Changes Of Upper-airway Morphology After No-extraction Therapy Of Skeletal Class Ⅲ Malocclusion

Objective:①Analyzed the changes of the upper-airway morphology afterno-extraction therapy of skeletal class Ⅲ malocclusion in the early permanentdentition, and to research the interrelation between the craniofacial structuresand the surrounding structures of the upper-airway.②Compare the differenceof the upper-airway structure between skeletal class Ⅰ and class Ⅲmalocclusion before/after treatment with average angle vertical facial type in theearly permanent dentition.Methods:①15adolescents among12-16years old of skeletal class Ⅲmalocclusion with normally vertical growth pattern were selected.Cephalometric analysis of the craniofacial structures and upper-airwaydimension and hyoid bone position was performed before and afternon-extraction treatment. The data were analyzed paired sample t-test andPearson correlation analysis.②Cephalograms of15skeletal class Ⅰmalocclusion adolescents with average angle vertical facial type were collected,and measure the same items. Then compare with the skeletal class Ⅲmalocclusion before and after treatment by independent sample t-test separately. Results:1.①In class Ⅲ malocclusion, after treatment, the SNB anglesignificant reduced and the ANB angle significant increased(P＜0.01), theMP-SN angle increased(P＜0.05), the upper incisors were significantly labialinclined and the lower incisors were significantly retracted(P＜0.01); themeasurements of PNS-R were larger than before and the SPP-SPPW and PASboth reduced(P＜0.05); the hyoid bone moved back and down aftertreatment(H-PNS、H-FH、H-Or、H-CVP，P＜0.05).②In Pearson correlationanalysis, there were positively correlated between changes of SPP-SPPW andPAS and changes of SNB angle(P＜0.05), also the changes of H-Or werepositively correlated with the changes of MP-SN angle(P＜0.05).2.①PNS-R of Class Ⅲ malocclusion before treatment were narrowerwhile SPP-SPPW, U-MPW, PAS and V-LPW were wider than the class Ⅰmalocclusion (P＜0.05); in addition, H-PNS, H-FH, H-MP and H-Or of ClassⅢ malocclusion before treatment all narrower(P＜0.05).②Compare with theclass Ⅰ malocclusion, SPP-SPPW, U-MPW and V-LPW of Class Ⅲmalocclusion after treatment were still wider(P＜0.01), but the PNS-R、PASwere not statistically different between two group.(P＞0.05)；H-PNS, H-MPand H-CVP of Class Ⅲ after treatment were smaller(P＜0.05).Conclusion: Compared with the class Ⅰ malocclusion adolescents, ClassⅢ malocclusion nasopharyngeal airways were narrower but oropharynx andhypopharynx were larger, in addition, the Hyoid position of Class Ⅲmalocclusion on the front and high. Non-extraction treatment measures haveboth a negative and a positive impact on the Class Ⅲ malocclusion patient’supper-airway and hyoid position, but in the end its upper-airway sagittaldiameter still tend to be wider than the malocclusion adolescents whose sagittal development was normal. The change in position of the mandible and sagittaldiameter of the pharynx and hyoid horizontal position changes are closelyrelated. Changes the vertical position of the hyoid bone to the growth anddevelopment are closely related.