Objective: To clarify the movement pattern of the maxillary dentition connected with an archwire, when intrusive force is applied from an anchor screw.
Method: We developed a new finite element method, by which long-term orthodontic movement could be simulated. At various locations with an intrusive force applied, movement patterns of the maxillary dentition were simulated and visualized.
Result: When an intrusive force was applied to an incisor, anterior teeth intruded along with a counterclockwise rotation of the whole dentition. In this case, anterior teeth could be intruded properly by placing a single anchor screw at the median. When an intrusive force was applied to a molar, posterior teeth intruded along with a clockwise rotation of the whole dentition. The molar tipped buccally, but it could be prevented by using a lingually prebent archwire. When an intrusive force was located near the second premolar, the whole dentition intruded with bowing of the archwire, because the line of action of the force passed near the center of resistance of the whole dentition. In all cases, intrusive force was distributed to neighboring teeth with the progress of the movement. Elastic deformation of the archwire was not noticeable. The long-term movement pattern turned out to be very different from the initial movement pattern.
Conclusion: Not only the tooth near the intrusive force intruded, but also the whole dentition moved and rotated. The long-term movement pattern could not be predicted only from the initial movement pattern.