Three-dimensional cone beam computed tomography definition of the anatomical subregions of the upper airway: a validation study

Successive measurement errors of consecutive computed tomography for airway-related craniofacial dimensional measurements

Background/purpose

The use of computed tomography (CT) for craniofacial measurements is common in medical imaging, but concerns about accuracy and reliability persist, especially with different CT technologies. This study assessed the accuracy of twenty-six common measurements on consecutive CT images from the same patients, using multidetector CT (MDCT) and cone-beam CT (CBCT) with two software programs (Amira and Dolphin).

Materials and methods

Ten adult subjects with consecutive CBCT scans within one year were randomly selected. Another ten subjects with consecutive MDCT scans were paired with the CBCT group based on age, gender, race, occlusion, and craniofacial pattern. All digital imaging and communications in medicine (DICOM) files were randomly coded and analyzed using the two software programs. Intra-examiner reliability was assessed using the intraclass correlation coefficient. Successive measurement errors from consecutive scans for both imaging modalities and software programs were compared.

Results

For most skeletal linear and angular measurements, Dolphin showed greater successive measurement errors compared to Amira. Eight of the 26 common measurements had errors greater than one unit (millimeter or degree). Despite almost perfect intra-examiner reliability for upper airway analysis, average successive measurement errors were notably high, particularly for intraoral and oropharyngeal airway volumes. The successive Dolphin measurement error for oropharyngeal airway volume on CBCT images was over three times that on MDCT images.

Conclusion

Given the substantial successive measurement errors observed during consecutive CT scanning for the upper airway, this study does not support the quantitative use of CT for analyzing changes in airway dimensions for research purposes.

Correlation between the three-dimensional hyoid bone parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions

OBJECTIVE

This study aimed to explore the relationship between three-dimensional (3D) measurements of the hyoid bone (HB) and pharyngeal airway space (PAS) in relation to sagittal and vertical malocclusion.

METHODS

A total of 368 cone-beam computed tomography (CBCT) scans were classified into three skeletal groups (Class I, II, and III) and subdivided by vertical growth patterns (hypodivergent, normodivergent, and hyperdivergent). PAS dimensions, including nasopharyngeal, oropharyngeal, hypopharyngeal, and total airway spaces, were measured in surface area, volume, minimum constricted area (MCA), length, and width, HB position and dimension were analyzed in 3D using InVivo 6.0.3 and Dolphin 11.8 software. Data were analyzed using two-way ANOVA, and Bonferroni post-hoc tests, with P ≤ 0.05 considered significant.

RESULTS

The study found that patients with skeletal Class III and hypodivergent growth pattern had the highest sagittal position of the hyoid bone, while those with skeletal Class II and hyperdivergent pattern had the lowest hyoid length. Nasopharyngeal airway space width was significantly lower in skeletal Class III patients, while volume and area were lower in hyperdivergent patients. Oropharyngeal and hypopharyngeal dimensions were also affected by skeletal class and growth pattern, with hyperdivergent patients having the lowest values. Total pharyngeal volume, area, and minimum constricted area were also affected, with hyperdivergent patients having the lowest values and skeletal Class II patients having the lowest minimum constricted area.

CONCLUSION

Pharyngeal airway dimensions and hyoid bone parameters vary with malocclusions. The hyoid bone's position influences the airway, identifying patients at risk for airway obstruction and sleep-disordered breathing.

Prediction of Pharyngeal 3D Volume Using 2D Lateral Area Measurements During Swallowing

This study evaluated the validity of pharyngeal 2D area measurements acquired from the lateral view for predicting the actual 3D volume in healthy adults during swallowing. Seventy-five healthy adults (39 females, 36 males; mean age 51.3 years) were examined using 320-row area detector computed tomography (320-ADCT). All participants swallowed a 10 mL honey-thick barium bolus upon command while seated in a 45° semi-reclining position. Multi-planar reconstruction images and dynamic 3D-CT images were obtained using Aquilion ONE software. Pharyngeal 2D area and 3D volume measurements were taken before swallowing and at the frame depicting maximum pharyngeal constriction. Pharyngeal volume before swallowing (PVhold) was accurately predicted by 2D area (R2 = 0.816). Adding height and sex to the model increased R2 to 0.836. Regarding pharyngeal volume during maximum constriction (PVmax), 2D area also exhibited acceptable predictive power (R2 = 0.777). However, analysis of statistical residuals and outliers revealed a greater tendency for prediction errors when there is less complete constriction of the pharynx as well as asymmetry in bolus flow or movement. Findings highlight the importance of routinely incorporating anterior-posterior views during VFSS exams. Future work is needed to determine clinical utility of pharyngeal volume measurements derived from 320-ADCT.

Accuracy of deep learning-based upper airway segmentation

INTRODUCTION

In orthodontic treatments, accurately assessing the upper airway volume and morphology is essential for proper diagnosis and planning. Cone beam computed tomography (CBCT) is used for assessing upper airway volume through manual, semi-automatic, and automatic airway segmentation methods. This study evaluates upper airway segmentation accuracy by comparing the results of an automatic model and a semi-automatic method against the gold standard manual method.

MATERIALS AND METHODS

An automatic segmentation model was trained using the MONAI Label framework to segment the upper airway from CBCT images. An open-source program, ITK-SNAP, was used for semi-automatic segmentation. The accuracy of both methods was evaluated against manual segmentations. Evaluation metrics included Dice Similarity Coefficient (DSC), Precision, Recall, 95% Hausdorff Distance (HD), and volumetric differences.

RESULTS

The automatic segmentation group averaged a DSC score of 0.915±0.041, while the semi-automatic group scored 0.940±0.021, indicating clinically acceptable accuracy for both methods. Analysis of the 95% HD revealed that semi-automatic segmentation (0.997±0.585) was more accurate and closer to manual segmentation than automatic segmentation (1.447±0.674). Volumetric comparisons revealed no statistically significant differences between automatic and manual segmentation for total, oropharyngeal, and velopharyngeal airway volumes. Similarly, no significant differences were noted between the semi-automatic and manual methods across these regions.

CONCLUSION

It has been observed that both automatic and semi-automatic methods, which utilise open-source software, align effectively with manual segmentation. Implementing these methods can aid in decision-making by allowing faster and easier upper airway segmentation with comparable accuracy in orthodontic practice.

3D analysis of upper airway morphology related to obstructive sleep apnea severity

BACKGROUND

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder characterized by repetitive collapse of the upper airway during sleep. However, little evidence is available on the differences between the sub-regions of the upper airway morphology and OSA severity. Since orthodontists frequently perform cone beam computed tomography (CBCT) in the neck area, we aimed to investigate the relationship and the differences between upper airway morphology and OSA severity using CBCT.

MATERIALS AND METHODS

The medical records, CBCT imaging of 21 OSA patients diagnosed by polysomnography, and the apnea-hypopnea index (AHI) results were included to classify OSA severity as mild, moderate, or severe. The minimum cross-sectional areas (MCA) and volumes of the upper pharyngeal airway boundaries in four sub-regions: nasopharynx, retropalatal, retroglossal, and hypopharynx were measured. Dolphin Imaging software was used for upper airway segmentation. The correlation coefficient (r), one-way ANOVA, and the least significant difference post hoc multiple comparison test were applied to fulfill the objectives.

RESULTS

A statistically significant relationship was found between the MCA of the nasopharynx and the AHI (r = -0.473, P < 0.05). Furthermore, a difference was found between mild and moderate and moderate and severe OSA severity in the MCA results of the retroglossal region (P < 0.05). However, no relationship was found between the upper airway volume and OSA severity.

CONCLUSIONS

MCA was moderately negatively correlated to AHI only in the nasopharynx subregion. Moderate OSA presented significantly less MCA than mild and severe OSA only in the oropharynx and retroglossal subregions.

A 3-Dimensional Evaluation of the Effects of Unilateral Vertical Mandibular Distraction Osteogenesis on Airway Volume Among Patients With Hemifacial Microsomia

OBJECTIVE

The aim of this study was to evaluate the volumetric airway changes using three-dimensional images following unilateral vertical mandibular distraction osteogenesis (uVMD) among patients with hemifacial microsomia (HFM).

DESIGN

This retrospective study analyzed cone-beam computed tomography (CBCT) scans of patients with HFM at three different timepoints; pretreatment (T0), posttreatment (T1), and at least 6 months post-distraction (T2). The individuals underwent uVMD between December 2018-Januaray 2021. The nasopharyngeal (NP) volume, oropharyngeal (OP) volume, and the area of maximum constriction (MC) were measured. Wilcoxon signed-rank test was used to compare the airway volumes between T0-T1, T1-T2, and T0-T2.

RESULTS

Five patients met the inclusion criteria (mean age = 10.4 years; 1 female, 4 males). Intraclass correlation analysis showed excellent interrater reliability (r > .86, P < .001). Posttreatment, the OP airway volume exhibited a significant mean increase of 56% (P = .043) from T0 to T1, but decreased from T1-T2 by 13%. Likewise, the total airway volume presented with a significant mean increase of 48% between T0-T1 (P = .044), and a decrease of 7% from T1-T2. The changes in the NP airway volume and area of MC were not statistically significant (P > .05), but an increase in the mean values were observed.

CONCLUSION

Surgical intervention with uVMD may significantly increase the OP airway volume and the total airway volume among patients with HFM immediately after distraction. However, the statistical significance diminished after six months post-consolidation, but the mean percent change may remain of clinical significance. The NP volume did not seem to show significant changes in response to uVMD.

