A massive cochrane systemic review tells us a lot about class II treatment

This is an update regarding the Cochrane systemic review we covered in a previous post on Class II malocclusion in children and its treatment comparisons with that achieved in adolescence.

Class II malocclusion develops with the precocious eruption of a child’s permanent teeth. This is when they are referred to an orthodontist for treatment using dental braces to reduce the protrusion and subsequent prominence of the teeth.

Treatment is initiated early on due to the absurd appearance of these teeth in the mixed dentition period which causes significant distress in growing children. Additionally, these teeth also have a higher tendency for injury.

When children are brought in for treatment at a young age, the orthodontist is faced with a moral deadlock between treating them early and waiting until the child is older to treat them then.

This Cochrane review update fills us in on the new knowledge we have retrieved regarding orthodontic treatment for Class II malocclusion and its effectiveness guarded by age.

As I mentioned before, Cochrane reviews are kept up to date consistently as new leads in research are discovered. It is this that allows Cochrane reviews to be comparatively superior to static conventional literature.

This study

“Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents”

Was conducted by Klaus BSL Batista, Badri Thiruvenkatachari, Jayne E Harrison, and Kevin D O’Brien, a team of researchers from Manchester, North of England, and the paper was published in the Cochrane Database of Systemic Reviews.

What they asked

The authors tried to answer these three main questions:

  1. What are the effects of treatment provided in 1 or 2 phases (early vs adolescent)?
  2. What are the effects of later treatment with functional appliances vs untreated controls?
  3. Are there any differences in the effects of the various types of functional appliances?

What they did

They followed standard Cochrane methodology and only included randomised trials in the review.

The PICO was:

  • Participants: Children receiving orthodontic treatment in order to correct prominent upper incisors.
  • Intervention: Any type of functional appliance
  • Control: Delayed or no treatment or other functional appliance
  • Outcomes: Primary outcome was overjet. Secondary outcomes were skeletal relationships, trauma, and self-esteem.

Standard electronic and relevant hand searches were conducted. The trials for bias was also evaluated using the Cochrane Risk of Bias tool.

What they found out

The review included 27 studies with data derived from a total of 1251 participants, out of which:

  • 4 trials looked at early treatment for children aged 7 to 11 years old.
  • 20 trials evaluated the treatment of children aged 10 to 15 years old.
  • 7 trials evaluated the treatment of children aged 9 to 13 years.

These studies were then divided into two main groups:

  • Group 1: Studies that looked at early treatment (two-phase) and followed the participants until all treatment was completed when they were older.
  • Group 2: Studies of later (adolescent) treat,ent (one-phase).

They discovered that most of the studies were rated as high or unclear risk of bias, which mainly stemmed from issues with blinding, concealment allocation, and randomisation. Another main reason for attrition bias was due to “drop-outs”.

The main findings of this study were:

Early treatment:
When the treatment was provided early on to the children with Class II malocclusion, the only effect of the treatment was a 12% reduction in the incidence of incisal trauma.

At the end of all treatments, 19% of the early treatment group were found to have experienced trauma. On the other hand, 31% of those that did not partake in the early treatment group experienced trauma.

There were no effects of early treatment on the final occlusion, self-esteem, and skeletal pattern.

Adolescent treatment:
Functional appliances were successful in reducing the overjets of these patients. Interestingly enough, removable functional appliances statistically reduced the ANB by 2.37 degrees (95% CI 1.7 – 2.37).

The use of fixed functional appliances did not have any significant effect.

Furthermore, only minor differences were discovered between the Twin Block and other functional appliances.

My thoughts

As with the previous review, I thought that this one was also well-put-together. However, again, there are several important points to consider. Firstly, when they assessed the study with the risk of bias tool, they identified multiple biases. This meant that the quality of evidence for the main findings ranked low (some were also ranked moderate).

There was also a strong effect caused by the attrition bias. However, this is an unfortunate reality for most orthodontic studies that operate on the basis of prolonged treatment durations and difficult long-term patient recalls. Nevertheless, this presents a significant problem which is why we need to discern the findings accordingly.

Most importantly, though, we found out that there was a reduction in trauma with early treatment. The quality of evidence here was moderate. Despite this “good” finding, we must remember that even when treatment was started early on, 19% of the treated children still suffered some sort of incisal trauma. It is not a full-proof solution but interesting, nonetheless.

The adolescent treatment data was also clinically relevant. It is also important that you look at the effect sizes fro the study. For instance, the removable functional appliance reduced the ANB by 2.4 degrees (low strength of evidence). It is you who must decide if this is clinically significant.

Final thoughts

We can confidently conclude that functional appliances are effective at reducing overjets, mostly as a result of tooth movement. The skeletal changes were very small. Overall I feel that Cochrane is a reputable journal site and their reviews are very high-standard so this study was worthwhile.

We can take away these points from this complex study:
Early treatment results in a reduction in incisal trauma, but it does not eliminate trauma.
There is an absence of evidence on any other benefits of early treatment.
Adolescent treatment with functional appliances reduces overjets. There are minimal differences between appliances.

Cochrane Database of Systemic Reviews: doi.org/10.1002/14651858.CD003452.pub4

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