November 01, 2021

What is best for orthodontic space closure? Ni-Ti, Power Chain or active ligatures?

Space closure following extractions significantly contributes to treatment duration.  We use several methods of applying force to close space. But which is best?

When we commit the crime of tooth amputation (extraction of teeth), we need to close any residual spaces.  Most of the time, we use sliding mechanics or staged retraction of canines.  When we are space closing, we need to decide on the best method of applying force.  This new systematic review looks at the effectiveness of closed Ni-Ti spring, power chain, or active ligatures.

A team from Chennai did this study. The European Journal of Orthodontics published the paper.

Orthodontic space closure in sliding mechanics: a systematic review and meta-analysis

Biju Sebastian et al.  Ejo advanced access. doi:10.1093/ejo/cjab047

What did they ask?

They wanted to

“Compare the difference forces delivery systems for space closure during orthodontic treatment in terms of several different clinical outcomes”.

What did they do?

They did a systematic review. So, in effect, this was an update of a systematic review that I posted about several years ago.

The PICO was

Participants: Orthodontic patients of any change treated with fixed appliances and needing space closure.

Interventions: Space closure with Ni-Ti coil springs, elastomeric chains, NiTi coil springs

Comparison: All methods of applying force in space closure.

Outcomes:  Primary outcome was the rate of tooth movement measured in mm/month. Other outcomes were pain/discomfort, perio effects, etc.

The authors did a standard systematic review with electronic and hand searches, papers’ identification, selection criteria’s application, data extraction, assessment of bias, and relevant meta-analysis.

In addition to carrying out a traditional meta-analysis of trials using similar outcomes. The authors decided to do a network meta-analysis to make indirect as well and direct comparisons of studies.  Finally, they used the GRADE approach to classify the strength of evidence.

What did they find?

The investigators presented a large amount of data and did several meta-analyses. Unfortunately, I do not have the space to look at all these here. But the main findings were.

They divided the results up into split-mouth and parallel-group studies.  Their final selection of papers included 13 RCTs. Of these, seven were split-mouth, and six were parallel-group.

Parallel group studies

  • Ni-Ti coil springs were better than the power chain with a mean difference of 0.24mm/month (95% CI= 0.003-0.45).
  • Ni-Ti springs closed space faster than active ligatures by 0.53mm/month (95% CI=0.44-0.63).

Split mouth studies

There were no differences between the interventions.

Finally, the Network Meta-analysis showed similar results.

  • The Ni-Ti springs performed better than the active ligature by 0.42mm/month (95% CI= -0.57, -0.28)
  • The Ni-Ti was better than the power chain with a mean difference of -0.17 (95% CI= -0.29, -0.05).

When the investigators looked at the overall quality of the evidence, they felt that the level of evidence was moderate.

They concluded:

“There is moderate certainty evidence favouring the use of Ni-Ti coil springs for space closure when compared to active ligatures and low evidence when compared to power chain”.

What did I think?

This study was a carefully done systematic review that followed a standard methodology.  The findings suggest there may be some advantages in terms of the rate of space closure when using Ni-Ti coils. Nevertheless, you now need to decide whether these differences are clinically significant.  When you do this, have a look at the 95% Cis. You will see that they are very close to containing zero.  From this, I think that the differences are not clinically significant even though they are statistically significant.

We also need to consider these findings considering the certainty of evidence. This is moderate to low. As a result, I conclude that there is minimal difference between the methods of applying space closing force.  I feel that our decision on which one we use should be based on our personal preference.  Personally, I do not like using power chains because they are plaque traps, and I hate it when you remove them, you get a “plaque shower”. I also do not like active ligatures because they need changing. So, I would continue with the Ni-Ti springs because they are easy to use and relatively hassle-free.



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Have your say!

  1. Hello Mr O’Brien
    Thank you for a wonderful occasionally irregular blog. Its my goto space when I want to find some intelligent answers. I have always believed that constant retraction force like a NiTi coil spring would not give the incisors adequate chance to express the torque in the slots and therefore the incisors would to some extent tip backwards. If that is an objective then there is no problem but if the angulation of the incisors must not be allowed to change during space closure I have believed that a rest period of approximately 2 weeks would allow that to happen to some extent. I lightly activate space closure mechanics every 5 weeks which in my opinion allows root torque to express itself between activations and found that I got less tipping of the incisors than if I activated more frequently. Was there any mention of loss of torque of the incisors in this study when using NiTi coil springs compared to for example active ligatures?

  2. As it was my research thesis, Out of these niti spring is much better and if we compare niti spring and SS spring then ss spring is much cost efficient and rate of space closure is much.

