagnostic imaging obtained of a patient should include a formal interpretive report commenting on the findings within the imaging. Ordering of limited field of view (FOV) CBCT scans and failing to report on abnormal findings present outside of the region of interest (ROI) is a potential medicolegal issue.

Symmetrical Midfacial Growth After Pediatric Mandibular Reconstruction With Free Fibula Flap

BACKGROUND

Free fibula is the workhorse flap for mandibular reconstruction and is increasingly being used in pediatric patients. However, craniomaxillofacial growth and development involve interdependent processes, and it remains unknown whether mandibular reconstruction with free fibula allows symmetric growth of the midface.

PURPOSE

The study evaluated midfacial symmetry after pediatric mandibular defect reconstruction.

STUDY DESIGN, SETTING, SAMPLE

This retrospective cohort study included pediatric patients aged ≤14 years who underwent mandibular reconstruction with free fibula flap. Postoperative computed tomography data were obtained at predefined follow-up time points. Midfacial symmetry was evaluated based on 3-dimensional (3D) cephalometry.

PREDICTOR VARIABLE

The predictor variable was the side of the midface (affected or healthy side relative to the mandibular defect).

MAIN OUTCOME VARIABLES

The primary outcome variable was postoperative midfacial symmetry (at 1 week, 6 months, 1 year, 2 years, and >3 years, or after the age of 18 years), assessed in horizontal, vertical, and anteroposterior dimensions using 3D cephalometry. Another outcome variable was patient satisfaction based on a self-evaluation using visual analog scoring.

COVARIATES

Sex, age, diagnosis, and type of denture restoration.

ANALYSES

Paired t tests were performed to assess the relationship between the predictor and outcome variables, with the significance level of P < .05.

RESULTS

A total of 13 patients were included in this study (9 males and 4 females; mean age: 12.23 ± 2.39 years). The average distance from upper first molar point (U6) to the horizontal plane on the affected side became greater than on the healthy side (difference: 0.7 ± 0.5 mm to 1.6 ± 1.4 mm, P < .05), while the average distance from pterygomaxillary fissure to coronal plane on affected side became shorter than that on the healthy side (difference: 0.6 ± 0.6 mm to 1.2 ± 1.1 mm, P < .05) from 1 year after the surgery. There were no statistically significant differences in the remaining measurements between the 2 sides (P > .05). All the patients were satisfied with their postoperative facial symmetry.

CONCLUSIONS AND RELEVANCE

There were no severe midface deformities after pediatric mandibular reconstruction with free fibula flap. Meanwhile, pediatric mandibular reconstruction and proper occlusion could promote midfacial growth and symmetry.

Three-Dimensional Enlow's Counterpart Analysis: Neutral Track

The aim of this study is to provide a novel method to perform Enlow's neutral track analysis on cone-beam computed tomography (CBCT) images. Eighteen CBCT images of skeletal Class I (ANB = 2° ± 2°) subjects (12 males and 6 females, aged from 9 to 19 years) with no history of previous orthodontic treatment were selected. For each subject, 2D Enlow's neutral track analysis was performed on lateral cephalograms extracted from CBCT images and 3D neutral track analysis was performed on CBCT images. A Student's t-test did not show any statistically significant difference between the 2D and 3D measurements and therefore the method proposed by this study to realize the neutral track analysis on 3D images is valid and superimposable on that described by Enlow on lateral cephalograms. Further studies with a large sample and different skeletal class subjects are needed to confirm the results of this research.

Cross Sectional Analysis of Eurasian Skull Anatomy for 3D Cephalometry-Normative Data Reveal Four Different Skull Types

The unsolved problem in three-dimensional surgical planning for patients with facial deformity, dysgnathia, or asymmetry is the lack of a normative database of "norm skulls" that can be used as treatment objectives. A study was conducted on 90 Eurasian persons (46 male and 44 female adults) for whom cone beam-computed tomography images were available. Inclusion criteria were adult patients with a skeletal Class I pattern, proper interincisal relationship with normal occlusion, the absence of an open bite both in the anterior and posterior region, and a normal and balanced facial appearance; patients with dysgnathia and malformations were excluded. A total of 18 landmarks were digitized and 3D cephalometric measurements were performed and analyzed by means of proportions calculated from the landmarks. Male and female skulls were analyzed, as well as subdivisions revealed by cluster analysis. The data showed that four subtypes of skulls were distinguishable with statistical significance (p < 0.05). A male and a female type subdivided in a brachiocephalic and dolichocephalic phenotype could be identified. For each type, a mean shape was calculated by a Procrustes transformation, which, in turn, was used to create four template skulls from a male and a female skull. This was accomplished by fitting the polygon models of the two skulls to each of the two subtypes based on the landmarks marked on them using a thin plate spline transformation. The normative data of the subtypes can individually serve as a guide for orthodontic surgery in the Eurasian population, which is especially helpful in 3D planning and the execution of craniofacial operations.

The application of a fully digital approach in the treatment of skeletal class III malocclusion: a preliminary study

BACKGROUND

Skeletal malocclusion patients have facial malformations and occlusal dysfunctions that require orthodontic-orthognathic joint treatment, while the combination treatment takes time and requires close communication between surgeons and orthodontists. Thus, improving the efficiency and effectiveness of the combination treatment is necessary, and it is still a challenge. Now, digital technology provides us with an excellent alternative. Despite the widespread use of digital technology in orthognathic surgery simulation and clear aligner orthodontic therapy, it has not been fully integrated into the combined orthognathic and orthodontic treatment process, and the components remain independent.

METHODS

A fully digital approach to seamlessly integrating various parts of the combined treatment through digital technology was investigated in this study in order to achieve an efficient transition. Five patients with skeletal Class III malocclusion were enrolled, and all made fully digital treatment plans at the beginning of actual implementation, which included the design of pre-surgical orthodontic, orthognathic surgery, and post-surgical orthodontic. Then, every aspect of the clinical operation was carried out in accordance with the fully digital routine. After the entire treatment process was completed, the skeleton and dentition discrepancy between virtual planning and the actual result was evaluated.

RESULTS

All participants completed the fully digital treatment process, and no complication was observed. The linear deviation of the skeletal anatomy was less than 1 mm, and the angular deviation was less than 1 degree. Except in one case in the lower dentition, the deviation of the virtual dental design from the real alignment was less than 2 mm. Furthermore, with one exception of maxillary anterior-posterior dimension, the linear deviations of the skeleton were not statistically significant. Therefore, the simulation accuracy of the fully digital approach was clinically acceptable.

CONCLUSIONS

The digital treatment approach is clinically feasible and has achieved satisfactory results. The discrepancy between virtual design of the entire digital process and actual post-treatment situation was acceptable in clinic. A fully digital approach was proved effective in the treatment of skeletal Class III malocclusion, with which the efficient transition of treatment procedures was realized.

What Is the Linear Accuracy of Regional Voxel-Based Registration for Orthognathic Surgery Landmarks?

