Dimensional stability of model produced by modified putty-wash polyvinyl-siloxane impression

A modified putty-wash polyvinyl siloxane (P/W-PVS) impression technique was recently introduced. The concept is to use putty impression material initially impressed around the prepared abutment to a rubbery but not completely polymerized consistency. The pre-polymerized putty impression is washed by light viscosity impression material to make a final impression.

Objective: The aim of this study was to evaluate dimensional stability of the models produced by two different P/W-PVS impression techniques, Group 1—the modified P/W impression technique (Experiment) and Group 2—the 2-step P/W impression technique (Control).

Methods: The master model was fabricated from two implant abutment replicas (Easy Abutment, NobelBiocare) embedded into type 4 gypsum stone apart with the distance of 28mm. Each abutment was scored on two locations along its long axis on the facial aspect. Fifteen modified- and fifteen 2-step-P/W-PVS impressions (Imprint 3, 3M/ESPE) were made on the master model. Group 1 models (n=15) and Group 2 models (n=15) were formed using type 4 gypsum stone. Thirty models were examined, coded and digitally imaged on the standardized index with the constant camera-object distance and magnification. An examiner measured both intra- and inter-abutment distances from and between each abutment using computer software (Adobe Photoshop 7.0). All measurements were recorded and later were decoded to assign to a proper group. The data was statistically analyzed (One-Way ANOVA, p<0.01) to compare all distances between two groups and the known distance from the master model. Results: There is no statistically significant difference (p >0.01) of intra- and inter-abutment distances between Group 1 and Group 2, Group 1 and the master model, and Group 2 and the master model.

Conclusion: Dimensional stability of models produced by the modified P/W-PVS impression technique was equivalent to the master model and models produced by the 2-step P/W-PVS impression technique.