Assessment of zygomatic bone using cone beam computed tomography in a Turkish population

Assessment of Malar Prominence in Adolescents: Evaluating the Diagnostic Accuracy of a New Angle for Vector Profile Classification

INTRODUCTION

The prominence of the malar region plays a crucial role in facial aesthetics; however, standardized diagnostic parameters for assessing midfacial deficiencies remain limited. This study introduced and evaluated a novel cephalometric parameter, the double W-key ridge (DWK) angle (formed between the double W plane and the key ridge point), in comparison with the established sella-nasion-orbitale (SNO) angle for assessing malar prominence. This study aimed to present a novel perspective for evaluating malar prominence, referred to as the DWK angle. The objectives of this study were to compare the mean SNO and DWK angles between positive and negative vector profiles, assess their correlation, evaluate their diagnostic accuracy using receiver operating characteristic (ROC) analysis, and examine the influence of sex on these parameters.

MATERIALS AND METHODS

This retrospective study analyzed the lateral cephalograms and profile photographs of 60 young adolescents (aged 11-14 years) from the Department of Orthodontics, Yogita Dental College. Based on clinical photographs, records were classified into positive and negative vector profile groups (n=30 each). The same observer obtained cephalometric measurements of the SNO and DWK angles. Reliability testing was conducted using the intraclass correlation coefficient. Statistical analyses, including Mann-Whitney U tests, Spearman's rank correlation, mixed-model analysis, and ROC curve analysis using the area under the curve (AUC), were performed to assess the relationship, diagnostic accuracy, and potential sex differences in these measurements.

RESULTS

Mean SNO and DWK angles were significantly higher in the positive vector group (SNO, 53.97°; DWK, 104.2°) than in the negative vector group (SNO, 44.1°; DWK, 94.6°) (p<0.001). A strong positive correlation (r=0.74, p=0.001) was observed between these two angles. ROC analysis demonstrated high diagnostic accuracy for both angles (AUC: 0.947 for SNO and 0.961 for DWK), with a sensitivity and specificity of 90%. No significant sex-based differences were found in either of the vector groups.

CONCLUSION

DWK angle is a stable and reliable cephalometric parameter for differentiating between adolescents' positive and negative vector profiles. The strong correlation and high diagnostic accuracy suggest that both SNO and DWK angles can effectively be utilized in orthodontics and maxillofacial planning to assess malar prominence.

A deep learning-based automatic segmentation of zygomatic bones from cone-beam computed tomography images: A proof of concept

OBJECTIVES

To investigate the efficiency and accuracy of a deep learning-based automatic segmentation method for zygomatic bones from cone-beam computed tomography (CBCT) images.

METHODS

One hundred thirty CBCT scans were included and randomly divided into three subsets (training, validation, and test) in a 6:2:2 ratio. A deep learning-based model was developed, and it included a classification network and a segmentation network, where an edge supervision module was added to increase the attention of the edges of zygomatic bones. Attention maps were generated by the Grad-CAM and Guided Grad-CAM algorithms to improve the interpretability of the model. The performance of the model was then compared with that of four dentists on 10 CBCT scans from the test dataset. A p value <.05 was considered statistically significant.

RESULTS

The accuracy of the classification network was 99.64%. The Dice coefficient (Dice) of the deep learning-based model for the test dataset was 92.34 ± 2.04%, the average surface distance (ASD) was 0.1 ± 0.15 mm, and the 95% Hausdorff distance (HD) was 0.98 ± 0.42 mm. The model required 17.03 seconds on average to segment zygomatic bones, whereas this task took 49.3 minutes for dentists to complete. The Dice score of the model for the 10 CBCT scans was 93.2 ± 1.3%, while that of the dentists was 90.37 ± 3.32%.

CONCLUSIONS

The proposed deep learning-based model could segment zygomatic bones with high accuracy and efficiency compared with those of dentists.

CLINICAL SIGNIFICANCE

The proposed automatic segmentation model for zygomatic bone could generate an accurate 3D model for the preoperative digital planning of zygoma reconstruction, orbital surgery, zygomatic implant surgery, and orthodontics.

The Volume Difference Along the External Surface of the Zygomatic Bone: A Novel Method of Measuring Zygomatic Bone Asymmetry

ABSTRACT

This study introduced the volume difference along the external surface (VDAES) of the zygomatic bone as a novel approach to assess zygomatic bone asymmetry and was the first to describe a distinctive, 4-step method of measuring it. VDAES has a potential to be used as an objective tool to evaluate dislocation and can assist surgeons in predicting risks of long-term cosmetic complications in patients with zygomaticomaxillary complex fractures. After having measured 100 healthy study participants, the observed median VDAES was 1.48 cm3 for all study participants, 2.02 cm3 for males, and 1.09 cm3 for females, with the gender difference being significant (P = 0.003). Additional studies are needed to test the hypothesis of whether VDAES is more relevant than conventional methods of clinically evaluating zygomatic bone asymmetry.

Tomographic analysis of nasomaxillary and zygomaticomaxillary buttress bone thickness for the fixation of miniplates

The purpose of this study was to evaluate the bone thickness of the nasomaxillary and zygomaticomaxillary buttresses to identify the most favourable region for the installation of miniplates. Bilateral tomographic images of 103 individuals were evaluated, for a total of 206 nasomaxillary and zygomaticomaxillary buttresses. Measurements of bone thickness were performed in the parasagittal reconstructions along three vertical lines on the nasomaxillary buttress (21 measurement points) and four vertical lines on the zygomaticomaxillary buttress (28 measurement points). The vertical line measurements for each buttress were compared using the Kruskal-Wallis test. Spearman's correlation coefficient was used to determine the correlation between the thicknesses obtained and patient sex and side (right/left). The level of significance adopted was 5%. The nasomaxillary and zygomaticomaxillary buttresses presented statistical differences in thickness at their respective points (P=0.001). The analysis of the nasomaxillary buttress showed that the thicker bone for the installation of miniplates follows the long axis of the upper canine at a distance of 3mm from the root apex. For the zygomaticomaxillary buttress, thicker bone to install miniplates was found distal to the distobuccal root of the first molar, at a distance of 3.5mm from the limit of the infraorbital foramen.