PURPOSE

While regional voxel-based registration (R-VBR) has been shown to have excellent reproducibility and angular accuracy, there are limited data on the linear accuracy of R-VBR for common orthognathic surgery landmarks, or on whether angular accuracy correlates with linear accuracy. The purpose of this study was to estimate the linear accuracy of R-VBR for several skeletal landmarks commonly used in orthognathic surgical planning, and to measure the correlation between angular and linear discrepancies.

MATERIALS AND METHODS

This is a retrospective cross-sectional study of consecutive patients treated at a single center with nonsegmental LeFort I and bilateral sagittal split osteotomy surgery from January 2019 to November 2020. Cone beam computed tomography at the preoperative (T0) and immediate postoperative (T1) stages were analyzed to measure the postoperative positional changes of 11 orthognathic landmarks in 4 regions of interest (ROI) using R-VBR performed twice by two examiners. Pairwise correlation analysis and canonical correlation analysis were performed for the angular discrepancies (primary predictor variable) and the linear discrepancies (primary outcome variable) to measure the correlation between the two.

RESULTS

In cone beam computed tomography analysis of 28 eligible subjects (16 males, 12 females; mean age 18.9 years, range 15 to 25), the mean absolute (MA) angular discrepancies ranged from 0.15° to 0.55°, while the corresponding MA linear discrepancies ranged from 0.05 to 0.41 mm. There was a strong correlation between angular and linear discrepancies that was statistically significant (P = .001 to .04, Spearman's rank correlation coefficient 0.38 to 0.87).

CONCLUSIONS

For nonsegmental LeFort I osteotomies and bilateral sagittal split osteotomy, R-VBR has excellent linear accuracy within a single voxel size (0.3 mm) for commonly used orthognathic landmarks in the maxillary and distal mandibular ROI. The MA linear discrepancy for the proximal mandibular segment ROI was greater than a single voxel size, with a maximum of 0.41 mm.

Condylar and ramus volume in asymmetric and symmetric skeletal class III malocclusion: A cone-beam computed tomography study

Background/purpose

Among the craniofacial structures, the mandible is the only bony structure with movable joints. Each part (including condyle process, coronoid process, and ramus) of mandible would interaction with the muscles and proceed different osteogenesis progress. The objective of this study was to evaluate the mandibles with symmetric and asymmetric skeletal Class III jaw relations by quantifying differences in the condyle process, coronoid process and ramus on CBCT (Cone-beam computer tomography) images. Our hypothesis was that CBCT would reveal no voluminal differences between deviated and non-deviated mandibular segments in asymmetric skeletal Class III.

Materials and methods

CBCT imagines were collected from dental department, KMUH and then divided into symmetric Class III group (Menton deviation < 4mm) and asymmetric Class III group (Menton deviation≧4mm). The mandibular structure would be segmented to ramus, condylar and coronoid process. Each volume was measured. Independent t test was used for comparison between groups, and paired t test was applied for comparison between both segmented parts within each group.

Results

Significant differences between deviation and non-deviation sides in the asymmetric group were found in condylar and ramus segments for volumetric quantitative measurements. There has no significant difference in ramus parts between groups. Significant greater condylar volume was found in non-deviation side of asymmetric group.

Conclusion

The results demonstrated that in the side with greater mandible growth potential, the condylar and the ramus volume would be greater as well. CBCT is a useful and accurate modality for quantification and evaluation of mandibular asymmetry.

Using the anterior cranial base to provide a reliable reference plane for patients with or without facial asymmetry

INTRODUCTION

This study aimed to investigate the midsagittal reference plane (MSP) reliability derived from the 3-dimensional characteristics of patients with or without facial asymmetry in the anterior cranial base (ACB).

METHODS

We divided the cone-beam computed tomography (CBCT) images of 60 adult patients into maxillofacial symmetry and asymmetry groups. The ACB models were 3-dimensionally constructed, and then symmetrical characteristics were evaluated with surface asymmetry for each group. The reliability of the MSP derived from the symmetry of the anterior cranial base (MSPACB) was assessed in comparison with the true craniofacial symmetry plane determined using the morphometric method.

RESULTS

The ACB was symmetrical, as demonstrated by slight surface asymmetry. The MSPACB was reliable for maxillofacial asymmetrical analysis as the intraobserver and interobserver measurements using the MSPACB were of excellent agreement, and there was no significant difference between MSPACB and morphometric method in asymmetrical measurements in both groups. The MSPACB remained stable (maximum deviation <0.32 mm) when cranial landmark identification errors (1 mm and 4 mm) were simulated.

CONCLUSIONS

MSPACB is reliable for patients with or without facial asymmetry in maxillofacial asymmetry analysis, which is beneficial to patients with severe midfacial asymmetry or trauma when conventional landmarks are displaced or disappear. When using MSPACB for patients with cranial malformations or those whose ACBs differ from normal dimensions, caution should be taken.

“3D Counterpart Analysis”: A Novel Method for Enlow’s Counterpart Analysis on CBCT

The aim of this study was to propose a novel 3D Enlow’s counterpart analysis traced on cone-beam computed tomography (CBCT) images. Eighteen CBCT images of skeletal Class I (ANB = 2° ± 2°) subjects (12 males and 6 females, aged from 9 to 19 years) with no history of previous orthodontic treatment were selected. For each subject, a 2D Enlow’s counterpart analysis was performed on lateral cephalograms extracted from the CBCT images. The following structures were identified: mandibular ramus, middle cranial floor, maxillary skeletal arch, mandibular skeletal arch, maxillary dento-alveolar arch, mandibular dento-alveolar arch. The differences between each part and its relative counterpart obtained from the 2D analysis were than compared with those obtained from a 3D analysis traced on the CBCT images. A Student’s t-test did not show any statistical significant difference between the 2D and 3D measurements. The landmarks proposed by this study identified the cranio-facial structures on the 3D images in a way that could be superimposed on those described by Enlow in his analysis performed on 2D lateral cephalograms.

The untold history of planning in orthognathic surgery: a narrative review from the beginning to virtual surgical simulation

We aimed to produce a narrative review of planning orthognathic surgery, chronologically. Also, to present flaws of methods and the future of orthognathic surgery planning. The search was carried out mainly in PubMed, SCOPUS, Embase, and Cochrane databases. Also was complemented by manual search in reference lists from identified studies and in grey literature. The first orthognathic surgery was reported in 1849, and it took more than a century for the development of the traditional orthognathic 2D planning. Besides the advances, surgeons observed failures and lacks on 2D method in representing with reliability the facial and maxillary tridimensional structure (3D). With technological developments in 90s and 2000s, methodological improvements were granted, and the 3D protocol was created. The CASS and Charlotte protocols were the earliest 3D planning protocols conceived. Since then, some steps were simplified, and new technologies are being developed and added to create a more reliable and precise way of planning orthognathic surgery.

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.

