Comparative study of cephalometric measurements using 3 imaging modalities

Three-dimensional quantitative temporomandibular joint changes in skeletal class I malocclusion treated with extraction and non-extraction protocols: a comparative study of fixed orthodontic appliances and clear aligners

OBJECTIVE

This study aimed to evaluate the positional and morphological changes in the temporomandibular joint (TMJ) in adult patients with skeletal Class I malocclusion treated with fixed orthodontic appliances (FAs) and clear aligners (CAs), both with and without premolar extractions.

METHODS

This retrospective study involved 120 adult patients divided into non-extraction and extraction groups, each further subdivided equally into those treated with FAs and CAs. Cone beam computed tomography (CBCT) was used to assess the TMJ measurements before (T0) and after treatment (T1). Statistical analyses were conducted to compare the mean changes in intra- and inter-groups. A significance level of p ≤ 0.05 was considered.

RESULTS

In the non-extraction group, specifically in FAs, significant increases were observed in TMJ parameters; anteroposterior condylar position (APCP) and mediolateral condylar inclination (MCI). Conversely, significant decreases were noted in vertical condylar position (VCP) and vertical condylar inclination (VCI). In the extraction group, significant increases were noted in APCP and anterior joint space (AJS), while posterior joint space (PJS) and anteroposterior condylar joint position (APCJP) decreased. For inter-group comparisons, the extraction group showed significant increases in APCP in FAs compared to CAs, and a significant decrease in APCJP in FAs compared to CAs.

CONCLUSION

FAs significantly impact condylar positions and joint spaces, especially in extraction cases. Monitoring TMJ parameters during orthodontic treatment is crucial to ensure positive outcomes and prevent TMJ disorders (TMDs). These findings may guide the selection of orthodontic appliances based on individual malocclusion characteristics.

Feasibility of occlusal plane in predicting the changes in anteroposterior mandibular position: a comprehensive analysis using deep learning-based three-dimensional models

BACKGROUND

A comprehensive analysis of the occlusal plane (OP) inclination in predicting anteroposterior mandibular position (APMP) changes is still lacking. This study aimed to analyse the relationships between inclinations of different OPs and APMP metrics and explore the feasibility of OP inclination in predicting changes in APMP.

METHODS

Overall, 115 three-dimensional (3D) models were reconstructed using deep learning-based cone-beam computed tomography (CBCT) segmentation, and their accuracy in supporting cusps was compared with that of intraoral scanning models. The anatomical landmarks of seven OPs and three APMP metrics were identified, and their values were measured on the sagittal reference plane. The receiver operating characteristic curves of inclinations of seven OPs in distinguishing different anteroposterior skeletal patterns and correlations between inclinations of these OPs and APMP metrics were calculated and compared. For the OP inclination with the highest area under the curve (AUC) values and correlation coefficients, the regression models between this OP inclination and APMP metrics were further calculated.

RESULTS

The deviations in supporting cusps between deep learning-based and intraoral scanning models were < 0.300 mm. The improved functional OP (IFOP) inclination could distinguish different skeletal classification determinations (AUC Class I VS Class II = 0.693, AUC Class I VS Class III = 0.763, AUC Class II VS Class III = 0.899, all P values < 0.01) and the AUC value in skeletal Classes II and III determination was statistically higher than the inclinations of other OPs (all P values < 0.01). Moreover, the IFOP inclination showed statistical correlations with APMP metrics (rAPDI = -0.557, rANB = 0.543, rAF-BF = 0.731, all P values < 0.001) and had the highest correlation coefficients among all OP inclinations (all P values < 0.05). The regression analysis models of IFOP inclination and APMP metrics were yAPDI = -0.917x + 91.144, yANB = 0.395x + 0.292, and yAF-BF = 0.738x - 2.331.

CONCLUSIONS

Constructing the OP using deep learning-based 3D models from CBCT data is feasible. IFOP inclination could be used in predicting the APMP changes. A steeper IFOP inclination corresponded to a more retrognathic mandibular posture.

