3M ESPE manual Single Stage Impression Technique, Addressing Undercuts, Functional Impressions

Figure 6

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Suggestions When Using the Dentures as Trays for Final Impressions

Single Stage Impression Technique

When using a one-stage impression technique — using a single phase impression material — use a MEDIUM BODY VISCOSITY. Light body can result in too thin a layer of impression material and undercuts can be an issue. Heavy body impression material can compress the tissues resulting in excessive future adjustments.

Although border molding is recommended and extremely effective, some doctors may choose not to border mold, and instead use a technique that has proven successful for them in the past.

Addressing Undercuts

Typically, severe undercuts are not present in patient’s wearing a denture that is 10+ years old. Additionally, border molding with a heavy body impression material will help to relieve and insulate against under cuts.

With that said, If severe undercuts exist within the ridge of the denture, it is advisable to relieve the denture from the tissue using 3 small pieces of Celara Rapid Repair Tabs — acting as a tripod of tissue stops (Figure 6). This can be easily accomplished by softening the tab and placing 3 small pea-sized pieces on the tissue surfaces of the denture in three areas and having the patient bite lightly into occlusion. This technique will lift the denture(s) off the tissue slightly, approximately 1mm per arch, assuring adequate thickness of impression material to enable the cast to come out of the undercut without breaking — providing the impression is properly boxed. When doing

a two-stage impression technique, the heavy body material usually relieves the denture slightly. If severe undercuts exist, the denture base can be relieved with Rapid Repair Tabs prior to border molding.

Functional Impressions

When hyperplasia exists and it is necessary to heal the tissues prior to making the new denture, a tissue conditioning treatment regime can be used. When a functional impression technique is used as the final impression, and it becomes hard after being worn for several days, it is recommended a final wash of polyvinylsiloxane be made over the functional impression as a final wash. These functional impression materials can slump, resulting in an inaccurate impression, and the functional impressions can become hard and non-resilient, resulting in possible fracturing of the cast upon removal.

Occasionally, the hyperplasia occurs from the occlusion and must be treated after the new dentures are fabricated.