Partial Prosthesis in Dentistry

Watch Dental Video about Partial Prosthesis

A partial prosthesis is a removable denture.

Unlike with a total prosthesis, some of the original teeth remain in place with a partial prosthesis. In the picture you see a partial prosthesis in the upper jaw. Partial prosthesis are more and more often being replaced with implant-supported dentures. Partial prosthesis are still frequently used as provisional solutions, for example, during the implant healing process. Recently, partial prosthesis made of plastic have become popular. However, these strain the remaining teeth even more than partial prosthesis made of metal. Thus, plastic is not recommended.

Partial prosthesis are anchored to the remaining teeth by different retaining elements. The retaining elements are separated into bracket and bracketless elements. The most common retaining element is the molded bracket. This type of bracket should only be used in the short-term because the curved bracket strains the bracket teeth immensely. The group of bracketless retaining instruments contains a large number of anchors and joints. These anchors are installed into the prosthesis and the tooth crown. The bracketless construction improves the aesthetics, but the tooth on which the anchor is attached undergoes more strain.

The anchor teeth should experience less strain with specific prosthesis geometry. This geometry is rarely used in everyday operations, mostly because the majority of partial prosthesis are created by the technician, not by the dentist. In general, the technician values prosthesis stability and aesthetics more than functionality. If optimal prosthesis geometry is implemented, prosthesis fractures are more likely.  We will try to explain optimal prosthesis geometry in the video entitled "Partial Prosthesis" using the following example.

Zahnprothese auf Gipsmodell

dentures

You see a lower jaw that is partially teethed; the 6th tooth is a prosthetic tooth. The prosthetic bracket is retained on the 6th tooth. The bracket is open towards the front. This construction is bad – but why? Imagine you are chewing; the prosthesis yields slightly due to the mucosa, and this yielding leads to bracket deflection. Bracket deflection means the bracket tooth is lifted upward by the bracket, or the bracket is “activated”.

Now imagine you are chewing gum and the prosthesis is lifted up from the base.  In this case, the bracket is detached from the tooth, or it is “deactivated.”  To be more exact, the bracket is “deactivated” while chewing and “activated” when detaching forces are in effect. The bracket is invisible but it should have been designed to be open towards the back. Brackets that are open towards the back are deactivated during chewing and activated when detaching forces are applied.

Furthermore, the lever arm has to be extended. The bracket is now located on the 4th instead of the 6th tooth. Unfortunately, this makes the bracket more visible. However, the extension of the lever arm reduces the strain on the anchor tooth; this is the correct prosthesis construction.

Despite such finesse – and regardless of whether it is the anchor or bracket – partial prosthesis strain the remaining teeth, especially those on which the prosthesis is attached, known as the anchor teeth. Over time, this leads to loss of teeth and the prosthesis must be expanded. Eventually, the last tooth is lost, ultimately resulting in a total prosthesis.

Today these problems are much less prevalent thanks to improvements in implantology.

Click here to see the video: Partial Prosthesis

 

This post is also available in: German

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