Measurement of Upper Airway Volume in Children with Craniofacial Abnormalities

OBJECTIVE(S)

Previous literature has established a high prevalence of upper airway obstruction in children with craniofacial abnormalities. This study aims to perform quantitative airway volume measurements in patients with craniofacial abnormalities and compare them to age and sex-matched controls.

METHODS

We performed a retrospective review of the records of all children with craniofacial abnormalities who underwent head-and-neck computed tomography (CT) imaging at a single tertiary-care center between 1/1/13 and 12/31/20 using the ICD-10 codes Q75.1, Q75.4, and Q87.0. These patients were then matched by age and sex to patients with isolated craniosynostosis (Q75.0). CT scans were imported into Dolphin Imaging software, and airway volumes were measured for the nasal cavity, nasopharynx, oropharynx, and hypopharynx. The primary outcome was the total airway volume, defined as the sum of these measurements.

RESULTS

Thirty subjects with craniofacial syndromes were matched to 30 patients with isolated craniosynostosis (controls). In both groups, 18 subjects (60%) were male (p = 0.99). The average ages for syndromic patients and controls were 12.1 and 12.9 months, respectively (p = 0.84). On average, the total airway volumes of syndromic patients were 25% lower than those of controls (p = 0.02). Syndromic patients had 39% smaller nasal cavity volumes (p < 0.001) and 32% smaller nasopharyngeal volumes (p < 0.01). Significant volume differences were not observed for the oropharynx or hypopharynx.

CONCLUSION

We present a unique technique to measure airway volumes in patients with craniofacial abnormalities. These findings will help practitioners to further understand the anatomy and pathophysiology of disturbed breathing in children with craniofacial syndromes.

LEVEL OF EVIDENCE

III Laryngoscope, 134:2915-2921, 2024.

Cephalometric Screening Assessment for Superior Airway Space Narrowing-Added Value of Three-Dimensional Imaging

Background: Assessing the morphology of the superior airway space is a crucial diagnostic step in the treatment planning of patients with obstructive sleep apnea syndrome (OSAS) or prior to orthognathic surgery. The aim of this study is to evaluate the necessary scope of a two-dimensional cephalometric assessment and the necessity of three-dimensional imaging in the identification of superior airway space narrowing (SASN). Methods: The computed tomography studies of 100 non-obese, non-OSAS patients were evaluated and analyzed retrospectively. Multiplanar reconstructions were created and underwent cephalometric evaluation. The three-dimensional superior airway morphology was segmented and measured for the minimal cross-sectional area (Amin) and volume (V0). Patients were grouped according to Amin < 80 mm2 and V0 < 12 cm3. Cephalometric parameters (CPs) were analyzed according to Amin and V0 with an unpaired t-test, Pearson correlation, and ROC-curve analysis. Results: The CPs regarding sagittal airway space dimensions (IPAS, MPAS, SPAS) and mandibular body length (GoGn) show the strongest correlation to the three-dimensional minimal cross-sectional area (Amin). The ROC-curve analysis classifying for SASN led to an AUC of 0.86 for IPAS, 0.87 for MPAS, 0.88 for SPAS, and 0.63 for GoGn. Three-dimensional imaging may further improve the diagnostic accuracy in the identification of SASN for IPAS below 13.5 mm, MPAS below 10.2 mm, SPAS below 12.5 mm, and GoGn below 90.2 mm. Conclusions: Two-dimensional cephalometric sagittal airway space diameters and mandibular body length are useful initial screening parameters in the identification of superior airway space narrowing. Nevertheless, as the correlation of two-dimensional cephalometric parameters with three-dimensional upper airway space narrowing is varying and highly dependent on acquisition circumstances, indications for three-dimensional imaging, if possible, in the supine position to evaluate upper airway space morphology should be provided generously, especially in patients with low but normal airway space parameters in two-dimensional cephalometry.

Medium-term effects of rapid maxillary expansion on nasal cavity and pharyngeal airway volumes considering age as a factor: A retrospective study

OBJECTIVES

The medium-term effects of rapid maxillary expansion (RME) on nasal cavity (NC) and upper airway (UA) dimensions based on chronological age are still unclear. This retrospective study evaluated the medium-term changes occurring in the NC and pharyngeal airways (PA) after RME in two distinct age-based cohorts of patients.

METHODS

This retrospective study included 48 subjects who underwent RME grouped in two cohorts: a 6-9-year-old group (EEG group: early expansion group - 25 subjects) and an 11-14-year-old group (LEG group: late expansion group - 23 subjects). NC and PA volumes were analyzed from CBCT imaging segmentation before RME (T0) and twelve months after RME (T1). The amount of maxillary expansion (PW) and minimal cross-sectional area (CSmin) were also considered.

RESULTS

All PAs' volumetric sub-regions, CSmin and PW showed a significant volumetric increment (p < 0.05). Inter-group comparisons showed significant differences (p < 0.05) for nasopharynx and CSmin parameters (p < 0.05), while no significant changes were recorded for the other UA's sub-regions and PW (p > 0.05). According to a deviation analysis, part of the UA increase (more marked for the nasopharynx area) may have occurred due to reduced adenotonsillar tissues, which were larger in the EEG group.

CONCLUSIONS

Twelve months after treatment, clinicians should not expect changes in the UAs dimensions to be solely related to treatment effects of RME; instead, normal craniofacial growth changes and spontaneous regression of the adenotonsillar tissue could represent the most significant factors influencing UAs changes.

CLINICAL SIGNIFICANCE

From the clinical perspective, the results of the present study encourage caution when considering the therapeutic effects of RME on airways dimensions.

Facial soft tissue changes and volumetric analysis of upper airways in patients undergoing surgically assisted rapid maxillary expansion using a transpalatal distractor

OBJECTIVE

To verify changes in facial soft tissue using the RadiANT-DICOM-viewer and Dolphin Imaging software, through linear measurements of tomographic points in a 3D reconstruction of the face and volumetric evaluation with three-dimensional measurements of the upper airways of patients with transverse maxillary discrepancy undergoing Surgically Assisted Rapid Maxillary Expansion (SARME).

METHODS

Retrospective, transverse, and descriptive study, through the analysis of computed tomography scans of the face of patients with transverse maxillary discrepancy, treated from July 2019 to December 2022. The sample consisted of 15 patients of both sexes, aged 21-42 years old, who underwent surgically assisted rapid maxillary expansion using the transpalatal distractor. Analysis was performed through linear, angular, and three-dimensional measurements in millimeters, in the preoperative and late four-month postoperative period, in frontal 3D tomographic images of the face, in the region of the width of the nose and alar base and also angular measurement in the lateral tomography for the angle nasolabial and upper airways of rhinopharynx, oropharynx and hypopharynx.

RESULTS

There was an increase in nasal width with an average of 1.3467mm and an increase in the alar base with an average of 1.7333mm. A significant difference was found in the pre- and postoperative assessments of the measurements of nasal width, alar base and nasolabial angle, as well as the upper airways in all their extension. The results favour a better understanding of the professional and the patient regarding the diagnosis and management of patients with transverse maxillary width discrepancies.

CONCLUSION

Although our study shows an increase in soft tissues after SARME, no aesthetic changes are observed clinically, and all patients report significant respiratory improvement. SARME may therefore contribute to the improvement of professionals working in the field of oral and maxillofacial surgery and orthodontics.

LEVEL OF EVIDENCE

Level 4.

Evaluation of upper airway characteristics in patients with and without sleep apnea using cone-beam computed tomography and computational fluid dynamics

OBJECTIVE

To determine if upper airway characteristics and airway pressure change significantly between low risk, healthy non-OSA subjects, and OSA subjects during respiration using cone-beam computed tomography (CBCT) imaging and steady-state k-ω model computational fluid dynamics (CFD) fluid flow simulations, respectively.

MATERIALS AND METHODS

CBCT scans were collected at both end-inhalation and end-exhalation for 16 low-risk non-OSA subjects and compared to existing CBCT data from 7 OSA subjects. The CBCT images were imported into Dolphin Imaging and the upper airway was segmented into stereolithography (STL) files for area and volumetric measurements. Subject models that met pre-processing criteria underwent CFD simulations using ANSYS Fluent Meshing (Canonsburg, PA) in which unstructured mesh models were generated to solve the standard dual equation turbulence model (k-ω). Objective and supplemental descriptive measures were obtained and statistical analyses were performed with both parametric and non-parametric tests to evaluate statistical significance at P < .05.

RESULTS

Regarding area and volumetric assessments, there were statistically significant mean differences in Total Volume and Minimum CSA between non-OSA and OSA groups at inhalation and exhalation (P = .002, .003, .004, and .007), respectively. There were also statistically significant mean differences in volume and min CSA between the inhalation and exhalation for the non-OSA group (P < .001 and .002), respectively.

CONCLUSION

While analysis of the CFD simulation was limited by the collected data available, a finding consistent with published literature was that the OSA subject group simulation models depicted the point of lowest pressure coinciding with the area of maximum constriction.

Pharyngeal airway subdivisions in 3-dimensional analysis: Differences between anterior and posterior anatomic boundaries

INTRODUCTION

This study aimed to evaluate if there were differences between anterior and posterior anatomic boundaries used for the 3-dimensional determination of pharyngeal airway.

