الفهرس 
Comparison between continuous and interrupted force in orthodontic canine retraction
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Abstract
Objective: The aim of this study is to compare the effect of continuous force (NiTi closed coil spring) and the interrupted force ( laceback) on the canine retraction by a split-mouth technique using cone beam CT. Materials & Methods: A sample of 8females with age range from 19 to 24 years was collected. All cases were indicated for upper first premolars extractions with moderate anchorage. Fixed orthodontics will be the treatment plan with the extraction of first premolars to solve crowding or to retract the anterior protrusion in upper arch. Canine retraction with split mouth technique, using continuous and interrupted force, by NiTi coil spring and lacebaks respectively. Superelastic NiTi closed-coil springs generating 150g of force will be used on one side (continuous force group). Superelastic NiTi closed-coil springs, will be placed from the first molar to the canine and will be activated for 3 times their original length. Lacebaks made from 0.010 inch ligature wire will be applied on the contra lateral side (intermitted force group). The coil or the laceback allocation will be randomly decided. The closed coil springs will be controlled and lacebacks will be reapplied at each appointment. Upper and lower impressions will be taken before retraction and after space closure to clinically evaluate the rate of space closure. Cone beam computed tomography will be taken before and after retraction to compare the position of the canines and the anchor tooth in three dimensional measures. Results The rate of retraction of the light continuous force (Niti coil spring) is faster than the intermitted force (laceback) Less control with the coil spring, which cause more canine root tipping and rotation. The lace-back retracts the canine in a slower rate but with less tipping and rotation of the canine. Anchorage control is better with the lace back group. 2.Conclusion: the laceback retraction shows more control less anchorage loss but slower than the continuous force