A study comparing the accuracy of single step versus dual step putty wash technique: An in vitro study
Dr. Mohammad Altaf Tantray, Sandeep Koul Bali, Shabir Ahmad Shah
Background: An accurate impression is the preliminary requirement for the accurately fitting indirect dental restoration. Multiple techniques have been described for making definitive impression in fixed prosthodontics. Putty wash technique that has gained popularity can be categorized as single step putty wash technique and dual step putty wash technique. Single step technique in which putty and light body are mixed simultaneously. No spacer is used in this technique. In dual step putty wash technique, custom tray is made in putty with spacer followed by wash impression. The space for wash bulk can be created by polyethylene sheets, temporary crowns and grinding the impression. Several factors influence the quality of impression like technique, type of impression material, material bulk, type of tray and others.
Aims and Objectives: This study was conducted to evaluate and compare the accuracy of the dies fabricated from single step and dual step putty wash techniques.
Materials and Methods: Master model consists of the mandibular arch acrylic typodont (Nissin) with second right premolar prepared to receive porcelain fused metal crown. Sharp notches are prepared 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 single step and dual step impression techniques. Twenty casts are made by the impressions in Type IV dental stone high strength (Ultrarock, Kalabhai, Karson Pvt. Ltd., India). The casts are then grouped as Group I with Ten casts from the impressions of single step impression technique and Group II with Ten casts from the impressions of dual step impression technique.
Results: The average height of the abutment on the group I and II stone casts are 5.608mm and 5.746mm with standard deviation of 0.147 and. 025 respectively as shown in table 1. Abutment height on group I and II stone casts deviated from that of master model by -1.25%, and 1% respectively as is given in table 1. The abutment height measurements when subjected to one way ANOVA, p-Value was 0.0093 that is highly significant. The average width of the abutment on the group I and II stone casts are 4.334mm and 4.273mm with standard deviation of 0.08 and 0.04 respectively as shown in table 1. Abutment width on group I and II stone casts deviated from that of master model by 1.1%, 0.234% and 0.68% respectively as is given in table 1. The abutment width values when subjected to one way ANOVA, p-Value was 0.0.049 which is significant.
Conclusion: The dual step dual mix impression technique with 2mm spacer thickness results in the dies that exhibited less variation compared to single step impression technique.