3D Airway changes using CBCT in patients following mandibular setback surgery ± maxillary advancement

Changes of pharyngeal airway structure and function in patients with skeletal class III malocclusion one year after orthognathic surgery

PURPOSE

This study aimed to analyze changes in the pharyngeal airway structure and function in patients with skeletal Class III malocclusion one year after orthognathic surgery.

MATERIALS/METHODS

In this research, cone-beam computed tomography (CBCT) images of 30 patients (14 men and 16 women; mean age 20-30 years) with skeletal Class III malocclusion who underwent Lefort I osteotomy and bilateral sagittal split osteotomy were obtained before and one year after the surgery. Changes in pharyngeal airway structure were achieved by comparing CBCT data, and changes in function were achieved by comparing fluid dynamics models. The pharyngeal airway was analyzed by Element 3D (E3D) and the nasal airway 3D model was reconstructed. The meshing was implemented in ICEM-CFD (ANSYS, Canonsburg, PA, USA), and improved the mesh quality. The meshes were imported into Fluent (ANSYS, Canonsburg, PA, USA) to stimulate a fluid analysis.

RESULTS

The minimal anteroposterior diameter, minimal cross-sectional area and volume of pharyngeal airway were significantly reduced after surgery. There was no significant difference in the nasopharyngeal cross-sectional area. Pharyngeal airway resistance increased significantly after surgery, wall shear stress changed little before and after surgery. The anatomic structure of pharyngeal airway changed after surgery, but the morphological change of pharyngeal airway was not significant.

CONCLUSIONS

One year after surgery, the anatomical structure and function changed compared with those before surgery, and the changes of minimal cross-sectional area of pharyngeal airway should be considered when designing the treatment plan for the patients.

Correlation analysis of airway space and condylar morphology in bilateral idiopathic condylar resorption patients

To evaluate the airway space in bilateral idiopathic condylar resorption (ICR) patients and analyse the correlation between the morphological characteristics of the condyles and airway parameters. In all, 35 female patients with bilateral ICR (mean age: 21.6 years) and 35 age-matched female controls (mean age: 21.3 years) were included. Airway parameters were measured using CBCT. Independent T-tests were used to analyse the differences between the bilateral ICR group and the control group, and then the correlation between airway parameters and condylar parameters was detected using Pearson correlation analysis. p < .05 was considered statistically significant. Patients with bilateral ICR showed a significant decrease in airway volume, minimum axial area and sagittal sectional area (p < .05). The bilateral condylar axial angle positively correlated with airway volume and sagittal sectional area (p < .05). In contrast, the bilateral condylar neck angle negatively correlated with sagittal sectional area (p < .05). None of the condylar parameters showed a correlation with minimum axial area of the airway in the bilateral ICR group (p > .05). Bilateral ICR significantly affects patients' airway space. The condylar axial angle and neck angle correlate with airway parameters.

Evaluation of Minimum Axial Airway Area and Airway Volume in Orthognathic Surgery Patients

The aim of this study was to compare preoperative and postoperative linear, planar, and volumetric measurements in the pharyngeal airway in orthognathic surgery patients. Preoperative and postoperative cone beam computed tomography (CBCT) images of 60 patients, who underwent maxillary advancement with mandibular setback (Group I, n=25) and bimaxillary advancement (Group II, n=35), were compared. The airway was divided into 3 regions as nasopharynx, oropharynx, and hypopharynx. Linear and planar measurements were made on the reference sections of each region. The minimum axial airway area, the volume of 3 regions, and total airway volume were also measured. Regarding the linear, planar, and volumetric measurements, while there was a statistically significant increase in the measurements for all three regions in Group II, in Group I only the measurements in the nasopharyngeal region demonstrated a statistically significant increase postoperatively ( P <0.05). There was an increase in minimum axial airway areas in both groups; however, it was only statistically significant in Group II ( P <0.05). There was a statistically significant increase in total airway volumes in both groups ( P <0.05). A positive and good correlation was found between the percent increase in the minimum axial area and the percent increase in the total volume ( P <0.05). While bimaxillary advancement surgery results in a significant increase in the pharyngeal airway, mandibular setback with maxillary advancement caused an increase in the total airway. Changes that may occur in the airway should be considered while planning orthognathic surgery.

A community detection analysis of malocclusion classes from orthodontics and upper airway data

OBJECTIVE

The interaction between skeletal class and upper airway has been extensively studied. Nevertheless, this relationship has not been clearly elucidated, with the heterogeneity of results suggesting the existence of different patterns for patients' classification, which has been elusive so far, probably due to oversimplified approaches. Hence, a network analysis was applied to test whether different patterns in patients' grouping exist.

SETTINGS AND SAMPLE POPULATION

Ninety young adult patients with no obvious signs of respiratory diseases and no previous adeno-tonsillectomy procedures, with thirty patients characterized as Class I (0 < ANB < 4); 30 Class II (ANB > 4); and 30 as Class III (ANB < 0).

MATERIALS AND METHODS

A community detection approach was applied on a graph obtained from a previously analysed sample: thirty-two measurements (nineteen cephalometric and thirteen upper airways data) were considered.

RESULTS

An airway-orthodontic complex network has been obtained by cross-correlating patients. Before entering the correlation, data were controlled for age and gender using linear regression and standardized. By including or not the upper airway measurements as independent variables, two different community structures were obtained. Each contained five modules, though with different patients' assignments.

CONCLUSION

The community detection algorithm found the existence of more than the three classical skeletal classifications. These results support the development of alternative tools to classify subjects according to their craniofacial morphology. This approach could offer a powerful tool for implementing novel strategies for clinical and research in orthodontics.

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.

Effect of Orthopedic Treatment for Class III Malocclusion on Upper Airways: A Systematic Review and Meta-Analysis

The aim of this systematic review is to compare the effect on the upper airways of orthopedic treatment for skeletal Class III malocclusion with untreated controls. Nine databases were searched up to August 2020 for randomized or nonrandomized clinical trials comparing orthopedic Class III treatment (facemask or chin-cup) to untreated Class III patients. After duplicate study selection, data extraction, and risk of bias assessment (Risk Of Bias In Non-randomized Studies - of Interventions [ROBINS-I]), random-effects meta-analyses of Mean Differences (MDs)/Standardized Mean Differences (SMD) and 95% Confidence Intervals (CIs) were performed, followed by the Grading of Recommendations Assessment, Development and Evaluation assessment evidence-quality. A total of 10 papers (9 unique nonrandomized studies) with 466 patients (42.7% male; average age 9.1 years) were finally included. Limited evidence indicated that compared to normal growth, maxillary protraction with facemask was associated with increases in total airway area (n = 1; MD = 222.9 mm²; 95% CI = 14.0-431.7 mm²), total nasopharyngeal area (n = 4; SMD = 1.6; 95% CI = 1.2-2.0), and individual airway dimensions (upper-airway MD = 2.5 mm; lower-airway MD = 2.1 mm; upper-pharynx MD = 1.6 mm; lower-pharynx MD = 1.0 mm; all n = 6). Subgroup/meta-regression analyses did not find any significant effect-modifiers, while the results were retained 2-5 years postretention. Our confidence in these estimates was, however, very low, due to the inclusion of nonrandomized studies with methodological issues. Limited data from 2 chin-cup studies indicated smaller benefits on airway dimensions. Existing evidence from controlled clinical studies on humans indicates that maxillary protraction for skeletal Class III treatment might be associated with increased airway dimensions, which are, however, mostly minor in magnitude.