The effect of one-step vs. two-step impression techniques on long-term accuracy and dimensional stability when the finish line is within the gingival sulcular area

A selection of abstracts of clinically relevant papers from other journals. The abstracts on this page have been chosen and edited by John R. Radford.

Abstract

All the polyvinyl siloxane impression materials tested met acceptable linear dimensional characteristics as defined by ADA specification.

Main

Levartovsky S, Zalis M et al. J Prosthodont 2014; 23: 124–133

How accurate do impression materials have to be? The benchmark adopted by these investigators was ADA specification No. 19: an elastomeric impression is sufficient if it is shown to have less than of 0.5% dimensional change (after 24 hours). Impressions were recorded of a rectangular, aluminium master cast with a simulated gingival sulcus. This model differed from the ADA standard stainless steel die. Using either a one- or two-step impression method, Express^™ R and Express^™ F (3M^™ ESPE^™) and President putty/wash (Coltène), and storing these impressions from 2 to 144 hours, all met the ADA specification for the planar distance discrepancy only (ca. 1.5 cm from the middle of the 'abutment'). Some of the conclusions made in the body of the text are at odds with what is shown in Figure 6C. Of note, these authors cited a study that reported 'the conventional alginate...would be acceptable after 30 minutes and 48 hours of storage' using the ADA specification.