Accuracy of a New Experimental Injection Impression Technique

Objectives: The aim of this study was the assessment of a new putty wash injection impression technique (INJ-T) in comparison to a conventional 2-step putty wash (2step-T) and a 1-step putty wash (1step-T) impression technique. Methods: The new impression technique is based on the injection of the low viscosity material into the replaced preliminary putty impression through preformed channels. A milled metal maxilla with 4 artificial abutments was used as a master model. Each of the 3 impression techniques had 10 replications under dry and under wet conditions with artificial saliva (Fusayama) using the polysiloxane impression material provil novo putty fast set and medium C. D. fast set (Heraeus-Kulzer). The dimensions of the stone dies (fuji-rock; G C Tokio) were measured with an electronic micrometer with an accuracy of 0.003 mm. Results: The measurement of the abutment dimensions showed statistically significant differences among the 3 impression techniques (p<0.05, Wilcoxon). The INJ-T showed slightly reduced dimensions of the abutments with a median of -0.009 mm. The 1step-T showed the best accuracy with a median of -0.004 mm. The 2step-T showed significantly reduced dimensions with a median of -0.023 mm (-0.37%). Under wet conditions the INJ-T showed the best results with a median of -0.003 mm and a low standard deviation (0.013 mm). The 2step-T had a median of +0.003 mm but a high standard deviation (0.163 mm). The 1step-T produced the worst results under wet conditions. Conclusion: The new injection technique showed better accuracy than the 2-step putty wash technique under dry conditions and better accuracy than the 2-step and 1-step putty wash techniques under artificial wet conditions. The results of this in vitro study indicate a possible clinical suitability of the injection impression technique especially under difficult moist conditions.