Nanotechnology in dentistry – A review

INTRODUCTION

Nanotechnology, the science of manipulating matter at the atomic and molecular levels, has catalyzed revolutionary developments across medical sciences.^[1,2] In dentistry, nanotechnology – termed nanodentistry – has led to the emergence of innovative materials, devices, and diagnostics.^[3] Nanoscale materials exhibit properties distinct from bulk substances, including enhanced mechanical strength, unique optical behaviors, and superior surface interactions,^[4] offering significant advantages in oral healthcare.

This review explores current applications, recent advances, potential benefits, and safety concerns of nanotechnology in dentistry, aiming to provide a comprehensive overview for clinicians and researchers.

PRINCIPLES OF NANOTECHNOLOGY IN DENTISTRY

At the nanoscale, materials display altered physical, chemical, and biological properties due to increased surface area and quantum effects.^[5] Gold nanoparticles, for instance, exhibit surface plasmon resonance, enabling sensitive optical detection systems.^[6] Silver nanoparticles (AgNPs) provide potent antimicrobial effects by disrupting bacterial membranes and inducing reactive oxygen species generation.

APPLICATIONS IN DENTAL SPECIALTIES

Nanotechnology has significantly advanced restorative dentistry through the development of nanocomposites and nano-glass ionomer cements (GICs). Nanocomposites incorporate silica, zirconia, or nanodiamond fillers at the nanoscale, providing superior flexural strength, enhanced polish retention, and reduced polymerization shrinkage compared with conventional microhybrid composites.^[12-14] These features translate into restorations with better wear resistance, gloss stability, and esthetic outcomes, particularly important for anterior teeth. In addition, nanodiamonds have demonstrated antibacterial action by reducing biofilm adhesion, offering a dual benefit of mechanical durability and caries-preventive potential.^[15]

The integration of multifunctional fillers has further enriched nanocomposites. For instance, nano-titanium dioxide (TiO₂) introduces photocatalytic antimicrobial effects under light activation, while maintaining translucency and strength.^[16,17] Recent clinical trials confirm that nano-filled composites exhibit superior marginal integrity and lower incidence of secondary caries over time, supporting their routine use in long-term restorative care.^[18] Table 2 shows the nanoparticle types and their antimicrobial mechanisms.

In parallel, nano-modified GICs, especially those reinforced with nano-hydroxyapatite (nHA) or nano-glass fillers, show marked improvements in fluoride release, compressive strength, and aesthetics.^[19-21] The addition of nHA enhances the bond with dentin and enamel, improving resistance to microleakage while simultaneously supporting remineralization at the tooth–restoration interface.^[22] These properties make nano-GICs especially useful for high-caries-risk patients and in minimally invasive restorative approaches. Importantly, the preventive and therapeutic functions of these materials align with the contemporary philosophy of bioactive, patient-centered restorative dentistry.

Nanotechnology has transformed preventive dentistry. nHA pastes and varnishes promote remineralization and reduce hypersensitivity, outperforming conventional fluoride pastes in several trials.^[23] AgNPs represent another significant innovation in preventive oral care. Incorporated into mouthrinses, varnishes, and dental coatings, AgNPs exhibit potent and sustained antibacterial action against a wide spectrum of oral pathogens, particularly Streptococcus mutans, a primary contributor to dental caries. Unlike conventional silver salts, which are prone to causing tooth discoloration, properly stabilized AgNPs maintain their antimicrobial efficacy without inducing significant staining.^[24]

Chitosan-based nanoparticles have also gained attention for their dual function in preventive dentistry. Chitosan, a natural polysaccharide with inherent biocompatibility, forms nanoparticles that can be loaded with fluoride, enabling controlled release over time. This controlled fluoride delivery not only enhances the caries-preventive effect but also exerts intrinsic antimicrobial activity, providing a synergistic approach to plaque control and enamel protection.^[25] Zinc oxide (ZnO) nanoparticles demonstrate broad-spectrum antimicrobial properties against bacteria, fungi, and biofilms. Importantly, ZnO exhibits lower cytotoxicity compared to AgNPs, making it a safer alternative for long-term or repeated use in preventive products such as toothpaste, mouthwashes, and dental varnishes.^[26] Nano-calcium phosphate compounds have shown promising results in early caries reversal.^[27,28]

