Assessment of Dentine Tubule Occlusion and Remineralisation Using Serial-Block-Face SEM

Objectives: To determine the level of tubule occlusions and degree of remineralisation by Sensodyne repair and protect and rapid-relief toothpastes containing Novamin^® and Stannous fluoride (SF) respectively using serial-block-face scanning electron microscopy (SBF-SEM).
Methods: Bovine dentine discs (n=6) were etched with 1% citric acid for 30 seconds, washed with deionised water and were randomly divided in to two treatment groups (n=3). Discs were halved with one half treated with one of the toothpastes and one as control. The toothpaste treatment consisted of two brushing cycles a day for two minutes over 7 days with storage in artificial saliva between brushing. Blocks were cut from the discs, embedded in resin and glued to a pin, 600 60nm slices were cut by a diamond knife in a microtome with back scattered electron images taken of the block after each section producing imaging depth of approximately 36µm. Mineral density by measuring grey scale values, tubule occlusion and diameter were measured every 3µm to the depth of 30 µm away from the surface.
Results: SBF-SEM data showed that 100% of the tubules were blocked at the surface when treated with Novamin^® compared to 83% for SF. Occlusion percentage decreased with increasing depth away from the surface. 20% and 14% of tubules were occluded at 30 µm respectively. The tubule diameter significantly (p<0.05) reduced from 0.8±0.05µm to 0.66±0.21 µm after treatment with NovaMin^®, no significant (p>0.05) change was seen after SF treatment. Grey scale values around the tubules showed significant differences (p<0.05) between the control and treated samples with NovaMin^® significantly higher (p>0.05) than SF.
Conclusions: Tubule occlusion and depth of penetration was quantifiable by SBF-SEM. Both treatments occluded over 80% of tubules at the surface. Novamin^® produced better levels of occlusion both at the surface and at 30µm below the surface and resulted in increased dentine remineralisation.