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ARTÍCULOS CIENTÍFICOS

ORTOPEDIA MAXILAR

DR. MED. HANS-JOACHIM MULLER
Ortopedia Maxilar
Universidad de Hamburgo, Alemania
Asesor Asociación Mexicana de Ortopedia Maxilar, A.C.
Hamburgo, Alemania

3.) Activador de Andresen

When Andresen a Norwegian Orthodontist- Introduced the ACTIVATOR some 60 years ago it seemed to be like a revolution in in the method of fretting malocclusions. Until then the common appliances had been fixed to the teeth in order to apply their forces via wires soldered to bands. All this was very stable and left the patient out of consideration concerning compliance. Andresen however had confidence in his functional activator.Functional means that the patient himself had to apply the forces of muscles in order to let the activator become active.Active in a way to change bite relationship means that by applying muscle force bone structure can be altered.

That was new! Now of course we all know that the main factor for moving teeth are muscles in action but still the discussion about how bone structure is changing under the influence of functional appliances has not come to and end yet. The degree of changes in the bone structure is dependent on a few factors which of course we as experienced orthodontists take into consideration whenever we start correcting a malocclusion.

Secondly we must find out about the compliance of our patient. We cannot expect a removable appliance to work when it most of the time is being removed from the mouth. Then there is the type of malocclusion which is to be treated. We must put ourselves into a position from which we can evaluated the direction of growth of the facial bone structure. Not only lateral x-rays can help us but as well photographs of the patient and of his family can give us advice of where the journey of growth may go and how it can be influenced by our work. Now back to Andresen and his ACTIVATOR:

To correct a class ll malocclusion we need to construct it in the proper way always having the above in mind. After having taken impressions of the upper and lower jaws we let the patient bite forward into a wax wall to produce the construction bite. The degree of forward movement and opening of the lower jaw is dependent on the degree of the class II malocclusion.

The upper and the lower casts are than set with the help of the contraction bite into a fixture. Now the components as the labial arches and the spurs can be bent and attached to the models and finally the resin is been applied. After curing the activator is being finished and polished always having in mind where to reduce resin and whether to leave a bite plane or to erase it when necessary because of vertical growth tendency.

When expansion of the upper jaw is needed an expansion screw can be build in but there should be enough resin in the lower part to be reduced while expansion goes on in the upper. Parents and their children}n then are being instructed how to put the activator in place and about its general use.

Normally they are instructed to wear the activator at night and at least 2 to 3 hours during daytime in order to achieve the goal. That means a class II malocclusion of one premolar,1 PB, can be corrected in a little bit more than a years time if circumstances are well arranged. The activator however is not an instrument for bite correction of class II malocclusion only.

Patients with temporo-mandibular joint problems can be treated with it as well, because with the help of the construction bite the processes articularis of the lower joint is moved out of the fossa in order to let the cartilage structure of the discus recover.
Very often the so called second phenomena of sudden pain relief is being achieved at the moment when the activator is being insert. Even after accidental fracture «of theprocessus articularis the activator can be of some help because it's positioning the lower jaw into the correct position to the upper. The deviated midline is being corrected and the fracture can heal because the broken fragment is uprightening itself by the tension of muscular bandage without being compressed. The Activator leads to a stabilized function.

One of the big questions was whether such quite simple appliance can achieve stable results and whether these results can be proved. In order to get an answer we made a research on class II cases being treated with an activator and compared them with those not being treated. We were measuring the angle ANB which seemed to us a good indicator for changes in the relationship of the lower and the upper jaw. We could prove that relatively to the direction of growth the angle ANB could be reduced under the influence of the activator _when subscribed at the right period of growth and when accepted by the patient.

These factors like construction of the appliance, state of growth, direction of growth and necessity of cooperation determine the success of all functional appliances which have been developed after the origin-the Andresen activator had been accepted by the orthodontists.

There are many variations and only a few of them can be mentioned here. First of all the group of the ìmonoblocksî, appliances which are made out of on piece having different wires to guide the teeth into place. (bionator etc.). These are being followed by the skeletal functional appliances (U-Bugel,Frankel, Federaktivator, Hansa-Gerat).

And finally the VDP (Karwetzky) and the double spur appliance, where an upper and a lower plate are separate and only being guided by spurs into a saggital correct position. Treatment is achieved by function and this makes all these appliances very modern. Andresen must have known this or not?.

Conferencia dictada: Reunión de Ortopedia Dentofacial, 26-30 nov. 1996, San Miguel Allende, Mexico.

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