Effects of dentifrice containing hydroxyapatite on dentinal tubule occlusion and aqueous hexavalent chromium cations sorption: a preliminary study.

In order to endow environmental protection features to dentifrice, hydroxyapatite (HA) was added to ordinary dentifrice. The effects on dentinal tubule occlusion and surface mineralization were compared after brushing dentine discs with dentifrice with or without HA. The two types of dentifrice were then added to 100 µg/ml of hexavalent chromium cation (Cr(6+)) solution in order to evaluate their capacities of adsorbing Cr(6+) from water. Our results showed that the dentifrice containing HA was significantly better than the ordinary dentifrice in occluding the dentinal tubules with a plugging rate greater than 90%. Moreover, the effect of the HA dentifrice was persistent and energy-dispersive spectrometer (EDS) revealed that the atomic percentages of calcium and phosphorus on the surface of dentine discs increased significantly. Adding HA to ordinary dentifrice significantly enhanced the ability of dentifrice to adsorb Cr(6+) from water with the removal rate up to 52.36%. In addition, the sorption was stable. Our study suggests that HA can be added to ordinary dentifrice to obtain dentifrice that has both relieving dentin hypersensitivity benefits and also helps to control environmental pollution

Plugging rates of dentinal tubules.

<p>The dentinal tubule plugging rate (<i>n</i> = 8) of the HA dentifrice group was significantly higher than that of the ordinary dentifrice group. *: <i>P</i><0.01, compared with the ordinary dentifrice group.</p

EDS spectra of dentifrice before and after sorption of chromium element.

<p>There is chromium element in the precipitates from both ordinary and HA dentifrice after sorption.</p

Concentration- and time-dependent removal rate of aqueous hexavalent chromium cations by dentifrices.

<p>The aqueous hexavalent chromium cations removal rate of the HA dentifrice group is always higher than that of the ordinary dentifrice group.</p

Dentinal tubule occlusion after mechanical brushing with distilled water.

<p>(SEM, 5000×) (a, d) Dentinal tubules were empty with no occlusion. (b, e) Almost all dentinal tubules were empty with very few dentinal tubules showing little occluding materials. (c, f) Most of the dentinal tubules showed various levels of sediment blockage.</p

Atomic percentages of calcium and phosphorus in dentine discs.

<p>The lines on top of the bars stand for standard deviation. *: <i>P</i><0.01, the differences of the atomic percentage (<i>n</i> = 8) of Ca or P among groups were statistically significant. Based on mean rank, the order of the atomic percentages of Ca or P is: HA dentifrice group>ordinary dentifrice group>distilled water group.</p

Dentinal tubule occlusion of dentine discs after treatment.

<p>(SEM, 5000×) (a, d) Dentinal tubules were empty without any occluding materials. (b, e) The majority of dentinal tubules were empty and a small number of dentinal tubules showed a sparse existence of occluding materials. The chunky occluding materials locate in the middle of the dentinal tubules with clear boundaries between the precipitate and dentin. (c, f) The majority of the dentinal tubules were blocked by materials. The occluding materials adhered to the dentinal wall with blurred boundaries between part of the precipitate and dentin.</p