Automatic 3-Dimensional Cephalometric Landmarking via Deep Learning

The increasing use of 3-dimensional (3D) imaging by orthodontists and maxillofacial surgeons to assess complex dentofacial deformities and plan orthognathic surgeries implies a critical need for 3D cephalometric analysis. Although promising methods were suggested to localize 3D landmarks automatically, concerns about robustness and generalizability restrain their clinical use. Consequently, highly trained operators remain needed to perform manual landmarking. In this retrospective diagnostic study, we aimed to train and evaluate a deep learning (DL) pipeline based on SpatialConfiguration-Net for automatic localization of 3D cephalometric landmarks on computed tomography (CT) scans. A retrospective sample of consecutive presurgical CT scans was randomly distributed between a training/validation set (n = 160) and a test set (n = 38). The reference data consisted of 33 landmarks, manually localized once by 1 operator(n = 178) or twice by 3 operators (n = 20, test set only). After inference on the test set, 1 CT scan showed "very low" confidence level predictions; we excluded it from the overall analysis but still assessed and discussed the corresponding results. The model performance was evaluated by comparing the predictions with the reference data; the outcome set included localization accuracy, cephalometric measurements, and comparison to manual landmarking reproducibility. On the hold-out test set, the mean localization error was 1.0 ± 1.3 mm, while success detection rates for 2.0, 2.5, and 3.0 mm were 90.4%, 93.6%, and 95.4%, respectively. Mean errors were -0.3 ± 1.3° and -0.1 ± 0.7 mm for angular and linear measurements, respectively. When compared to manual reproducibility, the measurements were within the Bland-Altman 95% limits of agreement for 91.9% and 71.8% of skeletal and dentoalveolar variables, respectively. To conclude, while our DL method still requires improvement, it provided highly accurate 3D landmark localization on a challenging test set, with a reliability for skeletal evaluation on par with what clinicians obtain.

Structure-Aware Long Short-Term Memory Network for 3D Cephalometric Landmark Detection

Detecting 3D landmarks on cone-beam computed tomography (CBCT) is crucial to assessing and quantifying the anatomical abnormalities in 3D cephalometric analysis. However, the current methods are time-consuming and suffer from large biases in landmark localization, leading to unreliable diagnosis results. In this work, we propose a novel Structure-Aware Long Short-Term Memory framework (SA-LSTM) for efficient and accurate 3D landmark detection. To reduce the computational burden, SA-LSTM is designed in two stages. It first locates the coarse landmarks via heatmap regression on a down-sampled CBCT volume and then progressively refines landmarks by attentive offset regression using multi-resolution cropped patches. To boost accuracy, SA-LSTM captures global-local dependence among the cropping patches via self-attention. Specifically, a novel graph attention module implicitly encodes the landmark's global structure to rationalize the predicted position. Moreover, a novel attention-gated module recursively filters irrelevant local features and maintains high-confident local predictions for aggregating the final result. Experiments conducted on an in-house dataset and a public dataset show that our method outperforms state-of-the-art methods, achieving 1.64 mm and 2.37 mm average errors, respectively. Furthermore, our method is very efficient, taking only 0.5 seconds for inferring the whole CBCT volume of resolution 768×768×576 .

3D Cephalometric Normality Range: Auto Contractive Maps (ACM) Analysis in Selected Caucasian Skeletal Class I Age Groups

The objective of this paper is to define normal values of a novel 3D cephalometric analysis and to define the links through an artificial neural network (ANN). Methods: One hundred and fifteen CBCTs of Class I young patients, distributed among gender-adjusted developmental groups, were selected. Three operators identified 18 cephalometric landmarks from which 36 measurements were obtained. The repeatability was assessed through the ICC. Two-dimensional values were extracted by an automatic function, and the mean value and standard deviation were compared by paired Student’s t-tests. Correlation coefficient gave the relationships between 2D and 3D measurements for each group. The values were computed with the ANN to evaluate the parameters normality link and displayed by Pajek software. Results: The ICC assessed an excellent (≥0.9) repeatability. Normal values were extracted, and compared with 2D measurements, they showed a high correlation on the mid-sagittal plane, reaching 1.00, with the lowest 0.71 on the lateral plane. The ANN showed strong links between the values with the centrality of the go-sagittal plane compared to the rest. Conclusions: The study provides a set of 3D cephalometric values obtained by the upper and lower 95% CI for the mean divided into the developmental stage subgroups. The two-dimensional measurements showed variable concordance, while the ANN showed a centrality between the parameters.

3-D cephalometry of the the orbit regarding endocrine orbitopathy, exophthalmos, and sex

Purpose

This study aimed at evaluating the orbital anatomy of patients concerning the relevance of orbital anatomy in the etiology of EO (endocrine orbitopathy) and exophthalmos utilizing a novel approach regarding three-dimensional measurements. Furthermore, sexual dimorphism in orbital anatomy was analyzed.

Methods

Orbital anatomy of 123 Caucasian patients (52 with EO, 71 without EO) was examined using computed tomographic data and FAT software for 3-D cephalometry. Using 56 anatomical landmarks, 20 angles and 155 distances were measured. MEDAS software was used for performing connected and unconnected t-tests and Spearman´s rank correlation test to evaluate interrelations and differences.

Results

Orbital anatomy was highly symmetrical with a mean side difference of 0.3 mm for distances and 0.6° for angles. There was a small albeit statistically significant difference in 13 out of 155 distances in women and 1 in men concerning patients with and without EO. Two out of 12 angles showed a statistically significant difference between female patients with and without EO. Regarding sex, statistically significant differences occurred in 39 distances, orbit volume, orbit surface, and 2 angles. On average, measurements were larger in men. Concerning globe position within the orbit, larger distances to the orbital apex correlated with larger orbital dimensions whereas the sagittal position of the orbital rim defined Hertel values.

Conclusion

In this study, little difference in orbital anatomy between patients with and without EO was found. Concerning sex, orbital anatomy differed significantly with men presenting larger orbital dimensions. Regarding clinically measured exophthalmos, orbital aperture anatomy is an important factor which has to be considered in distinguishing between true exophthalmos with a larger distance between globe and orbital apex and pseudoexophthalmos were only the orbital rim is retruded. Thus, orbital anatomy may influence therapy regarding timing and surgical procedures as it affects exophthalmos.

Statistical and individual characteristics-based reconstruction for craniomaxillofacial surgery

PURPOSE

In craniomaxillofacial (CMF) surgery planning, a preoperative reconstruction of the CMF reference model is crucial for surgical restoration, especially the reconstruction of bilateral defects. Current reconstruction algorithms mainly generate reference models from the image analysis aspect, however, clinical indicators of the CMF reference model mostly consider the distribution of anatomical landmarks. Generating a reference model with optimal clinical evaluation helps promote the feasibility of an algorithm.

METHODS

We first build a dataset with 100 normal skull models and then calculate a statistical shape model (SSM) and the distribution of normal cephalometric values, which indicate the statistical features of a population. To further generate personalized reference models, we apply non-rigid registration to align the SSM with the defect skull model. An evaluation standard to select the optimal reference model considers both global performance and anatomical evaluation. Moreover, we develop a landmark detection network to improve the automatic level of the algorithm.

RESULTS

The proposed method performs better than methods including Iterative Closest Point and SSM. From a global evaluation aspect, the results show that the RMSE between the reference model and the ground truth is [Formula: see text] mm, the percentage of vertices with error below 2 mm is [Formula: see text]% and the average faces distance is [Formula: see text] mm (better than the state-of-the-art method). From the anatomical evaluation aspect, the target registration error between the landmark pairs is [Formula: see text] mm. In addition, the clinical application confirms that the reference model can meet clinical requirements.

