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.