ABSTRACT
Objective: To investigate the effects and mechanism of microscrew implant anchorage (MIA) in speeding up the closure of extraction space by one step and retraction of anterior teeth. Methods: Twenty-three patients with teeth extraction and required strong posterior anchorage were treated with MIA to close the extraction space. The extraction spaces were closed by two methods respectively. The extraction spaces were closed by the method of one step and retraction of anterior teeth(Ni-Ti spring from MIA to the hook on the wire combined with the elastic pull from MIA to cuspid) on the experiment sides and by the traditional one step method(Ni-Ti spring from MIA to the hook on the wire alone) on the control sides. Which side treated as trial side or control side was selected at random. The period of the space closing, the way and position of anterior teeth movement were observed on each side and the period of the space closing of two sides were tested by paired t test. Results: ①The average period of the spaces closing which was (6.69±1.07) months on the trial side and (9.56±1.19) months on the control side was significantly different (P<0.05).② After the closure of extraction spaces, the cuspid achived better position on the trial side than the contral side on which cuspid presented distal-lingual rotation. Conclusion: The extraction spaces can be closed in all cases by two methods respectively. Using MIA to close the extraction space by one step and retraction of anterior teeth can not only shorten the period of space closing but also achieve nice outcome by moving the cuspid in spongy bone.
ABSTRACT
Objective To investigate the changes of soft and hard tissues after extraction space closure with micro-screw implant as orthodontic anchorage. Methods Twenty cases were selected randomly with the first premolars extraction. Micro-screw implant was used as orthodontic anchorage. Sliding technique was used to close the extraction space. The lateral cephalograms before and after the treatment were evaluated.Results The upper incisors moved 7. 15 mm palatelly, 1. 63 mm intruded. The upper first molar moved 0. 80 mm distally, 1. 80 mm intruded. The lower incisors moved 4. 65 mm distally, 0.48 mm extruded. The lower first molar moved 0. 18 mm mesially, 1.18 mm extruded. A point, B point, upper lip, lower lip showed distal movement. Conclusions Micro-screw implant can provide acceptable and reliable anchorage in the process of extraction space closure, and improve the profile. Besides, it produces skeletal change on the maxilla.