[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.


CONCLUSIONS
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.
Institute of Orthodontics, College of Stomatology, Shandong University, China.
Dong-xu
DX
Liu
Chun-ling
CL
Wang
Chuan-yun
CY
Fu
Xiao-yan
XY
Zhang
Xiao-zhong
XZ
Zheng
D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000502:physiology*; D008954:Models, Biological; D010513:Periodontal Ligament / Q000502:physiology*; D014087:Tooth Movement Techniques