  3. Niti springs more often irritate gingiva and rather i found more debris accumulation.

  4. The No-Ti Springs do mot give the .20 SS wire long enough time to express itself to up Wright the root. Can cause the root move outside the alveolar housings. The ligature tie backs are slower but allows for the translation of the tooth.

  5. I much preferred power chain. It worked well, took seconds to change and the patients OH was good or bad whichever method one used.

    • Let us not forget the basics of sliding mechanics. The arch wire needs to be stainless steel. When you apply a retraction force the initial movement is that of tipping until the diagonal edges of the bracket contact the arch wire. This is when tipping stops and uprighting begins and it happens due to the stiffness of the stainless steel wire. If the force is continuous such as with a niti coil spring then chances of binding is high and tipping is more. ATB’s allow for uprighting and they need to be changed every so often but not at every subsequent appointment. According to me what is best for orthodontic space closure, I think it is ‘Time’, you need to apply a force and give it time to allow the teeth to upright and the forces need to be optimal, unless otherwise we have a method to apply apply a force through the centre of resistance of a tooth which would be perfect. If you rush it you would see tipping, binding, arch wire bending in the extraction space (row boat effect), root and bone resorption etc, as the basic laws of physics and biomechanics do not change whatever be the material we use.

  6. Does anybody use closing loops any longer? I have experimented with all sorts of different space closing approaches over my 40+ years in our wonderful profession. I have always came back to closing loops as my preferred approach. Specifically preformed T loops. Sometimes old school is the best school IMO.

  7. I was unable to access the full paper but here are some questions and comments.
    1) Here, Portland Oregon, the home of Alastiks, the originator of elastic modules for orthodontics, we have been using power chains from their introduction. What power chains were used ? It is documented that there are differences in decay rates of chains depending on manufacturer, whether colored or not, latex or not, and especially how fresh they are. (We would store them in a fridge till needed)
    2) Comments about plaque accumulation are relevant but NI-TI springs can also accumulate plaque and can irritate the gingiva as mentioned.
    Here at OHSU we used to use KX modules from molar hook to arch wire hook (they did not go around each bracket as chains) Power chain can also be used in a similar way from hook to hook (not around brackets) with the middle section attached to brackets with light ligatures to keep them away from the gingiva. Power chain can also be doubled up. There are many possible ways to use them.
    3) Were the arch wires used in this study the exact same size and material in all groups ?
    What it boils down to is personal preference .

  8. Agree with Dr. Srinivasa, Faster is not always better, the elements of the force system need time to recover before repeated activation. NiTi coils provide continues force with no recovery which can, and often does, lead to undesirable events: such as: vertical and horizontal arch wire distortion, tipping and loss of torque control of the. anterior segment and increase in the overbite all of which add to treatment time. I say this having experienced same when, experimenting with coil use, my patient went to visit his grandmother and did not return for 3 months. “An ounce of prevention is worth a pound of cure” so said our friend Ben Franklin.

  9. Been in Active clinical practice for 5 Decades…I second the opinion!
    Even in TAD supported Retractions ( which I do a whole lot) the NiTi springs are the preferred choice…even there the final mm closure is with a ‘closing loop’ AW to get that final contact at the extraction site! Nothing is better…old practices are still platinum
    Cheers and Regds

  10. When looking at spaceclosure I do not look at the crowns but more important is the position of the roots.I used 16-16 beta titanium segmented arches in a 18slot-system with power-chains. when space was closed I activated the wire with a tipback to move the roots of the canines.Using segmented arches and low forces prevented the extrusion of the incisor-segment following the bending of the archwire and tipping-movement of the canines. I found great variation in spaceclosing time because force and friction are only part of the game. Occlusal interference and the bonesituation especially when you close the space for a missing second bicuspid in the lower arch are of more importance. So I used Biteplates in the upper arch when closing space in lower arches.

  11. NiTi springs, elastomeric chain and active ligatures have been around for decades. Orthodontic researchers have also been around for decades. I cannot understand why our profession has no definitive answer to this and other simple questions. They know how to do the study, so why has no academic team yet delivered the answer.

  12. If you had to pay for your Niti pushcoils out of your own pocket Prof, you’d take the powerchain plaque shower 🙂

  13. O’Bie is trying to sell Niti coil springs, eh? JK 😉
    I always felt that Niti springs were somewhat overly effective. I did once have a nice molar rotation thanks to using a short one pitted against a canine. It was one of my very first cases that flared up and regretfully caused me to shift to the albeit less efficient, more appealing, plaque-showering donut chains. I guess I could revisit this again now with stronger evidence.

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