Evaluation of nanohydroxyapatite-containing toothpaste for occluding dentin tubules

Purpose: To compare dentin tubule occlusion by dentifrices containing either nanohydroxyapatite (10%nHAP and 15%nHAP), sodium monofluorophosphate (Na-MFP) or NovaMin (NovaMin). Methods: All 80 participants wore four intraoral appliances bearing dentin blocks while using one of the four test dentifrices (n = 20/dentifrice) twice daily for 14 days. The four appliances were removed in pairs after 7 and 14 days. One treated block from each of the test periods (7 and 14 days) and their untreated controls were examined with SEM to determine the level of tubule occlusion. The remaining two treated blocks and their controls were used to determine tubule permeability to dye solution. Effectiveness was compared statistically (ANOVA/Tukey's) based on % area covered by deposited precipitate layer (%DPL), % dye penetration inhibition (%DPI) and percentage of fully-open (%FOT), partially-occluded (%POT) and completely-occluded (%COT) tubules in each block calculated relative to the number of tubules in their control blocks. Results: SEM showed increased %COT and %DPL overtime. After 7 and 14 days, %COT, %POT, %DPL and %DPI were significantly lower with Na-MFP when compared to 10%nHAP (P < 0.01), NovaMin (P < 0.05) and 15%nHAP (P < 0.001), the three of which were not significantly different from each other in those four variables. A reverse trend was observed with %FOT (P < 0.001). Within the same dentifrice, no difference in %COT, %POT, %FOT, %DPI and %DPL after 7 and 14 days, except with Na-MFP in which %DPL significantly (P < 0.05) increased with usage. In conclusion, nanohydroxyapatite-containing and NovaMin-containing toothpastes showed equal and more effectiveness in occluding dentin tubules than Na-MFP toothpaste.