METHODS

The sample included 150 cone-beam computed tomography scans from healthy patients divided according to (1) age: 6-11, 12-16, and ≥16 years; (2) sex: female and male; (3) anteroposterior skeletal pattern: Class I, II, and III; (4) vertical pattern: brachyfacial, mesofacial, and dolichofacial; and (5) craniocervical inclination (CCI): natural head posture, head flexion, and head extension. Anatomic regions were created to determine the correspondences between structures anteriorly and posteriorly to the pharyngeal airway.

RESULTS

The location of the epiglottis, vallecula, hyoid, C2, and C3 were statistically different according to the CCI, and the location of vallecula, C3, and C4 were different according to sex. However, no statistically significant differences were observed between the frequencies of anterior and posterior anatomic region locations among age and different anteroposterior and vertical skeletal patterns. Posterior landmarks tend to be located below the anterior ones; consequently, the anatomic subregion they define will also be located below.

CONCLUSIONS

Anterior and posterior structures and vertical and anteroposterior skeletal patterns may determine upper airway limits regardless of age. However, the studies must be paired according to sex, and CCI must be standardized.

Comparison of invisalign mandibular advancement and twin-block on upper airway and hyoid bone position improvements for skeletal class II children: a retrospective study

BACKGROUND

This study is to evaluate and compare the improvement of upper airway morphology and hyoid bone position in children with Class II mandibular retrusion treated with Invisalign mandibular advancement (MA) and Twin-Block (TB) appliances, utilizing cone beam computed tomography (CBCT).

METHODS

32 children aged between 8 and 11.5 years old were included in this study, with an average age of 10.2 years old. These children were divided into two groups, MA and TB, with 16 children in each group. Changes in upper airway morphology and hyoid bone position before and after treatment were analyzed using CBCT.

RESULTS

(1) Changes in upper airway before and after treatment: the oropharynx volume (Or-V), the oropharynx minimum cross-sectional area (Or-mCSA), the hypopharynx volume (Hy-V), and the hypopharynx minimum cross-sectional area (Hy-mCSA) in both the MA and TB groups increased after treatment, and the differences were statistically significant (P < 0.05) compared to pre-treatment status. (2) Changes in hyoid bone position before and after treatment: The distances between H point and third cervical vertebra (H-C3), H point and pogonion (H-RGN), H point and mandibular plane (H-MP), H point and Frankfort horizontal plane (H-FH), H and S point (H-S), and H point and palatal plane (H-PP) in both the MA and TB groups increased after treatment, and the differences were statistically significant (P < 0.05).

CONCLUSION

Both MA and TB appliances effectively improved the structural narrowness of the upper airway and reduced respiratory resistance, thus improving breath quality. However, MA showed more effectiveness in improving the narrowest part of the hypopharynx compared to TB. Both appliances also promoted anterior downward movement of the hyoid bone, which opens the upper airway of the oropharynx and hypopharynx and helps the upper airway morphology return to normal range.

Reliability of gender determination from paranasal sinuses and its application in forensic identification-a systematic review and meta-analysis

This systematic review aims to determine whether linear or morphometric analysis of paranasal sinuses can be used for accurate determination of gender and to appraise which sinus can be evaluated for accurate gender determination.A comprehensive search of the specialized databases (PubMed/MEDLINE, Science Direct, Clinical Key, ProQuest, Google Scholar, Epistomonikos, LILACS, OpenGrey) and other institutional repositories was performed for including the studies which assessed paranasal sinuses for gender determination. Quality assessment was carried out with the AQUA tool. The meta-analysis was performed with the eligible study data at 95% CI and p ≤ 0.05 in the random-effects model.Forty-six studies evaluating frontal sinus (13), maxillary sinus (26), frontal and maxillary sinus (5), or three paranasal sinuses (2) were included. All the included studies assessed height, length, width, and volume, respectively, and other additional parameters (area, perimeter) if wherever applicable. Frontal sinus had significantly higher values for males compared to females except for left height (LH) and left volume (LV). Maxillary sinus measurements were significantly higher in males contrasted to females except for LH. Sub-group analyses revealed that analyses involving the population had statistically significant results for all the measured parameters for both the sinuses (p < 0.05 and p = 0.00, respectively).Measurements obtained from assessing sinuses reveal that there are variations in size, among populations in different geographic regions. Hence, more studies with improved sample sizes and standardized measurement protocols should be carried out on different populations to see the diversity and their reliability.

Upper airway changes after rapid maxillary expansion: three-dimensional analyses

The objective of this study was to evaluate volumetric changes in the upper airway using Cone Beam Computed Tomography (CBCT) in orthodontic patients with maxillary transversal hypoplasia undergoing maxillary disjunction. The influence of factors such as sex, age, and growth pattern on airway volumetric changes was also assessed. The sample consisted of 50 growing patients from the dental clinic of Cardenal Herrera CEU University of Valencia. Airway volume was measured in mm3 before treatment (T0) and after palatal disjunction (T1). The final sample included 37 subjects in the treatment group and 13 in the control group. The volume gained exclusively from the disjunction treatment was determined to differentiate it from natural growth. The control group showed a mean volume increase from 10,911.3 ± 1,249.6 mm3 to 13,168.9 ± 1,789.7 mm3, representing a mean increase of 2,257.6 mm3 or + 20.9%. The treatment group exhibited an increase from 14,126.3 ± 4,399.8 mm3 at T0 to 18,064.1 ± 4,565.9 mm3 at T1, corresponding to a gain of 3,937.8 mm3 or + 31.8%. Significant differences in airway volume were observed after palatal disjunction compared to the control group. The expansion of the maxilla led to a significant increase in airway volume in the treated patients, estimated at 5,183 mm3 (+ 41.5%).

Deep Learning Models for Automatic Upper Airway Segmentation and Minimum Cross-Sectional Area Localisation in Two-Dimensional Images

OBJECTIVE

To develop and validate convolutional neural network algorithms for automatic upper airway segmentation and minimum cross-sectional area (CSAmin) localisation in two-dimensional (2D) radiographic airway images.

MATERIALS AND METHODS

Two hundred and one 2D airway images acquired using cone-beam computed tomography (CBCT) scanning were randomly assigned to a test group (n = 161) to train artificial intelligence (AI) models and a validation group (n = 40) to evaluate the accuracy of AI processing. Four AI models, UNet18, UNet36, DeepLab50 and DeepLab101, were trained to automatically segment the upper airway 2D images in the test group. Precision, recall, Intersection over Union, the dice similarity coefficient and size difference were used to evaluate the performance of the AI-driven segmentation models. The CSAmin height in each image was manually determined using three-dimensional CBCT data. The nonlinear mathematical morphology technique was used to calculate the CSAmin level. Height errors were assessed to evaluate the CSAmin localisation accuracy in the validation group. The time consumed for airway segmentation and CSAmin localisation was compared between manual and AI processing methods.

RESULTS

The precision of all four segmentation models exceeded 90.0%. No significant differences were found in the accuracy of any AI models. The consistency of CSAmin localisation in specific segments between manual and AI processing was 0.944. AI processing was much more efficient than manual processing in terms of airway segmentation and CSAmin localisation.

CONCLUSIONS

We successfully developed and validated a fully automatic AI-driven system for upper airway segmentation and CSAmin localisation using 2D radiographic airway images.

The Reliability of Three-Dimensional Landmark-Based Craniomaxillofacial and Airway Cephalometric Analysis

Cephalometric analysis is a standard diagnostic tool in orthodontics and craniofacial surgery. Today, as conventional 2D cephalometry is limited and susceptible to analysis bias, a more reliable and user-friendly three-dimensional system that includes hard tissue, soft tissue, and airways is demanded in clinical practice. We launched our study to develop such a system based on CT data and landmarks. This study aims to determine whether the data labeled through our process is highly qualified and whether the soft tissue and airway data derived from CT scans are reliable. We enrolled 15 patients (seven males, eight females, 26.47 ± 3.44 years old) diagnosed with either non-syndromic dento-maxillofacial deformities or OSDB in this study to evaluate the intra- and inter-examiner reliability of our system. A total of 126 landmarks were adopted and divided into five sets by region: 28 cranial points, 25 mandibular points, 20 teeth points, 48 soft tissue points, and 6 airway points. All the landmarks were labeled by two experienced clinical practitioners, either of whom had labeled all the data twice at least one month apart. Furthermore, 78 parameters of three sets were calculated in this study: 42 skeletal parameters (23 angular and 19 linear), 27 soft tissue parameters (9 angular and 18 linear), and 9 upper airway parameters (2 linear, 4 areal, and 3 voluminal). Intraclass correlation coefficient (ICC) was used to evaluate the inter-examiner and intra-examiner reliability of landmark coordinate values and measurement parameters. The overwhelming majority of the landmarks showed excellent intra- and inter-examiner reliability. For skeletal parameters, angular parameters indicated better reliability, while linear parameters performed better for soft tissue parameters. The intra- and inter-examiner ICCs of airway parameters referred to excellent reliability. In summary, the data labeled through our process are qualified, and the soft tissue and airway data derived from CT scans are reliable. Landmarks that are not commonly used in clinical practice may require additional attention while labeling as they are prone to poor reliability. Measurement parameters with values close to 0 tend to have low reliability. We believe this three-dimensional cephalometric system would reach clinical application.

