Class II correction: A matter of timing?
There is no question that the use of headgear is declining internationally. This trend relates to the advent of novel approaches with a reduced onus on compliance. My use of headgear has also reduced. I now have an ‘annual headgear fit’ as a teaching exercise with our postgraduate students. We do know, however, that headgear can be incredibly effective and versatile.
While many are resigned to the fact that compliance with headgear is often suboptimal, is the effectiveness of headgear-activator combinations influenced by age or the stage of dental development?
This study carried out in Malmo was designed to answer this question. The European Journal of Orthodontics published this study.
Authors: Jenny Kallunki, Lars Bondemark and Liselotte Paulsson
Eur J. Orthod. 2021. doi: 10.1093/ejo/cjab026
What did they do?
They did a randomised controlled trial involving 56 participants.
Participants: All participants were aged 9 (±1) years at the start of the trial. They were in the mixed dentition and had an increased overjet (of 6mm or more) with the first molars at least half cusp Class II bilaterally.
Interventions: They randomly allocated the participants to start headgear-activator treatment either in the mixed dentition (MD group) or late mixed dentition (LMD group) at 9 or 11 years old. One orthodontist carried out all of the treatment. They defined success by full overbite and overjet reduction and molar correction. Importantly, they defined failure as a lack of full correction or discontinuation due to poor compliance.
They used a modified headgear activator with a postured bite taken in an edge-to-edge relationship in both groups, with high-pull headgear attached to flying tubes to allow delivery of 400g of force bilaterally. They asked the participants to wear the appliance for 10–12 hours per day and reviewed them at 8-weekly intervals. The clinicians retained the occlusal correction by using the headgear activator as a night-time retainer for six months.
Primary outcome: Cost comparisons
Secondary outcomes: They also measured OHRQoL, dental and skeletal treatment effects, lip competence, and incisal trauma
What did they find?
In the early (MD) group, the mean active treatment time was 1.1 years, with discontinuation of treatment in 8 of the 30 participants (27%). In the LMD group, the average treatment time was marginally longer (1.2 years), with 6 out of 21 (29%) failing to complete treatment. They observed no significant differences between the groups for either treatment time or unsuccessful therapies. Similarly, the authors found no difference between the groups concerning the number of appointments (approx. 10) or chair time (approx. 4 hours) in each group.
The mean societal costs were also similar in both groups (at approx. 2,000 to 2,200 euro). During treatment, lip incompetence reduced from 67% to 27% in the MD group and 43% to 10% in the LMD group. Before treatment in both groups, the prevalence of dental trauma was high (MD= 20%; n= 6; LMD= 38%; n= 8), although only three further episodes occurred during the study period.
What did I think?
I thought that this was an innovative and exciting study. The authors essentially evaluated the effect of treatment timing on the effectiveness of Class II correction in pre-adolescence and pre-pubertal children.
Overall, the results are unsurprising. The intervention worked reasonably well both at age nine and age 11. Nevertheless, a significant proportion of the participants (27% to 29%) did not have a successful outcome. This finding mirrors previous randomised controlled trials evaluating the effectiveness of Class II correction using alternative means.
The study was a significant undertaking with recruitment spanning six years. The authors did the study well and reported in line with accepted guidelines. Some may contest the decision to define the ‘mixed dentition’ and ‘late mixed dentition’ purely on chronological age. We know that gender-related differences do exist, and these were not accounted for. Similarly, I could not see how they defined these stages. Still, I assume ‘late mixed dentition’ represents a stage when the first premolars have erupted with the second primary molars retained.
The economic evaluation was also an interesting aspect to consider. This data is of particular relevance to the provision of orthodontics in countries with publicly funded systems. These will also vary considerably internationally. Undeniably, the mean societal cost of 2,000 to 2,200 euro is considerable, particularly given that the intervention is often followed by fixed appliance therapy. It would be interesting to see whether any difference between the mixed dentition and late mixed dentition groups emerges after completing fixed appliance therapy.
The relevance of the findings
I mentioned at the outset that I now rarely use headgear. I, therefore, also very infrequently use headgear-activator combinations. It may be that the intervention evaluated in the study is used less frequently internationally. Nevertheless, the study is interesting. It may be possible to apply some of the findings to other functional appliances (and indeed to the use of functional appliances or headgear alone). It is worth noting that the mean overjet reduction in both groups was limited (2.8 to 3.5mm). This effect may reflect the mild nature of some of the participants (with a threshold overjet of 6mm being included) and the failure rate due to non-compliance.
What can we conclude?
The authors found that the costs and effects of headgear treatment used at either 9 or 11 years were similar. As expected, most of the changes observed were dento-alveolar, with no significant difference observed between intervention in the mixed and late mixed dentitions stages concerning the quality of life, lip competence, and incidence of trauma. Therefore, based on this study, the timing of Class II correction might matter little in the growing child.
Professor of Orthodontics, Queen Mary University of London, UK