Synonyms
Full denture, total denture, 28er, “The Third
Introduction
A large part of prosthodontics deals with the replacement of teeth in the case of complete tooth loss. In the course of life it can happen that you lose your teeth due to various influences, such as caries, periodontal damage or an accident. If you lose only part of your teeth, they can be fitted with a bridge or an interim prosthesis.
However, if there are no more teeth in the upper jaw, these tooth replacements are no longer possible. In order to still be able to chew and speak and also to achieve a good aesthetic result, there is the possibility of either replacing the missing teeth with implants or making a total prosthesis. Alternatively, a total prosthesis can be fixed on implants for improved hold and more pleasant comfort.
Placing implants, however, is a very costly, lengthy, complicated and expensive surgical procedure, especially if all teeth have to be replaced. Since many patients shy away from this procedure or do not have the financial means, a total prosthesis, also called a 28er, is usually the method of choice. It also represents the standard care that is covered by health insurance companies. But how exactly is such a total prosthesis made and why does it not fall out of the mouth?
The anatomical structure of the upper jaw
In order to understand which parts of the upper jaw are covered by the total denture and which parts are important for its manufacture, knowledge of the anatomical structures in the upper jaw is important. The part where the teeth were present is called the alveolar ridge. It is covered by the mucous membrane and consists of bony alveoli, in which the teeth used to sit.
In case of incorrect, overloading or non-loading, the bony structures are degraded, which can be one of the reasons for later loss or improper “fitting” of the prosthesis. Along the center there is a midline (Raphe Palatini), which has a bone bulge, the torus palatinus. The general bony base is the maxilla.
The palate is divided into a hard (front) and soft (back) palate. The prosthesis later covers the hard part. The mucous membrane covering the structures is connected to the underlying part with varying degrees of firmness and is equipped with different glands.
Thus, it is more likely to find fatty tissue in the front and tissue occupied by many glands facing the throat. These parts can also be pressed in with varying degrees of pressure, which is known as resilience. In the area of the wisdom teeth the maxilla has a kind of elevation, the tuber maxillae.
The total prosthesis should not be externally distinguishable from a natural denture once it has been inserted in the patient’s mouth. Whether the patient smiles, speaks or eats, the prosthesis should simulate normal gums and natural teeth as much as possible. Until then, however, it is a complex and lengthy manufacturing process, which also requires a lot of time in the dental laboratory to decide whether the prosthesis should be made.
As a rule, the prosthesis is made entirely of plastic. Both the gums and the teeth are made of plastic. This makes it possible to use any kind of tooth color and shape and also makes the gums as natural as possible.
At the beginning the denture for the upper jaw is set up in wax. This means that the impressions taken by the dentist and cast in plaster by the technician are placed in an articulator (a device for simulating the chewing movement). The matching teeth are then placed on it in wax.
These have been adjusted to the patient in advance. In this way a small round person gets different teeth than a large thin one. The concept of placement varies from dentist to dentist (bilaterally balanced or anterior canine guidance).
The teeth are placed in the wax in such a way that they correspond to the optimal way as in a real dentition. Once the teeth are set up, the various tooth movements are performed. This ensures that the patient can later move the jaws to the right, left, front or back without any problems.
If this is correct, more wax is applied and the gums are modelled. This means that the wax is processed with various instruments to make it look like real gums. In the next step, the wax model is transferred to plastic, the finished end product.
Different plastics and manufacturing methods are used. It can be stuffed cold or injected warm.Thus the wax disappears and is replaced by liquid plastic, which hardens. The teeth remain in their position.
In the following step the denture is processed. The denture is polished to a high gloss, simulating the dentition in the upper jaw. The different movements are also checked again, so that the denture can finally be placed in the patient’s mouth. The modern plastics are already so far developed that they are no longer harmful to the body. However, incompatibilities or allergies can still occur.
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