The forward-acting double plate, abbreviated VDP, is one of the latest and probably most effective advancements on the numerous double plates. In principle, these are offset activators split into two parts for the upper jaw and two parts for the lower jaw. Just like the double-plate braces, they bring the lower jaw as far forward as possible in order to treat an Angle-Class II distal occlusion. In rare cases, the reverse version of this appliance is used to counteract the protrusion of the lower jaw. This appliance is called retrusive double plate.
In order to do this, the double plates are conveniently joined together by a mechanical element. These are usually rigid metal lugs similar to the Müller thorns or the more recent forward-acting double plates. The advantage of the forward-acting double plates is that they do not impede speech quite so much because they take up less space and they can also hold the lower jaw forward, even when the mouth is slightly open. With mono-blocks such as the Activator and the Bionator, the lower jaw quickly sags backwards when the mouth is slightly open which means that it loses its effect. Since many children breathe through the open mouth at night, this can be an advantage of this double plate. Under certain circumstances this is still an acceptable appliance today, especially if it is used together with a Headgear-strap combination.
