Active tie back also known as Berman tie consists of elastomeric separator or module connected to a posted or crimpable hook via long ligature wire.
Maurice Berman came first with this idea but it was then promoted by the MBT group as low cost and faster way of closing space with less anchorage loss.
Evidences about mechanics of space closure
A. NITI coil spring vs tie back in enmass space closure (Samuel 1993)
There was no difference in tooth position produced by the two systems after space closure but spring is generally better than active tie. There was also no evidence of greater patient discomfort with the springs.
B. Heavy vs light NITI coil spring in enmass space closure (Samuel 1998)
The effectiveness of 150gm and 200gm spring are the comparable but 100gm spring is less effective.
C. NiTi coil spring vs power chain elastic (PCS) vs active tieback in enmass space closure (Dixon and O’Brien 2002)
Coil spring closes space faster than other methods per unit time. For example, the time required to close a 6 mm extraction space would be on average 17 months using an active ligature, 10 months using elastic chain and 7.5 months with coil spring.
D. NITI coil spring vs PCE in enmass space closure (Nightingale and S. P. Jones, 2003)
The rates of space closure achieved with elastomeric chain and nickel titanium coil springs were similar. However, one might well disagree with the conclusion that there is no clinical significance in a difference between 0.84 mm/month closure with elastic chain and 1.04 mm/month for NT coils. This difference of 0.2 mm/month may not sound much, but would equate to 11.4 weeks difference in the time required to close a 6 mm space.
E. NiTi coil springs vs Class II elastics in canine retraction (Sonis 1994)
NITI coil springs produces twice rate of tooth movement per unit time compared to Class II elastics of the same force level.
F. NiTi Coil Springs vs. active tie Elastics in Canine Retraction (Sumaya 2011)
Generally, NITI coil spring is better than active tie.
NiTi spring vs PCE in enmass space closure (Hisham & Almuzian, 2018/ meta-analysis)/ updated review will be published soon!
Based on limited number of studies with moderate quality, a fast but small space closure can be achieved using NiTi coil spring when compared to PCE, the mean difference is around 0.2 mm/month in the favour of the former.
Hope this helps.
What do you think?