***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: AIM To compare the rates of orthodontic space closure for : Active ligatures , polyurethane powerchain ( Rocky Mountain Orthodontics , RMO Europe , Parc d'Innovation , Rue Geiler de Kaysersberg , 67400 Illkirch-Graffenstaden , Strasbourg , France ) and nickel titanium springs . SAMPLE Patients entering the space closure phase of fixed orthodontic treatment attending six orthodontic providers . Twelve patients received active ligatures ( 48 quadrants ) , 10 patients received powerchain ( 40 quadrants ) and 11 patients , nickel-titanium springs ( 44 quadrants ) . METHOD Patients were r and omly allocated for treatment with active ligatures , powerchain or nickel titanium springs . Upper and lower study models were collected at the start of space closure ( T(o ) ) and 4 months later ( T(1 ) ) . We recorded whether the patient wore Class II or Class III elastics . Space present in all four quadrants was measured , by a calibrated examiner , using Vernier callipers at T(o ) and T(1 . ) The rate of space closure , in millimetres per month ( 4 weeks ) and a 4-monthly rate , was then calculated . Examiner reliability was assessed at least 2 weeks later . RESULTS Mean rates of space closure were 0.35 mm/month for active ligatures , 0.58 mm/month for powerchain , and 0.81 mm/month for NiTi springs . No statistically significant differences were found between any methods with the exception of NiTi springs showing more rapid space closure than active ligatures ( P < 0.05 ) . There was no effect of inter-arch elastics on rate of space closure . CONCLUSIONS NiTi springs gave the most rapid rate of space closure and may be considered the treatment of choice . However , powerchain provides a cheaper treatment option that is as effective . The use of inter-arch elastics does not appear to influence rate of space closure A split-mouth r and omized clinical trial was used to determine whether ion implantation of beta-titanium archwire would facilitate sliding space closure .  After bilateral maxillary first premolar extraction s , 0.19 x 0.025-inch beta-titanium arch wires , ion-implanted on one half only , were placed in 30 subjects aged 10 to 42 years wearing unimplanted 0.022 inch slot appliances .  Nickel-titanium springs ( 150 g ) were placed bilaterally to close the extraction spaces . Space closure was measured intraorally at monthly intervals until either the space on one side closed or 6 months had elapsed . The median rates of space closure were not significantly different between the ion-implanted and the unimplanted sides . The average rate of space closure on these beta-titanium wires , with or without ion implantation , was similar to the rate reported on stainless steel arch wires OBJECTIVE To investigate the force retention , and rates of space closure achieved by elastomeric chain and nickel titanium coil springs . DESIGN R and omized clinical trial . SETTING Eastman Dental Hospital , London and Queen Mary 's University Hospital , Roehampton , 1998 - 2000 . SUBJECTS , MATERIAL S AND METHODS Twenty-two orthodontic patients , wearing the pre-adjusted edgewise appliance undergoing space closure in opposing quadrants , using sliding mechanics on 0.019 x 0.025-inch posted stainless steel archwires . Medium-spaced elastomeric chain [ Durachain , OrthoCare ( UK ) Ltd. , Bradford , UK ] and 9-mm nickel titanium coil springs [ OrthoCare ( UK ) Ltd. ] were placed in opposing quadrants for 15 patients .  Elastomeric chain only was used in a further seven patients . The initial forces on placement and residual forces at the subsequent visit were measured with a dial push-pull gauge [ Orthocare ( UK ) Ltd ] . Study models of eight patients were taken before and after space closure , from which measurements were made to establish mean space closure . MAIN OUTCOME MEASURES The forces were measured in grammes and space closure in millimetres . RESULTS Fifty-nine per cent ( 31/53 ) of the elastomeric sample maintained at least 50 per cent of the initial force over a time period of 1 - 15 weeks . No sample lost all its force , and the mean loss was 47 per cent ( range : 0 - 76 per cent ) . Nickel titanium coil springs lost force rapidly over 6 weeks , following that force levels plateaued . Forty-six per cent ( 12/26 ) maintained at least 50 per cent of their initial force over a time period of 1 - 22 weeks , and mean force loss was 48 per cent ( range : 12 - 68 per cent ) . The rate of mean weekly space closure for elastomeric chain was 0.21 mm and for nickel titanium coil springs 0.26 mm . There was no relationship between the initial force applied and rate of space closure . None of the sample failed during the study period giving a 100 per cent response rate . CONCLUSIONS In clinical use , the force retention of elastomeric chain was better than previously concluded . High initial forces result ed in high force decay . Nickel titanium coil springs and elastomeric chain closed spaces at a similar rate Conventional orthodontic therapy often uses force magnitudes in excess of 100 g to retract canine teeth . Typically , this results in a lag phase of approximately 21 days before tooth movement occurs . The current project was undertaken to demonstrate that by using lower force magnitudes , tooth translation can start without a lag phase and can occur at velocities that are clinical ly significant . Seven subjects participated in the 84-day study . A continuous retraction force averaging 18 g was applied to 1 of the maxillary canines , whereas a continuous retraction force averaging 60 g was applied to the other . The magnitude was adjusted for each canine to produce equivalent compressive stresses between subjects . Estimated average compressive stress on the distal aspect of the canine teeth was 4 kPa or 13 kPa . The moment-to-force ratios were between 9 and 13 mm . Tooth movement in 3 linear and 3 rotational dimensions was measured with a 3-axis measuring microscope and a series of dental casts made at 1- to 14-day intervals . The results showed a statistical difference in the velocity of distal movement of the canines produced by the 2 stresses ( P = .02 ) . The lag phase was eliminated and average velocities were 0.87 and 1.27 mm/month for 18 and 60 g of average retraction force . Interindividual velocities varied as much as 3 to 1 for equivalent stress conditions . It was concluded that effective tooth movement can be produced with lower forces and that because loading conditions were controlled , cell biology must account for the variability in tooth velocities measured in these subjects 
    Output:
    
- The results of clinical research support laboratory results that nickel-titanium coil springs produce a more consistent force and a faster rate of closure when compared with active ligatures as a method of force delivery to close extraction space along a continuous arch wire ; however , elastomeric chain produces similar rates of closure when compared with nickel-titanium springs .
Clinical and laboratory research suggest little advantage of 200 g nickel-titanium springs over 150 g springs .