Physicochemical and antibacterial evaluation of novel nano α-TCP–AgNPs biocomposites for direct pulp-capping applications

Background: Nano α-tricalcium phosphate (nano α-TCP) and silver nanoparticles (AgNPs) both possess bioactive qualities needed for pulp-capping materials. AgNPs effectively combat microbial infections without sacrificing cell viability, while nano α-TCP releases calcium and phosphate ions necessary for dentin regeneration. To assess the connection between composite structure and function, a thorough characterization utilizing Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), ion-release analysis, and pH measurements is necessary. Purpose: This study aimed to develop and evaluate a novel biocomposite composed of nano α-TCP and AgNPs for application in direct pulp capping. The investigation focused on the material's chemistry and physical properties, as well as its antibacterial activity against Streptococcus mutans and Lactobacillus acidophilus. Methods: We prepared combinations of nano α-TCP and AgNPs with varying concentrations of AgNPs. Subsequently, we analyzed the composites using XRD, FTIR, and SEM. The investigation also evaluated pH stability and the release of ions (Ca²⁺ and PO₄³⁺) at 1, 3, 72, and 504 h. Antibacterial assays were performed against Streptococcus mutans and Lactobacillus acidophilus. Results: FTIR and XRD analyses confirmed that the functional groups and crystallinity in the nano α-TCP matrix remained unchanged following incorporation of AgNPs. SEM imaging demonstrated that the particles were uniformly distributed with minimal agglomeration. The 1% AgNPs concentration showed the best results, with a steady release of ions, a stable alkaline pH that helped with mineralization, good mechanical strength (according to ISO 9917-1), and strong antibacterial activity. The 1% AgNPs concentration also had the most potent antibacterial effect. Conclusion: The nano α-TCP/AgNPs composites, particularly the 1% AgNPs formulation, exhibited sustained calcium and phosphate ion release, stable alkaline pH, adequate compressive strength, and strong in vitro antibacterial activity against Streptococcus mutans and Lactobacillus acidophilus. These physicochemical and antibacterial properties highlight that this biocomposite is a promising candidate for future direct pulp-capping applications. However, its cellular responses and dentin regenerative potential must be confirmed through dedicated in vitro and in vivo studies.