Effect of maxillary molars distalization using clear aligners and fixed orthodontic appliances on the positional and dimensional temporomandibular joint parameters: a three-dimensional comparative study

OBJECTIVE

The use of clear aligners (CAs) for orthodontic treatment has substantially increased in recent decades. However, limited empirical evidence exists regarding their potential effects on the temporomandibular joint (TMJ). The aim of this study was to assess the effect of maxillary molar distalization on the positional and dimensional TMJ parameters between CAs and conventional fixed orthodontic appliances (FAs) in skeletal class II malocclusion.

METHODS

This is a retrospective cohort study examined 70 adult patients with skeletal class II malocclusion with similar baseline characteristics based on American Board of Orthodontics (ABO) discrepancy index scores. The patients were treated by maxillary distalization movement by CAs or FAs, of which there were two equal groups of 35 patients were included in each group. CBCTs on TMJs were performed before and after treatment through Anatomage Invivo Dental 6.0. The measured parameters included inclination, position, condyle and articular fossa dimensions, and the volumetric joint spaces.

RESULTS

In both groups, linear measurements of the maxillary molar position revealed significant improvement after treatment (P < 0.001). Regarding TMJ parameters, intra-group comparisons revealed significant changes in FA group in the anterioposterior condylar inclination and condylar position across the three planes. Additionally, the pretreatment-centric condylar position in the glenoid fossa was 45.7% and 40% in the CA and FA groups, respectively. After treatment, these percentages changed to 51.4% and 31.4%, respectively. In inter-group comparisons, significant changes were noted in the mediolateral condylar position, which was more inward in the FA group than the CA group.

CONCLUSION

The FA group had more significant dimensional and positional changes in the mandibular condyle than the CA group; nevertheless, the changes are considered clinically negligible.

Accuracy of web-based automated versus digital manual cephalometric landmark identification

AIM

The purpose of this study was to assess the accuracy of two web-based automated cephalometric landmark identification and analysis programs. Manual landmark identification using Dolphin Imaging software was used as reference.

MATERIALS AND METHODS

105 cephalograms were selected and divided into three groups of 35 subjects each, Class I, II and III. Radiographs were traced using Dolphin imaging software. WebCeph™ (South Korea) and Cephio™ (Poland) were used for the automated cephalometric analysis. Bland-Altman limits of agreement and the concordance correlation coefficient (CCC) were calculated. Kruskal Wallis test was used to compare the accuracy of WebCeph™ and Cephio™ measurements between the three groups. Mann-Whitney U test was used to compare the absolute difference between cephalometric measurements obtained using WebCeph™ and Cephio™.

RESULTS

The mean difference (MD) between AI and manually-derived measurements was less than 1 mm/degree and ranged from 0.01 to 0.8 except for upper lip protrusion (MD 1.35°), nasolabial angle (MD 5.01°), SN-GoGn (MD 1.41°), Ramus height (MD 1.46°), and IMPA (MD 1.94°). The mean CCC was 0.91 (range 0.60 to 0.96). No statistically significant differences were found between the three malocclusion groups for most of the measurements (P > 0.05).

CONCLUSIONS

For most of the measurements, automated cephalometric measurements were clinically acceptable. Few differences were found between Webceph™ and Cephio™ for most measurements. Measurements including SNA, SN-PP, IMPA as well as soft tissue measurements require extra consideration and manual adjustment of respective landmarks for higher precision and improved efficiency.

Pre- and Post-Operative Cone Beam Computed Tomography Assessment of the Temporomandibular Joint in Patients with Orthognathic Surgery

This study aimed to compare the pre- and post-operative temporomandibular joint (TMJ) condylar position in dentofacial deformity (DFD) patients who had orthognathic surgeries using cone beam computed tomography (CBCT). A retrospective study evaluating the pre- and post-operative CBCT for 79 DFD patients (equivalent to 158 TMJs) (mean age = 26.62 ± 9.5 years) with a bilateral sagittal split osteotomy with or without Le Fort I surgeries (n = 29 Class II DFD, n = 50 Class III DFD) was performed. This included the compartmental measurement of TMJ spaces, in addition to the measurement of intercondylar distances and angles. Condylar position centricity was assessed using the Pullinger and Hollender formula. Clinical data were analysed for DFD class, the type of surgery and post-operative CBCT timing. Pre- and post-operative measurements were compared statistically using a paired t-test, Wilcoxon signed-rank test, and Stuart-Maxwell test. TMJ condyles tended to relocate post-operatively in a posterosuperior position with internal rotation in Class II DFD and a superior position with internal rotation in Class III DFD. However, the overall changes were within <0.5 mm translation and <4° rotation and the number of concentrically positioned condyles (according to the Pullinger and Hollender formula) did not change significantly. Orthognathic surgery is associated with minor post-operative translational and rotational condylar positional changes in Class II and III DFDs.

