The Activator was the first “functional orthodontic” brace that has been internationally recognized. Before that there was already the “jumping-the-bite appliance” of Kingsley (1879) and the monobloc of Robin (1902), but without much influence. It was originally introduced in 1935 by Viggo Andresen. The Activator is a removable appliance that encloses both teeth quadrants simultaneously (double retainer). It is manufactured in such a way that it shifts the lower jaw via the bite.
For a long time, many orthodontists believed that they could actually control muscle function with this appliance and so influence the growth of the lower jaw. A change in muscle function by the activator – as well as by similar double braces of all kinds – rather belongs to the realm of legends.
Recent research since 1995 has also made it clear that a lasting influence on the facial skull with appliances like the activator is hardly possible: (It is rarely possible to achieve any sustained growth of more than about one millimetre.
So, at the end of the day, the therapeutic effects of the Activator are not really any better than that of the fixed brace, but the treatment does last substantially longer although the results are generally not really acceptable unless a fixed brace is used as well.
As the Activator impairs speech and is therefore rather debilitating from a social point of view, most patients do not wear this brace for long enough which means that 30%-50% of all treatment fails. Even though Andresen’s hypothesis has turned out to be a fallacy, the Activator is still a very popular appliance in Germany – at least with orthodontists , as its application requires little skill and effort, but is highly profitable. But not with the young patients who resist using this particular appliance and generally only wear it at night when it has little or no effect.
Variations on the Activator
In the 1950’s and 1960’s, just about every self-respecting orthodontist in Germany introduced a double-retainer under his own name. But all of these were really just variants of the Activator and worked in just the same way. These include Balter’s Bionator which is a slightly smaller activator, Klammt’s flexible-open activator, Bimmler’s bite former (both of these are skeletonized activators with wire elements) and Karwetzky’s U-Arch activator which was a two-piece activator joined together with wire.
We could continue the list of such braces ad infinitum but this would really be more of a demonstration of vanity than an enrichment of orthodontics.
One outsider in this series is Fränkel’s functional regulator, which, when in place in the mouth, consists just of wires and plastic strips. This particular appliance managed to combine certain cumbersomeness with great inefficiency, but it still has its fans amongst orthodontists. Unfortunately, the functional regulator is getting more and more out of the moth box, accompanied by – never proven – claims that this appliance can permanently influence facial growth. As with the activator, however, this is beyond the effect of removable appliances.
Whilst all the above mentioned appliances are now obsolete and shouldn’t be used on children any longer, there is one big exception: the combined activator & headgear. Once again, several different people have brought out their own activator/headgear combinations (Teuscher-Activator, Van-Beek-Activator, Bass-Apparatus, Dynamax, Hansaplatte, etc).
As they are quite similar to each other one can talk of an activator-headgear combination in all of these cases. All these appliances have an extra effect because of the headgear & strap combination and they are so effective that almost every back-bite can be corrected within a reasonable period of time just by wearing the appliance at night.
Likewise, the Twinblock is still a very passable double-brace, even by today’s standards and, although it has to be worn all day, this does result in very short treatment duration. The Twinblock is the standard device that is used for back-bite patients in Great Britain. If it is worn all day, the Twinblock is very effective and can correct almost any back-bite within about 9 – 12 months. It would take years to achieve this with an Activator! However, as is the case with all removable appliances, the Twinblock does have quite a high failure rate.
It should not be forgotten that almost any backbite can be corrected quickly and silently with fixed braces and elastics that can be hooked in by the patient. Against this background, it is obvious to use the activator and its modifications only in justified exceptional cases. The fixed appliance and a few small elastics make the same job much easier and faster!