Three-dimensional comparison between the effects of mandibular advancement device and maxillomandibular advancement surgery on upper airway

BACKGROUND

The efficacy of mandibular advancement devices (MAD) and maxillomandibular advancement (MMA) in improving upper airway (UA) patency has been described as being comparable to continuous positive airway pressure (CPAP) outcomes. However, no previous study has compared MAD and MMA treatment outcomes for the upper airway enlargement. This study aimed to evaluate three-dimensionally the UA changes and mandibular rotation in patients after MAD compared to MMA.

METHODS

The sample consisted of 17 patients with treated with MAD and 17 patients treated with MMA matched by weight, height, body mass index. Cone-beam computed tomography from before and after both treatments were used to measure total UA, superior/inferior oropharynx volume and surface area; and mandibular rotation.

RESULTS

Both groups showed a significant increase in the superior oropharynx volume after the treatments (p = 0.003) and the MMA group showed greater increase (p = 0.010). No statistical difference was identified in the MAD group considering the inferior volume, while the MMA group showed a significantly gain (p = 0.010) and greater volume (p = 0.024). Both groups showed anterior mandibular displacement. However, the mandibular rotation were statistically different between the groups (p < 0.001). While the MAD group showed a clockwise rotation pattern (-3.97 ± 1.07 and - 4.08 ± 1.30), the MMA group demonstrated a counterclockwise (2.40 ± 3.43 and 3.41 ± 2.79). In the MAD group, the mandibular linear anterior displacement was correlated with superior [p = 0.002 (r=-0.697)] and inferior [p = 0.004 (r = 0.658)] oropharynx volume, suggesting that greater amounts of mandibular advancement are correlated to a decrease in the superior oropharynx and an increase in the inferior oropharynx. In the MMA group, the superior oropharynx volume was correlated to mandibular anteroposterior [p = 0.029 (r=-0.530)] and vertical displacement [p = 0.047 (r = 0.488)], indicating greater amounts of mandibular advancement may lead to a lowest gain in the superior oropharynx volume, while a great mandibular superior displacement is correlated with improvements in this region.

CONCLUSIONS

The MAD therapy led to a clockwise mandibular rotation, increasing the dimensions of the superior oropharynx; while a counterclockwise rotation with greater increases in all UA regions were showed in the MMA treatment.

Impact of 3-dimensional anatomical changes secondary to orthognathic surgery on voice resonance and articulatory function: a prospective study

An evaluation was made of the impact of orthognathic surgery (OS) on speech, addressing in particular the effects of skeletal and airway changes on voice resonance characteristics and articulatory function. A prospective study was carried out involving 29 consecutive patientssubjected to OS. Preoperative, and short and long-term postoperative evaluations were made of anatomical changes (skeletal and airway measurements), speech evolution (assessed objectively by acoustic analysis: fundamental frequency, local jitter, local shimmer of each vowel, and formants F1 and F2 of vowel /a/), and articulatory function (use of compensatory musculature, point of articulation, and speech intelligibility). These were also assessed subjectively by means of a visual analogue scale. Articulatory function after OS showed immediate improvement and had further progressed at one year of follow up. This improvement significantly correlated with the anatomical changes, and was also notably perceived by the patient. On the other hand, although a slight modification in vocal resonance was reported and seen to correlate with anatomical changes of the tongue, hyoid bone, and airway, it was not subjectively perceived by the patients. In conclusion, the results demonstrated that OS had beneficial effects on articulatory function and imperceptible subjective changes in a patient's voice. Patients subjected to OS, apart from benefitting from improved articulatory function, should not be afraid that they will not recognise their voice after treatment.

Correlation between the three-dimensional maxillomandibular complex parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions

OBJECTIVES

This study aimed to determine the three-dimensional (3D) correlation between maxillomandibular complex parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions.

METHODS

This retrospective cross-sectional study included the CBCT scans of 368 patients with a mean age of 23.81 ± 3.01 years. The patients were classified into three groups (skeletal Class I, II, and III). Each class group was divided into three subgroups based on vertical growth patterns (hypo-, normo-, and hyperdivergent). The maxillomandibular complex was evaluated in the three planes using 16 skeletal measurements. Naso-, oro-, hypo-, and total pharyngeal airway spaces were assessed in terms of width, volume, surface area, and minimum constricted area (MCA). Two-way ANOVA followed by the Bonferroni post-hoc test were used.

RESULTS

The nasopharyngeal airway space was significantly lowest regarding sagittal and lateral widths in the skeletal Class III patients, the lowest volume and surface area were in hyperdivergent patients, and MCA was the highest in Class II and hypodivergent patients. The oro- and hypopharyngeal sagittal width, volume, surface area, and MCA were the lowest in the hyperdivergent patients, and oropharyngeal lateral width and hypopharyngeal sagittal width were the highest in skeletal Class III. The total pharyngeal volume, surface area, and MCA were the lowest in the hyperdivergent patients, and skeletal Class II patients had the lowest MCA.

CONCLUSIONS

The pharyngeal airway dimensions differ with various sagittal and vertical malocclusions. These differences could apply to diagnosis, treatment planning, and possible changes following orthodontic/orthopedic or surgical treatment.

Does surgically assisted maxillary expansion improve obstructive sleep apnoea in adults? A systematic review and meta-analysis

Introduction The aim of this systematic review and meta-analysis was to evaluate the effects of maxillary expansion on adults with obstructive sleep apnoea (OSA).Methods Electronic searches up to July 2021 in eight electronic databases were conducted. Study selection, data extraction, risk of bias evaluation using ROBINS-I, quality of evidence assessment using GRADE and meta-analyses were performed.Results The electronic searches yielded 1,007 studies. Following the application of the eligibility criteria, 15 articles were fully read and five studies were included. The studies evaluated the effects of surgically assisted rapid maxillary expansion in adults with OSA. The meta-analysis demonstrated an improvement in Apnoea-Hypopnea Index (AHI) (MD = -9.91, CI = -14.57 to -5.25), Oxygen Desaturation Index (ODI) (MD = -7.95, CI = -12.23 to -3.67), and Epworth Sleepiness Scale (ESS) (MD = -4.40, CI = -6.39 to -2.40). ROBINS-I indicated serious, no information and critical risk of bias for the included studies. The quality of the evidence was very low.Conclusion The findings herein suggest that maxillary expansion could improve OSA in adults in the short term.

BSSRO Improves Mandibular Morphology Mainly through Correction of Body Length and Volume in Patients with Asymmetric Mandibular Prognathism

Purpose: The purpose of this study is to analyze the change and stability of mandibular morphology in patients with asymmetric mandibular prognathism after bilateral sagittal split ramus osteotomy (BSSRO). Methods: We retrospectively analyzed fifty patients with asymmetric mandibular prognathism from the West China Hospital of Stomatology, Sichuan University, between January 2018 to March 2021. The spiral CT data before surgery, within two weeks after surgery, and at more than six months after surgery of each patient were collected. According to the deflection direction of the chin, the bilateral mandibles were defined as the long side and the short side. The morphological data of the bilateral condyle, the mandibular ramus, and the mandibular body were analyzed to determine the effect and stability of BSSRO on asymmetric mandibular prognathism. Results: It was found that the long-side mandible had greater condylar volume and diameter, mandibular ramus height and volume, and mandibular body length and volume (p < 0.05) before surgery. After surgery, the volume of the mandibular ramus increased, while the length and volume of the mandibular body decreased (p < 0.05) at the long side of the mandible; the morphological changes of the mandibular ramus and body at the short side of the mandible were not statistically significant (p > 0.05). When comparing the long and short sides of the mandible, the long side still had greater height and volume of the mandibular ramus (p < 0.01). The volume difference of the mandibular body from the two sides was corrected (p > 0.05), and the length difference of the mandibular body from the two sides was overcorrected (p < 0.05). At more than six months after surgery, the volume of the mandibular ramus and body increased, while their height decreased at the long side of the mandible (p < 0.05). For the other side, or the short side, the volume of the ramus and body increased, too. However, their height decreased (p < 0.01). Conclusion: The results of this study suggested good effect and stability of BSSRO on asymmetric mandibular prognathism, except for the correction of ramus height and volume.

Comparison of airway changes after maxillomandibular advancement with or without genial tubercle advancement in obstructive sleep apnea using cone-beam computed tomography

INTRODUCTION

This study compared the airway changes of patients with obstructive sleep apnea (OSA) after maxillomandibular advancement (MMA) with or without genial tubercle advancement (GTA) using cone-beam computed tomography.

METHODS

The authors retrospectively studied 26 patients with moderate to severe OSA who underwent MMA with or without GTA. Airway changes were determined from preoperative and postoperative 3-dimensional reconstructed cone-beam computed tomography images. The Wilcoxon signed rank test, Mann-Whitney U tests, and Spearman correlation coefficients were used in data analysis.

RESULTS

Airway was changed in all dimensions significantly after MMA with or without GTA. There was no significant difference in horizontal surgical changes between MMA and MMA with the GTA group. The mean increase in total airway volume was 66.8% for MMA alone and 74.7% for MMA with GTA (P = 0.39). Patients who underwent MMA had a larger percentage change of segmented upper airway volume than patients with MMA and GTA (106.6% vs 85.3%; P = 0.65). The group with MMA and GTA had a greater percentage change of segmented lower airway volume than the MMA alone group (80.1% vs 56.3%; P = 0.42).

CONCLUSIONS

Differences in airway changes between MMA alone and MMA with GTA were not statistically significant. Performing the GTA concomitantly with MMA may not cause greater improvement in the pharyngeal airway in patients with OSA compared with MMA alone.

