[A three-dimensional finite element study on the influence of different protraction force on cranio-maxillary complex].

PURPOSE

To offer scientific basis for clinical use of maxillary protraction by establishing and using a three-dimensional finite element model (3-D FEM) of maxillary deficiency and study the influence of protraction force on cranio-maxillary complex.

METHODS

A 3-D FEM of cranio-maxillary complex of maxillary deficiency was established from a 9-year old female by using thin-slice high resolution CT scanning and digital image transfer and transcription. And 6 forces from 3N to 8N downward the level with an angle of 30° were loaded at the area of maxillary canine. The displacement and stress distribution of the cranio-maxillary complex were analysed by using ANSYS 10.0 software package.

RESULTS

Under these forces, the displacement of N,A,ANS points had a same trend in Y,Z directions. The maxilla moved forward and upward, and the posterior of maxillary dental arch had a trend of medial movement. With the force increasing, all of the displacement and stress increased. When the force was greater than 5N per side, the change was more significant.

CONCLUSIONS

The cranio-maxillary complex shows forward and upward displacement and coarctation of upper arch with the force of maxillary protraction. The force greater than 5N should be used carefully.