Fixation impression: the art of precision in dentistry

When teeth are lost, the importance of impressions in prosthetic dentistry becomes particularly clear. This essential technique makes it possible to create an exact negative image of the dentition. What dentists see directly in patients' oral cavities must be meticulously transmitted to the dental technicians. This blog post highlights the fascinating process of impression taking, where the negative model is finally transformed into a precise positive mold. This transition acts as a crucial link between the dental examination and the technical implementation in the laboratory. Let's dive into the world of fixation impressions and their crucial role in the fabrication of precise dental restorations.

Step-by-step procedure for the perfect fit

The fabrication of dentures is a precision work. In addition to determining the jaw relation, the fixation impression is one of the most important steps in the fabrication of a combined fixed-removable denture, such as a telescopic prosthesis, consisting of fixed primary telescopes, firmly anchored on smoothed residual teeth, and removable secondary telescopes. The friction between the primary and secondary telescopes ensures a secure and stable hold in the jaw. To ensure that both elements slide perfectly into each other, a "state of the art" fixation impression of the primary telescopes with an customized tray is required. Let's get started on understanding a masterful fixation impression using telescopic dentures as an example. Because taking an impression of prepared tooth stumps and implants in one jaw is a real challenge for practitioners, a step-by-step procedure is recommended.

The steps to the fixation impression of a telescopic prosthesis

From precise preparation to final fixation - the fixation impression of a telescopic prosthesis is a complex process that requires the utmost care. Each step aims to create a customized solution which is both aesthetically pleasing and functionally perfect.

Fixation impression Step 1:

The dentist grinds residual teeth in the dentition which are intended to receive the primary telescopes. Without residual teeth, it is necessary to use implants.

Fixation impression Step 2:

Using a rim-lock impression tray made of medical stainless steel - a standardized impression tray, each for the upper and lower jaw, filled with impression material - the dentists take a true-to-the-original impression of the dentition. While the intact teeth and the ground tooth stumps are imprinted very well, the situation is different for deeper areas such as gingiva, folds or frenulum of the lips and tongue. In these cases, it is required to use a customized tray for a true-to-the-original impression, a unique item which can be exclusively manufactured by dental technicians.

Fixation impression Step 3:

The impression of the rim-lock impression tray goes to the dental technicians. They use the impression to create the saw-cut model (or saw model for short) for the individual die representation of the prepared teeth for fixed dentures, using the example of the telescopic denture to accommodate the primary telescopes. The prepared tooth dies and teeth or tooth segments can be removed individually and scanned individually for digital fabrication of the primary telescopes. This enables the dental technician to directly view prepared abutments in a circular examination and allows better marginal adaptation, even with difficult subgingival preparation margins or in approximal areas. Based on the saw-cut model, the dental technicians fabricate the primary telescopes with optimal insertion direction. They look like a cone and have a small ball on the front, or alternatively a barb. Are you wondering what the function of the ball or barb is? You will learn more about this in the next step. The primary telescopes are returned to the dentist for fitting, including a customized tray made on the basis of the saw model.

Fixation impression Step 4:

The dentists insert the primary telescopes and check whether the fit is correct. This is followed by the fixation impression, also known as the over-impression. The individual tray filled with impression material takes the true-to-the-original impression of the dentition with the primary telescopes. The dentist collects all the primary parts in the customized impression tray during fixation impression-taking using the small ball or the barb and at the same time forms model analogs. In other words, the small balls or the barbs fix the primary telescopes in the impression material of the customized impression tray as a negative mold. The work is then returned to the dental laboratory.

Fixation impression Step 5:

Based on the collected primary parts and the model analogs including a dental impression, the dental technicians fabricate the master model. It serves as the basis for the precisely fitting denture framework with ceramic veneer of the removable secondary telescope.


Impressions are indispensable in dentistry when teeth need to be replaced or splints or brackets need to be fabricated. The analog version with impressions by hand is laborious and requires a lot of manual expertise compared to the digital images of an intraoral impression. Impression taking with an intraoral scanner and the digital workflow are the technology of the future in the dental practice.