Accuracy of conventional versus cone-beam CT-synthesised lateral cephalograms for cephalometric analysis: A systematic review

OBJECTIVE

To assess the accuracy of cone-beam computed tomography (CBCT)-synthesised lateral cephalograms (CSLCs) compared with conventional lateral cephalograms for cephalometric analysis in human participants and skull models.

METHODS

The authors performed a search of PubMed, Scopus, Google Scholar and Embase databases on 4 October 2021. Included studies met the following criteria: published in English; compared conventional lateral cephalograms and CSLCs; assessed hard- and soft-tissue landmarks; and were performed on human or skull models. Data extraction from eligible studies was performed by two independent reviewers. The quality of evidence was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist tool - diagnostic accuracy studies.

RESULTS

A total of 20 eligible articles were included in this systematic review. Of these 20 studies, 17 presented with a low risk of bias, while three were found to have a moderate risk of bias. Hard- and soft-tissue analyses were evaluated for each imaging modality. The findings reveal that CSLCs are accurate and comparable to conventional lateral cephalograms for cephalometric analysis and demonstrate good inter-observer reliability. Four studies reported a higher accuracy with CSLCs.

CONCLUSION

Overall, the diagnostic accuracy and reproducibility of CSLCs were comparable to conventional lateral cephalograms in cephalometric analysis. It is justified that patients who have an existing CBCT scan do not need an additional lateral cephalogram, minimising unnecessary radiation exposure, expenses and time for the patient. Larger voxel sizes and low-dose CBCT protocols can be considered to minimise radiation exposure.

REGISTRATION

This study was registered with PROSPERO (CRD42021282019).

Oropharyngeal complex differences related to sex and occlusal factors in adolescents aged 12-17 years

OBJECTIVE

To investigate oropharyngeal complex differences related to sex and occlusal factors in adolescents.

METHODS

A cross-sectional study was conducted with 108 patients aged 12-17 years. The oropharyngeal complex was evaluated by imaging exams. Occlusal variables included molar relationship, facial growth pattern, maxilla shape, tooth loss, anterior crossbite, and anterior open bite. Statistical analysis included independent t-test, Mann-Whitney, ANOVA, and Kruskal-Wallis tests. The significance level was 5%.

RESULTS

There were increases of the tongue measurement (p = 0.026) and the hyoid approach at the base of the mandible among boys (p = 0.016) and the distance from the hyoid at the base of the mandible among girls (p = 0.039). There was shortening of the soft palate measurements (p = 0.003 and p = 0.007) and tongue (p = 0.018) among adolescents with an anterior crossbite.

CONCLUSION

Findings suggest sex, age, and anterior crossbite can be related to oropharyngeal morphology.

Impact of Mandibular Angle Osteotomy Using a Geometric Mathematical Design on the Aesthetic Osteotomy Line: A Retrospective Observational Study

BACKGROUND

Mandibular angle osteotomy (MAO) is a frequently described technique in Eastern females. The success hinges on the precise positioning of the osteotomy line. The geometric mathematical method is viable. Therefore, we explored the impact of mandibular angle osteotomy using aesthetic standards and printed digital osteotomy templates (DOTs) on the aesthetic osteotomy line.

METHODS

This retrospective observational study included female patients with prominent mandibular angle (PMA) who underwent MAO at our hospital between January 2020 and March 2021. Thirty-three female patients were included, 22 in the DOTs group using new DOTs, and 11 in the traditional group using traditional free-hand techniques.

