Nanoparticles for dentine tubule infiltration: an in vitro study

Nanosized particles of hydroxyapatite were produced by a hydrothermal synthesis technique. Reaction time and starting pH were varied in order to produce a range of particle dimensions and morphologies. The particles were suspended in alcohol and used for in-vitro trials of dentinal tubule infiltration in etched sections of clinically extracted human molars. Particles were of rod-like morphology, and decreased in aspect ratio as the starting pH was raised. Particles prepared at pH 12 had a mean length of approximately 70 nm and diameter of approximately 30 nm. These showed the most promising infiltration results, with up to 90% of the tubules being fully or partially occluded. Comparisons were made with commercially-available 40 nm spherical silica particles. Information on the depth of infiltration was obtained from sections of dentine prepared using focussed ion beam milling (FIB-SEM).