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.

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Objectives: This study aimed to determine the anteroposterior depth (APD) of the pharyngeal airway (PA) where post-operative PA obstruction was predicted, using computer fluid dynamics (CFD), in order to prevent obstructive sleep apnoea after mandibular setback surgery. Settings and sample population: Nineteen skeletal Class III patients (8 men; mean age, 26.7 years) who required mandibular setback surgery had computed tomography images taken before and 6 months after surgery. Methods: The APD of each site of the four cross-sectional reference planes (retropalatal airway [RA], second cervical vertebral airway, oropharyngeal airway and third cervical vertebral airway) were measured. The Maximum negative pressure (Pmax) of the PA was measured at inspiration using CFD, based on a three-dimensional PA model. Intersite differences were determined using analysis of variance and the Friedman test with Bonferroni correction. The relationship between APD and Pmax was evaluated by Spearman correlation coefficients and non-linear regression analysis. Results: The smallest PA site was the RA. Pmax was significantly correlated with the APD of the RA (r s = .628, P < .001). The relationship between Pmax and the APD-RA was fitted to a curve, which showed an inversely proportional relationship of Pmax to the square of the APD-RA. Pmax substantially increased even with a slight reduction of the APD-RA. In particular, when the APD-RA was 7 mm or less, Pmax increased greatly, suggesting that PA obstruction was more likely to occur. Conclusions: The results of this study suggest that APD-RA is a useful predictor of good PA ventilation after surgery. K E Y W O R D S computational fluid dynamics, mandibular setback surgery, obstructive sleep apnoea, pharyngeal airway depth, skeletal class III How to cite this article: Shirazawa Y, Iwasaki T, Ooi K, et al. Relationship between pharyngeal airway depth and ventilation condition in mandibular setback surgery: A computational fluid dynamics study.

The craniofacial morphology of children with unilateral cleft lip and palate (UCLP) differs from that of children without clefts. 1 Maxillary arch constriction is frequently observed in operated patients with UCLP. 2 Therefore, rapid maxillary expansion (RME) is often required in children with UCLP; in children without clefts, improvements in nasal airway ventilation and dentition expansion may be required. 3 However, improvements in nasal airway ventilation associated with RME in children with UCLP are unclear, particularly in cases involving nasal airway ventilation obstruction. 4 In studies investigating RME in patients with UCLP, the volume 5 and cross-sectional area 6 of the nasal airway reportedly increase. However, nasal septum deviation and the other nasal airway forms are often associated with abnormalities in patients with UCLP. 7 Therefore, it has been unclear whether expansion of nasal Objectives: Rapid maxillary expansion (RME) improves nasal airway ventilation in non-cleft palate children. Children with unilateral cleft lip and palate (UCLP) may have nasal obstruction and experience an increased risk of obstructive sleep apnoea. The effect of RME in UCLP children is unclear. This retrospective study evaluated RMEinduced changes in ventilation parameters in children with UCLP using computational fluid dynamics. Setting and Sample Population: Nineteen patients (10 boys, mean age 10.7 years)who required RME had cone-beam computed tomography images taken before and after RME. Twenty control participants (11 boys, mean age 11.1 years) received regular orthodontic treatment.Methods: Nasal airway ventilation parameters (air pressure, air velocity and airflow rate) were analysed via computational fluid dynamics, and nasal cross-sectional area (CSA) was measured.Results: Maximum pressure, velocity and nasal resistance were significantly reduced by RME in the UCLP group. Air flow rate and CSA on the cleft side significantly were increased by RME in the UCLP group. Conclusions:In children with UCLP, increasing the quantity of airflow and CSA on the cleft side by RME substantially improved nasal ventilation. K E Y W O R D S children, computational fluid dynamics, nasal airway, rapid maxillary expansion, unilateral cleft lip and palate 202 | IWASAKI et Al.width diameter and dentition improves nasal airway ventilation.Recently, computational fluid dynamics (CFD) has been used for evaluation of airway ventilation. 8 Regardless of upper airway shape, CFD reproduces the flow of air and can evaluate air current in the nasal airway alone. Therefore, we speculated that CFD evaluation may be more precise in the evaluation of complicated nasal airways in children with UCLP.The current study investigated improvements in nasal airway ventilation associated with RME in patients with UCLP via CFD in which nasal airway ventilation could be evaluated without being influenced by the complexity of nasal airway shape.

Study Objectives: Obstructive sleep apnea (OSA) is a respiratory disorder caused by the obstruction of the upper airway during sleep. The most common cause of pediatric OSA is adenotonsillar hypertrophy. Adenotonsillectomy is the first-line treatment for pediatric OSA; however, OSA persists in a significant number of patients due, in part, to the method of evaluating enlarged adenoids and tonsil tissue. The reason for these effects on OSA severity is not clear. This study aimed to establish a method to diagnose the need for adenoidectomy or tonsillectomy. Methods: Twenty-seven Japanese children (mean age 6.6 years) participated in this study, undergoing polysomnography and computed tomography examination. Pharyngeal airway morphology (adenoids and tonsil tissue size, volume, and cross-sectional area [CSA]) and pressure on the upper airway were evaluated at each site using computational fluid dynamic analysis. Results: Apnea-hypopnea index (AHI) showed a strong linear association with maximum negative pressure (P max ) (AHI = −0.055* events/h P max −1.326, R 2 = .805). The relationship between minimum CSA (CSA min ) and P max was represented by an inversely proportional fitted curve (P max = −4797/CSA min −5.1, R 2 = .507). The relationship between CSA min and AHI was also represented by an inversely proportional fitted curve (AHI = 301.6 events/h/CSA min 1.22 , R 2 = .680). P max greatly increased if CSA min became ≤ 30 mm 2 . The negative pressure of each site increased when CSA measured ≤ 50 mm 2 . Conclusions: In children, when the CSA for each site is ≤ 50 mm 2 , AHI is likely to be elevated, and the patient may require tonsillectomy or adenoidectomy.