Dye leakage and SEM study of roots obturated with Thermafill and dentin bonding agent

The apical seal of roots obturated with a dentin bonding agent and Thermafi ll with and without the use of sodium hypochlorite as an irrigating solutio n was compared by a dye leakage test. Roots obturated with Thermafill and a zinc oxide eugenol sealer were used as controls. Thirty-eight roots were p repared chemomechanically and divided into three experimental groups. The t eeth of group 1 were filled with Thermafill and the dentin bonding agent us ing sodium hypochlorite as the irrigant. The teeth of group 2 were filled i n the same way but saline solution was used as the irrigant. Before the roo t canal was filled the smear laver was removed from the root canal walls of both groups by rinsing the root canal with a 17% EDTA solution. The teeth of group 3 were filled with Thermafill and a zinc oxide eugenol sealer. The teeth were immersed in 2% methylene blue solution. The root fillings of gr oups 1 and 2 leaked significantly more than those of group 3. The resin-den tin-guttapercha interface of group 1 was observed by scanning electron micr oscopy and showed a typical hybrid layer. An intimate contact between resin and dentin was present in group 2, but a resin-dentin interdiffusion zone was only occasionally observed. The use of dental adhesives and the hybrid layer formation did not improve the seal of Thermafill root canal fillings.