Cationic Poly(amino acid)/Black Phosphorus Hydrogel for Immediate and Durable Relief of Dentin Hypersensitivity Through Ion Flow Blockade, Photo-Thermal Occlusion, and Biomineralization.

Dentin hypersensitivity (DH) stems from exposed dentinal tubules, where external stimuli induce fluid movement, stimulate pulp nerves, and cause acute pain. A significant challenge in current DH management is that most commercially available desensitizing agents often lack both immediate and long-term efficacy. To address this, a black phosphorus (BP) nanosheet-composited methoxy poly(ethylene glycol)2k-block-poly(L-methionine)27-block-poly(L-lysine)5 (PMK5) cationic hydrogel (PMK5/BP) operates through three steps to relieve DH, including ion flow blocking, the photo-thermal effect of BP, and sustained release phosphate ions to enhance biomineralization, thereby achieving immediate efficacy and the potential for long-term efficacy in DH treatment. The application of PMK5 alone significantly reduces electrical conductivity from 0.21 to 0.08 mS, demonstrating immediate efficacy. With BP and 7 min of irradiation, the diameter of human dentinal tubules in the PMK5/BP group decreases to a range of 0-1.70 µm, which is smaller than that in the DH-model group. Furthermore, after treated human dentin slices are immersed in saliva for seven days, the dentinal tubule occlusion rate remains high at 91.82%, matching the immediate rate of 96.33%, indicating excellent one-week stability. PMK5/BP also exhibits higher levels of calcium (Ca) and phosphorus (P). These results demonstrate that PMK5/BP provides an efficient clinical approach to DH treatment.