Synthesis and characterization of lithium- and strontium-releasing smart bioactive glasses for direct pulp capping application

OBJECTIVES: Vital pulp therapy is an effective approach for prolonging tooth lifespan; however, none of the currently available pulp capping materials exhibit anti-inflammatory properties. This study evaluated the anti-inflammatory activity and reparative dentin-forming capacity of smart bioactive glasses (BGs) designed to sequentially release lithium and strontium ions as novel pulp capping materials. METHODS: Lithium- and strontium-releasing phosphate BGs (Li/Sr-BGs) were prepared by mixing lithium-containing BG with four BGs exhibiting different strontium release profiles. Ion release from Li/Sr-BGs was measured over 100 days. The effects of Li/Sr-BGs on odontoblastic differentiation were examined using human dental pulp stem cells (DPSCs) and lipopolysaccharide-stimulated inflamed DPSCs (IF-DPSCs). Anti-inflammatory effects were evaluated in IF-DPSCs, and the in vivo efficacy of Li/Sr-BGs as direct pulp capping materials was assessed using a rat pulpitis model. RESULTS: Li/Sr-BGs exhibited stepwise ion release characterized by rapid lithium release followed by sustained strontium release. Li/Sr-BGs promoted odontoblastic differentiation of DPSCs and IF-DPSCs in accordance with the amount of strontium released. Furthermore, all Li/Sr-BGs restored the proliferative capacity of IF-DPSCs and suppressed inflammatory marker expression. In the rat pulpitis model, Li/Sr-BG treatment prevented pulp necrosis on day 3 and promoted reparative dentin formation by day 28. SIGNIFICANCE: Li/Sr-BGs demonstrated sequential therapeutic effects on dental pulp tissue, first suppressing inflammation and subsequently enhancing odontoblastic differentiation. These findings suggest that smart Li/Sr-BGs are promising next-generation direct pulp capping materials for vital pulp therapy.