The effect of alveolar bone loss and miniscrew position on the tooth displacement during intrusion of maxillary anterior teeth : finite element analysis

Abstract

The purpose of this study was to investigate the intrusion pattern of maxillary anterior teeth according to alveolar bone height and miniscrew position. Finite element analysis was performed to simulate the movement pattern of maxillary anterior teeth under intrusion force. A standard three-dimensional finite element model was constructed, and varied the position of miniscrews and hooks after setting the alveolar bone loss in 0, 2, 4 mm. The applied intrusion force was 80 g for 4 anterior teeth, 100 g for 6 anterior teeth. The following results were observed:

1. Intrusion force applied at the archwire level induced initial labial tipping with intrusion of the anterior teeth (central incisor, lateral incisor, canine).

2. With reduced alveolar bone heights, under the same load, the study indicated an increase of tooth proclination.

3. Labial tipping of anterior teeth segment was reduced when retraction force was added to vertical intrusion force.

4. The amount of tooth displacement was larger in 6 anterior teeth more than 4 anterior teeth. In the case of canine, intrusion was increased but labial tipping was decreased.

5. Stress was concentrated at the apex than cervical area of PDL in all cases. And stress was also increased as bone loss increased.

6. When a miniscrew was inserted between two central incisors, high stress concentration was significant at the central incisors than other teeth. On the other hand, when miniscrews were inserted at distal to canines and intrusion force were applied at distal to lateral incisors, stress was the lowest and distributed evenly across all the teeth.

The results of this study indicate that it is thought to be able to induce initial tooth movement close to pure intrusion when miniscrews were inserted at distal to maxillary canines and intrusion force were applied at distal to lateral incisors.