A new method for the quantitative analysis of endodontic microleakage

The aim of this in vitro study was to evaluate the apical seal obtained wit h three commonly used root canal sealing cements: Sealapex, AH Plus or Tops eal, and Sealite, using a new method based on the quantitative analysis of I-125-radiolabeled lysozyme penetration. One hundred thirteen teeth with st raight single root canals were instrumented to master apical point #25/30. These were divided into three groups: (i) negative control (4 roots) covere d with two layers of nail polish, (ii) test group (105 roots) obturated by laterally condensed gutta-percha with the three cements; and (iii) positive control (4 roots) obturated without cement. The groups were then immersed in I-125 lysozyme solution for a period of 1, 7, 14, or 28 days. After remo val, six sections of 0.8 mm length each were made of each root with a fine diamond wire. Each section was analyzed for activity by a gamma counter, co rrected for decay, and used to quantify protein penetration. Leakage was hi gh in the positive control and almost negligible in the negative control. A H Plus (Topseal) and Sealapex showed similar leakage behavior over time, wi th AH Plus (Topseal) performing better. Sealite showed acceptable leakage u p until day 14, after which a large increase occurred, presumably due to th ree-dimensional instability.