Abstract: PURPOSE: To investigate the relationships among tongue volume, hyoid position, airway volume and maxillofacial form in paediatric patients with Class Ⅰ, Class Ⅱ and Class Ⅲ malocclusion. METHODS: Data of 112 children with malocclusion in the Department of Stomatology, Wuxi Children's Hospital from December 2015 to December 2018 were collected. The children were divided into three groups according to Angle's classification: Class Ⅰ (n=42), Class Ⅱ (n=38) and Class Ⅲ (n=32). Tongue volume was evaluated by oral B-ultrasound, the hyoid position was obtained by lateral cephalogram, then the airway volume and maxillofacial form were evaluated by cone-beam CT (CBCT). Relationship among tongue volume, hyoid position, airway volume and maxillofacial form were analyzed. The data were processed by SPSS 20.0 software package. RESULTS: The tongue volume of Class III was significantly larger than that of Class I and Class II (P<0.05); H-FH and H-MP of Class II were significantly larger than those of Class I and Class III, and H-VL was significantly smaller than that of Class I and Class III (P<0.05). H-FH and H-MP of Class III were significantly smaller than those of Class I, and H-S was significantly larger than that of Class I (P<0.05); V throat of three types was the largest in Class Ⅲ, followed by Class I and Class Ⅱ, with significant difference (P<0.05). V nose of three types was the largest in Class Ⅱ, followed by Class I and Class Ⅲ, with significant difference (P<0.05). SNB angle of three types was the largest in Class Ⅲ, followed by Class Ⅰ and Class Ⅱ, with significant difference (P<0.05). ANB angle was the largest in Class I, followed by Class Ⅱ and Class Ⅲ, with significant difference (P<0.05). Tongue volume was positively correlated with V throat, V nose, and SNB, and negatively correlated with H-FH and ANB (P<0.05). H-FH and H-MP were negatively correlated with SNB angle and positively correlated with H-MP and ANB angle (P<0.05). CONCLUSIONS: Children with Class Ⅲ malocclusion have larger tongue volume, upward displacement of hyoid, and smaller nasopharyngeal volume. Children with Class II malocclusion have small tongue volume, downward displacement of hyoid, and small oropharyngeal volume. Tongue volume, hyoid position, airway volume and maxillofacial form are significantly correlated in paediatric patients with malocclusions, the influence of mandibular recession on the shape of upper airway should be considered during orthodontic treatment, in order to achieve the best aesthetic and therapeutic effects.

Key words: Malocclusions, Tongue volume, Hyoid position, Airway volume, Maxillofacial form