Computational fluid dynamic analysis of the nasal respiratory function before and after postero-superior repositioning of the maxilla.

Morphological changes in the upper airway and the resulting alteration in the nasal respiratory function after jawbone repositioning during orthognathic surgery have garnered attention recently. In particular, nasopharyngeal stenosis, because of the complex influence of both jaws, the effects of which have not yet been clarified owing to postero-superior repositioning of the maxilla, may significantly impact sleep and respiratory function, necessitating further functional evaluation. This study aimed to perform a functional evaluation of the effects of surgery involving maxillary repositioning, which may result in a larger airway resistance if the stenosis worsens the respiratory function, using CFD for treatment planning. A model was developed from CT images obtained preoperatively (PRE) and postoperatively (POST) in females (n = 3) who underwent maxillary postero-superior repositioning using Mimics and ICEM CFD. Simultaneously, a model of stenosis (STENOSIS) was developed by adjusting the severity of stenosis around the PNS to simulate greater repositioning than that in the POST. Inhalation at rest and atmospheric pressure were simulated in each model using Fluent, whereas pressure drop (ΔP) was evaluated using CFD Post. In this study, ΔP was proportional to airway resistance because the flow rate was constant. Therefore, the magnitude of ΔP was evaluated as the level of airway resistance. The ΔP in the airway was lower in the POST compared to the PRE, indicating that the analysis of the effects of repositioning on nasal ventilation showed that current surgery is appropriate with respect to functionality, as it does not compromise respiratory function. The rate of change in the cross-sectional area of the mass extending pharynx (α) was calculated as the ratio of each neighboring section. The closer the α-value is to 1, the smaller the ΔP, so ideally the airway should be constant. This study identified airway shapes that are favorable from the perspective of fluid dynamics.

A cone-beam computed tomographic assessment of the proximity of the maxillary canine and posterior teeth to the maxillary sinus floor: Lessons from 4778 roots.

INTRODUCTION: When tooth roots protrude into the maxillary sinus, apical root resorption and tipping may occur during horizontal tooth movement across the sinus floor. Three-dimensional cone-beam computed tomography (CBCT) images may provide detailed information without distortion and overlap. We evaluated the relationships between the maxillary tooth root apices and the maxillary sinus floor using CBCT. METHODS: We evaluated 4778 roots from 76 men (aged 27.6 ± 10.4 [mean ± standard deviation] years; range, 18-69 years), and 225 women (aged 30.4 ± 12.0 years; range, 18-68 years). The positional relationships between the maxillary tooth root apices, including the canine, premolar (first and/or second), and molar (first and/or second), and the inferior wall of the maxillary sinus were comprehensively evaluated on 2 cross-sectional CBCT images (ie, the sagittal and coronal planes). These distances were measured in both images simultaneously. RESULTS: The sagittal plane distances were significantly larger than coronal plane distances, except for the distobuccal root of the first molar. Pearson correlation test revealed a significant negative correlation between the distance and the patient's age. CONCLUSIONS: Our study provides valuable information for planning orthodontic tooth movement through the maxillary sinus, which may help to predict the occurrence and severity of root resorption.

Alveolar bone morphology in patients with a unilateral palatally displaced maxillary lateral incisor: A cone-beam computed tomography study.

INTRODUCTION: Lingual displacement of the maxillary anterior teeth is 1 of the most common forms of malocclusion. The labial alveolar bone is thinner for the maxillary lateral incisor than for the central incisor and canine; however, the alveolar bone width at the actual position of the maxillary lateral incisor has not been examined. We investigated the morphologic characteristics of the alveolar bone around palatally displaced maxillary lateral incisors using cone-beam computed tomography and a split-mouth model. METHODS: Twenty-seven patients with a unilateral palatally displaced maxillary lateral incisor were included. Axial, sagittal, and horizontal measurements were recorded at 3 levels (ie, 25%, 50%, and 75% of the root length) using cone-beam computed tomography. All obtained data were statistically analyzed using paired t tests. RESULTS: The labial alveolar bone width at 25% of root length was significantly lesser on the affected side. At all 3 levels, the distance between a line tangential to the labial alveolar bone of the central incisor and canine and the position of the labial alveolar bone of the lateral incisor was significantly greater on the affected side. At 50% and 75% of root length, the horizontal distance between the posterior nasal spine and the labial alveolar bone of the lateral incisor was significantly lesser on the affected side. CONCLUSIONS: Palatal displacement of maxillary lateral incisors is significantly associated with decreased alveolar bone width at the apical level and asymmetry. However, a further elaborate investigation is necessary to determine the clinical relevance of the study.

Computational Fluid Dynamic Study of Nasal Respiratory Function Before and After Bimaxillary Orthognathic Surgery With Bone Trimming at the Inferior Edge of the Pyriform Aperture.

PURPOSE: This study aimed to evaluate the influence of maxillary impaction orthognathic surgery on nasal respiratory function and the efficacy of bone trimming at the inferior edge of the pyriform aperture. MATERIALS AND METHODS: The participants were 10 patients (3 male and 7 female patients) with mandibular prognathism who underwent bimaxillary orthognathic surgery with maxillary impaction. The surgical procedures performed were Le Fort I osteotomy with bone trimming at the inferior edge of the pyriform aperture and bilateral sagittal split osteotomy. Three-dimensional models of the nasal cavity were reconstructed from preoperative and postoperative computed tomography images. Furthermore, we remodeled the nasal valve region based on the postoperative models by adding a 1-mm and 2-mm stenosis to investigate the effects of bone trimming at the inferior edge of the pyriform aperture on the pressure effort. The 3-dimensional models were simulated with computational fluid dynamics, and the results of the pressure effort and the cross-sectional area (CSA) were compared for the anterior, middle, and posterior parts of the nasal cavity. The Wilcoxon signed rank test and Spearman rank correlation coefficients were used for statistical comparisons (P < .05). RESULTS: In the preoperative and postoperative models, there were considerable correlations between the CSA and the pressure effort in each part of the nasal cavity. The postoperative pressure effort showed a tendency to decrease and the CSA showed a tendency to increase in each part of the nasal cavity. In four 2-mm stenosis models, the pressure effort in the anterior nasal cavity was larger than the preoperative pressure effort and the CSA of the anterior nasal cavity was smaller than the preoperative CSA. CONCLUSIONS: Bone trimming at the inferior edge of the pyriform aperture appears to be useful for avoiding nasal respiratory complications with maxillary impaction.