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A clinical comparison between nickel titanium springs and elastomeric chains.

OBJECTIVES
To compare the rates of maxillary canine retraction and molar anchorage loss when using either NiTi springs or elastomeric chains delivering a known force with sliding edgewise mechanics.


METHODS
Twelve patients who required maxillary canine retraction into first premolar extraction sites as part of their orthodontic treatment were selected. In a split-mouth design, these patients received precalibrated NiTi springs (112 quadrants) and pre-measured elastomeric chains (12 quadrants), all delivering initial forces of approximately 200 g and being reactivated at 28 day intervals. Space closure and forward movement of the maxillary first molars were evaluated using maxillary impressions, which were taken before the start of canine retraction and then at 28 day intervals until canine retraction was almost complete.


RESULTS
Statistical analysis revealed that the mean rate of space closure with NiTi springs (1.85 mm/month) was only 0.17 mm/month greater (p = 0.011) than that produced with the elastomeric chains (1.68 mm/month). The mean rates of anchorage loss for the NiTi springs and elastomeric chain were 0.46 mm/month and 0.45 mm/month respectively. This difference was not statistically significant. These amounts of forward molar movement were calculated to be between one quarter and one third of the average space closure per month, even in the presence of a fixed transpalatal arch.


CONCLUSION
The results indicate that the rates of space closure and molar anchorage loss using either NiTi springs or elastomeric chains, if reactivated every 28 days, are likely to be similar.