Efficiency of maxillomandibular advancement for the treatment of obstructive apnea syndrome: a comprehensive overview of systematic reviews

OBJECTIVES

To evaluate the efficiency of maxillomandibular advancement using aggregated individual patient data from multiple studies.

MATERIALS AND METHODS

This overview was structured according to the PICO strategy. It adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist and was recorded on the international prospective register of systematic reviews (PROSPERO-CRD42020206135). Searches were conducted in the PubMed/MEDLINE, Scopus, Embase, Web of Science, LILACS, and Cochrane databases for studies published until January 1, 2021. Data from the included studies were collected by one author, while another reviewed the compilation.

RESULTS

Twelve systematic reviews were included. The outcome measures studied were the apnea-hypopnea index, respiratory disturbance index, mean oxygen saturation, lowest oxygen saturation, sleepiness data, posterior air space, sella-nasion point A angle, sella-nasion point B angle, surgical success, and surgical cure in patients who underwent surgery. The AMSTAR scale presented moderate evaluations, with grades varying between 6 and 10 points. The Glenny scale revealed that the study selection did not include all languages. Only three reviews identified quality assessments conducted by at least two reviewers and only five related possible searches for unpublished data.

CONCLUSIONS

Bimaxillary advancement surgery improved respiratory indicators, sleepiness data, and increased upper airway size. However, it is necessary to standardize the surgical criteria to establish measurable efficiency of the procedure.

CLINICAL RELEVANCE

This overview makes a critical analysis of the results of the selected systematic reviews with the aim of presenting the most clinically relevant data on the maxillomandibular advancement for treating obstructive apnea syndrome, with a focus on improving respiratory, anatomical, and quality of life indices. There are no overviews that approach this theme from a well-structured perspective.

Associations between the severity of nasal septal deviation and nasopharynx volume in different ages and sexes: a cone-beam computed tomography study

Background

Nasal septum deviation (NSD) can cause serious anatomical and clinical complications. It can change the breathing pattern and thus alter the anatomy of the airway structures. Despite its importance, the association between NSD with the nasopharynx volume (NPV) has not been assessed before. Therefore, we aimed to investigate it for the first time.

Methods

Archival CBCTs of 202 patients older than 17 years and without any history of trauma or pathology of the nasopharynx and without any orthodontic/orthognathic treatments were evaluated (129 women, 73 men, mean age: 36.24 ± 14.61 years). All included CBCTs must have been taken with a 12 × 8 field of view and fully covered the nasopharynx areas. The extent of NSD (°) and NPV (mm³) were measured. NSDs were categorized as mild (NSD ˂ 9°), moderate (9 ≤ NSD ≤ 15°), and severe (NSD ˃ 15°). Associations between sex, age, NSD, and nasopharynx volume were assessed using independent-samples t test, chi-square, one-way ANOVA, Tamhane post hoc test, Pearson and point-biserial correlation coefficients, and multiple linear regressions (α = 0.05).

Results

Mean NSDs were 11.27 ± 4.69° (range 1–19.5), 11.58 ± 4.63°, and 10.70 ± 4.76° in the sample, females, and males, respectively (P > 0.05). Of females, 27.9%, 40.3%, and 31.8% had mild, moderate, and severe NSDs. These were 35.6%, 39.7%, and 24.7% in males (P > 0.05). Mean NPVs were 4.88 ± 1.49, 4.80 ± 1.43, and 5.04 ± 1.60 mm³ in the sample, females, and males, respectively (P > 0.05). Mean NPVs were 6.41 ± 1.21, 4.87 ± 0.73, and 3.30 ± 0.65 mm³ in mild, moderate, and severe NSD groups (all P values = 0.000). Mean ages were 27.06 ± 6.49, 29.80 ± 9.64, and 54.73 ± 8.45 years in mild, moderate, and severe NSD groups (severe group being older than the other two groups, P = 0.000). NSD was strongly, negatively correlated with NPV (R = − 0.793, P = 0.000). Sex was not correlated with NPV or NSD (P ≥ 0.189). Age was negatively and positively correlated with NPV and NSD, respectively (P = 0.000). Modeling NSD (β = −0.776, P = 0.000) as a predictor for NPV rendered age effect insignificant (P > 0.05).

Conclusions

It was found, for the first time, that the more deviated the nasal septum, the smaller the nasopharynx volume. Aging might increase NSD and through it, reduce the nasopharynx volume. Sex might not affect NSD or NPV.

Short-Term and Long-Term Changes of Nasal Soft Tissue after Rapid Maxillary Expansion (RME) with Tooth-Borne and Bone-Borne Devices. A CBCT Retrospective Study

The objective of the study was to assess the changes in nasal soft tissues after RME was performed with tooth-borne (TB) and bone-borne (BB) appliances. Methods. This study included 40 subjects with a diagnosis of posterior cross-bite who received tooth-borne RME (TB, average age: 11.75 ± 1.13 years) or bone-borne RME (BB, average age: 12.68 ± 1.31 years). Cone-beam computed tomography (CBCT) was taken before treatment (T0), after a 6-month retention period (T1), and one year after retention (T2). Specific linear measurements of the skeletal components and of the soft-tissue region of the nose were performed. All data were statistically analyzed. Results. Concerning skeletal measurements, the BB group showed a greater skeletal expansion of the anterior and posterior region of the nose compared to the TB group (p < 0.05) immediately after RME. Both TB and BB RME induce a small increment (>1 mm) of the alar base and alar width, without significant differences between the two expansion methods (p > 0.05). A high correlation was found between skeletal and soft-tissue expansion in the TB group; instead, a weaker correlation was found in the BB group. Conclusion. A similar slight increment of the alar width and alar base width was found in both TB and BB groups. However, the clinical relevance of these differences, in terms of facial appearance, remains questionable.

Three-Dimensional Pharyngeal Airway Space Changes Following Isolated Mandibular Advancement Surgery in 120 Patients: A 1-Year Follow-up Study

Lack of evidence exists related to the three-dimensional (3D) pharyngeal airway space (PAS) changes at follow-up after isolated bilateral sagittal split osteotomy (BSSO) advancement surgery. The present study assessed the 3D PAS changes following isolated mandibular advancement at a follow-up period of 1 year. A total of 120 patients (40 males, 80 females, mean age: 26.0 ± 12.2) who underwent BSSO advancement surgery were recruited. Cone-beam computed tomography (CBCT) scans were acquired preoperatively (T0), immediately following surgery (T1), and at 1 year of follow-up (T2). The volume, surface area, and minimal cross-sectional area (mCSA) of the airway were assessed. The total airway showed a 38% increase in volume and 13% increase in surface area from T0 to T1, where the oropharyngeal region showed the maximum immediate change. At T1−T2 follow-up, both volumetric and surface area showed a relapse of less than 7% for all sub-regions. The mCSA showed a significant increase of 71% from T0 to T1 (p < 0.0001), whereas a non-significant relapse was observed at T1−T2 (p = 0.1252). The PAS remained stable at a follow-up period of 1 year. In conclusion, BSSO advancement surgery could be regarded as a stable procedure for widening of the PAS with maintenance of positive space at follow-up.

A semi-automatic approach for longitudinal 3D upper airway analysis using voxel-based registration

OBJECTIVES

To propose and validate a reliable semi-automatic approach for three-dimensional (3D) analysis of the upper airway (UA) based on voxel-based registration (VBR).

METHODS

Post-operative cone beam computed tomography (CBCT) scans of 10 orthognathic surgery patients were superimposed to the pre-operative CBCT scans by VBR using the anterior cranial base as reference. Anatomic landmarks were used to automatically cut the UA and calculate volumes and cross-sectional areas (CSA). The 3D analysis was performed by two observers twice, at an interval of two weeks. Intraclass correlations and Bland-Altman plots were used to quantify the measurement error and reliability of the method. The relative Dahlberg error was calculated and compared with a similar method based on landmark re-identification and manual measurements.

RESULTS

Intraclass correlation coefficient (ICC) showed excellent intra- and inter-observer reliability (ICC ≥ 0.995). Bland-Altman plots showed good observer agreement, low bias and no systematic errors. The relative Dahlberg error ranged between 0.51 and 4.30% for volume and 0.24 and 2.90% for CSA. This was lower when compared with a similar, manual method. Voxel-based registration introduced 0.05-1.44% method error.

CONCLUSIONS

The proposed method was shown to have excellent reliability and high observer agreement. The method is feasible for longitudinal clinical trials on large cohorts due to being semi-automatic.

Correlation Analysis between Three-Dimensional Changes in Pharyngeal Airway Space and Skeletal Changes in Patients with Skeletal Class II Malocclusion following Orthognathic Surgery

Introduction

Studies on the pharyngeal airway space (PAS) changes using three-dimensional computed tomography (CT) have shed more light on patients with Class III than Class II malocclusion. This paper focuses on analyzing the long-term changes in the PAS and evaluating the postoperative association between these PAS and skeletal changes in patients with skeletal Class II malocclusion who have undergone orthognathic surgery.

Methods

The records of 21 patients with skeletal Class II malocclusion who had undergone orthognathic surgery were included. The anatomical modifications in both jaws, changes in volume, sectional area (SA), minimum sectional area (MSA), and anterior-posterior (AP) and transverse (TV) width in the airway at one month before surgery (T0), and one month (T1) and one year (T2) after surgery were analyzed using CT images. The association between the skeletal and airway changes was evaluated between T0, T1, and T2.

