Effect of post preparation on the apical seal.

Apical leakage was analyzed quantitatively in extracted teeth with varied levels of remaining gutta-percha. The effect of the method of gutta-percha removal on the apical seal was also evaluated. Ninety teeth were prepared so that 30 teeth had 3 mm of gutta-percha, 30 teeth had 5 mm, and 30 teeth had 7 mm. An additional 75 teeth were divided into three groups of 25 each. A different method of gutta-percha removal was used for each group: hot instrument, mechanical rotary instrument, and chemical solvent. An electrochemical method was used to analyze apical microleakage. Measurements of leakage of each sample were obtained at 24-hour intervals for 30 days. The data suggest that the mechanical method is the most desirable for gutta-percha removal in post preparation. As the level of gutta-percha increased to 7 mm the degree of leakage decreased. At least 5 mm of gutta-percha is necessary for an adequate apical seal.