[A study on the intrinsic compensative mechanism of craniofacial soft and hard tissue structures of Uygur adults with normal occlusion].

Objective: To study the intrinsic compensative mechanism of craniofacial soft and hard tissue structures of Uygur adults with normal occlusion and establish standard cephalometric values to evaluate craniofacial soft and hard tissue structures of normal Uygur adults.
Methods: Lateral cephalometric radiographs of 93 Uygur adults with normal occlusion (43 men and 50 women) were evaluated with the same standard. Their age ranged from 18 to 25 years old, and they had normal and well-balanced faces without receiving any orthodontic treatment. Based on the study of craniofacial soft and hard tissue structures with normal occlusion, the horizontal tendency, the vertical tendency pattern and the medial pattern of craniofacial soft and hard tissue structures were compared, and the intrinsic compensative mechanism in the inner structures of the horizontal and the vertical tendency patterns was investigated. Finally 21 indexes were analysed by mean squar deviation and Newman-Keuls test.
Results: The obvious compensative changes in the horizontal and vertical tendency patterns were found in teeth, skeleton and soft-tissues. 1. When the horizontal tendency was compared with the medial pattern, the value of ODI and angles of FH-NA and FH-NB increased (P < 0.01), while the angle of SN-PP decreased (P < 0.01). It showed that the anterior maxilla rotated in the counter-clockwise direction, and the anterior mandible rotated in the clockwise direction. The angle of U1-L1 increased (P < 0.01), which meant that the inclination of anterior teeth decreased. 2. When the vertical tendency was compared with the medial pattern, the value of ODI decreased (P < 0.01), while the height of ANS-Me, U1-PP, L1-MP, and the thickness of LL-SnPg increased (P < 0.01); The angle of L1-MP decreased (P < 0.05), while the length of Sn-Stms increased (P < 0.05). These results showed that there was an obvious positive relationship between hard and soft tissues. The soft tissue thickness could compensate the changes of hard tissues to keep the facial patterns harmony.
Conclusion: Normal occlusion depends on the homeostasis of teeth, skeleton and soft tissues, but doesn't only depend on the normal craniofacial soft and hard tissue structures respectively. The intrinsic compensative mechanism plays an important role in forming normal occlusion, therefore, doctors should choose the best treatment to obtain optimal individual intrinsic compensative mechanism and achieve an optimal balance between the craniofacial structures and the occlusion.