CONCLUSION

To the best of our knowledge, we propose the first CMF reconstruction method considering the global performance of reconstruction and anatomically local evaluation from clinical experience. Simulated experiments and clinical cases prove the general applicability and strength of the method.

[A cone-beam computed tomography evaluation of three-dimensional changes of circummaxillary sutures following maxillary protraction with alternate rapid palatal expansions and constrictions]

OBJECTIVE

To assess three-dimensional (3D) changes of circummaxillary sutures following maxillary protraction with alternate rapid palatal expansions and constrictions (RPE/C) facemask protocol in maxillary retrusive children, and to investigate the relationship between the changes of circum-maxillary sutures and zygomaticomaxillary suture (ZMS) maturation, and to explore the factors of maxilla forward movement with RPE/C and facemask.

METHODS

In the study (clinical trial registration No: ChiCTR2000034909), 36 maxillary retrusive patients were recruited and block randomized to either the rapid palatal expansion (RPE) group or the RPE/C group. Patients aged 7 to 13 years, Class Ⅲ malocclusion, anterior crossbite, ANB less than 0°, Wits appraisal less than -2 mm, and A-Np less than 0 mm were included in the study. The RPE group received rapid palatal expansion, whereas the RPE/C group received alternate rapid palatal expansions and constrictions, and both with facemask protraction. Head orientations of cone-beam computed tomography (CBCT) images were implemented by Dolphin 11.7. 3D measurements of circummaxillary sutures on CBCT images were evaluated using Mimics 10.01 before (T0) and after treatment (T1). The changes were analyzed with independent t test, two-way ANOVA, Pearson correlation and regression analysis.

RESULTS

Two subjects in the RPE/C group were lost to follow-up. A total of 34 patients reached the completion criteria and were analyzed. Compared with the RPE group, sagittal changes of circummaxillary sutures were significantly increased in the RPE/C group with 1.21 mm advancement of zygomaticotemporal suture, 2.20 mm of ZMS, 1.43 mm of zygoma-ticofrontal suture (P < 0.05, respectively). Except for the zygomaticotemporal suture, the rest forward sagittal changes of other circummaxillary sutures showed no major difference in terms of the ZMS maturation. The Spearman's correlation in RPE/C indicated a strong positive correlation of sagittal changes between ZMS and point A (P < 0.01) with a regression analysis R²=42.5%.

CONCLUSION

RPE/C might be more effective on the treatment of maxillary retrusive children. As one of the major mechanical loading sutures during orthopedic therapy, ZMS showed a strong positive correlation with point A on sagittal changes.

[A cone-beam computed tomography evaluation of three-dimensional changes of circummaxillary sutures following maxillary protraction with alternate rapid palatal expansions and constrictions]

OBJECTIVE

To assess three-dimensional (3D) changes of circummaxillary sutures following maxillary protraction with alternate rapid palatal expansions and constrictions (RPE/C) facemask protocol in maxillary retrusive children, and to investigate the relationship between the changes of circum-maxillary sutures and zygomaticomaxillary suture (ZMS) maturation, and to explore the factors of maxilla forward movement with RPE/C and facemask.

METHODS

In the study (clinical trial registration No: ChiCTR2000034909), 36 maxillary retrusive patients were recruited and block randomized to either the rapid palatal expansion (RPE) group or the RPE/C group. Patients aged 7 to 13 years, Class Ⅲ malocclusion, anterior crossbite, ANB less than 0°, Wits appraisal less than -2 mm, and A-Np less than 0 mm were included in the study. The RPE group received rapid palatal expansion, whereas the RPE/C group received alternate rapid palatal expansions and constrictions, and both with facemask protraction. Head orientations of cone-beam computed tomography (CBCT) images were implemented by Dolphin 11.7. 3D measurements of circummaxillary sutures on CBCT images were evaluated using Mimics 10.01 before (T0) and after treatment (T1). The changes were analyzed with independent t test, two-way ANOVA, Pearson correlation and regression analysis.

RESULTS

Two subjects in the RPE/C group were lost to follow-up. A total of 34 patients reached the completion criteria and were analyzed. Compared with the RPE group, sagittal changes of circummaxillary sutures were significantly increased in the RPE/C group with 1.21 mm advancement of zygomaticotemporal suture, 2.20 mm of ZMS, 1.43 mm of zygoma-ticofrontal suture (P < 0.05, respectively). Except for the zygomaticotemporal suture, the rest forward sagittal changes of other circummaxillary sutures showed no major difference in terms of the ZMS maturation. The Spearman's correlation in RPE/C indicated a strong positive correlation of sagittal changes between ZMS and point A (P < 0.01) with a regression analysis R2=42.5%.

CONCLUSION

RPE/C might be more effective on the treatment of maxillary retrusive children. As one of the major mechanical loading sutures during orthopedic therapy, ZMS showed a strong positive correlation with point A on sagittal changes.

Cephalometric measurements performed on CBCT and reconstructed lateral cephalograms: a cross-sectional study providing a quantitative approach of differences and bias

Background

Cephalometric analysis is traditionally performed on skull lateral teleradiographs for orthodontic diagnosis and treatment planning. However, the skull flattened over a 2D film presents projection distortions and superimpositions to various extents depending on landmarks relative position. When a CBCT scan is indicated for mixed reasons, cephalometric assessments can be performed directly on CBCT scans with a distortion free procedure. The aim of the present study is to compare these two methods for orthodontic cephalometry.

Methods

114 CBCTs were selected, reconstructed lateral cephalometries were obtained by lateral radiographic projection of the entire volume from the right and left sides. 2D and 3D cephalometric tracings were performed. Since paired t-tests between left and right-side measurements found no statistically significant differences, mean values between sides were considered for both 2D and 3D values. The following measurements were evaluated: PNS-A; S-N; N-Me; N-ANS; ANS-Me; Go-Me; Go-S; Go-Co; SNA, SNB, ANB; BaŜN; S-N^PNS-ANS; PNS-ANS^Go-Me; S-N^Go-Me. Intraclass correlation coefficients, paired t-test, correlation coefficient and Bland–Altman analysis were performed to compare these techniques.

Results

The values of intra- and inter-rater ICC showed excellent repeatability and reliability: the average (± SD) intraobserver ICCs were 0.98 (± 0.01) and 0.97(± 0.01) for CBCT and RLCs, respectively; Inter-rater reliability resulted in an average ICC (± SD) of 0.98 (± 0.01) for CBCT and 0.94 (± 0.03) for RLC. The paired t-tests between CBCT and reconstructed lateral cephalograms revealed that Go-Me, Go-S, PNS-ANS^Go-Me and S-N^Go-Me measurements were statistically different between the two modalities. All the evaluated sets of measurements showed strong positive correlation; the bias and ranges for the 95% Limits of Agreement showed higher levels of agreement between the two modalities for unpaired measurements with respect to bilateral ones.

Conclusion

The cephalometric measurements laying on the mid-sagittal plane can be evaluated on CBCT and used for orthodontic diagnosis as they do not show statistically significant differences with those measured on 2D lateral cephalograms. For measurements that are not in the mid-sagittal plane, the future development of specific algorithms for distortion correction could help clinicians deduct all the information needed for orthodontic diagnosis from the CBCT scan.

