(1) Background: Streptococcus mutans (S. mutans) is the principal pathogen involved in the formation of dental caries. Other systemic diseases have also been associated with specific S. mutans serotypes (c, e, f, and k). Silver nanoparticles (SNP) have been demonstrated to have good antibacterial effects against S. mutans; therefore, limited studies have evaluated the antimicrobial activity of biofunctionalized SNP on S. mutans serotypes. The purpose of this work was to prepare and characterize coated SNP using two different organic components and to evaluate the antimicrobial activity of SNP in clinical isolates of S. mutans strains and serotypes; (2) Methods: SNP with bovine serum albumin (BSA) or chitosan (CS) coatings were prepared and the physical, chemical and microbiological properties of SNP were evaluated; (3) Results: Both types of coated SNP showed antimicrobial activity against S. mutans bacteria and serotypes. Better inhibition was associated with smaller particles and BSA coatings; however, no significant differences were found between the different serotypes, indicating a similar sensitivity to the coated SNP; (4) Conclusion: This study concludes that BSA and CS coated SNP had good antimicrobial activity against S. mutans strains and the four serotypes, and this study suggest the widespread use of SNP as an antimicrobial agent for the inhibition of S. mutans bacteria.

Nanoscale zero-valent iron (nZVI) has proved to be an effective tool in applied environmental nanotechnology, where the decreased particle diameter provides a drastic change in the properties and efficiency of nanomaterials used in water purification. However, the agglomeration and colloidal instability represent a problematic and a remarkable reduction in nZVI reactivity. In view of that, this study reports a simple and cost-effective new strategy for ultra-small (< 7.5%) distributed functionalized nZVI-EG (1–9 nm), with high colloidal stability and reduction capacity. These were obtained without inert conditions, using a simple, economical synthesis methodology employing two stabilization mechanisms based on the use of non-aqueous solvent (methanol) and ethylene glycol (EG) as a stabilizer. The information from UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy suggests iron ion coordination by interaction with methanol molecules. Subsequently, after nZVI formation, particle-surface modification occurs by the addition of the EG. Size distribution analysis shows an average diameter of 4.23 nm and the predominance (> 90%) of particles with sizes < 6.10 nm. Evaluation of the stability of functionalized nZVI by sedimentation test and a dynamic light-scattering technique, demonstrated very high colloidal stability. The ultra-small particles displayed a rapid and high nitrate removal capacity from water.

This study evaluated push-out bond test (POBT), surface roughness, and antimicrobial properties against Enterococcus faecalis of bioceramic sealers supplemented with silver nanoparticles (AgNPs). The sealers tested were CeraSeal^®, EndoSequence^® BC Sealer^TM, and Bio-C^® Sealer. The POBT was measured with a Universal Testing Machine, and the type of failure was evaluated with a stereomicroscope. The roughness average (Sa) and peak–valley height (Sy) values were evaluated by atomic force microscopy. The bacterial growth inhibition was evaluated using a disk diffusion test, and antimicrobial activity was determined with the plate microdilution method. The POBT showed no significant difference between sealers with and those without NPs in cervical and apical thirds (p > 0.05). In the middle third, the adhesion force was significant for Endosequence BC Sealer^® (p < 0.05). The results showed that the Sa and Sy parameters, when AgNPs were added, did not show a statistically significant difference compared to the groups without nanoparticles (p > 0.05). All tested sealers showed bacterial growth inhibition, but no significant difference was found. Their efficacy, in descending order of antibacterial activity when AgNPs were added, is as follows: EndoSequence^® BC Sealer^TM > Bio-C^® Sealer > CeraSeal^®. The incorporation of AgNPs into bioceramics improves antimicrobial activity without affecting mechanical properties.

This study aimed to evaluate the effect of the incorporation of silver nanoparticles (AgNPs) of 5.57 nm size into dental alginates on their deformation and antimicrobial properties. Six experimental groups were prepared: 2 different alginates with 0.25 wt% AgNPs, 2 different alginates with 0.5 wt% AgNPs (5.57 nm), and 2 unmodified control alginate groups. The presence of AgNPs was confirmed using X-ray diffraction analysis with a Bruker D8 Advance diffractometer. Antimicrobial activity was evaluated using the Kirby-Bauer disk diffusion method (direct contact) against E. coli and S. aureus cultures incubated on Mueller–Hinton (M-H) agar at 37 °C for 24 h. The results demonstrated that the addition of 0.25% and 0.5% AgNPs significantly enhanced the antimicrobial properties of alginate (p < 0.05), showing clear inhibition zones against the tested microorganisms. In terms of mechanical properties, AgNPs-modified samples exhibited improved elastic recovery compared to the control group (p > 0.05). These findings suggest that incorporating silver nanoparticles into alginates could enhance their antimicrobial properties without compromising the mechanical integrity required for dental applications.

Background/Objectives. The use of antibiotic pastes in the Lesion Sterilization Tissue Repair (LSTR) technique has increased due to their ability to disinfect necrotic primary teeth without mechanical instrumentation. Tri-antibiotic mixtures (TAP) and Chloramphenicol-Tetracycline-Zinc Oxide (CTZ) paste remain the most common options, although their composition and dosing lack standardization. Evidence indicates that silver and zinc oxide nanoparticles enhance antimicrobial performance by disrupting biofilms and modulating inflammatory pathways, suggesting potential benefits when incorporated into intracanal medications. This study aimed to evaluate the antimicrobial activity of a chloramphenicol–tetracycline paste modified with silver nanoparticles (SNPs) and zinc oxide nanoparticles (ZnONPs) against wild Enterococcus faecalis, comparing its MIC, MBC, and inhibition zones with those of a commercial CTZ paste. Methods. SNPs and ZnONPs (1 × 10⁻² M) were synthesized and characterized using UV–Vis spectroscopy and dynamic light scattering (DLS). Two antibiotic pastes (1%) were formulated, including a nanoparticle-modified version with a 4% reduction in antibiotic content. Commercial CTZ paste was prepared according to the manufacturer’s instructions. Wild E. faecalis strains were isolated from necrotic primary teeth (N = 30). MIC, MBC, and inhibition zones were determined using microdilution and Kirby–Bauer assays. Results. AB Paste and Nanopaste showed larger inhibition zones (ZOI) than the other formulations (p < 0.001). MIC and MBC analyses showed no significant differences among antibiotic formulations and SNPs (p > 0.05). Conclusions. Both the nanoparticle-free antibiotic paste and the nanoparticle-modified paste demonstrated greater inhibitory activity than commercial pastes and Nanoparticles. Despite containing 4% less antibiotics, the Nanopaste showed equivalent efficacy, indicating that reducing the drug content does not compromise antimicrobial performance and that SNPs contribute to this effect.