Degradation of the sealing properties of a zinc oxide-calcium sulfate-based temporary filling material by entrapped cotton fibers

During root canal therapy cotton may be placed in the pulp chamber before p lacement of a temporary filling. This study evaluated the effect on the sea ling of a zinc oxide-calcium sulfate-based temporary filling material when fibers of the internal cotton passed through the filling material and reach ed the external surface of the temporary filling. Glass tubes were filled w ith a 3.5 mm thickness of the temporary filling incorporating a bundle of c otton fibers that passed from the inner surface of the restoration to the o uter surface. The time for methylene blue stain to penetrate the filling wa s compared among four groups. Group I (large bundles of fibers) had 20 to 4 0 fibers, group 2 (medium bundles) had 10 to 15 fibers, group 3 (small bund les) had 3 to 5 fibers, and group 4 (negative controls) had no cotton fiber s. All samples with cotton fibers leaked within 12 min. None of the negativ e controls leaked within the 21-day observation time. These results demonst rate that even a very small amount of cotton trapped between the wall of th e tube and the filling material dramatically reduced the sealing quality of the temporary restoration.