Comparative evaluation of dimensional accuracy of dental casts obtained from three putty wash impression techniques and matrix impression technique: An Invitro study

The therapeutic success of fixed Prosthodontics is often determined by the accuracy of the impression that is being made. Any flaw in the impression making greatly magnifies the risk of failure of the finished restoration. Among the various impression materials, elastomers are the ideal medium of choice in contemporary trends of FPD. The PVS elastomers enjoy the maximum superiority over the other elastomers as supported by numerous clinical studies.9,12,13,15,18 To further replenish the validity of PVS elastomers regarding its accuracy in reproduction of tissue surface this study was aimed at comparison of accuracy of the stone cast obtained from single stage putty-wash, double stage putty-wash with polyethylene spacer, double stage putty-wash with 2mm spacer and matrix impression technique. In group I category of impressions, putty and wash material were used simultaneously. In group II category of impressions, initially putty impression was made using a polyethylene spacer followed by addition of wash material to make final impression. In group III category of impressions, initially putty impression was made over the abutment preparation covered with a coping of 2 mm thickness followed by final impression with wash material after removal of the 2 mm coping. In group IV category of impressions, initially matrix is made with inter occlusal record material, then it is relined with high viscous material and the entire matrix is picked up using medium viscous material. Ten impressions were made in each group, poured with type IV dental stone and the casts were obtained, followed by the analysis of the dimensional accuracy of the cast with the master model and the results were evaluated. When the working casts of the four groups were compared with the master model, it showed that all the groups exhibited minimum deviation which is of very minor statistical significance as determined by one sample t- test. The accuracy of the techniques from a statistical point is that the cast obtained from group III impressions exhibited maximum reproduction of the master model closely followed by groups II and IV and then by group I. Even though percentage deviation of statistical significance was observed by one sample t – test, the relative accuracy of each technique and clinical significance analyzed by means of one way ANOVA followed by multiple range test by Tukey-HSD procedure revealed that the subtle changes observed in the accuracy of various impression techniques used could be of a highly negligible clinical significance. Within the limitation of this study, the following conclusion can be drawn, 1. The accuracy of stone casts obtained from double stage putty wash with 2 mm spacer was the maximum, followed by matrix impression technique and double stage putty wash with polyethylene spacer, then by single stage putty wash impression technique. 2. The discrepancy between various impression techniques were of minor statistical deviation and hence considered clinically negligible, thus endorsing the close ramification of these four techniques with respect to reproduction of tissue detail ensuring its successful application in routine clinical procedures