RESULTS

Regarding the width of the excised bone, the postoperative deviation from the preoperative plan was not significant in the DOTs group (0.5 ± 0.3 mm, P > 0.05), while the deviation was significant for the traditional group (2.5 ± 1.2 mm, P<0.05). The preparation time was longer in the DOTs group than in the traditional group (82 ± 11 vs. 53±4 min, P < 0.001). The osteotomy time and the operation time were shorter in the DOTs group than in the traditional group (osteotomy: 54 ± 5 vs. 73 ± 6 min; preparation: 124 ± 10 vs. 169 ± 13 min; both P < 0.001). The Likert (4.0 ± 0.5 vs. 1.0 ± 0.6, P = 0.006) and FACE-Q scores (17.5 ± 1.7 vs. 15.6 ± 1.3, P = 0.029) were higher in the DOTs group.

CONCLUSIONS

The new method of positioning the new aesthetic osteotomy line based on geometric analysis might provide a possible osteotomy method that strongly suggests effectiveness, safety, individualization, and accuracy, with a shorter operation and higher patient satisfaction.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

MRI-based cephalometrics: a scoping review of current insights and future perspectives

OBJECTIVE

This review aims to explore the current status of magnetic resonance imaging (MRI) as a cephalometric tool, summarize the equipment design and methods, and propose recommendations for future research.

METHODS

A systematic search was conducted in electronic databases, including PubMed, Ovid MEDLINE, Scopus, Embase, Web of Science, EBSCOhost, LILACS, and Cochrane Library, using broad search terms. The articles published in any language till June 2022 were considered. Cephalometric studies conducted using the MRI dataset on human participants, phantom or cadaver were included. Two independent reviewers assessed the final eligible articles using the quality assessment score (QAS).

RESULTS

Nine studies were included in the final assessment. Studies used various methods, including 1.5 T or 3 T MRI systems and 3D or 2D MRI datasets. Among the imaging sequences, T1-weighted, T2-weighted and black bone MR images were used for cephalometric analysis. In addition, the reference standards varied among studies, such as traditional 2D cephalogram, cone-beam CT and phantom measurements. The mean QAS of all the included studies was 79% (± 14.4%). The main limitation of most studies was the small sample size and the heterogeneity of the methods, statistical tools used, and metric outcomes assessed.

CONCLUSIONS

Despite the heterogeneity and lack of metrological evidence on the effectiveness of MRI-based cephalometric analysis, the preliminary results demonstrated by in vivo and in vitro studies are encouraging. However, future studies exploring MRI sequences specific to cephalometric diagnosis are required for wider adoption of this technique in routine orthodontic practice.

Morphological changes in alveolar bone thickness and height after orthodontic proclination or labial movement combined with autogenous soft tissue grafting: a CBCT evaluation

BACKGROUND

Autogenous soft tissue grafting is indicated in thin gingival biotypes before orthodontic proclination or labial movements to increase the keratinized gingiva and prevent gingival recession. However, its effect on local alveolar bone remodeling is unclear. The aim of this study was to investigate the effects of autogenous soft tissue grafting on local alveolar bone after orthodontic proclination or labial movements.

METHODS

Sixteen patients with a thin scalloped gingival biotype, narrow keratinized gingiva, or thin cortical bone requiring orthodontic proclination or labial movement of teeth were included. Cone-beam computed tomography (CBCT) images were obtained before grafting and at least 6 months after surgery. Sixty mandibular teeth were included, and the vertical bone level and horizontal labial bone thickness were measured. The results were compared using paired t-tests or Wilcoxon signed-rank test.

RESULTS

The horizontal labial bone thickness increased, especially at 6 mm below the cementoenamel junction (CEJ) in the mandibular central and lateral incisors (P < 0.05). The total alveolar bone area of the canines, first premolars, and second premolars increased at 3, 6, and 9 mm below the CEJ, respectively, and the differences were statistically significant (P < 0.05). Additionally, vertical bone height increased minimally on the labial side, but the differences were not statistically significant (P > 0.05).

CONCLUSIONS

New bone regeneration was observed on the labial (pressure) side after autogenous soft tissue grafting, which may represent a mechanism to effectively prevent gingival recession and maintain periodontal health.

IRB APPROVAL

All the experimental procedures involving humans in this study were approved by the Medical Ethics Committee of Xiangya Stomatological Hospital, Central South University ( No. 20190048).

