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News Bulletin : ADA News Bulletin August 2010
44 AUGUST 2010 opinion page Visco-gel [Dentsply] is a material designed for tissue conditioning and temporary relining. It comes in a liquid and powder and can be mixed to varying consistencies, from watery to very thick. It can be used to record functional impressions. Examine the fit and shape of the old dentures, paying attention to the lateral extension of the flanges and especially whether they provide adequate lip and cheek support. Look at the occlusion -- this will invariably be poor and lack vertical dimension. Often the fit of the upper is not the cause of complaint and is no worse than marginal. If this is the case it may be put aside for the moment. Apply adhesive to the tissue surface of the lower. Mix the Visco-gel, adding powder incrementally and let stand for a minute. If the contour of the denture is adequate, the viscosity of the mix should be moderate; if substantial recontouring is needed the viscosity should be that of thin dough. Place enough of the mixture to allow for proper extension; invert the denture, dust the surface with powder and let stand for a few minutes to allow for some setting. The Visco-gel will initially flow and excess should be wiped away. Seat the dentures and request they not be removed except for rinsing. Explain that the material will continue setting slowly and mould to fit the mouth (like new shoes mould to fit over time). Some material may form 'dags' and fall away. Have the patient return after 24 hours. At the next appointment the patient will invariably report some improvement in the retention of the lower. The functional impression should have extended into passive 'freeway' regions of the sulci, virtually underneath pressure from the lips, cheeks and tongue. Over-extension may have occured if excess has flowed onto the vertical facial/lingual walls, rendering them bulbous. In this case adjustment can be done with a scalpel and a rubber wash impression taken over the hardened gel. Examine the surface for imperfections; air bubbles again may be repaired with a fine wash of rubber. Apply adhesive to the upper, including the occlusal surfaces. Select a rubber material of suitable viscosity (heavier body will allow for broader extension and facial support). Take the impression in a similar manner to that of a reline, with the lower denture in place. When the material is set, record centric occlusion using either wax or rubber. Ask the patient to return in a few hours. Pour the casts using hard stone and warm water for faster set. When the setting is advanced, articulate the dentures, secure with sticky wax and place on an articulator. Remove the lower denture and, with a large ball of softened red wax, create a crude lower occlusal rim to record the old centre and lip lines. Clean the dentures and return to the patient. Arrange a try-in appointment. Instruct the laboratory as to how new anteriors should be placed relative to the originals. Specify that the facial and lingual walls of the lower should be somewhat concave, tapering up to the occlusal like an inverted 'V'. Give some consideration to using narrow posteriors and positioning them slightly lower than one would expect in a natural dentition, so as to encourage the tongue seating over these teeth and aiding retention. DISCUSSION The above approach has a number of advantages. The impression technique is basically a refinement of that used for relines and usually gives a superior result. No laboratory cost is incurred for the manufacturing of special trays. The number of appointments is reduced as the impression and registration visits are combined. Registering centric occlusion is simplified. Admittedly, accurate recording of the desired incisal positions is challenging, but this is often the case when using wax bite-blocks. It may be argued that the problem of full dentures is easily solved by utilizing implants, either to support fixed prostheses or help retain removable dentures. This is like suggesting road trauma would be reduced if motorists drove late model, five star sedans. The majority of presenting patients consider the cost of implants prohibitive and will not proceed. Furthermore, many are senior and of compromised health and, as such, are less than ideal candidates for elective surgery. Using earlier dentures as an aid to constructing new may, at first glance, appear a compromise compared with 'starting from scratch.' On the other hand, the way the technique presents is less important then the way it works and the underlying principles remain basically the same. Generally, the procedure which proves most reliable, in the hands of each particular operator, should usually be considered the one in the best interests of the patient. Mark Knapp DISCLAIMER The statements made in the above article are published on the authority of the author and have not been peer-reviewed. They do not necessarily reflect the views of the ADA and publishing them is not to be regarded as an endorsement of them by the ADA.
ADA News Bulletin September 2010