Accurate transfer of bimaxillary orthognathic surgical plans using computer-aided intraoperative navigation

Objective

To examine the accuracy of computer-aided intraoperative navigation (Ci-Navi) in bimaxillary orthognathic surgery by comparing preoperative planning and postoperative outcome.

Methods

The study comprised 45 patients with congenital dentomaxillofacial deformities who were scheduled to undergo bimaxillary orthognathic surgery. Virtual bimaxillary orthognathic surgery was simulated using Mimics software. Intraoperatively, a Le Fort I osteotomy of the maxilla was performed using osteotomy guide plates. After the Le Fort I osteotomy and bilateral sagittal split ramus osteotomy of the mandible, the mobilized maxilla and the distal mandibular segment were fixed using an occlusal splint, forming the maxillomandibular complex (MMC). Realtime Ci-Navi was used to lead the MMC in the designated direction. Osteoplasty of the inferior border of the mandible was performed using Ci-Navi when facial symmetry and skeletal harmony were of concern. Linear and angular distinctions between preoperative planning and postoperative outcomes were calculated.

Results

The mean linear difference was 0.79 mm (maxilla: 0.62 mm, mandible: 0.88 mm) and the overall mean angular difference was 1.20°. The observed difference in the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was < 1 mm in 40 cases.

Conclusions

This study demonstrates the role of Ci-Navi in the accurate positioning of bone segments during bimaxillary orthognathic surgery. Ci-Navi was found to be a reliable method for the accurate transfer of the surgical plan during an operation.

Randomized Controlled Clinical Trial to Assess the Utility of Computer-Aided Intraoperative Navigation in Bimaxillary Orthognathic Surgery

ABSTRACT

Accurate application of the preoperative surgical plan in actual surgical settings is of paramount importance in orthognathic surgery. This randomized controlled clinical trial aimed to evaluate the accuracy of computer-aided intraoperative navigation (Ci-Navi) compared with that of conventional navigation methods in bimaxillary orthognathic surgery. Fifty-two patients were randomly divided into 2 groups. Group A (n = 26) patients underwent surgery assisted with Ci-Navi and group B (n = 26) patients underwent surgery assisted with conventional intraoperative navigation methods. During the operation, after LeFort I osteotomy, the mobile maxilla was repositioned to the designated position either using assistance from real-time Ci-Navi (group A) or using an intermediate splint (group B). Intra- and intergroup linear and angular differences between preoperative planning and postoperative outcomes were calculated. In group A, the overall mean linear difference was 0.79 mm (0.62 mm for the maxilla and 0.88 mm for the mandible) and the overall mean angular difference was 1.20°. In 23 cases, the difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm. In group B, the overall mean linear difference was 1.98 mm (1.76 mm for the maxilla and 2.02 mm for the mandible) and the overall mean angular difference was 2.08°. The difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm in 15 cases. This study demonstrates the utility of Ci-Navi is superior to the conventional methods in aiding the accurate repositioning of bony segments in bimaxillary orthognathic surgery.

Three-dimensional evaluation of long-term skeletal relapse following Le Fort I maxillary advancement surgery: a 2-year follow-up study

The aim of this study was to assess relapse following Le Fort I (LFI) maxillary advancement with superior or inferior repositioning at 2 years of follow-up. A total of 50 patients (26 female, 24 male; age range 15-56 years) with skeletal class II or III, who underwent bimaxillary surgery with LFI maxillary advancement in combination with either superior or inferior repositioning and also mandibular advancement/setback, were recruited. Preoperative (T0), immediate postoperative (T1), and 2-year postoperative (T2) cone beam computed tomography scans were acquired. Data were imported into a validated module to assess the skeletal movement (T0-T1) and relapse (T1-T2). Overall, the majority of the translational and rotational movements showed a relapse of <1 mm and <1°. Patients undergoing maxillary advancement with inferior repositioning in combination with mandibular advancement showed the highest amount of translational relapse in a superior (0.86 ± 0.85 mm, P < 0.0001) and posterior direction (-0.65 ± 1.11 mm, P < 0.0001). In relation to patients who received a bone graft, inferior repositioning with mandibular setback showed the highest maxillary relapse in a superior direction (1.20 ± 1.56 mm, P = 0.0719) with counterclockwise pitch rotation (2.15 ± 0.64°, P = 0.3759). Amongst the non-grafted procedures, superior repositioning with mandibular setback exhibited the highest relapse in a medial direction (1.38 ± 2.78 mm, P = 0.3981). Maxillary advancement was found to be a highly stable procedure with a lack of superoinferior stability in patients undergoing inferior repositioning.

Does maxillary yaw exist in patients with skeletal Class III facial asymmetry?

INTRODUCTION

This study aimed to evaluate maxillary skeletal and dental yaw in patients with skeletal Class III facial asymmetry and investigate its correlation with menton deviation.

METHODS

Initial cone-beam computed tomography data from 60 patients with skeletal Class III malocclusion were used. There were 30 patients in both the symmetrical group (menton deviation <2 mm) and the asymmetrical group (menton deviation >4 mm). After reconstruction of 3-dimensional (3D) cone-beam computed tomography data, maxillary yaw and 3D positions of skeletal and dental landmarks were measured and compared between the groups. After that, correlations between menton deviation and the other variables were assessed.

RESULTS

No significant difference was noted in maxillary skeletal and dental yaw between the 2 groups. In the assessment of 3D positions, translation of the maxillary bone and maxillary dentition toward the menton deviation was observed (P <0.01). Maxillary skeletal and dental yaw was not significantly correlated with menton deviation in the asymmetrical group.

CONCLUSIONS

Maxillary skeletal and dental yaw was not evident in either group. Therefore, when planning maxillary surgery for patients with skeletal Class III facial asymmetry malocclusion, it may be appropriate to shift the focus of decompensation from maxillary yaw to maxillary translation.

Reliability of cephalometric landmark identification on three-dimensional computed tomographic images

Our aims were to evaluate the reliability of three-dimensional (3D) cephalometric landmark identification in 3D images, and to propose an improved protocol for determining these landmarks. Computed tomographic (CT) images of 13 landmarks were obtained. One that did not show any artifacts, asymmetry in maxillofacial structures, or bony defects, was selected. Two orthodontic practitioners identified 3D cephalometric landmarks 10 times at one-week intervals. The distances of 26 landmarks were measured on the basis of three reference planes (coronal, horizontal, and sagittal). Ten mean (SD) measurements from each examiner were calculated, and the maximum and minimum values and the difference from the 10 measurements of each one were measured at a 95% confidence interval. Interexaminer differences for the three planes were found in the upper right first molar, point A, both gonions, left orbitale, and both porions. The lower right first molar, foramen magnum, gnathion, nasion, and pogonion showed interexaminer differences in two planes. Menton, basion, posterior nasal spine, upper and lower left first molar, and right mental foramen showed interexaminer differences in only one plane. With reference to intraexaminer differences, poor repeatability was observed for gonion, orbitale, condylion, and porion. Reliable 3D landmarks are the meeting point of sutures, distinct structures at converging planes, landmarks positioned in the midline, distinct anatomical structures such as the mental foramen, and teeth using multiplanar views.

