Growth patterns in identical twins

I was interested in the online case report by Sugawara et al mainly because of their finding that 1-phase and 2-phase results “showed identical dentofacial characteristics,” whereas my own study on 12 identical twins found large contrasts between twins treated with functional orthodontics at a young age and their identical siblings treated at an older age by fixed appliances.

In looking for possible reasons, I see that, in this recent case report, both patients were finished with fixed appliances, as have nearly all previous group comparisons of 1- and 2-stage treatments. We know that fixed appliances are quite powerful and to some extent put the teeth and their supporting bones into a “straitjacket.” Surely, if it were desired to compare the effects of early and late treatments, there should be a group treated with growth guidance, but without fixed appliances, as was done in my own research.

In a previous randomized trial comparing early vs later treatment, the authors reported, “We were so impressed with the progress of the children receiving early treatment that we discussed whether it was ethical to deny the control children.” However, they later reported that “The differences created disappeared when both groups received comprehensive fixed appliance treatment.” Is it possible that the similarities of “comprehensive fixed treatment” overwhelmed the differences created by the early treatment? Could this give us an alternative explanation for why they all finished with similar results?

There is substantial evidence to suggest that the facial skeleton is more easily influenced before the age of 8 years, but, because of the apparent overwhelming evidence of these previous studies, few orthodontists treat early. It is therefore important that we have sound evidence on this central issue, especially since this same flaw seems to be present in so many other studies. Logic is more important than evidence.

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Apr 8, 2017 | Posted by in Orthodontics | Comments Off on Growth patterns in identical twins
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