A Three-dimensional Study On Upper Airway In Preadolescent Children With Different Sagittal And Vertical Skeletal Patterns

Objective:The aims of the study were to compare the 3-dimensional pharyngeal airway morphology and volumes in healthy children with different sagittal and vertical skeletal facial patterns with CBCT and Mimics 16.0, and to investigate possible significant relationships and correlations among the studied cephalometric variables and the airway morphology in these children,in order to provide guidance for reasonable and effective orthodontic treatment planning.Methods:One hundred healthy children (70 boys,30 girls; mean age:13.82 years) were divided into two groups and to be studied. A group of subjects with a normodivergent facial pattern (n=60; FH-MP angle between 23.5° and 30.5°) was divided into three subgroups according to ANB angle:Class I (0.7°≤ ANB≤4.7°), Class II (ANB>4.7°), Class III (ANB<0.7°). A second group of subjects with a normal sagittal facial pattern (n=60; ANB angle between 0.7°and 4.7°) was divided into three subgroups according to the FH-MP anglerlow angle (FH-MP< 23.5°, normal angle(23.5°≤FH-MP≤30.5°), high angle(FH-MP>30.5°. The gender ratio in all subgroups are all the same. All of the patients took CBCT examinations under the same condition and then the software MIMICS 16.0 was used to build 3D models for upper airway. The nasopharyngeal airway,velopharyngeal airway, glossopharyngeal airway were separated and studied. Eleven related indicators were selected to be measured and the statistical software SPSS17.0 was used to analyze data of upper airway.The one way ANOVA analysis was done to compare the differences among the subgroups. To the different indicators, further LSD pairwise comparison between indexes were done. At last,correlation analysis between cephalometric variables and upper airway related indicators were performed.Results:1、In preadolescent children with different sagittal skeletal patterns, all of the sagittal linear diameters exist significant differences (P<0.05).There is significant difference (P<0.01) between Class I and Class III in the velopharyngeal upper bound plan sagittal diameter length (PNSL) and Class I subjects is significantly larger than that of Class III subjects. Patients in the Class II group are found to have significantly smaller both velopharyngeal and glossopharyngeal lower bound plan sagittal diameter length(UTL, ETL) than other groups(P<0.01).And there is no significant difference (P> 0.05) in the comparison of both the height (PNSH,UTH, ETH) and width (PNSW, UTW, ETW) of each segment of the upper airway (P> 0.05).2、In preadolescent children with different saggital skeletal patterns,there are no significant differences (P>0.05) between the nasopharyngeal airway volume (PNSV) in each group,but the nasopharyngeal airway volume in Class II group was the lowest. The velopharyngeal volume(UTV),glossopharyngeal volume (ETV) and the total volum(V) of the Class II subjects was significantly lower when compared with that of the Class I and Class III subjects(P<0.01),and the volumes were highest in the Class Ⅲ group and lowest in the Class II group.3% In preadolescent children with different vertical skeletal patterns.there are no significant differences (P>0.05) in the nasopharyngeal lower bound plan sagittal diameter length (PNSL).Patients in the high-angle group group are found to have significantly smaller both velopharyngeal and glossopharyngeal lower bound plan sagittal diameter length(UTL, ETL) than other groups(P<0.01).And there is no significant difference (P> 0.05) in the comparison of both the height (PNSH,UTH, ETH) and width (PNSW, UTW, ETW) of each segment of the upper airway (P> 0.05).4、In preadolescent children with different vertical skeletal patterns, there are no significant differences (P>0.05) between the nasopharyngeal airway volume (PNSV) in each group,but the nasopharyngeal airway volume in high-angle group was the lowest. The velopharyngeal volume(UTV),glossopharyngeal volume (ETV) and the total volum(V) of the high-angle subjects were significantly lower when compared with that of the low-and normal-angle subjects(P<0.01),and the volumes were highest in the low-angle group and lowest in the high-angle group.5、There is a positive correlation between the PNSL and SNA(r=0.198), and no correlation between the PNSV and the cephalometric variables.There are significant negative correlations between the UTL、ETL、UTV、ETV and the ANB. MP-FH. The UTL has a significant positive correlation with SNA.Conclusions:1、In preadolescent children,the growth and development of craniofacial morphology,either the skeletal pattern or the vertical skeletal pattern may have an impact on the morphology of the upper airway.2、The sagittal skeletal pattern is the contributory factor for the variation of all segments of the upper airway. The sagittal diameter length of nasopharyngeal in Class III group is the smallest, but there is no difference between the nasopharyngeal volums. The sagittal diameter and the volum of the velopharyngeal and glossopharyngeal airway tend to be the same trend:Class Ⅱ<Class I< Class III.The effects of the sagittal skeletal pattern on upper airway transverse diameter and height are limited.3、Smaller nasopharyngeal and velopharyngeal sagittal diameter lengths were seen in connection with the retraction of the maxilla. Smaller velopharyngeal and glossopharyngeal sagittal diameter lengths and volumes were seen in connection with mandibular retraction.4、The vertical skeletal pattern is the contributory factor for the variation of velopharyngeal and glossopharyngeal airway. The sagittal diameter lengths and the volums of the velopharyngeal and glossopharyngeal airway tend to be the same trend: high angle< average angle< low angle.The effects of the vertical skeletal pattern on upper airway transverse diameter and height are also limited.5、The CBCT and Mimics software is very useful and accurate in the evaluation of the upper airway morphology, the analysis on upper airway can be taken into account in the diagnosis and orthodontic treatment plan.