Abstract:

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　Athree-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 tippingmovement, the bodilymovement and the rootmovement|2. The graph of the center rotationwas 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 1.47×10-2MPa and -2.81×10-2MPa, and during the bodily movement the results were 1.10×10-2MPa and -1.86×10-2MPa, while during the root movement were 0.96×10-2MPa and -2.58×10-2MPa.Con- clusion　1. Different force system (M/F) leads to differenttypes of toothmovement. 2. It is necessaryto adjustthe force system accurately to obtain prescient tooth movement, especiallywhenM/F changes between-9.15∶1 and-10.90∶1. 3. This study sug- gested that the tooth movement style and the force system (M/F) should be controlled to protect the periodontal tissue.

Key words: upper central incisor, finite element analysis, computer simulation, tooth movement, moment force