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Lottanti S, Tauböck TT et al. J Endod 2014; 40: 721–724

This study found, although blindingly obvious, that gutta percha shrinks on cooling. The amount of shrinkage shown by either E&Q (Master) gutta-percha and Obtura® SybronEndo gutta percha when cooled from 75 °C to 37 °C, and was about 2%. B & L BIOTECK gutta percha shrunk the least. Also reported, were the temperatures when gutta percha(s) were extruded from three different brands of guns, all set at 200 °C. SuperEndo-Beta gun consistently delivered gutta percha at higher temperatures and, depending on the brand of gutta percha, as high as 103.9 °C. When considering therefore the above ca. 2% value for shrinkage, this would be an underestimate with certain combinations of gutta percha and extrusion guns. Thermocouples were used to measure intracanal temperature and needle tip temperature. In view of this shrinkage, the investigators suggest that Schilder's classic incremental down pack and incremental backfill technique (Dent Clin North Am 1967; 723–744) may offer 'some advantages over more recent continuous down pack and backfill techniques'.