Elastic impression materials include alginate, as well as the silicone and polyether materials that offer high levels of precision and detail.  Recently, next-generation alginates and alginate substitutes have become available.  These retain the advantages of traditional alginates and avoid some of their disadvantages.  Alginates are the most-used impression material in the dental office, and while they seem basic, achieving good alginate impressions, whether with standard or next-generation materials, requires attention and a standardized technique involving good tray selection, mixing of the alginate, impression taking and pouring of the stone or plaster model.