SEM evaluation of demineralized dentin treated with professional-strength NaF topical pastes.

PURPOSE: To qualitatively explore the effects of prescription-strength topical NaF pastes on patent tubules in a pH cycling model comprising remineralization and demineralization phases.

METHODS: 3 mm diameter dentin cores were extracted from bovine teeth, mounted in acrylic rods, ground and polished, and initially demineralized in 10 mL unstirred 50% citric acid (pH = 1.2) for 2 minutes to remove the smear layer and expose the dentin tubules. 72 acceptable specimens were then divided into six groups (12 per group) and subjected to a two-phase pH cycling study. The six pastes evaluated were as follows: fluoride-free Silly Strawberry, Clinpro 5000 and Clinpro Tooth Crème, MI Paste Plus, Sensodyne NUPRO 5000 and Topex Renew. First, the specimens were subjected to a remineralization regimen (Phase A), with each day comprising inverted immersion of specimens in three paste treatments (10 g paste: 20 mL distilled water) performed for 1 minute apiece with the immersion in artificial saliva (pH = 7.0) for 2 hours in between each treatment as well as overnight. After 7 days, the specimens were imaged using field emission scanning electron microscopy (FESEM). The remaining six specimens from each group were then cycled through a demineralization regimen (Phase B), with each day comprising inverted immersion of specimens in three rounds of a 1-minute treatment (10 g paste: 20 ml distilled water) followed immediately by a 3-minute static acid challenge (0.3% citric acid, pH = 3.8) with 2 hours in artificial saliva in between each round as well as overnight. After 3 days, the specimens were again imaged using FESEM.

RESULTS: After the Phase A regimen (i.e. remineralization phase), treatment with Silly Strawberry (fluoride-free), Sensodyne NUPRO 5000 and Topex Renew yielded qualitatively similar tubule pore appearance, whereby deposits appeared to have formed around the tubule openings. Clinpro 5000, MI Paste Plus and Clinpro Tooth Crème appeared to occlude dentin tubules as shown by the relatively smaller diameter tubule openings. Relative comparisons among these pastes revealed Clinpro 5000 appeared especially effective in narrowing and incorporating mineral within the tubule, while the MI Paste Plus and Clinpro Tooth Crème appear to produce comparable tubule occlusion. After the Phase B regimen (i.e. resistance to demineralization), qualitative comparisons revealed the fluoride-free, MI Paste Plus, NUPRO and Renew pastes did not appear to occlude dentin tubules as well as Clinpro 5000 and Clinpro Tooth Crème.