Objectives: The purpose of this study was to evaluate the optimal upper threshold levels of a number of individuals and determine the most suitable upper threshold. Methods: A phantom model and ten patients were used in this study. The phantom was made of acrylic resin and urethane resin and had nine pillar-shaped air spaces. The subjects were ten female patients with jaw deformities who were not affected by respiratory disease. The optimal threshold levels were determined using the "calculation of CT value disparities" (CCTD) technique, which we devised. In other words, the mean CT values along two lines (air space and soft tissue) were calculated and the optimal threshold level was determined as the level that produced the maximum difference between the CT values measured inside and outside of the air-space border. Results: The optimal upper threshold levels of the nine phantom holes calculated using the CCTD technique in the front-on standing position and side-on standing position were 2434 HU and 2456 HU, respectively. The optimal upper threshold level of the ten patients calculated using the CCTD technique was 2472 HU. The true threshold level of each patient was defined as the optimal threshold level calculated using the CCTD technique. The mean threshold level was defined as 2472 HU. The absolute differences between the volume measurements obtained with these two measures were considered. Therefore, the no error values were 2460 HU and 2470 HU. Conclusions: We consider that the most suitable upper threshold level for extracting the airway is from 2460 HU to 2470 HU.
Objectives:To clarify the associations among tongue volume, hyoid position, airway volume and maxillofacial form using cone beam computed tomography (CBCT) data for children with Class-I, Class-II and Class-III malocclusion.
Setting and SamplePopulation: Sixty children (mean age, 9.2 years) divided into Class-I, Class-II and Class-III malocclusion groups according to the A-nasion-B angle. Material and Methods: Cone beam computed tomography was used for threedimensional reconstruction of the maxillofacial region and airway. The hyoid position and the tongue, airway and oral cavity volumes were evaluated. Upper airway ventilation status was calculated using computational fluid dynamics. The groups were compared using analysis of variance and Kruskal-Wallis tests; relationships among the parameters were assessed using Pearson's and Spearman's rank correlation tests.
Results:The tongue volume was larger in Class-III patients (50.63 cm 3 ) than in Class-I patients (44.24 cm 3 ; P < 0.05). The hyoid position was lower (49.44 cm), and anatomical balance (AB; tongue volume/oral cavity volume; 85.06%) was greater in Class-II patients than in Class-I patients (46.06 cm, 80.57%, respectively; P < 0.05 for both).The hyoid height showed a positive correlation with AB (r = 0.614; P < 0.001).
Conclusions:Children with Class-III malocclusion have large tongue volumes and small AB; the reverse is true for children with Class-II malocclusion. The hyoid position is closely associated with AB in children with malocclusion.
These findings indicate that PNAM for infants with UCLP enhanced symmetry in the maxillary alveolar arch and nasolabial form. In addition, the posterior movement of the anterior points of the maxillary alveolar arch was correlated with the improvement of columella deformation.
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