Results

After surgery, the ANS, A point, and PNS demonstrated significant posterior and superior movement. The B point and the pogonion exhibited substantial anterior and superior movement. The total and inferior oropharyngeal volumes (vol 3, vol 4) notably increased, while the nasopharyngeal volume (vol 1) decreased. The anterior-posterior movement at the ANS and PNS after surgery was significantly associated with the total volume, vol 2, vol 3, SA 1, MSA, and TV width 1, while substantial association with the total volume was found at the pogonion.

Conclusion

Thus, an ideal treatment plan can be formulated for patients with skeletal Class II malocclusion by considering the postoperative PAS changes.

Long-term three-dimensional effects of orthognathic surgery on the pharyngeal airways: a prospective study in 128 healthy patients

OBJECTIVE

To investigate volumetric and circumferential pharyngeal airway space (PAS) changes and stability over time as evaluated with cone beam computed tomography (CBCT) before and after orthognathic surgery 2 years postoperatively.

MATERIALS AND METHODS

One hundred twenty-eight patients underwent bimaxillary orthognathic surgery at the Department of Maxillofacial Surgery of University Hospitals, Leuven, Belgium, were recruited prospectively. Patients were divided into 4 groups based on the amount of mandibular advancement in 5 mm increments (< 0 mm, 0-5 mm, 5-10 mm, or > 10 mm). CBCT data was acquired preoperatively and 1-6 weeks, 6 months, 1 year, and 2 years postoperatively. Patients with a history of maxillofacial trauma or surgery, obstructive sleep apnoea syndrome, or craniofacial anomalies were excluded. Nasopharyngeal, oropharyngeal, and hypopharyngeal PAS volumes and constriction surface areas (mCSA) were measured and compared between each time point with a paired t-test.

RESULTS

The largest significant increase in oropharyngeal volume and mCSA were observed in the 5-10 mm (+ 13.3-21.7%, + 51.3-83.0%)) and > 10 mm (+ 23.3-44.6%, + 92.3-130.0%) mandibular advancement groups. This increase only remained stable 2 years postoperatively in the > 10 mm group. In other mandibular advancement groups, short-term oropharyngeal volume and mCSA increases were noticed, which returned to baseline levels 6 months to 1 year postoperatively.

CONCLUSION

Bimaxillary advancement osteotomy significantly increases oropharyngeal volume and mCSA, which remains stable between 6 months to 1 year postoperatively.

CLINICAL RELEVANCE

Long-term stable volumetric and mCSA enlargements were found with > 10 mm mandibular advancements over a period of 2 years. Return towards baseline levels was observed in the other mandibular advancement groups.

Intra-individual variation of upper airway measurements based on computed tomography

The aims of this study were (1) to quantify the intra-individual variation in the upper airway measurements on supine computed tomography (CT) scans at two different time points; and (2) to identify the most stable parameters of the upper airway measurements over time. Ten subjects with paired CT datasets (3-6 months interval) were studied, using computer software to segment and measure the upper airway. The minimum cross-sectional area of the total airway and all its segments (velopharynx, oropharynx, tongue base, and epiglottis) generally had the largest variation, while the length of the total airway had the lowest variation. Sphericity was the only parameter that was stable over time (relative difference <15%), both in the total airway and each subregion. There was considerable intra-individual variation in CT measurements of the upper airway, with the same patient instruction protocol for image acquisitions. The length of the total airway, and the sphericity of the total upper airway and each segment were stable over time. Hence, such intra-individual variation should be taken into account when interpreting and comparing upper airway evaluation parameters on CT in order to quantify treatment results or disease progress.

Three-dimensional assessment of the spheno-occipital synchondrosis and clivus after tooth-borne and bone-borne rapid maxillary expansion

OBJECTIVES

To assess changes in spheno-occipital synchondrosis after rapid maxillary expansion (RME) performed with conventional tooth-borne (TB) and bone-borne (BB) appliances.

MATERIALS AND METHODS

This study included 40 subjects with transverse maxillary deficiency who received TB RME or BB RME. Cone-beam computed tomography images (CBCT) were taken before treatment (T0), and after a 6-month retention period (T1). Three-dimensional surface models of the spheno-occipital synchondrosis and basilar part of the occipital bone were generated. The CBCTs taken at T0 and T1 were registered at the anterior cranial fossa via voxel-based superimposition. Quantitative evaluation of Basion displacement was performed with linear measurements and Euclidean distances. The volume of the synchndrosis was also calculated for each time point as well as the Nasion-Sella-Basion angle (N-S-Ba°). All data were statistically analyzed to perform inter-timing and intergroup comparisons.

RESULTS

In both groups, there was a small increment of the volume of the synchondrosis and of N-S-Ba° (P < .05). Basion showed a posterosuperior pattern of displacement. However, no significant differences (P > .05) were found between the two groups.

CONCLUSIONS

Although TB and BB RME seemed to have some effects on the spheno-occipital synchondrosis, differences were very small and clinically negligible.

Postoperative Changes in the Upper Airway Following Mandibular Distraction Osteogenesis in Pediatric Hemifacial Microsomia

BACKGROUND

Patients with hemifacial microsomia (HFM) may undergo unilateral mandibular distraction osteogenesis (MDO) before skeletal maturity in an effort to improve facial symmetry. Mandibular distraction osteogenesis's effect on airway volumes have been studied in the past, though to our knowledge, none have accounted for the effect of head and neck posture on airway morphology. This study aimed to tackle this shortcoming, using imaging to analyze the upper airway of patients with HFM before and after surgical intervention with MDO.

METHODS/DESCRIPTION

The authors retrospectively reviewed patients with a diagnosis of unilateral HFM whom underwent unilateral MDO with an oblique vector at age 4 to 14 years at a single institution from 2004 to 2019. Patients with pre- and post-MDO three-dimensional computed tomography scans of the upper airway within 12 months of distractor placement and removal, respectively, were included. Head and neck postures were determined by craniocervical, pitch, roll, and yaw angles. Pre- and post-operative pharyngeal airway volumes, pharyngeal surface area, minimum retropalatal cross-sectional areas (RP CSA) and retroglossal (RG) CSA and associated anteroposterior distances were measured using Mimics 22.0 (Materialise; Leuven, Belgium). Comparison was done using Kruskal-Wallis tests and linear mixed-effects models controlling for head and neck postures.

RESULTS

Ten patients met inclusion criteria. Mean age at pre-distractor placement computed tomography scan was 99 ± 35 months, and mean duration between pre- and post-surgery scans was 220 ± 90 days. Head and neck posture were found to be significant predictors of all airway dimensions. After controlling for significant factors with fixed effects linear modeling, surface area was found to be significantly smaller in patients after MDO by 189.48 mm2 (F[10.8] = -3.47, P = 0.0053), compared to their preoperative measurements. Surgery was not a significant predictor of changes in airway volume (F[11.6] = 0.52, P = 0.61), minimum RP CSA (F[12.2] =  -0.64, P = 0.53), minimum RG CSA (F[12.6] =  -1.64, P = 0.13), RP anteroposterior distance (F[14.0] = 0.30, P = 0.77), or RG anteroposterior distance (F[20.0] =  -0.04, P = 0.97).

CONCLUSIONS

Oblique vector MDO in patients with HFM is associated only with statistically significant changes in the surface area of the upper airway, and is not associated with statistically significant changes in dimensions like volume, CSA, or anteroposterior dimension. This is an important finding, as it may guide discussions surrounding risk/benefit ratio for MDO in childhood.

Cone beam CT evaluation of skeletal and nasomaxillary complex volume changes after rapid maxillary expansion in OSA children

OBJECTIVE

The first objective of this study was to evaluate skeletal changes and changes in dimensions and volume of the upper airways before and after rapid maxillary expansion (RME) therapy in children with obstructive sleep apnoea (OSA), by Cone Beam computed tomography (CBCT). The second objective was to evaluate if RME therapy could improve both the patency of the nasal airways and the Obstructive Sleep Apnoea Syndrome (OSAS).

METHODS

19 children with OSA and malocclusion took CBCT scans with a Dentascan and 3D reconstruction program before (T0) and 4 months after (T1) RME. Patients underwent an ENT visit with auditory and respiratory tests, including a daytime sleepiness questionnaire, a 19-channel polysomnography, and an orthognatodontic examination before orthodontic therapy (T0), after 2 months (T1) with the device still on, and 4 months after the end of the orthodontic treatment (T2).

RESULTS

In all cases opening of the mid-palatal suture was demonstrated. Nasal osseous width, volume of the total upper airways, nasal cavity and nasopharynx and oropharynx increased significantly (P, .001). The increased W-ANS, W-mid and WPNS were closed linked to the enlarged midpalatal suture (P, .001). The increased WPNS were closed linked to the enlarged pterygoid processes (P, .001). The increased V-NC and V-NPA was closely linked to the enlarged W-PNS (P, .001) as well as VOPA and consequently to the enlarged midpalatal suture and pterygoid processes.

CONCLUSION

RME treatment had a positive effect on children affected by chronic snoring and OSA, causing an increase in volume of the nasal cavity and nasopharynx, with expansion of the nasal osseous width and maxillary width. Enlarged nasal width at the PNS plane contributed to the increase in nasopharynx volume. Enlarged maxillary width showed a direct correlation to increased airways volume, bringing a functional improvement. The results show that the RME therapy can restore and improve a normal nasal airflow with disappearance of obstructive sleep breathing disorder.

