Are Bonded retainers better than vacuum-formed retainers, a new RCT?
In the last decade, researchers have done several clinical trials and systematic reviews to understand the short-term effectiveness of different retention regimes. One of the significant questions that they are trying to answer is the comparative efficacy of bonded and vacuum-formed retainers. A recent study has investigated this issue in detail.
I have written several blog posts about retainer research, and after reviewing various papers, it appears that there are not many significant differences between the two main types of retainers. Therefore, when deciding on a retention regime, it is important to take into account the patient’s preferences. A new paper supports this conclusion.
A team from Brazil and Michigan, USA, did this study. Orthodontics and Craniofacial Research published the paper.
Silvio Augusto Bellini-Pereira et al
Orthodontic and Craniofacial Research: Advanced access. DOI: 10.1111/ocr.12753
What did they ask?
The aim of this study was to
“Compare the clinical effectiveness of V Bend bonded retainers versus Vacuum formed retainers (VFRs) regarding their capacity to maintain treatment stability and survival rates after 12 months”.
What did they do?
They did a single centre 2-arm parallel-group RCT with a 1:1 allocation ratio. The PICO was
Completed orthodontic patients with a satisfactory occlusion at the conclusion of their treatment. They had treated the patients with any form of orthodontic treatment.
V Bend Bonded retainers to the maxillary and mandibular teeth.
Maxillary and mandibular vacuum formed retainers. They asked the patients to wear the retainers at night only.
The study’s primary outcome was the change in Littles Irregularity Index. Other outcomes included changes in arch dimensions, overjet, overbite, and participant interviews about removable retainer wearing time.
The team collected data from scans of the teeth at the time of fixed appliance removal (T0), and after 3 months (T1), 6 months (T2) and 12 months (T3).
Before beginning the study, they conducted a sample size calculation that indicated a need for 17 patients in each group. To compensate for potential dropouts, they increased the sample size to 25 patients for each group..
Importantly, the study was conducted well, using a pre-prepared block randomization method and opaque envelopes to conceal the treatment allocation. An independent operator was responsible for opening the envelopes immediately before allocating retainers. All stages of the randomisation and allocation process were carried out by this operator.
Their statistical analysis was relevant to the study design and the data.
What did they find?
The team enrolled 50 patients into the study. No patients dropped out and they were all analysed.
At the start of the retention, there were no differences between the groups of patients.
There were no differences in any outcomes up to 6 months after placing the retainers.
At 12 months, the only significant differences were in the Little’s Index scores for the upper and lower arches.
|Vacuum formed retainer
There were no differences in the retainer’s survival rates after 12 months.
They pointed out that even though the VFs were less effective, no patient had a LII greater than 2mm after 12 months. As a result, both retainer regimes were effective.
Their final conclusions were;
“Bonded retainers were more effective in maintaining the alignment of the incisors compared to vacuum formed retainers after 12 months”.
What did I think?
The study’s results were consistent with other research, showing that although there were variations in relapse, they had no significant clinical impact..
The study also revealed that only 40% of the participants wore their VFRs for the recommended duration. This could account for the differences in relapse observed after the 12-month period.
Importantly, the authors of this study stated that they will track these patients for another five years, providing valuable insights into long-term maintenance.
It seems that this paper supports the widely accepted belief that there are only slight variations in the effectiveness of different retention methods. Therefore, I think we can use this knowledge to involve our patients in selecting their own retention treatment. This would be an excellent example of implementing evidence-based healthcare practices.
Emeritus Professor of Orthodontics, University of Manchester, UK.