September 21, 2020

What are the complications of Class II malocclusion treatment?

There are many ways to treat Class II malocclusion in adolescents.  They all seem to have similar effects. But do some have more and different complications?  This intriguing new systematic review provides us with great information for our patients.

Class II malocclusion may be treated in many ways. Investigators have done a large number of trials into the effect of functional appliances.  When we evaluate this work, we can divide these into removable or fixed appliances.   Interestingly, when investigators have used traditional orthodontic outcomes, for example, cephalometrics or measures of occlusion, there are minimal differences between interventions. However, there is an increasing amount of information on other effects that are particularly relevant to our patients. These include discontinuation rates, pain and perceptions of treatment.  These investigators did this review to evaluate these results.

A team from the London Hospital, in the East End of London did this review. The AJO-DDO published the paper.

What did they ask?

They wanted to find information on:

“The compliance and patient experiences during the wear of Class II correctors.”

What did they do?

They did an excellent systematic review of the literature. They followed the standard steps of electronic and hand searching, identification of the papers, assessment of Risk of Bias and extraction of data.

The PICOS for the review was:

Participants: Orthodontic patients less than 18 years old with Class II malocclusion.

Intervention: Treatment with a Class II appliance

Comparison: A comparison or control group was not essential

Outcomes: Prevalence of emergencies and complications. Patient experiences and oral health quality of life.

Study design: RCTs, CCTs, observational cohort and prospective case series (>10 patients).

They evaluated bias with the Cochrane Risk of Bias tool for the RCTs and the Newcastle-Ottowa Scale for the other studies.

Importantly, they decided to carry out a meta-analysis that only included studies with low or unclear risk of bias.

What did they find?

They found a total of 27 unique datasets.  Of these, 9 were RCTs, 6 were controlled clinical trials, 1 was a prospective case series, 8 were prospective observational studies, and 3 were qualitative studies. Interestingly, they pointed out that nearly all the studies were done in a hospital or dental school setting.  They identified data from 1676 participants, and most were treated with some form of functional appliance.  They divided these into 682 removable functional appliance patients and 682 fixed functionals. The remaining patients were treated with headgear (186) and the Carriere (42) appliances.

When they looked at the risk of bias for the randomised trials. They found that only 1 study was low risk, 2 were unclear, and 6 were high risk.  For the non-randomised studies, they felt that 6 were low and 9 were moderate quality.

They decided that 12 of the studies could be used in the meta-analysis.  This included 3 RCTs, 1 cohort, 3 CCTs, I cross-sectional and 1 case-control study.  They selected these based on their quality in terms of risk of bias.

They provided a large amount of data. I am only going to mention what I felt were the most clinically relevant findings.

These were:

  • They found that complications were high in fixed and hybrid functional appliances (69%) when compared to removable functionals (34%).
  • The mean number of emergencies for removable appliances was 0.8 (95% CI= 1.1-1.2) and 2 (95% CI=0.9-2.0) for fixed functionals.  However, heterogeneity was high at 88% for removable and 94% for fixed.
  • Treatment discontinuation was higher for removable appliances at 35% (95% CI= 28%-42%) compared with fixed designs at only 1% (95% CI= 1%-10%).  Again, the heterogeneity was moderate being between 34% and 66%.
  • In general,  the qualitative studies reported a significant negative impact with removable functional appliances.
What did I think?

I thought that this was an ambitious and complex systematic review. Importantly, they looked at the effects of treatment from a patient’s point of view.  This approach is refreshing because these findings are more useful than the endless analyses of cephalometrics and occlusal index scores.  As a result, this study adds to our knowledge.

When I looked at the findings, I thought that they were clinically valid. In many ways, it not surprising that the failure rate of removable appliances appears to be associated with negative impacts on quality of life.  It is also a common clinical experience that there are more complications with fixed functional appliances.  However, I did not appreciate the marked difference in failures until now.

I also felt that it was good to see a team of reviewers identify several studies and then exclude a fair number, because of a high risk of bias or low quality.  This is markedly different from the current trend in orthodontic systematic reviews to include everything that they find in a meta-analysis regardless of quality.  Importantly, they also highlighted the heterogeneity in their results and explained how this influences the uncertainty in the data.