Clinical impact of two types of mandibular retention devices - A CAD/CAM design and a traditional design - On upper airway volume in obstructive sleep apnea patients

OBJECTIVE

This pilot randomized crossover study evaluated the outcomes of two custom-made mandibular retention devices (MRDs), a computer-aided design (CAD)/computer-aided manufacturing (CAM) device (Narval CC™) and a non-CAD/CAM device (Narval™), on oropharyngeal airway volume in patients with obstructive sleep apnoea (OSA).

METHODS

12 OSA patients were recruited from an University Hospital for MRD therapy with either CAD/CAM or non-CAD/CAM first. A cone-beam computed tomography evaluation (CBCT) and polysomnography assessment was performed during baseline assessment and at the end of each study period.

RESULTS

Upper airway volume increased significantly with the CAD/CAM device (7725 +/- 6540 mm³, p = 0.008) but not with the non-CAD/CAM device (3805 +/- 7806 mm³, p = 0.13). The CAD/CAM device was also associated with a significant decrease in AHI (mean AHI after treatment 9.4±6.7 events/h, p = 0.003) and oxygen desaturation index (mean ODI of ≥ 3%/h 11.9 ± 6.8, p = 0.011). Changes in AHI (14.7 +/- 11.7 events/h, p = 0.083) and ODI (15.5 +/- 19.2, p = 0.074) were not statistically significant with the non-CAD/CAM device. The vertical dimension of occlusion increased significantly following treatment with both MRD devices (both p = 0.003), but was significantly less pronounced with the CAD/CAM device (mean difference: -2.7 +/- 1.7 mm, p = 0.003). Final mandibular protrusion after titration was the same with both devices (85%, p = 0.317).

CONCLUSION

The CAD/CAM (Narval CC^TM) device was associated with a significant increase in upper airway volume that may be caused by a lower degree of vertical separation between the jaws when compared to the non-CAD/CAM design.

Fully automatic segmentation of sinonasal cavity and pharyngeal airway based on convolutional neural networks

INTRODUCTION

This study aimed to test the accuracy of a new automatic deep learning-based approach on the basis of convolutional neural networks (CNN) for fully automatic segmentation of the sinonasal cavity and the pharyngeal airway from cone-beam computed tomography (CBCT) scans.

METHODS

Forty CBCT scans from healthy patients (20 women and 20 men; mean age, 23.37 ± 3.34 years) were collected, and manual segmentation of the sinonasal cavity and pharyngeal subregions were carried out by using Mimics software (version 20.0; Materialise, Leuven, Belgium). Twenty CBCT scans from the total sample were randomly selected and used for training the artificial intelligence model file. The remaining 20 CBCT segmentation masks were used to test the accuracy of the CNN fully automatic method by comparing the segmentation volumes of the 3-dimensional models obtained with automatic and manual segmentations. The accuracy of the CNN-based method was also assessed by using the Dice score coefficient and by the surface-to-surface matching technique. The intraclass correlation coefficient and Dahlberg's formula were used to test the intraobserver reliability and method error, respectively. Independent Student t test was used for between-groups volumetric comparison.

RESULTS

Measurements were highly correlated with an intraclass correlation coefficient value of 0.921, whereas the method error was 0.31 mm³. A mean difference of 1.93 ± 0.73 cm³ was found between the methodologies, but it was not statistically significant (P >0.05). The mean matching percentage detected was 85.35 ± 2.59 (tolerance 0.5 mm) and 93.44 ± 2.54 (tolerance 1.0 mm). The differences, measured as the Dice score coefficient in percentage, between the assessments done with both methods were 3.3% and 5.8%, respectively.

CONCLUSIONS

The new deep learning-based method for automated segmentation of the sinonasal cavity and the pharyngeal airway in CBCT scans is accurate and performs equally well as an experienced image reader.

Novel three-dimensional methods to analyze the morphology of the nasal cavity and pharyngeal airway

OBJECTIVES

To assess the intraexaminer and interexaminer reliabilities of novel semiautomatic methods to segment the nasal cavity (NC) and pharyngeal airway (PA) and to determine the minimal cross-sectional area (CS) and hydraulic diameter (HD) of the PA.

MATERIALS AND METHODS

To test reproducibility, two examiners analyzed the NC and PA independently in 10 retrospectively selected cone beam computed tomography (CBCT) images using semiautomatic segmentation. The PA centerline was determined to assess the minimal CS and HD. The intraclass correlation coefficient (ICC) was used to calculate intraexaminer and interexaminer reliabilities. Measurement errors were assessed by Dahlberg's formula and paired t-tests. The level of agreement was assessed using the Bland-Altman method.

RESULTS

Intraexaminer and interexaminer reliabilities were excellent (minimal ICC, 0.960). The error of the method was good except for interexaminer values for the oropharynx (P = .016). The minimal CS and HD measurements were reliable (minimal ICC, 0.993; narrow limits of agreement).

CONCLUSIONS

The novel methods for analysis of the NC and PA are reliable. The minimal CS and HD demonstrated excellent reliabilities, which are critical to detect the most constricted part of the PA. Separation of the oropharynx from the voids close to the retroglossal area is not trivial and should be considered with caution.

Upper airways after mandibular advancement orthognathic surgery: A 4-year follow-up

INTRODUCTION

The purpose of this study was to assess the stability of changes in the upper airways 4 years after orthognathic surgery in patients with skeletal Class II malocclusion.

METHODS

A retrospective clinical study was conducted including 33 cone-beam computed tomography images from 11 patients (average age of 35.91 years) followed up longitudinally for 4 years. The airways were measured with the help of the Dolphin Imaging software (Dolphin Imaging and Management Systems, Chatsworth, Calif) at 3 points: T1 (preoperative), T2 (6 months after surgery), and T3 (4 years after surgery). The parameters assessed were surface area (SA), minimum axial area, and volume (VOL) of the pharyngeal airway space. The times were compared using analysis of variance and Tukey's test. Pearson's analysis was performed to assess the correlation with surgical changes and age (P <0.05).

RESULTS

Four years after operating on the airway spaces, the means of SA and VOL were significantly higher than those observed before the surgery (P <0.05). The means at 6 months were intermediate, with no significant difference before the surgery and 4 years after it (P >0.05). There was no significant correlation of the changes in SA, VOL, and minimum axial area with the amount of mandibular advancement, counterclockwise rotation of the occlusal plane, and age of the patient (P >0.05).

CONCLUSIONS

Four years after mandibular advancement surgery in patients with skeletal Class II malocclusion, the increases in the airways remained stable.

Craniofacial and airway morphology of individuals with oculoauriculovertebral spectrum

OBJECTIVES

The objectives of this study were to characterize the craniofacial and airway morphology of oculo-auriculo-vertebral spectrum (OAVS) individuals using computed tomography (CT) examination.

SETTING AND SAMPLE POPULATION

This sample included individuals in the age range from 5 to 14 years, consisted of a group of 18 OAVS individuals (12 females and 6 males), Pruzansky-Kaban¹ IIB and III and by a paired control group matched by age and sex for comparison of morphometric and airway variables.

MATERIALS AND METHODS

Through the CT examination, airway analysis was performed using Dolphin Imaging® Software, and seven morphometric measurements were performed to evaluate craniofacial morphology by Materialize Mimics® Software. To compare airway and morphometric variables, the control group was used. Student's t test and Mann-Whitney U test were performed to compare differences between the groups.

RESULTS

Statistically significant differences were showed between the control and OAVS groups for the variables: total airway (TA) area, volume and MAA, RP area, RP volume, RP MAA, RG volume, RG MAA, total posterior height diff, Md incl and y-axis asymmetry. Pearson and Spearman's correlation showed mostly moderate correlations between Mand Occlusal canting AS with TA area and RP volume, Ax-Gn with TA area and Hy-C3 with TA volume.

CONCLUSIONS

The OAVS's airway was altered and worse than the control group. Our results suggest that the contralateral side of OAVS individuals is unaffected; however, longitudinal assessments are needed to confirm it. Hyoid bone and postural measures play an important role in interpreting airway features of individuals with and without OAVS.

Existence of a Neutral-Impact Maxillo-Mandibular Displacement on Upper Airways Morphology

Current scientific evidence on how orthognathic surgery affects the airways morphology remains contradictory. The aim of this study is to investigate the existence and extension of a neutral-impact interval of bony segments displacement on the upper airways morphology. Its upper boundary would behave as a skeletal displacement threshold differentiating minor and major jaw repositioning, with impact on the planning of the individual case. Pre- and post-operative cone beam computed tomographies (CBCTs) of 45 patients who underwent maxillo-mandibular advancement or maxillary advancement/mandibular setback were analysed by means of a semi-automated three-dimensional (3D) method; 3D models of skull and airways were produced, the latter divided into the three pharyngeal subregions. The correlation between skeletal displacement, stacked surface area and volume was investigated. The displacement threshold was identified by setting three ∆Area percentage variations. No significant difference in area and volume emerged from the comparison of the two surgical procedures with bone repositioning below the threshold (approximated to +5 mm). A threshold ranging from +4.8 to +7 mm was identified, varying in relation to the three ∆Area percentages considered. The ∆Area increased linearly above the threshold, while showing no consistency in the interval ranging from -5 mm to +5 mm.

