Impression Technique
for a Flabby Ridge

A flabby ridge is one which becomes displaceable due to fibrous tissue deposition. Most frequently seen in the upper anterior region. Usually occurs when natural teeth oppose an edentulous ridge. A flabby ridge causes instability of the denture. There are a number of different methods to overcome this problem, 3 of which will be discussed.

SURGERY

This involves removal of the fibrous tissue to leave a firm ridge. However removing the shock absorbing flabby ridge may lead to trauma of the underlying bone, and an increased bulk of denture material.

The other technique involves constructing a denture over the flabby ridge. The impression may be either mucostatic or mucodisplacive where a mucostatic impression technique is selected then good retention will be obtain when the teeth are out of occlusion. When the denture is put under load instability may occur.

With mucodisplacive impression techniques the denture will only fit well when the denture is under load, it may be unstable when at rest because the flabby ridge tends to recoil back into its original position displacing the denture.

WINDOW TECHNIQUE

A primary impression is taken in alginate loaded in a stock tray. The impression is then poured and a special tray is constructed on the model. The special tray is close fitting and has a hole or "window" over the area corresponding to the flabby ridge. An impression is taken in impression paste (mucodisplacive). Once this has set it is left in place and impression plaster (mucostatic) is painted over the flabby ridge and allowed to set and removed as one impression. The impression is removed as one, cast and the denture constructed on the resulting model.

SELECTIVE DISPLACIVE TECHNIQUE

This techniques aims to displace but not distort the flabby ridge as if in function. A primary impression is taken in a mucostatic impression material (e.g. impression plaster or alginate) and cast in stone. A spaced special tray for an impression compound impression is then constructed on this model. The tray is loaded with compound and an impression taken of the model of the patient's mouth. This reduces the risk of displacing the flabby ridge. The tray is then warmed and placed in the patient's mouth. It is adapted and border moulded to the tissues, and should be quite retentive. The impression is removed and warmed all over apart from the flabby ridge area. The impression is retaken, the flabby ridge is compressed but not distorted as the other portions of the impression compound sink into the tissues. The impression is removed inspected and re-tried in the mouth to check that it is stable. If any instability occurs then the impression should be reheated and re-taken. A wash impression may be taken in impression paste to obtain maximum detail and retention and stability.

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1) The flabby ridge has been marked on this patient

2) The preliminary cast and a spaced special tray

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3) Impression of the cast being taken in impression compound prior to being placed in the mouth

4) Flabby ridge impression after flaming and placing into the patient's mouth

The treatment of flabby ridges is controversial and no one treatment stands out against the rest, so it is often the method favoured by the clinician that is used.