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[Tooth movement in class II division 1 malocclusion after premolar extraction].

OBJECTIVE
To investigate the magnitude and pattern of tooth movement in class II division 1 malocclusion cases treated with extraction of upper first and lower second premolars.


METHODS
Thirty cases of class II division 1 malocclusion were examined with pre- and post-treatment lateral cephalometric radiographs. The movement of both front and posterior teeth, on both upper and lower jaws were measured and compared.


RESULTS
The crowns of the upper and lower central incisors moved distally for (3.59 +/- 2.39) mm and (2.32 +/- 1.58) mm, respectively. The root apexs moved distally for (1.19 +/- 2.44) mm and (1.56 +/- 0.98) mm. The labial inclinations of the upper and lower central incisors decreased by 9.87 degrees +/- 7.68 degrees and 2.64 +/- 3.99 degrees. The crowns of the upper and lower first molars moved mesially for (4.32 +/- 4.87) mm and (4.38 +/- 1.46) mm, respectively. The buccal root apexs moved mesially for (2.74 +/- 1.56) mm and (4.43 +/- 2.12) mm. The upper and lower first molars rotated 3.90 degrees +/- 4.55 degrees and 1.25 degrees +/- 6.06 degrees counterclockwisely. The changes were statistically significant (P<0.05).


CONCLUSION
The ratio of front and posterior teeth movement is 1 : 1.3 for maxillary teeth and 3 : 5 for mandibular teeth. Upper incisors move as controlled tipping and lower incisors exhibit bodily movement.