| Aims of the study The purposes of the study were to take a new approach to using cone beam CT combined with the correlative scanning data,which to build accurately a threedimensional model of the defect maxilla and its correlative tissues and the upper airway before and after restoration by prosthesis and to investigate the characteristic of air flow during the inspiratory phase before and after unilateral maxillary defect restoration by prosthesis with using the method of computer numerical simulation.Materials and methods The CBCT images,the patient before and after restored by prosthesis,and the optical scanning data of the patient prosthesis and oral scanning data based on the patient with unilateral maxillary defect after maxillary tumor resection were used to three-dimensionally reconstruct his defect maxilla and mandible and the complex after restoration and his prosthesis.The model of the patient's upper airway,before and after it restored by prosthesis,was analyzed with computer hydrodynamics.Results The models established by cone beam CT combined with optical scanning data have accurate geometry,which can freely rotate,zoom and observe its multi-angle with continuously smooth surface.These models have a good simulation of these anatomic structure.It can truly reflect the complex structure of the defect maxilla,mandible,prosthesis,the upper airway before and after restored by prosthesis,and the maxillary complex after prosthetic restoration.The result of CFD numerical simulation illustrated the distribution of air flow in the upper airway of the patient before and after restored by prosthesis.The cross section area and the contour which form anterior naris to the nasopharynx of velocity and pressure indicated that the maximum air flow is on both sides of anterior naris,airflow velocity reduced speed after prosthetic restoration.At the same time,abnormal airway has disappeared.The prosthetic restoration can reduce the vorticity volume substantially.After prosthetic restoration,the gas pressure of the anterior naris decreased.The pressure of the defect cavity over the obturator decreased significantly.The airflow in the defect side was separated,and made the spacious vertices of low velocity occurred in the total area of maxillary defect cavity.There are significant differences in the total area of the nasolabial tract and the air flow pattern between the patient who before and after restored by prostheses,and there was little difference in condition of before and after restoration by prostheses was found in the total area,gas flow pattern and trend of the nasal tract.Conclusions According this experimental method,with using the data of CBCT combined with optical scanning data to establish the model of maxillary defect after total unilateral resection of maxilla,the model of maxillary defect after prosthetic restoration,the model of prosthesis,the model of upper airway,before and after prosthetic restoration,was established successfully.The process of establishing the model was fast and accurate.The model can restore the anatomic structure of the correlative tissue and the geometric structure of the prosthesis.The results of numerical simulation provided that the volume of the ineffective cavity of upper airway is reduced and the air flow pattern is less complex than that before the restoration by prosthesis,which shows that the restoration by prosthesis can reduce the complexity of air flow of the upper airway in the patients with maxillary defect.The changes of the upper respiratory tract anatomical structure caused by unilateral maxillary resection,affected the patient who has a series of physiological functions.The numerical simulation of air flow in the upper airway of partial maxillary defect restored by prosthesis can help explain the reasons of the improvement of patients' physiological functions after prosthetic restoration. |
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