Topical cariostatic agents have become a reasonable alternative for managing dental caries in young children. Silver diamine fluoride (SDF) is a practical topical approach to arrest caries and avoid extensive and risky dental treatment. However, the literature demonstrates a parental hesitation towards accepting SDF because of black unaesthetic tooth discolouration following application. The rapid oxidation of ionic silver darkens demineralised tooth structure permanently. In this regard, nano-metallic antimicrobials could augment or substitute for silver, and thereby enhance SDF aesthetic performance. Recently, biomedical research has drawn attention to selenium nanoparticles (SeNPs) due to their antimicrobial, antioxidant, and antiviral potencies. Various in vitro studies have examined the effect of SeNPs on the virulence of bacteria. This narrative review explores practical issues when using SDF and suggests future directions to develop it, focusing on antimicrobial metals. Several methods are described that could be followed to reduce the discolouration concern, including the use of nanoparticles of silver, of silver fluoride, or of selenium or other metals with antimicrobial actions. There could also be value in using remineralising agents other than fluoride, such as NPs of hydroxyapatite. There could be variations made to formulations in order to lower the levels of silver and fluoride in the SDF or even to replace one or both of the silver and fluoride components completely. Moreover, since oxidation processes appear central to the chemistry of the staining, adding SeNPs which have antioxidant actions could have an anti-staining benefit; SeNPs could be used for their antimicrobial actions as well. Future research should address the topic of selenium chemistry to optimise how SeNPs would be used with or in place of ionic silver. Incorporating other antimicrobial metals as nanoparticles should also be explored, taking into account the optimal physicochemical parameters for each of these.

Background: Silver fluoride medicaments effectively arrest caries progression but cause permanent staining. Nanoparticles are increasingly utilised in paediatric dentistry due to their antimicrobial properties. Aim: This study reports the synthesis and characterisation of silver and selenium nanoparticles stabilised with natural agents. Methods: Six silver and selenium nanoparticles were chemically synthesised and stabilised using biocompatible eco-friendly capping agents, including casein, bovine serum albumin, chitosan, citrate, and tannic acid. Characterisation was performed using Tyndall scattering, UV-Vis spectroscopy, transmission electron microscopy, and ICP-OES. Results: The synthesised particles were spherical in shape, ranging in size from 2.5 to 24 nm for silver and 35 to 43 nm for selenium. Elemental analysis confirmed the absence of heavy metals. Conclusions: These findings highlight the successful synthesis of capped silver and selenium nanoparticles. The observed characteristics suggest potential relevance for future antimicrobial applications in paediatric dentistry.

Purpose: This study investigated the extent and distribution (surface coverage) of penetration of custom-synthesised silver nanoparticles functionalised with two different organic capping agents (casein capped and citrate capped silver nanoparticles). Materials and methods: Extracted human primary teeth were sectioned into dentine slices, etched to remove the smear layer, and treated topically with either the nanoparticles, silver fluoride (positive control) or deionised water (negative control). Following fixation, dehydration, and carbon coating, samples were examined using a scanning electron microscope (SEM) with backscattered electron detector. The presence of nanoparticles was verified with energy dispersive X-ray spectroscopy (EDS) for spot elemental analysis. Penetration depths were measured from longitudinal-view micrographs, and data were statistically analysed. Results: All silver nanoparticles treated specimens exhibited evident surface precipitation and intratubular infiltration. Citrate-capped nanoparticles demonstrated greater penetration (32.5 ± 8.9 μm) than casein-capped (19.3 ± 7.1 μm); however, this difference was not statistically significant ( p = 0.056). In contrast, silver fluoride exhibited significantly deeper and denser infiltration (117.7 ± 29.1 μm), forming continuous intratubular precipitates. EDS confirmed characteristic Ag peaks in all treated samples. Conclusion: Silver nanoparticles successfully infiltrated dentinal tubules. However, their penetration was shallower than silver fluoride, likely due to lower silver concentration. Their strong surface retention and controlled diffusion indicate potential for use as topical agents. Further optimisation of particle concentration and application protocol may enhance intratubular diffusion while maintaining biological safety.

Purpose: To evaluate the 12-month physicochemical stability of silver and selenium nanoparticles (NPs) fabricated initially for topical caries arrest. Materials and Methods: The nanoparticles were synthesised via chemical reduction and capped with naturally derived agents. Post-synthesis suspensions were washed and stored at 4 °C in the dark for 12 months. Stability was assessed by comparing the physicochemical properties at baseline and 12 months. The characterisation approaches included Tyndall scattering and UV–visible spectroscopy, transmission electron microscopy, and inductively coupled plasma optical emission spectroscopy. Results: As formulations aged, they showed differences in stability. Citrate-capped silver NPs (AgL1) retained a defined surface plasmon resonance and showed a 6.7% reduction in elemental concentration. Silver NPs capped with casein (Ag1) and bovine serum albumin (Ag2) showed moderate reductions in elemental concentration (26.9% and 54.8%, respectively), accompanied by the formation of larger particle populations (~20–40 nm). Their initial mean particle sizes were 3.6 ± 3.4 nm for Ag1 and 2.5 ± 0.8 nm for Ag2. In contrast, silver NPs capped with citrate and tannic acid (AgL2) exhibited a substantial reduction in elemental concentration (88.6%), accompanied by pronounced particle aggregation. Selenium nanoparticles were the least stable: UV–Vis absorption features collapsed, TEM showed agglomeration (>70–100 nm), and ICP–OES indicated a significant reduction in the measured elemental concentration in the analysed suspension especially in Se1 (99.9%) and Se2 (99.96%). Conclusions: Under refrigerated, dark storage for 12 months, citrate-capped silver nanoparticles showed preserved integrity, whereas others showed moderate to severe issues with colloidal and elemental stability.