Interaction of a Desensitizing Paste with Etched Dentin

Objective: To study in vitro the chemical and mechanical interaction of an arginine containing desensitizing paste with decalcified dentin during tooth brushing.

Method: Materials used were a commercial toothpaste (Sensitive Pro-relief, Colgate) and transverse dentin sections from extracted human molars.  Dentin specimens were ground, etched with a 32% phosphoric acid gel and rinsed with water.  Two specimens were used as control.  Remaining specimens (n = 6) were divided into two groups.  Group A specimens were brushed for 2 min. twice over a 24 h period using the toothpaste and a manual toothbrush and rinsed with water. In between brushing, specimens were stored in a phosphate buffer saline solution (PBS) at 37°C. For group B, brushing was conducted for 4 weeks following the same regimen as in group A.  After completion of respective procedures, all specimens were cleaned ultrasonically in water, dried at 37°C, and examined by SEM and EDXA.

Result: Group A displayed occlusion of all patent tubules with seamless plugs, a thin surface film, and scattered globular deposits in the matrix.  The globules contained mainly C, N, and O with <10% of Ca and P.  The plugs contained the same elements but were richer in Ca and P (~ 20%).  Group B showed preferential erosion of the plugs and whisker-like protrusions from the tubules.  Tentative analysis indicated the whiskers to be further enriched with Ca and P.

Conclusion: The dominance of C, N, and O in the reaction products formed initially suggests that they consist of a calcium arginine chelate deficient in Ca.  The chelate is effective in sealing tubules but prone to abrasion.  The compositional and structural transformations of the chelate observed with repeated application of the paste provide an insight into the remineralization effects of this paste previously reported (J Clin Dent, 20, Special Issue, 23-31, 2009).