The Utility of Nanobubbles for Removing the Smear Layer in Root Canal Treatment

Abstract

 Purpose: For successful pulpectomy or infected root canal treatment, it is necessary to completely irrigate the root canal following instrumentation, fill the root canal, and seal the crown. The smear layer, an unstructured accumulation of debris composed of organic and inorganic components, forms on the dentinal wall during instrumentation. Generally, EDTA or citric acid is used to remove the smear layer, which prevents access of intracanal medications. However, these irrigants may cause apical root fracture, subsequently inducing dentinal wall demineralization. We recently developed nanobubbles to enhance the delivery of medications to dentinal tubules. The aim of this investigation was to examine the utility of nanobubbles for removing the smear layer.

 Methods: An experimental model was established using porcine tooth roots in vitro. The following groups were compared: nanobubbles for 5 min, 17% EDTA for 1min, 3% EDTA for 2 min, 20% citric acid for 3 min, 4.25% citric acid for 5 min, and distilled water (control). Root canal cleanliness was assessed by scanning electron microscopy. Vickers hardness was determined at the depth of 100 μm from the dentinal wall.

 Results: There was no difference in root canal cleanliness between nanobubbles for 5 min and 20% citric acid for 3 min. Significant exposure of dentinal tubules was observed in nanobubbles compared with other irrigants (p<0.01, n=3). Vickers hardness after treatment with nanobubbles was almost the same compared with distilled water. Treatment with 17% EDTA, 20% citric acid and 4.25% citric acid, however, significantly reduced Vickers hardness compared with distilled water (p<0.05, n=3).

 Conclusion: This investigation demonstrated the utility of nanobubbles for removing the smear layer in root canal treatment.