A study evaluating the effect of delayed and repeat pours on the accuracy of controlled dual step dual mix putty wash impression technique: An in vitro study
Dr. Mohammad Altaf Tantray, Sandeep Koul Bali, Shabir Ahmad Shah
Background: The putty wash technique is most commonly used in making impressions with elastomers. It consists of polymerizing lower viscosity elastomer (light body, LB) against the higher viscosity elastomer (putty). The putty in perforated stock tray that supports the light body capturing fine details of the abutment preparation acts as custom tray. The putty custom tray carries controls and confines the light body against the abutment preparation. The spaces for light body in the putty custom tray can be created by polyethylene sheets, wax omvivac thermoplastic sheets, temporary crowns and grinding the putty. The temporary crown provides the controlled and uniform thickness to the wash bulk of light body to increase the accuracy of impression.
Aims: This study was conducted to evaluate the effect of delayed and repeat pours on the accuracy of controlled dual step dual mix putty wash impression technique.
Materials and Methods: The master model consisted of a dentate mandibular arch of an acrylic resin typodont (Columbia Dentoform Corp., Long Island City, USA) with second right premolar prepared to receive porcelain fused metal crown. The sharp notches are prepared on the buccal and lingual cusp tips of the abutment and at the mid facio-gingival margin with round bur. The master model abutment width and height are then measured by travelling microscope from buccal to lingual cusp tip notch and buccal cusp tip notch to mid facio-gingival margin notch respectively. Ten impressions of the master model are made by controlled dual step dual mix putty reline impression techniques. Thirty casts are made by pouring the impressions in Type IV dental stone high strength (Ultrarock, Kalabhai, Karson Pvt. Ltd., India).
Results: The average height of the abutment on the group I, II and III stone casts are 5.738 mm, 5.726mm and 5.700mm with standard deviation of 0.376, 0.0215 and 0.0379 respectively. The average width of the abutment on the group I, II and III stone casts are 4.304, 4.316 mm and 4.322mm with standard deviation of 0.084, 0.075 and 0.086 respectively.
Conclusion: The delayed and repeated pour of the addition silicone made with controlled dual step dual mix putty wash technique results in short and wider dies in relation to master model abutment dimensions.