Relationships of Reference Points, Planes and Skull Symmetry on Posterior-anterior Cephalograms in Healthy Young Adults

BACKGROUND

Radiological cephalometry is an important diagnostic tool for analyzing the shape and proportions of the skull. Standardized teleradiography of the skull in posterior-anterior (PA) projection provides orientation data on the symmetry and vertical relations of the skull. The comparison of individual findings with normal values places high demands on the selection of a control group. The aim of this study was to characterize a group to be used as a standard for cephalometric comparisons.

PATIENTS AND METHODS

PA teleradiographs of 23 healthy young adults were analyzed. Distances from reference measuring points to the median sagittal plane and the orbital horizontal plane were made. All individuals showed ideal occlusion. None of the participants had been subjected to orthodontic therapy or craniomaxillofacial surgery.

RESULTS

The measurement results showed a high degree of lateral symmetry of the skeletal reference points and planes. Comparison of the vertical reference lines confirmed the symmetrical constitution of the facial skeleton.

CONCLUSION

The study group is suitable for comparison with the cephalometric evaluations of other study groups.

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.

Total Face Approach (TFA) 3D Cephalometry and Superimposition in Orthognathic Surgery: Evaluation of the Vertical Dimensions in a Consecutive Series

Background: Cephalometry is fundamental in diagnosis, analysis, and planning of orthodontic-surgical treatment as it reveals skeletal relationship between the upper and lower jaw as well as facial aesthetic parameters. Nevertheless, 3D cephalometry has still not become the exam of choice in orthognathic treatment even though today CBCT (Cone Beam Computed Tomography) is routinely used in other branches of dentistry. Methods: In a sample of 13 patients undergoing bimaxillary orthognathic surgery a chin-vertex CBCT exam was prescribed prior to orthodontic treatment (OT) and 12 months after surgery (T1). The DICOM files uploaded to MaterialiseSimplant Ortho software pro 2.1 (Materialise Co., Leuven, Belgium) were analyzed following the multiplane 3D Total Face cephalometry protocol (TFA). Results: Results comparing pre-op and post-op TFA 3D cephalometry, were then evaluated considering reference values reported in literature. The CBCT, carried out pre- and post-surgery, were subsequently analyzed employing the superimposition method using cranial base as reference. The aim of this study is to evaluate the advantages and disadvantages of the two methods in orthognathic surgery. Conclusions: Multiplane 3D TFA allows the clinician to locate where major or minor skeletal discrepancies are found with respect to ideal parameters and is also useful in classifying skeletal intermaxillary relation. The superimposition method is highly intuitive but does not provide information on the quantity and location of osteotomic movement.

Assessment of maxillary canting on cone beam computed tomography and digital models: A retrospective study and proposal of a method

OBJECTIVES

The mounting of the plaster casts on articulator procedure is routinely performed in orthognathic surgery to assess canting of the maxillary occlusal plane, but the currently used protocols and reference plane could be source of errors which affect reliability. Nowadays the assessment of canting of the maxillary occlusal plane could be also performed with an entirely digital protocol. Aim of the study was to propose a method to evaluate canting in patients affected by Unilateral Condylar Hyperplasia, comparing the measurements performed on digital models matched on CBCT with those made on traditional articulator.

MATERIALS AND METHODS

A retrospective cross-sectional study was designed on 20 patients affected by vertical Unilateral Condylar Hyperplasia treated in the Units of Orthodontics and Maxillo-Facial Surgery. The canting of the maxillary occlusal plane was measured on plaster casts mounted on the conventional articulator and the measures were compared with those made on digital models matched on CBCT, according the protocol developed in our Unit. Molar, canine and basal difference were measured. To compare the two protocols and to test the agreement, we performed descriptive statistics, comparison between means and Bland Altman analysis. P value was set at 0.05.

RESULTS

Statistic comparison demonstrated agreement between measurements performed with the digital protocol and conventional physical method.

CONCLUSION

Measurements of canting with digital protocol are comparable to the physical standard method. A total digital protocol allows faster availability and storage of patient's data and better communication between orthodontist and maxillo-facial surgeon, especially in patients affected by three-dimensional malocclusions.

Sagittal Relationship between the Maxillary Central Incisors and the Forehead in Digital Twins of Korean Adult Females

OBJECTIVE

Digital twins of adult Korean females were created as a tool to evaluate and compare the sagittal relationship between the maxillary central incisors and the forehead before and after orthodontic treatment.

METHODS

Digital twins were reconstructed for a total of 50 adult female patients using facial scans and cone-beam computed tomography (CBCT) images. The anteroposterior position of the maxillary central incisor and the forehead inclination were measured.

RESULTS

The control group presented a mean of 6.7 mm for the sagittal position and 17.5° for forehead inclination. The study group showed a mean of 9.3 mm for the sagittal position and 13.6° for forehead inclination. Most Korean females seeking orthodontic treatment had their maxillary central incisor anterior to the glabella. In contrast, fewer Korean females who completed their orthodontic treatments had their maxillary central incisor anterior to the glabella. Furthermore, patients who had completed the orthodontic treatment were more likely to have the maxillary central incisor between the forehead facial axis and glabella.

CONCLUSION

The use of digital twins for three-dimensional (3D) analysis of the profile implies a high clinical significance. In addition, as the facial profile of Koreans is different from that of Caucasians, careful consideration should be made when setting treatment goals for the anteroposterior position of the maxillary central incisors.

Total Face Approach (TFA): A Novel 3D Approach to Describe the Main Cephalometric Craniomaxillofacial Parameters

The aim of this study is to propose a 3D skeletal classification and relative normal values of reference. Method: from a pool of 271 cone-beam computerized tomography images 108 chin-summit examinations of the skull were selected and divided into 3 traditional skeletal classes. The same Cone-beam Computerized Tomography (CBCT) images were then assessed using the cephalometric multiplanar analysis following the total face approach protocol. Results: the results of this study indicate standard 3D cephalometric norms for the vertical and sagittal evaluation of the skull. Conclusions: data obtained from our measurements allowed the creation of intervals supplying nosological classification that could be used in orthodontics, orthognatic surgery and implant surgery in fully edentulous patients.

Estimating Reference Shape Model for Personalized Surgical Reconstruction of Craniomaxillofacial Defects

OBJECTIVE

To estimate a patient-specific reference bone shape model for a patient with craniomaxillofacial (CMF) defects due to facial trauma.

METHODS

We proposed an automatic facial bone shape estimation framework using pre-traumatic conventional portrait photos and post-traumatic head computed tomography (CT) scans via a 3D face reconstruction and a deformable shape model. Specifically, a three-dimensional (3D) face was first reconstructed from the patient's pre-traumatic portrait photos. Second, a correlation model between the skin and bone surfaces was constructed using a sparse representation based on the CT images of training normal subjects. Third, by feeding the reconstructed 3D face into the correlation model, an initial reference shape model was generated. In addition, we refined the initial estimation by applying non-rigid surface matching between the initially estimated shape and the patient's post-traumatic bone based on the adaptive-focus deformable shape model (AFDSM). Furthermore, a statistical shape model, built from the training normal subjects, was utilized to constrain the deformation process to avoid overfitting.

