Do we need to retie ligature ties on aligning wires every 4 weeks?

In an ideal orthodontic world, we would see our patients every 4 weeks to tighten ligature ties. However, this is not always possible, and the interval sometimes increases to between six and eight weeks. I used to wonder whether this would affect the efficiency of tooth movement, particularly alignment. This issue has been examined in this new randomised controlled trial. 

I thought this study was interesting because it evaluated a real-world clinical problem in a well-conducted small study. 

A team from India did this trial. The Angle Orthodontist published the paper. 

What did they ask?

The aim of their study was to 

“Evaluate whether replacing stainless-steel ligature ties at each recall visit significantly enhances the efficiency of anterior de-crowding compared with maintaining the same ties throughout.” 

What did they do?

They conducted a prospective, single-blind, parallel-group randomised controlled trial. They registered the trial before the study began. 

The PICO was 

Participants:

Orthodontic patients aged 16 years or older, in good health, with moderate-to-severe anterior crowding who required premolar extractions. All received pre-adjusted edgewise braces. 

Intervention.

In this group, they did not replace the ligature ties at recall visits until they had resolved the anterior crowding. 

Comparator: 

In this group, they replaced the ties w at every 4-week recall visit. 

Outcomes:

The primary outcome was reduction in anterior crowding using Little’s irregularity index. They measured this from study casts for the initial study models and at each follow-up visit.

They calculated that they needed 12 patients in each group, but I couldn’t find any information about the expected difference used to determine this number.

Patients were randomly assigned to each group with a 1:1 ratio using an online tool. They kept the allocation by placing it in sealed envelopes.

Both the participants and the clinicians knew which group the patients were in. The data on Little’s Irregularity Index was collected using digital vernier calipers. 

What did they find? 

They enrolled 24 patients into the study. They excluded one participant because of repeated failures. 

There were no differences between the groups at the start of the study. 

When they examined the mean duration required for complete alignment of the anterior teeth, it was 68.73 ± 29 days in group 1 (ligature ties not replaced) and 65.33 ± 24.85 days in group 2 (ties replaced at each visit). This difference was not statistically significant. 

Their most important conclusion was:

“Replacing stainless steel ligature ties at each recall visit does not result in a clinically significant acceleration of anterior alignment during the initial phase of orthodontic treatment. Scheduling recall visits every eight weeks may increase efficient time management during the alignment phase.” 

What did I think? 

I always enjoy reading clinically relevant studies. The team conducted this study well, and it met most of the criteria for a good randomised clinical trial. My only concern is familiar to regular readers: this was a single-centre study restricted to the initial alignment phase, with a relatively small sample size. The findings may also be relevant only to extraction cases. 

One piece of information missing from this study was any reporting of treatment side effects. For example, did patients who were not seen every 4 weeks have more problems with archwires poking through the molar tubes? 

Nevertheless, the findings are interesting and may reflect our regular clinical experience. They certainly provide reassurance that it is possible to leave our patients with fully tied-in ligatures for longer than four weeks. 

It is nice to return to studies about day-to-day orthodontic treatment, and this study is a small addition to our literature.