Correlation between remaining length of root canal fillings after immediate post space preparation and coronal leakage

The seal provided by root canal fillings after post space preparation was s tudied using a pressure-driven radioactive tracer assay. The coronal part o f root canal fillings was immediately removed, using a hot plugger, to a re maining length of either 3, 5, 7, or 9. mm. Intact root canal fillings of 1 4 mm sewed as control. Application of air pressure of 130 mm Hg to the trac er solution drove it through the fillings and into phosphate-buffered salin e surrounding the apex. Leakage gradually increased for 28 days, and differ ences in the leakage through 3 to 9 mm fillings were demonstrated. In a pas sive system by which an additional group of teeth were tested none of these differences could be detected. It was concluded that: (a) root canal filli ngs of 3, 5, and 7 mm have an inferior seal, compared with that of an intac t filling; (b) the sealing is proportional to the length of the remaining f illing; and (c) a passive system is unable to detect these differences, eve n when conducted for as long as 28 days.