Barry G N, Heyman R A, Elias A
Oral Surg Oral Med Oral Pathol. 1975 May;39(5):806-11. doi: 10.1016/0030-4220(75)90042-0.
A comparison of the seal provided by gutta-percha root canal filling, heat-sealed gutta-percha, retrograde amalgam filling, and retrograde Durelon filling was made by observation of dye penetration around the above filling materials in extracted teeth. A small but not significant difference between gutta-percha, heat-sealed gutta-percha, and retrograde amalgam was noted. Retrograde Durelon filling gave a poor seal in comparison to gutta-percha and retrograde amalgam filling, but the difference between it and the heat seal was not significant.