In-vitro evaluation of coronal microbial leakage after post space tooth preparation

The aim of this in-vitro study was to determine the occurrence of coronal microbial leakage in endodontically treated teeth that have been prepared for post space, and also determine the minimum and maximum time required for the permanent restoration of the teeth after post space preparation.

This experimental study was conducted using a simple random sampling. Fifty extracted single-root teeth with approximately the same length were selected for this study. In order to assimilate the samples length, the crowns of all teeth were cut perpendicular to the long axis of the teeth at a distance of 15 mm from the apex. The canals of 40 teeth were filled with gutta-percha and sealer and prepared for post placement. The teeth were divided randomly into two equal groups of 20 each. In one group, temporary dressing (Cavisol) was used while in the other group, no dressing was used. Five of the teeth were considered as a positive and 5 as a negative control group. For evaluation of microbial leakage, "two-chamber setup" was used. The solution of Proteus mirabilis with fresh culture was injected in the upper chamber and incubated. If the bacteria pass through the dressing and obturation, the trypticase soy broth (TSB) media become turbid. TSB medium in the lower chamber (apex) were investigated every day in terms of occurrence of turbidity and the duration of occurrence of coronal leakage was recorded. The data were analyzed using independent t-test.

The leakage time in the group without temporary filling was within 7-21 days and it was within 28-47 days in group with temporary filling (P<0.001).

The minimum time required for microorganisms to enter the canal in group with and without dressing was 28 and 7 days respectively. It is suggested that the teeth with post space preparation receive permanent restoration after RCT in the shortest possible time, to reduce the need for retreatment.