Functionalized silk dental floss as a vehicle for delivery of bioactive minerals and ions to the tooth surface.

PURPOSE: To enable the commercially available silk dental floss to carry a series of desensitizing, alkalizing, and tooth strengthening pharmacons. METHODS: The hydroxy-groups of the serine and tyrosine residues of the commercial silk dental floss were exposed by degumming, and employed as the chemical anchors for the introduction of carboxy-groups to the surface. The affinity of the silk dental floss to a set of bioactive species was studied by SEM, EDS, and XFS. The acetylated silk was used as a control sample for the experiments elucidating the effect of the surface carboxy-groups on its affinity to a series of pharmacons. RESULTS: While unmodified silk has affinity to microcrystals of sodium carbonate, some affinity to hydroxyapatite particles and Sr2+, its carboxylation drastically increased the affinity to hydroxyapatite, Sr2+, Ca2+ and K+. The unmodified silk had some affinity to existing hydroxyapatite particles, but did not initiate the growth of hydroxyapatite on the surface. Carboxylation of silk enabled the growth of hydroxyapatite on its surface, and significantly increased its affinity to the existing hydroxyapatite particles. The unmodified silk had significant affinity to Zn2+, which exceeded its acylated derivatives. CLINICAL SIGNIFICANCE: The ability of the commercial and modified silk floss to carry a series of pharmacons makes them precursors for a series of new versatile materials with a potential for delivering small doses of bioactive agents in a targeted manner.

Pre-treatment of dentin with chondroitin sulfate or L-arginine modulates dentin tubule occlusion by toothpaste components.

PURPOSE: To evaluate the effect on dentin of chondroitin sulfate and L-arginine on dentin tubule occlusion. METHODS: The dentin samples were activated by submersion in an aqueous ( aq. ) solution of chondroitin sulfate ( ChS) or L-arginine prior to application of a commercial or custom-made toothpaste. After rinsing with water and ultrasonication, adhesion to dentin and occlusion of dentin tubules were evaluated by scanning electron microscopy and the elemental composition of the deposits was evaluated by energy-dispersive x-ray spectroscopy. RESULTS: Rinsing a dentin sample with a solution of ChS resulted in an increase in the adherence of dentifrices containing either titanium dioxide (TiO2 ) or calcium-based nanoparticles [ hydroxyapatite ( HA\ or calcium carbonate( to the dentin surface. ChS does not appear to enhance the adherence of dentifrices lacking TiO2. Pretreatment by L-arginine improved adherence of calcium carbonate nanoparticles, but less efficiently than ChS. Addition of nanoparticles of hydroxyapatite or calcium citrate to dentifrices improved their adherence to dentin without any pre-treatment. CLINICAL SIGNIFICANCE: The significant increase in adherence to the dentin surface of dentifrices of either TiO2 or calcium-supplying nanoparticles to the dentin surface following pre-treatment with ChS or L-arginine opens the door to the development of two-step dental treatments, which accomplish dentin tubule occlusion and help to deliver active dentifrice components to the dentin surface. The ability of the aqueous pastes of nanoparticles of hydroxyapatite or calcium citrate to occlude dentin tubules enables the formulation of desensitizing dentifrices, which also supply the mineral and organic nutrients to the tooth surface.