A quantitative three-dimensional comparative study of alveolar bone changes and apical root resorption between clear aligners and fixed orthodontic appliances

BACKGROUND

This study aimed to evaluate and compare the alveolar bone changes and to investigate the prevalence and severity of orthodontically induced inflammatory root resorption (OIIRR) of maxillary incisors in patients who received treatment with clear aligners (CA) versus conventional fixed appliances (FA), using cone-beam computed tomography (CBCT).

METHODS

One hundred sixty maxillary incisors from 40 patients with similar baseline characteristics based on the American Board of Orthodontics discrepancy index scores were divided into the CA and FA groups. The dentoalveolar quantitative changes were analyzed using pre- (T0) and post-treatment (T1) CBCT. The measured parameters included alveolar bone thickness (ABT), alveolar bone height (ABH), root length (OIIRR), and maxillary incisor inclinations.

RESULTS

Post-treatment, the average palatal and total ABT significantly decreased in central and lateral incisors in the FA group. In contrast, the CA group's average labial ABT of the lateral incisors decreased considerably. Regarding the ABH, both groups showed significant labial and palatal marginal bone resorption. In both groups, root lengths significantly decreased after treatment (p < 0.005). The inter-group comparison revealed that ABT and root length had significantly decreased in the FA group compared to the CA group, while the ABH showed no significant difference between the two groups. The mean absolute reductions of ABT and OIIRR in the CA group were significantly less (- 0.01 ± 0.89 and 0.31 ± 0.42) than those in the FA group (0.20 ± 0.82 and 0.68 ± 0.97), respectively.

CONCLUSIONS

CA and FA treatments appear to cause a significant ABT reduction and a statistically significant increased OIIRR in the maxillary incisor region, with a greater extent expected with FA treatment. However, the increased OIIRR values in the majority of both groups' cases were not clinically significant. Both treatment modalities resulted in a significant ABH reduction, with the highest found in the labial side of lateral incisors in the CA group.

Comparison of the accuracy of 2D and 3D cephalometry: a systematic review and meta-analysis

Objectives

To compare the measurement of cephalometric parameters using 3D images obtained from CBCT to 2D images obtained from a conventional cephalogram.

Methods

An electronic literature search was conducted using PubMed, Embase, Web of Science, CNKI, CENTRAL, and the grey literature database of SIGLE (up to May 2021). The selection of the eligible studies, data extraction, and an evaluation for possible risk of bias (Quality Assessment of Measurement Accuracy Studies tool) were performed independently by two authors. Inconsistencies were judged by a third author. Statistical pooling, subgroup analysis, a sensitivity analysis and an evaluation of publication bias were performed using Comprehensive Meta-Analysis (version 2.2.064, Biostat, Englewood, NJ).

Results

A total of eight articles were eligible for final meta-analysis. The differences in two of the skeletal measurement parameters [Ar(Co)-Gn, Me-Go] and one of the dental measurement parameters (U1-L1) were found to be statistically significant when using CBCT and conventional cephalograms (P = 0.000, P = 0.004, P = 0.000, respectively).

Conclusions

CBCT can be used as a supplementary option to support conventional cephalometric measurements. In clinical situations in which three-dimensional information is required, patients can benefit from CBCT analysis to improve diagnosis and treatment planning.

Accuracy of one-step automated orthodontic diagnosis model using a convolutional neural network and lateral cephalogram images with different qualities obtained from nationwide multi-hospitals

Objective

The purpose of this study was to investigate the accuracy of one-step automated orthodontic diagnosis of skeletodental discrepancies using a convolutional neural network (CNN) and lateral cephalogram images with different qualities from nationwide multi-hospitals.

Methods

Among 2,174 lateral cephalograms, 1,993 cephalograms from two hospitals were used for training and internal test sets and 181 cephalograms from eight other hospitals were used for an external test set. They were divided into three classification groups according to anteroposterior skeletal discrepancies (Class I, II, and III), vertical skeletal discrepancies (normodivergent, hypodivergent, and hyperdivergent patterns), and vertical dental discrepancies (normal overbite, deep bite, and open bite) as a gold standard. Pre-trained DenseNet-169 was used as a CNN classifier model. Diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis, t-stochastic neighbor embedding (t-SNE), and gradient-weighted class activation mapping (Grad-CAM).

