Effect of smear layer removal on the diffusion permeability of human roots

Ten human maxillary incisors, extracted because of periodontal disease or nonrestorable caries, were obtained and instrumented to a size #70 K-Flex file at the working length using a standard stepback technique. Tritiated water (³H₂O) was placed in the root canals and allowed to diffuse to the external surface of the roots until it reached a constant rate. The smear layer in each of the experimental roots was then removed using 0.5 M EDTA followed by 5.25% sodium hypochlorite (NaOCI). The constant rate diffusion of ³H₂O was remeasured. The roots were then stored in deionized H₂O for 2 months and the constant rate diffusion of ³H₂O was remeasured. A statistically significant difference was noted between all three groups. A decrease in the diffusion permeability of the root to ³H₂O was noted immediately after smear layer removal and the highest permeability was recorded after storage in the deionized water for 2 months.