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[Three dimensional finite element analysis of maxillary anterior teeth retraction with micro-implant anchorage and sliding mechanics].

OBJECTIVE
To investigate the biomechanical effects of micro-implant anchorage technique with sliding mechanics on maxillary anterior teeth retraction under different implant insertion heights and different retraction hook heights.


METHODS
The three dimensional finite element model of maxillary anterior teeth retraction force system was constructed with CT scanning and MIMICS software and the relationships between brackets, teeth, wire and micro-implant were simulating the clinical factions. Then the initial tooth displacement was calculated when the insertion heights were 4 mm and 8 mm and the retraction hook heights were 1, 4, 7, 10 mm respectively.


RESULTS
With retraction hook height added, the anterior teeth movement changed from lingual crown tipping to labial crown tipping and the intrusion movement was more apparent when the micro-implant was inserted in a higher location.


CONCLUSION
The ideal teeth movement control could be achieved by different insertion heights of micro-implant and different retraction hook heights in straight wire retraction force system.