Chairside technique for expediting indirect interim restorations

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Figure 2. Hot melt adhesive-made flexible cast. The use of flexible casts and dies for the chairside fabrication of interim restorations has been reported to overcome the drawbacks of the direct technique and provide a safe and biocompatible fabrication process. Because of the elasticity of these casts, removing the interim restoration after complete setting is easy, and the integrity of the casts is maintained. Unlike stone casts, the flexible cast can be reused if a new interim restoration is needed later. Different elastomeric impression materials and consistencies have been used to make flexible casts. Although materials such as polyvinyl siloxane have excellent dimensional stability, they are relatively expensive and adhere to the already set impression material. For this reason, a second alginate impression is usually made to produce the flexible cast. To overcome these limitations, this article proposes the use of hot melt adhesive material (HMA) for the fabrication of flexible casts. HMA is a thermoplastic material usually supplied in sticks, which are melted using an electric gun. It typically consists of a base material such as an ethylene-vinyl acetate copolymer with additives such as wax, resins, plasticizers, and pigments. HMAs do not adhere to elastomeric impression materials. This allows easy separation of impressions made with any material, including polyvinyl siloxane without the need for a separating agent. Obtaining the flexible cast from the definitive impression eliminates the need for an additional impression, reduces the time needed for the procedure, and improves the accuracy of flexible cast details. HMAs are also less expensive than elastomeric impression materials.