Results

In the ROC analysis, the mean area under the curve and the mean accuracy of all classifications were high with both internal and external test sets (all, > 0.89 and > 0.80). In the t-SNE analysis, our model succeeded in creating good separation between three classification groups. Grad-CAM figures showed differences in the location and size of the focus areas between three classification groups in each diagnosis.

Conclusions

Since the accuracy of our model was validated with both internal and external test sets, it shows the possible usefulness of a one-step automated orthodontic diagnosis tool using a CNN model. However, it still needs technical improvement in terms of classifying vertical dental discrepancies.

Quantification of three-dimensional morphology of craniofacial mineralized tissue defects in Tgfbr2/Osx-Cre mice

Craniofacial morphology is affected by the growth, development, and three-dimensional (3D) relationship of mineralized structures including the skull, jaws, and teeth. Despite fulfilling different purposes within this region, cranial bones and tooth dentin are derived from mesenchymal cells that are affected by perturbations within the TGF-β signaling pathway. TGFBR2 encodes a transmembrane receptor that is part of the canonical, SMAD-dependent TGF-β signaling pathway and mutations within this gene are associated with Loeys-Dietz syndrome, a condition which often presents with craniofacial signs including craniosynostosis and cleft palate. To investigate the role of Tgfbr2 in immature, but committed, mineralized tissue forming cells, we analyzed postnatal craniofacial morphology in mice with conditional Tgfbr2 deletion in Osx-expressing cells. Novel application of a 3D shape-based comparative technique revealed that Tgfbr2 in Osx-expressing cells results in impaired postnatal molar root and anterior cranial growth. These findings support those from studies using similar Tgfbr2 conditional knockout models, highlight the anomalous facial and dental regions/structures using tomographic imaging-based techniques, and provide insight into the role of Tgfbr2 during postnatal craniofacial development.

Temporomandibular joint morphology in Korean using cone-beam computed tomography: influence of age and gender

OBJECTIVES

The purpose of this study was to investigate the condylar morphology and position of Koreans using cone-beam computed tomography (CBCT) images. Analyzing the mean values of this study with reference to left and right sides, gender, and age will help to understand the size of the condyle and glenoid fossa, condylar morphology, and temporomandibular joint (TMJ) symmetry for establishing the standard temporomandibular joint structures of Koreans and then design the standard temporomandibular joint prosthesis for Koreans.

RESULTS

There was no significant result in the condyle size, condyle axis angle, joint space, fossa depth, and mandibular body size between the left and right sides (p > 0.05). On the other hand, the mediolateral width of the condyle and mandibular body size show significantly different with the gender (P < 0.05). Also, significant differences were found in condyle size, joint space, fossa depth, and mandibular body size according to age groups (p < 0.05).

CONCLUSIONS

Condylar position and morphology vary according to side, age, and gender. The results of this study are expected to help in customizing a treatment for the patients who need TMJ reconstruction by predicting the TMJ morphology according to age and gender and design the standard temporomandibular joint prosthesis for the Koreans.

Diagnostic accuracy of lateral cephalograms and cone-beam computed tomography for the assessment of sella turcica bridging

INTRODUCTION

The purpose of this research was to assess the diagnostic accuracy of sella turcica bridging on lateral cephalograms when compared with true sella turcica bridging determined via cone-beam computed tomography (CBCT).

METHODS

A cross-sectional study was conducted using CBCT images from which lateral cephalograms were generated. The study included 185 subjects (118 females and 67 males; age range, 10-30 years; mean age, 16.63 ± 4.20 years). Sella turcica landmarks and related measurements were calculated for both diagnostic modalities and analyzed by 1 examiner. Subjects were classified into 1 of 3 outcome groups: no bridging, partial bridging, and complete bridging. Diagnostic accuracy was evaluated using sensitivity, specificity, positive and negative predictive values, and receiver operator characteristic curves.

