The influence of different irrigation regimes on the cleanliness and physical properties of the root canal walls

Abstract

This thesis describes a series of investigations into the effects of root canal irrigants on dental root dentine. Imaging of human, ovine and bovine root dentine revealed no significant differences in tubule density or diameter. Canal volumes were estimated to be significantly different between human and bovine, but not between human and ovine teeth. EDAX identified significant differences in Ca/P ratios between ovine and bovine, and between ovine and human dentine at points up to 300μm from the root canal lumen. The Ca/P ratio of bovine dentine was significantly lower than human at the canal lumen only. Atomic Force Microscopy (AFM) revealed human and bovine root dentine to be significantly stiffer than ovine dentine at all depths from the canal lumen; human root dentine was stiffer than bovine dentine up to 300μm from the lumen. Animal teeth were concluded to be imperfect replacements for human teeth in endodontic research. Serial polishing down to 0.05μm aluminium oxide was refined for the gentle removal of laboratory-generated smear layers from sectioned dentine specimens, allowing analysis of subtle surface and sub-surface changes following exposure to root canal irrigants, and AFM analysis of smooth, flat dentine surfaces. A new 5-point scale was developed for scoring root canal cleanliness. NaOCl (5% & 10%) removed pulpal debris and predentine from canal walls after 5 minutes exposure at room temperature, with no evidence of chemical etching (score 4). NaOCl (2.5%) also resulted in a score of 4 in the coronal third, although in middle and apical thirds it was less effective (score 3). AFM analysis revealed no change in surface or sub-surface dentine stiffness after exposure to NaOCl, (5% & 10%, 5 minutes). Significant changes in dentine stiffness after exposure to 17% EDTA and 6% citric acid for 1 minute, were not increased after 2 minutes exposure.