Limits...
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.


Mesh generation of the upper airway 3D geometry in (a) overall, (b) amplified, and (c) cross-sectional view.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5384277&req=5

f2: Mesh generation of the upper airway 3D geometry in (a) overall, (b) amplified, and (c) cross-sectional view.

Mentions: Unstructured tetrahedral volume mesh was generated in ANSYS ICEM CFD (ANSYS 16.0) using hybrid mesh scheme (Fig. 2). A grid convergence analysis was performed by repeating the solution with five different element size meshes (Grid 1, Grid 2, Grid 3, Grid 4 and Grid5) to establish grid independence solutions. Similar element size was used in the pre-reatment and post-treatment models for reliable comparisons of the results. Changes in the average pressure and average velocity in a selected plane were used as convergence criteria. when the changes in those criteria were less than 1%, an acceptable level of grid-independence was achieved. As shown in Fig. 3, changes of the average pressure and average velocity between Grid 3 and Grid 4 were 0.32%, 0.93% for pretreatment model, and 0.38%, 0.02% for post-treatment model. It was suggested that changes in those criteria become practically negligible if Grid3 is used. Thus, all the data presented in the current work were from a simulation with Grid3, resulting in a computational grid of pre- and post-treatment typically consisting of 1.10 ± 0.05 million and 1.01 ± 0.09 million elements, respectively. The maximum skewness of the grids was 0.87. Then the 3D models were imported into the Reynolds Average Navier Stokes CFD solver (Fluent 16.0, Fluent Inc.).


Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients
Mesh generation of the upper airway 3D geometry in (a) overall, (b) amplified, and (c) cross-sectional view.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Mesh generation of the upper airway 3D geometry in (a) overall, (b) amplified, and (c) cross-sectional view.
Mentions: Unstructured tetrahedral volume mesh was generated in ANSYS ICEM CFD (ANSYS 16.0) using hybrid mesh scheme (Fig. 2). A grid convergence analysis was performed by repeating the solution with five different element size meshes (Grid 1, Grid 2, Grid 3, Grid 4 and Grid5) to establish grid independence solutions. Similar element size was used in the pre-reatment and post-treatment models for reliable comparisons of the results. Changes in the average pressure and average velocity in a selected plane were used as convergence criteria. when the changes in those criteria were less than 1%, an acceptable level of grid-independence was achieved. As shown in Fig. 3, changes of the average pressure and average velocity between Grid 3 and Grid 4 were 0.32%, 0.93% for pretreatment model, and 0.38%, 0.02% for post-treatment model. It was suggested that changes in those criteria become practically negligible if Grid3 is used. Thus, all the data presented in the current work were from a simulation with Grid3, resulting in a computational grid of pre- and post-treatment typically consisting of 1.10 ± 0.05 million and 1.01 ± 0.09 million elements, respectively. The maximum skewness of the grids was 0.87. Then the 3D models were imported into the Reynolds Average Navier Stokes CFD solver (Fluent 16.0, Fluent Inc.).

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.