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.
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.
“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.
Emeritus Professor of Orthodontics, University of Manchester, UK.