[Study of growth pattern of cranialfacial complex based on skeletal age in children with normal occlusion in Shandong province].

PURPOSE: To establish the normal values of cephalometric items for children with normal occlusion in Shandong province, and study the growth tendency of them and analyze the characteristics in different skeletal stages and sexes. METHODS: Lateral cephalograph was taken in 172 children of Han nationality with normal occlusion in Shandong province. The pictures were processed by WinCeph7.0, and statistical analysis was carried out using SPSS18.0 software Package. The results between sexes and 4 skeletal stages were compared. RESULTS: Facial contour in males were larger than in females. With growth of children, counter-clockwise rotation happened in mandibular plane, and males rotated more than females. Maxillary anterior tooth tilted more forword in males than in females, while mandibular anterior tooth positioned more upright in males than in females, and the protrution of maxillary and mandibular anterior tooth in males decreased along with growth. The lower lip in males was thicker than in females. CONCLUSIONS: The normal values and standard deviations of measuring items in different gender and bone-age group were established. Supported by Natural Science Foundation of Shandong Province (ZR2009CM109) and Natural Science Foundation of Science and Technology Bureau of Shandong Province(2006GG3208004).

[Study of the dento-facial features in children of Han nationality with normal occlusion in Shandong district].

PURPOSE: To establish the standard values of roentgengraphic cephalometry in children with normal occlusion in Shandong district and to make the facial model. METHODS: 156 children were selected to take lateral cephalograph, and were divided into two groups: mixed dentition and early permanent dentition. Cephalograms were analyzed for all subjects with WinCeph7.0. Data were obtained for student's t test between the two groups and between males and females. RESULTS: The norms with derivation for all measurement of X ray cephalometrical analysis on hard tissues were established. Meanwhile, the difference between males and females was compared and the facial model of children with normal occlusion was made. CONCLUSION: Gender difference was shown in linear measurements, with greater growth in males in general. The growing tendency of children from mixed dentition to early permanent dentition was that the maxilla of the male grows faster while the mandible of the female grows faster.

[FEM study on displacement, position of rotation center and stress distribution of PDL under various loading force systems].

OBJECTIVE: To investigate the displacement, the position of rotation center and the stress distribution of PDL under different loading force system (Moment/Force, M/F) by simulating clinical loading force system. METHODS: A three-dimensional finite element model of upper central incisor, which consists of 945 isoparametric elements and 1,245 nodes was developed. The displacement, the position of the rotation center and the stress distribution of PDL were analyzed under 13 types of loading force system. RESULTS: 1. Different force system led to different types of tooth movement. When M/F= -9.15:1, -10.30 - -10.50:1 and -10.90:1, it brought the result of controlled tipping movement, the bodily movement and the root movement; 2. The graph of the center rotation was a hyperbolic asymptotic line: Mx/Fy = -10.50 (horizontal axis) and L = 6.75 (vertical axis). Moreover, a little change of M/F between -9.15 and -10.90 led to apparent change of the position of rotation center. 3. The maximum strain and stress during the tipping movement were 1.47 x 10(-2) MPa and -2.81 x 10(-2) MPa, and during the bodily movement the results were 1.10 x 10(-2) MPa and -1.86 x 10(-2) MPa, while during the root movement were 0.96 x 10(-2) MPa and -2.58 x 10(-2) MPa. CONCLUSION: 1 . Different force system (M/F) leads to different types of tooth movement. 2. It is necessary to adjust the force system accurately to obtain prescient tooth movement, especially when M/F changes between -9.15:1 and -10.90:1. 3. This study suggested that the tooth movement style and the force system (M/F) should be controlled to protect the periodontal tissue.

[Study of tooth movement under different loading force system by FEM].

OBJECTIVES: To investigate different type of tooth movement under different force systems by simulating clinical loading force systems. METHODS: Develop a three-dimensional finite element model of upper central incisor, which consists of 945 isoparametric elements, 1245 nodes. Analyse the types of tooth movement under different force system with a horizontal force of 1 N being applied at the upper central incisor. RESULTS: Different force systems(M/F) lead to different types of tooth movement. This study showed the relation between them. When M/F =-9.15:1,it bringed the result of the controlled tipping movement, When M/F=-10.30 -10.50:1, it bringed the bodily movement; While M/F=-10.90:1, it lead to the root movement. CONCLUSION: This study suggested that it is necessary to adopt different loading force systems in order ot obtain determined tooth movement.