RESULTS AND CONCLUSION

The proposed method was evaluated using both synthetic and real patient data. Experimental results show that the patient's abnormal facial bony structure can be recovered using our method, and the estimated reference shape model is considered clinically acceptable by an experienced CMF surgeon.

SIGNIFICANCE

The proposed method is more suitable to the complex CMF defects for CMF reconstructive surgical planning.

Three-dimensional virtual surgical planning (3D-VSP) in orthognathic surgery: Advantages, disadvantages and pitfalls

In this article, the advantages, disadvantages and pitfalls of three-dimensional virtual surgical planning (3D-VSP) compared to traditional two-dimensional (2D) planning methods in orthognathic surgery are discussed, alongside a standardised protocol that can be utilised. A skeletal Class II, skeletal Class III and an anterior open bite clinical case along with their 3D-VSP management are presented, highlighting modifications that can be made to computer-aided design/computer-aided manufacture (CAD/CAM) cutting guide and plate designs.

Cephalometric Evaluation of Anterior Cranial Base Slope in Patients with Skeletal Class I Malocclusion with Low or High SNA and SNB Angles

Objective

In the cephalometric analyses, it is observed that both SNA and SNB angles are higher or lower than normal for some skeletal Class I patients. The aim of this study was to assess the correlation between low or high SNA, SNB angles, and anterior cranial base (ACB) slope.

Methods

One hundred and seventeen skeletal Class I patients (45 males with a mean age of 14.5 years, 72 females with a mean age of 14.4 years) were evaluated in three groups. Group 1(n=40): Control group, individuals with normal SNA(82°±2°), and SNB(80°±2°) values. Group 2 (n=37): Patients with SNA>84° and SNB >82°, Group 3 (n=40): Patients with both SNA and SNB values lower than 78°. On the cephalometric radiographs, three angulars (SN/FH; anterior cranial base, Ba-S/FH; posterior cranial base, SN-Ba; total cranial base) and seven linear (S-FH, N-FH, Δ, Ba-S, Ba-N, Ba-A, Ba-B) measurements were performed to analyze the vertical and horizontal positions of the S and N points and thereby the ACB slope. One-way ANOVA and Kruskal Wallis tests were used for statistical analysis.

Results

The ACB slope was observed to be relatively flatter in Group 2, and steeper in Group 3 (p<0.05). The location of the S and N points in the sagittal plane did not significantly affect the SNA and SNB. However, the vertical position of the S and N points was a factor determining the inclination of the ACB, therefore the SNA and SNB.

Conclusion

ACB slope directly affected SNA and SNB measurements. ACB might lead to misleading results when used as a reference plane.

Computed Tomography (CT)-Assisted 3D Cephalometry in Horses: Interincisal Angulation of Clinical Crowns

The angle encompassed between opposing incisors in horses is assumed to decline with age. Previous studies merely consider the overall profile view of clinical crowns presuming a generalized angle, neglecting potential tooth position-dependent differences. Cephalometric measurements from 3D computed tomographic thick-slab reconstructions of single incisors within a global reference frame were used to determine clinical crown interincisal angulation (IIA) of 48 horses. Based on predefined dentoalveolar landmarks, IIA was defined as the angle enclosed by the respective labial axis of the clinical crown (LACC). A measurement repeatability analysis was conducted including a comparison of third incisor teeth IIA with data obtained by cephalometric implementation of previously described landmarks for third incisor teeth (lingual/palatal border). The age-related angle course and differences between tooth positions were investigated considering LACCs of permanent incisors. Determining IIA by LACCs exhibited a high level of reproducibility applying for all tooth positions (mean coefficient of variation = 0.65 %; mean SD ± 0.89°). The comparison method for third incisor teeth revealed two times higher mean dispersion of repeated measurements, P = 0.017. A non-linear model slightly increased predictability of angular changes over time as against linearity assumption. The angle decline was more distinctive in younger horses and appears to approach a final value in older ones. Third incisor teeth exhibited significantly higher angle decline compared to first and second incisor teeth, P < 0.0001. According to the results, age determination of horses using clinical crown IIA is not recommended. Rather, 3D cephalometry may provide a promising tool to determine interdental and dentofacial angles of distinct tooth positions in health and disease.

Quantification of three-dimensional facial asymmetry for diagnosis and postoperative evaluation of orthognathic surgery

Background

To evaluate the facial asymmetry, three-dimensional computed tomography (3D-CT) has been used widely. This study proposed a method to quantify facial asymmetry based on 3D-CT.

Methods

The normal standard group consisted of twenty-five male subjects who had a balanced face and normal occlusion. Five anatomical landmarks were selected as reference points and ten anatomical landmarks were selected as measurement points to evaluate facial asymmetry. The formula of facial asymmetry index was designed by using the distances between the landmarks. The index value on a specific landmark indicated zero when the landmarks were located on the three-dimensional symmetric position. As the asymmetry of landmarks increased, the value of facial asymmetry index increased. For ten anatomical landmarks, the mean value of facial asymmetry index on each landmark was obtained in the normal standard group. Facial asymmetry index was applied to the patients who had undergone orthognathic surgery. Preoperative facial asymmetry and postoperative improvement were evaluated.

Results

The reference facial asymmetry index on each landmark in the normal standard group was from 1.77 to 3.38. A polygonal chart was drawn to visualize the degree of asymmetry. In three patients who had undergone orthognathic surgery, it was checked that the method of facial asymmetry index showed the preoperative facial asymmetry and the postoperative improvement well.

Conclusions

The current new facial asymmetry index could efficiently quantify the degree of facial asymmetry from 3D-CT. This method could be used as an evaluation standard for facial asymmetry analysis.

Three-dimensional characterization of mandibular asymmetry in craniofacial microsomia

Objectives

This study aimed to investigate the three-dimensional (3D) mandibular asymmetry in craniofacial microsomia (CFM) and its association with the Pruzansky–Kaban classification system.

Materials and methods

Cone-beam computed tomography images of 48 adult CFM cases were collected. The asymmetry of the mandibular body and ramus was analyzed with 3D landmarks. The mirrored mandibular model was registered on the original model, yielding a color-coded distance map and an average distance (i.e., asymmetry score) to quantify the overall mandibular asymmetry.

Results

The lengths of the mandibular body and ramus were significantly shorter on the affected than the contralateral side (p < 0.001). The ANB (p = 0.009), body and ramal lengths (both p < 0.001), and body and ramal length asymmetry (both p < 0.05) were significantly different between mild (types I/IIA) and severe (types IIB/III) cases. The mandibular asymmetry score correlated with mandibular body length asymmetry (r = 0.296, p = 0.046). CFM mandibles showed high variability in shape asymmetry.

Conclusions

CFM patients showed distinct body and ramal length asymmetries. In severe cases, mandibles were smaller, more retruded, and more asymmetric in length. The mandibular shape asymmetry was highly variable regardless of the Pruzansky–Kaban types, being a determinant in the extent of overall mandibular asymmetry.