Oropharyngeal 3-dimensional changes after maxillary expansion with 2 different orthodontic approaches

INTRODUCTION

The objective of this research was to compare the oropharyngeal volume and minimal cross-sectional area (MCA) changes after maxillary expansion using either the Damon system or Hyrax appliances as assessed through cone-beam computed tomography (CBCT) imaging.

METHODS

Patients aged between 11 and 17 years with skeletal maxillary transverse discrepancy in need of maxillary expansion were included and allocated randomly into 1 of the 2 treatment groups, Damon or Hyrax. Patients underwent CBCT imaging at 2 time points: T1, after initial clinical evaluation before treatment, and T2, after completion of full orthodontic treatment. The CBCT data were assessed using Dolphin software (Dolphin Imaging & Management Solutions, Chatsworth, Calif). In addition, a qualitative assessment of breathing function was done using the modified Nasal Obstruction and Septoplasty Effectiveness Scale questionnaire.

RESULTS

A statistically significant increase in the oropharyngeal volume (2.23 mL; P = 0.005) and MCA (29.72 mm²; P = 0.007) after the completion of treatment (T2 - T1) for the Hyrax group was suggested. No statistically significant difference was found in the Damon group for volume (1 mL; P = 0.311) and for MCA (7.32 mm²; P = 0.643). In addition, no statistically significant difference was found in the breathing function in both treatment groups (P >0.05).

CONCLUSIONS

Hyrax expansion followed by fixed appliances produced more dimensional upper airway changes at the oropharyngeal level than the Damon system approach. No breathing functional changes were noted in either samples.

The correlation of maxillomandibular advancement and airway volume change in obstructive sleep apnea using cone beam computed tomography

The purpose of this retrospective study was to evaluate the correlation of maxillomandibular advancement (MMA) and airway volume changes in patients with obstructive sleep apnea (OSA), and to determine the surgical skeletal movements necessary to achieve an increase in total airway volume (TAV) of ≥70%. Thirty patients with OSA treated by MMA were evaluated. Pre- and postoperative cone beam computed tomography images were used to determine the horizontal distance and angular changes in surgical parameters and linear, area, and volumetric airway parameters. Postoperatively, the horizontal distance of surgical parameters (A-point, UI, B-point, pogonion, and menton) and craniofacial angulation (SNA and SNB) increased significantly, similar to total surface area, TAV, and minimum cross-sectional area of the airway (p<0.0001). The total airway length decreased significantly (p<0.0001). The mean increase in TAV was 67.2%. There were positive correlations between linear surgical changes and the percentage change in TAV. All surgical parameters were predictive of a change in TAV ≥70%. The optimal surgical change was 6mm for A-point, 7.9mm for UI, 7.6mm for B-point, 11.2mm for pogonion, and 10mm for menton. In conclusion, maxillary advancement of less than 10mm was adequate in this study to obtain an increase in the TAV of at least 70%.

Transverse dentoalveolar response of mandibular arch after rapid maxillary expansion (RME) with tooth-borne and bone-borne appliances

OBJECTIVES

To assess and compare spontaneous expansion of mandibular posterior teeth between tooth-borne (TB) and bone-borne (BB) rapid maxillary expansion (RME).

MATERIALS AND METHODS

This study included 36 adolescents with bilateral maxillary crossbite receiving tooth-borne (average age: 14.4 ± 1.3 years) or bone-borne (average age: 14.7 ± 1.4 years) maxillary expansion. Cone beam computed tomography was acquired before expansion (T1) and after 6 months' retention (T2). Specific linear and angular measurements were performed in the coronal view to assess buccal inclinations and widths of mandibular posterior units. All data were statistically analyzed.

RESULTS

In both groups there was a significant increase in buccal-lingual inclination of mandibular posterior teeth ranging from 1.67° to 2.30° in the TB group and from 1.46° to 2.11° in BB group. Mandibular posterior widths showed an increase ranging from 0.80 mm to 1.33 mm in TB group and from 0.64 mm to 0.96 mm in the BB group. No differences between groups were found for linear or angular measurements.

CONCLUSIONS

A clinically significant gain of space in the mandibular arch should not be expected after RME.

Relating three-dimensional airway measurements to the apnea-hypopnea index in pediatric sleep apnea patients

OBJECTIVES

(a) To evaluate three-dimensional radiographic airway analysis as it relates to the pre-test probability for sleep apnea in pediatric patients, and (b) to develop cut-off values for measurements showing promising results.

SETTING AND SAMPLE POPULATION

A consecutive series of pediatric patients between the ages of 7 and 17 years, referred for a sleep study were recruited. Cone beam computed tomography (CBCT) scans were acquired for 103 subjects within one month following the sleep study.

METHODS

Three-dimensional airway analysis was performed including volumetric, area and linear measurements. Correlations with the apnea-hypopnea index (AHI) and receiver operating characteristic (ROC) curves were constructed. Sensitivity and specificity were calculated for prediction of AHI ≥ 5 and AHI ≥ 10.

RESULTS

99 CBCT scans were included (median age = 11 years). The nasopharyngeal volume (NPV) significantly correlated with AHI (rho≈-0.4, P < .05). In subjects aged 7-11 years, proposed cut-off values for NPV are 2400mm³ and 1600mm³ for AHI ≥ 5 and AHI ≥ 10, respectively. In subjects aged 12-17 years, proposed cut-off values for NPV are 3500mm³ and 2700mm³ for AHI ≥ 5 and AHI ≥ 10, respectively. Oropharyngeal cross-sectional area (OCSA) demonstrated significant predictive value in ROC curve analysis, and cut-off values for this airway measure are also proposed.

CONCLUSIONS

Contrary to findings in adults, the NPV shows promise when screening for sleep apnea in children when CBCT scans are available. The OCSA might also be of value when screening for sleep apnea especially in older children.

Comparison of the Pharyngeal Airway Volume Between Patients With Ectodermal Dysplasia and Unaffected Controls: A Cone-Beam Computed Tomography Study

PURPOSE

Ectodermal dysplasias (EDs) are a diverse set of hereditary conditions in which 2 or more ectodermal structures develop abnormally. The purpose of this study was to use cone-beam computed tomography (CBCT) scans to measure the pharyngeal airway volume and minimum cross-sectional area (MC) among patients with ED and compare them with healthy controls.

PATIENTS AND METHODS

The pretreatment CBCT scans of 9 individuals with ED and 61 controls were analyzed. Lateral cephalograms were created from the CBCT volumes and then traced and compared between the 2 groups. Airway volumes were evaluated by Dolphin 3D software (Dolphin Imaging, Chatsworth, CA) to compare the total pharyngeal volume, nasopharyngeal volume, oropharyngeal volume, hypopharyngeal volume, and MC. The mean airway volumes of the 2 groups were compared, and the odds ratio and relative risk of having an MC of less than 100 mm² in the ED group were calculated.

RESULTS

Intraclass correlation analysis showed excellent inter-rater reliability. All cephalometric features of controls were within the norms of patients with ideal skeletal-dental relationships. Patients with ED displayed significantly lower values for SNA (angle between sella-nasion and nasion-A point) (P = .018), ANB (angle between nasion-A point and nasion-B point) (P = .002), L1-MP (angle between long axis of mandibular incisor and gonion-menton plane) (P = .013), and L1-NB (distance between mandibular incisor and perpendicular line between nasion and B point) (P < .001). Although the ED group exhibited slightly smaller airway volumes for all subregions, the differences were not statistically significant for total pharyngeal volume, nasopharyngeal volume, oropharyngeal volume, hypopharyngeal volume, or MC (P > .05). The odds of having an MC of less than 100 mm² were almost 3 times greater among ED patients, and the relative risk of an MC of less than 100 mm² among ED patients was double that of controls.

CONCLUSIONS

Although the craniofacial structures of individuals with ED are characterized by maxillary and midface deficiency, the airway volumes among affected individuals may not be significantly different from those of unaffected controls. However, patients with ED displayed a higher risk of having an MC of less than 100 mm², which may be of clinical significance and warrants further investigations with larger samples.

Three-dimensional analyses of short- and long-term effects of rapid maxillary expansion on nasal cavity and upper airway: A systematic review and meta-analysis

INTRODUCTION

The purpose of this systematic review was to evaluate the three-dimensional (3D) changes occurring at short- and long-term follow-up after rapid maxillary expansion (RME) in nasal cavity (NC) and upper airway (UA) in growing patients.

METHODS

A literature search up to 1 July 2019 was performed. Randomized and non-randomized clinical trials and cohort studies comparing the effects of RME in a paediatric population using 3D analyses based on computed tomography (CT), cone-beam CT and MRI were included. The risks of bias of the included studies were assessed using the Cochrane Collaboration's risk of bias tool, the GRADE approach and a customized tool. The random-effects meta-analyses of the mean differences and 95% confidence intervals of NC and UA volume changes were carried out, followed by subgroup analyses.

RESULTS

Twenty-seven studies were included, with 18 selected for quantitative synthesis. Immediately after expansion, the nasopharynx and oropharynx increased significantly. After 3 months of retention, only the NC and nasopharynx showed a significant volume increase. Two studies mentioned the use of a sleep-disordered breathing questionnaire, and one study reported the difference before and after RME. None of the 27 articles included assessed the correlation between the skeletal widening and NC or UA volume changes after RME.

CONCLUSIONS

The existing evidence confirmed only the short-term positive effect of RME on expanding the volume of the NC and the upper part of the UA. However, long-term stability could not be sustained.