Functional impression

Functional impression of an edentulous upper jaw with an individual impression tray

A functional impression ( synonym : functional impression ) is understood in dentistry to be an impression process with which the jaw is molded and at the same time the edge design of a full denture is specified. A functional impression may also be necessary when making telescopic prostheses or partial prostheses . The impression is taken dynamically, which means that the patient makes movements of the mouth , tongue , cheek , lips , soft palate and facial muscles during the impression . The impression is then filled with plaster of paris. The resulting plaster model forms the working basis for the dental technician who fabricates the prosthesis.

Basics

If all teeth have been lost in a jaw, the teeth can be replaced with a full denture. A full denture holds on to the jaw through negative pressure and adhesive forces. In order to create a suction cup effect , the edge of the prosthesis must seal the prosthesis. The soft tissues in the mouth can loosen or pry off the prosthesis with various mouth and tongue movements. The prosthesis must therefore allow the various muscle ligaments a range of motion, such as the frenulum of the tongue or the frenulum and cheek frenulum . Furthermore, painful pressure points would arise if these ligaments rub against the edge of the prosthesis.

The aim is, on the one hand, to make the prosthesis as large as possible, but at the same time not to limit the scope for movement. The edge of the prosthesis, i.e. the functional edge, should only protrude slightly into the movable zone of the fold. Because the edge of the prosthesis seals the prosthesis, it is also referred to as a valve edge, although it is not a valve , but rather should not allow any "ventilation".

In the lower jaw, the functional impression also takes into account the freedom of movement of the floor of the mouth . The floor of the mouth rises and falls in interaction with the tongue. The prosthesis must not be lifted off the lower jaw and levered out.

Sublingual roll

In the lower jaw, a sublingual roll, a thickening on the inner edge of the prosthesis, can be attached, which extends to the premolars on both sides and in this region fulfills the role of the valve edge.

execution

Mucostatic impression

As a rule, an impression of the lower jaw is first taken with a standardized, standard impression tray in the appropriate size. This impression, known as a mucostatic impression (also: anatomical impression), is made at rest, i.e. without active mouth movements by the patient, with the aid of a ready- made spoon. The impression is then poured into a plaster model. When taking an impression, the main material groups used are alginate and plaster of Paris.

An individual impression tray is made on this first model, which is as close as possible to the size of the definitive prosthesis.

Mucodynamic impression

It follows the mukodynamische impression (also function impression), the detection of the denture base and the impression of the buccal sulcus is used and reproduces the intraoral tape and muscle structures. The individual impression tray is first fitted several times in the mouth. For this purpose, it is sanded off at the edge if necessary or built up piece by piece, for example using thermoplastic impression material with high flowability. To do this, the patient performs various movements, such as pointing the mouth, opening the mouth, sucking, laughing, stretching the tongue to the left and right, making faces and the like. Then the actual impression is taken. When taking an impression, the main material groups used are silicone , polyether , more rarely plaster of paris and alginate. While the impression is being taken, the patient repeats these movements.

Depending on the thickness of the edge of the prosthesis, the mucous membrane in the fold is under tension and thus seals the prosthesis. According to the impression, the outer and inner valve edge (edge of the prosthesis) can now be made by the dental technician.

Ready-made impression tray for edentulous teeth, here: lower jaw, according to Ash, size 1
Ready-made impression tray for edentulous teeth, here: upper jaw, according to Ash, size 3
Individual impression tray for the edentulous upper jaw
Individual impression tray for the edentulous lower jaw
Master model after a functional impression of the upper jaw
View of the denture base. First made of wax for try-in.

The impression is poured and the so-called master model is created on which the prosthesis is modeled and the teeth are attached.

Individual evidence

↑ Klaus M. Lehmann, Elmar Hellwig, Hans-Jürgen Wenz: Dental Propaedeutics: Introduction to Dentistry; with 32 tables . Deutscher Ärzteverlag, 2012, ISBN 978-3-7691-3434-6 , p. 359 ( google.com ).
↑ Hermann Böttger, Horst Gründler: The dental and dental technology procedure for the telescope system in prosthetics: telescope crowns, bars, attachments, joints, bolts and the peripheral areas of the precision mechanical fastening devices . Neuer Merkur GmbH, 1982, ISBN 978-3-921280-23-2 , p. 77 ( google.com ).
^ Arnold Hohmann, Werner Hielscher: Dental technology in questions and answers: questions about anatomy, prosthetics, orthodontics and materials science . Neuer Merkur GmbH, 1994, ISBN 978-3-921280-93-5 , p. 240 ( google.com ).

[1] Klaus M. Lehmann, Elmar Hellwig, Hans-Jürgen Wenz: Dental Propaedeutics: Introduction to Dentistry; with 32 tables . Deutscher Ärzteverlag, 2012, ISBN 978-3-7691-3434-6 , p. 359 ( google.com ).

[2] Hermann Böttger, Horst Gründler: The dental and dental technology procedure for the telescope system in prosthetics: telescope crowns, bars, attachments, joints, bolts and the peripheral areas of the precision mechanical fastening devices . Neuer Merkur GmbH, 1982, ISBN 978-3-921280-23-2 , p. 77 ( google.com ).

[3] Arnold Hohmann, Werner Hielscher: Dental technology in questions and answers: questions about anatomy, prosthetics, orthodontics and materials science . Neuer Merkur GmbH, 1994, ISBN 978-3-921280-93-5 , p. 240 ( google.com ).