| Some investigators have attributed the development of class II malocclusion to hyperextension of the head relative to the cervical column in the beginning of the 20th century, and the history for the investigators to study the relationship of craniofacial morphology and airway size is old. The detailed statistical relationship between head posture, craniofacial morphology, airway obstruction was demonstrated by Solow and Tallgren, who proposed a hypothesis to account for the association between them , so called " soft tissue stretching" . At present, there is a lot of arguments on the relationship between head posture, craniofacial morphology and pharyngeal airway. The detailed statistical relationship between head posture and malocclusions was researched by the foreign investigators hi the 90 times of the 20 th century, and they found preliminarily a statistical significant difference in in the head posture measurements of different malocclusions, but there was some difference between their conclusions because of their different control facts and methods. The relationship between head posture and craniofacial morphology was researched by the our investigators hi the 90 tunes of the 20 th century, but the reports about the relationship between head posture, malocclusions and pharyngeal airway were yet no found . To study the relationships of changes in pharyngeal airway position, head posture and craniofacial morphology, 81 young peoples with the age of 16 to 26 year-old were composed in our research. A lateral skull roentgenograph was taken of each people under natural head posture(mirror position). Using cephalometric-4-study and 33 parameters were measured for the analysis of relationship and variance. The results were as follow:1. No sex differences in head posture measurements were observed between males and females.2. Significant correlation was found between natural head posture and angle SNA, SNB, SN/MP, N-S-PNS, NSU, NSGn, ANS-PNS-Gn, NSH.3. There is more correlation between craniofacial morphology and FH/OPT -> FH/CVT than FH/VER, OPT/VER, CVT/VER .4. The craniofacial morphology in relation to FH/OPT > FH/CVT showed more correlation with mandibular than maxillar, sagittal dimensions than vertical dimensions ," S " (sella) point than "N" (nasion) point.5. On basis of " ANB" variables the subjects with class I , class II and class III skeletal morphlogy were identified , and the measurements of FH/OPT > FH/CVT were found significant different between the subjects with class II and class III.( P=0.011*, P=0.018*)6. On basis of "NSGn" variables the subjects with class I , class II and class III skeletal morphlogy were identified , and the measurements of FH/VER, FH/OPT, FH/CVT, OPT/VER, CVT/VER were found significant different between the subjects with class II and class ni(P=0.007**, P=0.000*", P=0.000*", P=0.008**, P=0.005**). The measurements of FH/OPT, FH/CVT, OPT/VER, CVT/VER were found significant different between the subjects with class I and class II(P=O.OOf* , P=0.007**, P=0.005**, P=0.019*). The measurements of FH/VER, FH/CVT, were found significant different between the subjects with class I and class ffl(P=0.016*, P=0.017*).In conclusion, 1. Significant correlation was found within natural head posture, pharyngeal airway position and cranifacial morphology, by the change of the position of the pharyngeal airway, natural head posture is correlated to craniofacial morphology which is quite related to the pharyngeal airway. 2. The difference between the head posture of subjects on basis of "NSGn"-5-variables is more significant than which on basis of "ANB" variables.So it is recommended that more dimensions of the cranifacial morphology are considered, not only vertical dimensions,but also sagittal dimensions, and the relationship not only to the " N " (nasion) point, but also to the " S " (sella) point, when the relationship of head posture and craniofacial morphology is examined.3. Significant difference was found between the head...
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