A silk fibroin-based hydrogel desensitizer achieving 660 μm dentin tubule occlusion for dentin hypersensitivity treatment

Dentin hypersensitivity (DH) causes sharp pain due to external stimuli transmitted through dentinal tubules (DTs) in exposed dentin. Current desensitizers struggle to provide sufficient DT occlusion depth and density, limiting long-term effectiveness under daily erosion and friction. Inspired by fish schooling behavior, we introduce an adaptive hydrogel desensitizer (STU) composed of "sardines" (tannic acid and silk fibroin) and "predators" (urea). The "sardines" form a tightly packed hydrogel "shoal" through hydrogen bonds, while the "predators" disrupt these bonds, transforming STU into a low-injection-force fluid (injection force <5 N) that rapidly infiltrates DTs upon application. As urea diffuses in saliva, hydrogen bonds re-form, reassembling the "shoal" to bond DT walls and achieve dense occlusion up to 660 μm within 3 min-nearly 3 times deeper than the current best. This occlusion remains effective under extended in vitro and in vivo erosion and friction, restoring dentin hardness to healthy levels (0.8 GPa) without noticeable mucosal damage in the rat cavity. Deep occlusion (>100 μm) and biocompatibility were further validated in a rabbit model with significantly smaller DTs. Along with its long shelf life (>10 m in dehydrated form), this desensitizer offers a promising clinical solution for instant, permanent relief from DH.