Clinical relevance

The 3D morphologic analysis provides better insights into real mandibular asymmetry. Although the Pruzansky–Kaban classification was applied, high individual variability of the mandibular morphology still existed within the types. Therefore, individualized analyses and treatment plans for CFM patients are highly recommended.

Outcome of facial contour asymmetry after conventional two-dimensional versus computer-assisted three-dimensional planning in cleft orthognathic surgery

Computer-assisted 3D planning has overcome the limitations of conventional 2D planning-guided orthognathic surgery (OGS), but difference for facial contour asymmetry outcome has not been verified to date. This comparative study assessed the facial contour asymmetry outcome of consecutive patients with unilateral cleft lip and palate who underwent 2D planning (n = 37)- or 3D simulation (n = 38)-guided OGS treatment for correction of maxillary hypoplasia and skeletal Class III malocclusion between 2010 and 2018. Normal age-, gender-, and ethnicity-matched individuals (n = 60) were enrolled for comparative analyses. 2D (n = 60, with 30 images for each group) and 3D (n = 43, with 18 and 25 images for 2D planning and 3D simulation groups, respectively) photogrammetric-based facial contour asymmetry-related measurements were collected from patients and normal individuals. The facial asymmetry was further verified by using subjective perception of a panel composed of 6 blinded raters. On average, the facial contour asymmetry was significantly (all p < 0.05) reduced after 3D virtual surgery planning for all tested parameters, with no significant differences between post-OGS 3D simulation-related values and normal individuals. No significant differences were observed for pre- and post-OGS values in conventional 2D planning-based treatment, with significant (all p < 0.05) differences for all normal individuals-related comparisons. This study suggests that 3D planning presents superior facial contour asymmetry outcome than 2D planning.

A Modified Method Using Double Computed Tomography Scan Procedure to Maintain Mandibular Width in Mandibular Reconstruction

OBJECTIVE

The purpose of this study was to evaluate the use of a modified template system and double computed tomography scan procedure to maintain mandibular width in cases of mandibular reconstruction.

STUDY DESIGN

Ten patients who underwent mandibular reconstruction with a fibular flap were enrolled. The surgeries were planned with a computer-aided surgical simulation (CASS) planning method. Following double computed tomography scan procedure, the template system was designed in a computer and was fabricated using a three-dimensional printing technique. The cutting guides were designed with the holes of the conventional reconstruction plate on the remnant mandibular segments. After surgery, the outcome evaluation was compared by first superimposing the post-operative computed tomography model onto the planned model and then measuring the differences between the planned and actual outcomes.

RESULTS

All surgeries were completed successfully using the template system. With the use of the templates, the largest linear root-mean-square deviation (RMSD) between the planned and post-operative remnant segments was 1.01 mm, and the largest angular RMSD was 4.05°.

CONCLUSIONS

The authors conclude that this template system and double computed tomography scan procedure provides a reliable method to maintain mandibular width in mandibular reconstruction using a fibular flap.

Development and Validation of Novel Three-Dimensional Craniofacial Landmarks on Cone-Beam Computed Tomography Scans

As cone-beam computed tomography (CBCT) scans become increasingly common, it is vital to have reliable 3-dimensional (3D) landmarks for quantitative analysis of craniofacial skeletal morphology. While some studies have developed and used 3D landmarks, these landmark sets are generally small and derived primarily from previous 2-dimensional (2D) cephalometric landmarks. These derived landmarks lack information in parts of the skull such as the cranial base, which is an important feature for cranial growth and development. The authors see a real need for development and validation of 3D landmarks, particularly bilateral landmarks, across the skull for improved cephalometric analysis. The primary objective of this study is to develop and validate a set of 61 3D anatomical landmarks on the face, cranial base, mandible, and teeth for use in clinical and research studies involving CBCT imaging. Each landmark was placed 3 times by 3 separate trained observers on a set of 10 anonymized CBCT patient scans. Intra-rater and inter-rater estimates of consistency and agreement were calculated using the intraclass correlation coefficient. Measurement error was calculated per landmark and per X, Y, and Z landmark coordinate. The authors had high ICC estimates within rates, indicating high consistency, and high ICC estimates among raters, indicate good agreement across raters. Overall measurement error for each landmark and each X, Y, and Z coordinate was low. Our results confirm the accuracy of novel 3D landmarks including several on the cranial base that will serve researchers and clinicians for use in future studies involving 3D CBCT imaging and craniofacial development.

Three-dimensional cephalometric analysis of the maxilla: Analysis of new landmarks

INTRODUCTION

Clinical evaluation of the midface including the paranasal and upper lip regions is highly subjective and complex. Traditional and 3-dimensional cephalometrics were not developed with the clinical appearance of these midfacial areas in mind and are therefore inappropriate surrogates for the clinical appearance of the midface, making them unsuitable as aids in diagnosing dentofacial deformities. The aim of this study was to evaluate traditional as well as newly defined landmarks and measurements and their correlation with clinical appearance of the midface.

METHODS

Fifty-two subjects who underwent full-field cone-beam computed tomography were recruited for this study. A single examiner assessed each subject's midfacial region (paranasal and upper lip), and a second examiner obtained traditional and newly defined cephalometric measurements for each subject. Both examiners were blinded to each other's data throughout the study. Statistical analysis was performed to assess the correlations of the traditional and novel cephalometric measurements with clinical midfacial findings. The impact of the soft tissue thickness in the paranasal region was also analyzed. The performance of any classification derived from statistically significant variables was analyzed with the use of micro-F scores and area under the receiver operating characteristic curve (AUC).

RESULTS

Both traditional (SNA) and newly defined measurements (SN_ANS, SN_PR, SN_NP, SN_h) had no statistically significant correlation with clinical paranasal diagnosis. However, in the absence of upper lip procumbency or protrusion, SN_NP and SN_h had statistically significant correlations with clinical paranasal diagnosis (P = 0.047 and P = 0.003, respectively). For upper lip analysis, both traditional (SNA) and newly defined measurements (SN_CEJ) had strong correlations with clinical upper lip diagnosis (P < 0.001). All statistically significant cephalometric variables had good intra- and interobserver reliability (correlation coefficients ≥0.972 and ≥ 0.968, respectively) except SNA, which had a low interobserver reliability (correlation coefficient 0.739). Fitted models for paranasal and upper lip analyses showed low micro-F scores, indicating low precision and recall. However, AUC values of 0.7019 and 0.6362 for the paranasal and upper lip analysis, respectively, suggest improved performance of the model when properly trained with a larger sample size.

CONCLUSIONS

Newly defined measurements SN_h and SN_NP correlated with clinical paranasal diagnosis only in the absence of upper lip procumbency and protrusion. SNA and SN_CEJ were strongly correlated with clinical upper lip diagnosis. However, fitted models based on this study sample yielded low micro-F scores, making the fitted models currently unsuitable for anything besides correlation with clinical findings. A larger sample size will be necessary to further clarify the potential roles of these measurements, especially given the reasonable AUC values. The findings of this study demonstrate the highly subjective and relative nature of midfacial diagnosis and the importance of clinical judgment despite the potential utility of some traditional and new measurements.