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Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

View Article: PubMed Central - PubMed

ABSTRACT

The changes of the upper airway after large retraction of the incisors in adult class I bimaxillary protrusion patients were assessed mainly focused on the anatomic variation and ignored the functional changes. This study aimed to investigate the changes of the upper airway in adult class I bimaxillary protrusion patients after extraction treatment using the functional images based on computational fluid dynamics (CFD). CFD was implemented after 3D reconstruction based on the CBCT of 30 patients who have completed extraction treatment. After treatment, pressure drop in the minimum area, oropharynx, and hypopharynx increased significantly. The minimum pressure and the maximum velocity mainly located in the hypopharynx in pre-treatment while they mostly occured in the oropharynx after treatment. Statistically significant correlation between pressure drop and anatomic parameters, pressure drop and treatment outcomes was found. No statistical significance changes in pressure drop and volume of nasopharynx was found. This study suggested that the risk of pharyngeal collapsing become higher after extraction treatment with maximum anchorage in bimaxillary protrusion adult patients. Those adverse changes should be taken into consideration especially for high-risk patients to avoid undesired weakening of the respiratory function in clinical treatment.

No MeSH data available.


(a) The upper airway was divided into nasal cavity, nasoparynx, oropharynx, and hypopharynx and (b) 3D model of each section was reconstructed respectively.
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f1: (a) The upper airway was divided into nasal cavity, nasoparynx, oropharynx, and hypopharynx and (b) 3D model of each section was reconstructed respectively.

Mentions: The three-dimensional models used in the calculation were developed from pre- and post-treatment CBCT data from patients selected. All CBCT scans were implemented with each patient awake in the position of the Frankfort horizontal plane parallel to the floor using the same CBCT scanner (KaVo Dental GmbH, Bismarckring, Germany. scan time: 8.9 seconds; slice thickness: 0.4 mm, 120 kV, 5 mA) by the same operator. Patients were guided to close their mouths with the maximum intercuspation and the tongues touching their hard palates during the scanning. The pre- and post-treatment CBCT scans of patients were collected as T1 and T2 data. Subsequently, the dataset was exported in DICOM (Digital Imaging and Communications in Medicine) file format, and then was read into MIMICS16.0 (Materialism’s Interactive Medical Image Control System) software. After that, the models were reorientated in three planes: in the coronal view, the most inferior points on the infraorbital margin (orbitale) lie on the same horizontal plane; in the sagittal view, the models were reorientated to make the Frankfort plane horizontal; in the axial view, the models were reorientated to make the line through the crista galli and the midpoint on the anterior margin of foramen magnum (basion) vertical16. The upper airway of interest was segmented by setting the threshold between −1024 Hounsfield Units (HU) and −480 HU, and the 3D anatomically accurate patient-specific models were reconstructed. An appropriate smoothing algorithm was used to transform the 3D model into a smooth one without the loss of the patient-specific characters in the shape of the upper airway (Fig. 1). After that, the stereolithography (STL) files of the 3D models were imported into ANSYS ICEM CFD (ANSYS 16.0) for model repairing and mesh generating.


Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients
(a) The upper airway was divided into nasal cavity, nasoparynx, oropharynx, and hypopharynx and (b) 3D model of each section was reconstructed respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384277&req=5

f1: (a) The upper airway was divided into nasal cavity, nasoparynx, oropharynx, and hypopharynx and (b) 3D model of each section was reconstructed respectively.
Mentions: The three-dimensional models used in the calculation were developed from pre- and post-treatment CBCT data from patients selected. All CBCT scans were implemented with each patient awake in the position of the Frankfort horizontal plane parallel to the floor using the same CBCT scanner (KaVo Dental GmbH, Bismarckring, Germany. scan time: 8.9 seconds; slice thickness: 0.4 mm, 120 kV, 5 mA) by the same operator. Patients were guided to close their mouths with the maximum intercuspation and the tongues touching their hard palates during the scanning. The pre- and post-treatment CBCT scans of patients were collected as T1 and T2 data. Subsequently, the dataset was exported in DICOM (Digital Imaging and Communications in Medicine) file format, and then was read into MIMICS16.0 (Materialism’s Interactive Medical Image Control System) software. After that, the models were reorientated in three planes: in the coronal view, the most inferior points on the infraorbital margin (orbitale) lie on the same horizontal plane; in the sagittal view, the models were reorientated to make the Frankfort plane horizontal; in the axial view, the models were reorientated to make the line through the crista galli and the midpoint on the anterior margin of foramen magnum (basion) vertical16. The upper airway of interest was segmented by setting the threshold between −1024 Hounsfield Units (HU) and −480 HU, and the 3D anatomically accurate patient-specific models were reconstructed. An appropriate smoothing algorithm was used to transform the 3D model into a smooth one without the loss of the patient-specific characters in the shape of the upper airway (Fig. 1). After that, the stereolithography (STL) files of the 3D models were imported into ANSYS ICEM CFD (ANSYS 16.0) for model repairing and mesh generating.

View Article: PubMed Central - PubMed

ABSTRACT

The changes of the upper airway after large retraction of the incisors in adult class I bimaxillary protrusion patients were assessed mainly focused on the anatomic variation and ignored the functional changes. This study aimed to investigate the changes of the upper airway in adult class I bimaxillary protrusion patients after extraction treatment using the functional images based on computational fluid dynamics (CFD). CFD was implemented after 3D reconstruction based on the CBCT of 30 patients who have completed extraction treatment. After treatment, pressure drop in the minimum area, oropharynx, and hypopharynx increased significantly. The minimum pressure and the maximum velocity mainly located in the hypopharynx in pre-treatment while they mostly occured in the oropharynx after treatment. Statistically significant correlation between pressure drop and anatomic parameters, pressure drop and treatment outcomes was found. No statistical significance changes in pressure drop and volume of nasopharynx was found. This study suggested that the risk of pharyngeal collapsing become higher after extraction treatment with maximum anchorage in bimaxillary protrusion adult patients. Those adverse changes should be taken into consideration especially for high-risk patients to avoid undesired weakening of the respiratory function in clinical treatment.

No MeSH data available.