RESULTS

Ten patients were diagnosed as complete bridging on CBCT, whereas 31 patients were diagnosed as complete bridging on lateral cephalogram. Although the lateral cephalogram detected all subjects with complete bridging, it incorrectly classified 12% of subjects. The percent agreement between both diagnostic methods was 55.68%, with a kappa statistic of 0.22 on the right sella turcica and 0.20 on the left sella turcica, indicating fair but statistically significant agreement. The overall accuracy of lateral cephalograms as a diagnostic modality in discriminating between no bridging and partial bridging was good as determined with the area under the curve values of 0.86 and 0.85 for right and left sides, respectively.

CONCLUSIONS

Although lateral cephalograms overestimate patients with complete bridging compared to CBCTs, they are a suitable screening modality for accurately suggesting complete sella turcica bridging and differentiating between patients with no bridging and partial bridging.

Surface-based 3-dimensional cephalometry: An objective analysis of cranio-mandibular morphology

INTRODUCTION

The purpose of this study was to apply a previously reported homologous model for quantifying and visualizing the three-dimensional (3D) cranio-mandibular morphology.

METHODS

Twenty-eight 3D cone-beam computed tomography (CBCT) images of Japanese patients (7 to 13 years of age) showing skeletal Class 1 malocclusions were used in this study. Wire mesh fitting was conducted for each patient based on the assignment of landmarks to each 3D surface (homologous modeling). Cranial and mandibular images were generated using surface rendering of the CBCT images. The mean and standard deviation of each point on the wire mesh were calculated as the normative mean. Two operators conducted the process twice for seven patients, with a one-week interval between fittings. The intra- and inter-examiner reliability were determined using the 95% confidence interval minimal detectable change (MDC₉₅) for random error and intra-class correlation coefficients (ICCs).

RESULTS

The intra- and inter-examiner reliability of the mesh fitting method were almost perfect. Normative ranges of the cranial and mandibular surfaces of Japanese were determined.

CONCLUSIONS

A clinical method that enables practitioners to quantify and visualize the hard tissues of a patient's face in three dimensions with almost perfect reliability is presented. This method allows practitioners to evaluate how patients' skeletal characteristics differ from normative means in three dimensions.

Orthodontic incisor retraction caused changes in the soft tissue chin area: a retrospective study

BACKGROUND

To investigate the area and morphological changes around the soft tissue chin after orthodontic incisor retraction.

METHODS

Fifty-nine female adults with bimaxillary protrusion requiring extraction of four premolars were included in the study. Cephalograms were taken before (T0) and after (T1) orthodontic treatment. The soft tissue changes, including the area, thickness and morphology were measured. Paired-t tests were performed for statistical comparisons. Pearson correlation analyses and backward multivariate regression analyses were used to identify the relationship between the soft tissue changes and incisor retraction.

RESULTS

Following the incisor retractions (5.35 ± 1.79 mm and 4.42 ± 1.62 mm for the upper and lower, respectively), there was a significant increase in the soft tissue thickness of L1c-LL (0.64 ± 1.67 mm, P = 0.025) and Pog-Pog' (0.44 ± 1.10 mm, P = 0.022), and a significant decrease in the soft tissue thickness of B-B' (1.21 ± 1.34 mm, P <  0.01). Changes in the area of soft tissue chin and lower lip were not statistically significant (P > 0.05). Pearson coefficient between the thickness changes of B-B' and the retraction of lower incisors was - 0.376. The multiple correlations between the soft tissue thickness changes and incisor retractions were Y = 1.02-0.42a + 0.42b for L1c-LL, and Y = 0.17-0.31b for B-B'.

CONCLUSIONS

The orthodontic incisor retraction could cause soft tissue thickness changes (i.e. an increase in L1c-LL and Pog-Pog' and a decrease in B-B') without area changes.

Prevalence and severity of apical root resorption during orthodontic treatment with clear aligners and fixed appliances: a cone beam computed tomography study

Background

Fixed appliances have been the mainstream for orthodontic treatment, while clear aligners, such as Invisalign system, have become increasingly popular. The prevalence of apical root resorption (ARR) in patients with clear aligners is still controversial. The aim of this study was to investigate and compare the prevalence and severity of ARR in patients treated with clear aligners and fixed appliances using cone beam computed tomography (CBCT).