Final comments

I suggest that as many people as possible read this paper. It is an addition to the literature and is relevant to all practitioners and trainees.

Finally, this study provides us with useful clinical information on the various risks and benefits of the types of Class II appliances. We can use this as part of our consent process.

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Have your say!

  1. Dear Dr Brian
    Though I agree that the study was patient centric aren’t the clinical relevant findings very obvious ones namely that complications are more with fixed functional appliances and compliance is poor with removable functional appliances as compared to the fixed functional appliances . I feel the study doesn’t add much to what we already know.
    Always enjoy and look forward to your blogs
    Dr Rekha Sharma

  2. The term “functional appliance” is an historical misnomer. The key element of all these appliances is that they arbitrarily reposition the mandible forwards in pediatric cases. In that way, they are simply mandibular advancement devices, similar to those used in adults for the treatment of mild-moderate obstructive sleep apnea. The difference is that the mandible is undergoing active growth in younger patients so, presumably, it grows into its new forward position, especially when using fixed ‘functional’ appliances since it is not free to move back, as predicted by the spatial matrix hypothesis. There is nothing “functional” in that mechanism.

  3. Dear Prof O’Brien

    In all but one of the studies (reference #31) cited in this review’s bibliography, the average age when having initiated Tx was above 10 years old and thus these kids’ class II skeletal retrusive phenotypes, and likely also their often-associated (w/DX: Cl II) transverse deficiencies, had been untreated/ignored (?) for several years since when first recognizable within their late primary/early mixed dentitions, McNamara, Bishara and others have documented that once a Class II skeletal is identified/Dx’d under the age of 6 years, it will always persist (i.e., not self-correct) beyond, and usually worsen without some sort of intervention. Retrognathic mandibles (i.e., 85-90% of all skeletal class II’s according to McNamara, are NOT maxillary protrusive) and bi-maxillary transverse deficiencies are also often co-morbidities with sleep and breathing problems; might you consider sir that the poor QOL and poor compliance observed in these late-treated adolescent patients might very likely have been consequential to associated with systemic co-morbidities (e.g., sleep and breathing hygiene problems)? Also please consider that pre-school/primary school-age children tend to be much more compliant and cooperative for orthodontic Tx when/if the provider understands/knows how to manage child-parent expectations, fears and anxieties that are sometimes associated with early interventions. As a pedodontist, I had received excellent training in orthodontic/dentofacial orthopedic assessment/diagnosis, cephalometrics and G&D from Samir Bishara(RIP),Tx mechanics/execution at the Univ of Iowa in the late 1980’s. I also had intensive didactic and clinical experiences in child development and behavior guidance from the Pedodontic faculty. Unfortunately these child management opportunities are seldom available to post-graduate orthodontic trainees. This void in the PG ortho curriculum seems to imply that these skills will not ever be necessary after graduation because orthodontic/dentofacial orthopedic intervention treatments are seldom, if ever, indicated before the average ages of the adolescents studied in this review.

    Prof., I think you are in optimal position per your global reputation for ‘wanting to do what’s best and scientifically supported for the most number of your patients and students. As prospective and blinded RCT’s were not even considered until shortly after WW II per the war atrocity Trials at Nuremburg, etc., please consider as being ‘scientific’ some of the published controlled ‘observational’ studies that support earlier intervention as being often therapeutic beyond straightening of the teeth. The Theory of Relativity, importance of handwashing prior to knowledge of Germ Theory/the microscope, prevention of Cholera, etc. had all been accomplished by data gleaned from controlled observational studies. Maybe it’s time that you and some of those of whom so highly respect you, consider reading some of these papers? Maybe start with one that is local to you that’d occurred near to you; the book ‘The Ghost Map’ (by Stephen Johnson) which discusses how Dr. John Snow, a British anesthesiologist, had used data derived from a very careful controlled observational trial to figure etiology of the mid 19th-Century Cholera epidemic near the Smithfield Market (Broad Street pump).

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