The effect of immediate vs. delayed post space preparation on the apical seal of a root canal filling: A study in an increased-sensitivity pressure-driven system

A 5 mm remaining length of root canal filling, after post space preparation , is commonly assumed to maintain sealing ability similar to that of the in tact filling. Post spaces were prepared either immediately using hot plugge rs, or later, using drills. The sealing ability of the fillings, 5 mm remai ning length, were compared with each other and with an intact root canal fi lling control, using radioactive tracer in a pressure-driven system. When n o pressure was applied, no differences could be detected between either of the groups and the control. When a pressure of 120 mm Hg was applied to the same teeth, the control group clearly maintained a better seal than each o f the experimental groups, which did not significantly differ from each oth er. These results suggest that (a) the pressure-driven system was more sens itive than the passive leakage assay that failed to detect differences even at 14 days; (b) a remaining root canal filling of 5 mm was inferior to the intact root canal filling; and (c) the immediate post space preparation wi th hot pluggers did not differ from a delayed preparation with drills.