Materials and methods

A total of 373 roots from 70 subjects, with similar baseline characteristics and the ABO discrepancy index scores (i.e., treatment difficulty), were included into two groups: the clear aligners group (Invisalign, Align Technology, California, USA) and fixed appliances group (Victory Series; 3 M Unitek, California, USA). Root length of each anterior tooth was measured on the CBCT images by two blinded investigators. The ARR on each tooth was calculated as the difference of root length before and after orthodontic treatment. Chi-square test and paired t test was used to compare the ARR between the two groups as well as before and after orthodontic treatments.

Results

Prevalence of ARR in the clear aligners group (56.30%) was significantly lower than that in the fixed appliances group (82.11%) (P < 0.001). The severity of ARR in the clear aligners group (0.13 ± 0.47 mm) was significantly less than that in the fixed appliances group (1.12 ± 1.34 mm) (P < 0.001). The most severe ARR was found on the maxillary canine (1.53 ± 1.92 mm) and lateral incisor (1.31 ± 1.33 mm) in the fixed appliances group; the least ARR was found on the mandibular canine (− 0.06 ± 0.47 mm) and lateral incisor (0.04 ± 0.48 mm) in the clear aligners group (P < 0.001).

Conclusions

The prevalence and severity of ARR measured on CBCT in patients with clear aligners were less than those in patients with fixed appliances.

Personal Computer-Based Cephalometric Landmark Detection With Deep Learning, Using Cephalograms on the Internet

BACKGROUND

Cephalometric analysis has long been, and still is one of the most important tools in evaluating craniomaxillofacial skeletal profile. To perform this, manual tracing of x-ray film and plotting landmarks have been required. This procedure is time-consuming and demands expertise. In these days, computerized cephalometric systems have been introduced; however, tracing and plotting still have to be done on the monitor display. Artificial intelligence is developing rapidly. Deep learning is one of the most evolving areas in artificial intelligence. The authors made an automated landmark predicting system, based on a deep learning neural network.

METHODS

On a personal desktop computer, a convolutional network was built for regression analysis of cephalometric landmarks' coordinate values. Lateral cephalogram images were gathered through the internet and 219 images were obtained. Ten skeletal cephalometric landmarks were manually plotted and coordinate values of them were listed. The images were randomly divided into 153 training images and 66 testing images. Training images were expanded 51 folds. The network was trained with the expanded training images. With the testing images, landmarks were predicted by the network. Prediction errors from manually plotted points were evaluated.

RESULTS

Average and median prediction errors were 17.02 and 16.22 pixels. Angles and lengths in cephalometric analysis, predicted by the neural network, were not statistically different from those calculated from manually plotted points.

CONCLUSION

Despite the variety of image quality, using cephalogram images on the internet is a feasible approach for landmark prediction.

A comparative study of digital lateral radiography and virtual cone-beam computed assisted cephalogram in cephalometric measurements

Objectives: To assess discrepancies in cephalometric measurements from digital lateral radiography and virtual cone-beam computed assisted tomography cephalogram. Materials and methods: Forty digital lateral radiographs and forty virtual cephalograms obtained by cone-beam computed assisted tomography were analyzed, corresponding to forty patients from the nstituto de Diagnóstico Maxilofacial in Lima, Peru. The principal investigator, who had been previously calibrated, made two measurements within a timespan of fifteen days using the analysis of Steiner and the NemoCeph software, and the difference between the obtained measurements was evaluated to determine if it was significant. Results: For digital lateral radiographs the difference varied between 0.00º - 0.45º and 0.01mm - 0.16mm, with statistical significance for distance between Pg and NB for lateral virtual cephalograms between 0.03º - 0.73º and 0.01mm - 0.43mm, with statistical significance for SE distance. The comparison between the two types of image in the first measurement showed a difference of 0.08º - 1.15º and 0.00mm - 1.43mm with statistical significance for four angular measurements and one linear. The comparison between the two types of image in the second measurement showed a difference of 0.13º - 1º and 0.02mm - 1.32mm with a statistically significant difference for three angular and two linear measurements. Conclusions: The difference between the two types of image is minimal; Both evaluated methods can be used effectively.