by v8.1m


Ortopedia Maxilar
Universidad de Hamburgo, Alemania
Asesor Asociación Mexicana de Ortopedia Maxilar, A.C.
Hamburgo, Alemania


When we talk of functional appliance we first should give some attention to function .

Function of the oral system includes more than only a correct bite .


3. Chewing- which means mastication-can only be assured when free movement of the mandible is possible. a frontal cross bite locks the mandible and is to be treated with a wooden spoon or if this is not effective with a bite plate.

a. A unilateral cross bite forces the mandible laterally in a way that the TMJ on one side is being distracted and on the other side compressed. It also has to be treated with an active “Schwarz-Platte” with bite planes on both sides. A bilateral cross bite is connected with a narrow upper jaw and frontal crowding, this as well means malfunction and can either be treated with a “Schwarz-Platte” with a symmetric expansion screw or with a rapid-jaw-expansion appliance.

1. A narrow maxilla is often connected with disturbed nose breathing . The same problem we meet on patients with Class II malocclusion . Those patients often suffer under enlarged tonsils adenoids. When these malocclusions are treated sufficiently nose breathing can be trained more easily.

a. Class II malocclusion patients are treated with “functional appliances” which are commonly known as “AKTIVATORS”, “BIONATORS” or “VDP” as examples of the group of removable appliances. A fixed functional apparatus is the “HERBST-SCHARNIER”. It increases the length and seize of the mandibula permanently.

Biting means the use of the front teeth which should work like a pair of scissors .

Patients with an open bite caused by thumb sucking or deviated swallow cannot cut their food sufficiently. The opposite malocclusion-the deep bite- can cause injuries of the palatinal gums which sometimes lead to permanent infections in this area.

1. 3.”Swallow right smile bright” – is the message of a teacher for myofunctional therapy.

2. Talking is closely connected with the above mentioned problems in breathing and swallowing. A narrow maxilla cannot give sufficient space for the tongue to move freely when forming words. Before we go into our main topic: the construction of a VDP- I will give you a summary of the functional appliances we use in our practice.

3. Each one of them has its special indication and has to be adapted to the individual demands of each patient. Because all functional appliances with the exceptions of the “HERBST-SCHARNIER” are removable appliances their influences is dependant of the cooperation of the patient .

All these appliances will work best when used while growth takes place. This can be found out either by questioning the parents or by looking at a radiography of the palm.

After we have secured to be at the optimal period of development we only have to decide which of the appliances suits best the malocclusion .

The “VORSCHUB DOPPEL PLATTE”:(VDP by Karwetzky )is a combination of single lower and upper plates which slide on to each other into the desired position when the mouth is closed. Two spurs are welded together with the upper expansion screw and angulated to the bite plane.

Referring to Prof. Karwetzky we can influence a desired centre of resistance by an individualized angulation of the slope and respective spurs in the lower and upper plates. Let me describe how they are produced: After we have done our impressions which should not only show all the teeth but as well the attached and movable gingiva as far as possible we have to prepare the wax bite .

Before we done the “construction bite” we exercise with our patients to move their lower jaw forward into a position where the edges of the upper and lower front teeth touch .A plate of pink wax is warmed up to about 50 o C and formed into a roll with the shape of the upper jaw.

This is being inserted into the mouth and the patient is asked to move his mandible forward and touch the wax roll as softly as a butterfly. Now we can adjust the position of the lower jaw respective to the degree of its distal position. If we have a difference of more than 6mm to neutral occlusion we rather not treat with only one appliance. Our “construction bite” now moves the lower jaw into an approximate “edge to edge” relation of the incisors having in mind that we avoid a midline deviation. The midline is being marked on the wax.

The degree of bite opening is determined by the vertical component of the malocclusion. This means that a deep bite configuration demands more bite opening than a vertical configuration .

With the help of the wax bite the technician inserts the properly trimmed models into the fixator. We start our work on the lower model: After it has been taken out of the fixator we drill with a 2mm size burr right into the middle of the models a small slot in which we later position the expansion screw. That we remove mesial and distal of the first molar some plaster to give enough room for the “Adams-Klammer”. We use stainless-nickel-free wires of the dimension 0.7mm for the labial bow and the “Adams-Klammern” and the C-Klammern. For the protruding springs and the springs for lateral movements we use 0.5mm spring hard. For protrusion as well foil springs are preferred.

All wire components are bent and an extension screw as well as the wire components are fixed onto the model together with the help of fixation wax. The lower extension screw has a small plane of soft plastic attached to it and can be build into the lower plate at a defined angle to the bite plane. We have to explain to the patient the way of functioning with the appliance very well. He has to know how to insert it and how to take it out of the mouth. He is being instructed how to turn the expansion screw if necessary and how to clean the VDP. He must know that it has to be in the mouth for at least 12 hours daily. When the patient closes his mouth with the appliance the lower jaw is forced to moved forward while the spurs slide down the angulated slope.

Asociación Mexicana de Ortopedia Maxilar, A.C.
9a Reunión Anual AMOM. 24-28 de Noviembre del 2004.
Cancún, Quintana Roo. México.

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