Nanotechnology has significantly advanced the development of endodontic materials, offering solutions to longstanding clinical challenges such as bacterial resistance, inadequate sealing, and compromised mechanical properties. One of the most impactful innovations is the incorporation of AgNPs into endodontic sealers. Due to their potent and broad-spectrum antimicrobial properties, AgNP-based sealers have demonstrated remarkable efficacy in inhibiting the growth and biofilm formation of Enterococcus faecalis, a pathogen frequently associated with persistent endodontic infections and post-treatment failures.^[29] By preventing the colonization and proliferation of resistant bacteria within the root canal system, AgNP-modified sealers contribute to improved treatment outcomes and reduced risk of reinfection.

In addition to silver, bioactive glass nanoparticles have emerged as valuable additives in endodontic sealers and pastes. These nanoparticles enhance the penetration into dentinal tubules, facilitating a deeper antimicrobial action while simultaneously promoting remineralization of the affected dentin. Bioactive glass nanoparticles enhance dentinal tubule penetration and promote remineralization.^[30]

Dimethylaminohexadecyl methacrylate and nanoparticles of amorphous calcium phosphate (DMAHDM + nACP) offer dual antimicrobial and remineralizing effects, supported by in vitro and ex vivo studies.^[31] Nanodiamonds in gutta-percha improve mechanical properties and reduce microleakage.^[32] Intracanal medicaments containing nanoparticles retain efficacy against resistant pathogens, including Candida albicans and E. faecalis.^[33] However, long-term stability and cytotoxicity require further research.^[34]

One of the most significant advancements is the reinforcement of polymethyl methacrylate (PMMA), the conventional material used for denture bases, with various types of nanoparticles. The addition of nanoparticles such as zirconia, TiO₂, and AgNPs into PMMA matrices enhances critical mechanical properties, including flexural strength and fracture toughness, making the dentures more resistant to functional stresses and accidental fractures Nanoparticles reinforce PMMA denture base resins, enhancing:

• Flexural strength

• Fracture toughness

• Antifungal properties against C. albicans.^[35,36]

TiO₂ nanoparticles integrated into PMMA reduce microbial colonization without compromising mechanical properties.^[37] AgNPs demonstrate significant antifungal effects, useful in preventing denture stomatitis.^[38,39]

Zirconia nanoparticles improve translucency and color stability in prosthodontic materials.^[40] Chlorhexidine-loaded nanoparticles incorporated into soft liners ensure sustained antifungal release.^[41,42] Recent systematic reviews and meta-analyses have corroborated these findings, confirming that nanotechnology-enhanced prosthetic materials provide superior performance in terms of mechanical strength, microbial resistance, and clinical longevity.^[43]

Nanostructured implant surfaces, characterized by nanoscale roughness and surface modifications, have been shown to accelerate the osseointegration process by enhancing the adhesion, proliferation, and differentiation of osteoblasts. These nano-modified surfaces not only promote faster bone-to-implant contact but also reduce bacterial adhesion, thereby lowering the risk of early peri-implant infections.^[44] nHA coatings enhance osteoblast attachment and mineralization, improving early bone healing.^[45] Plasma-sprayed silver coatings on titanium implants reduce peri-implantitis risk in preclinical studies.^[46]

In periodontology, nanofiber scaffolds and nanoparticles in regenerative matrices deliver growth factors effectively, promoting periodontal tissue regeneration.^[47] Moreover, polylactic-co-glycolic acid nanoparticles have been successfully utilized as carriers for bone morphogenetic protein-2. These nanoparticle systems allow for controlled, sustained release of growth factors, significantly enhancing bone regeneration in periodontal defects.^[48] Nanoscale surface modifications of dental implants accelerate osseointegration by enhancing osteoblast adhesion and differentiation while simultaneously reducing bacterial colonization.^[44] nHA coatings, in particular, significantly improve early bone healing and implant stability.^[45] Silver and titanium nano-coatings offer additional antimicrobial benefits, lowering peri-implant infection risks.^[46]

Nanotechnology has emerged as a transformative force in the field of oral diagnostics, offering unprecedented sensitivity, specificity, and non-invasive detection capabilities. One of the most significant breakthroughs is the development of salivary biosensors that incorporate gold nanoparticles. These biosensors exploit the unique optical and electronic properties of gold at the nanoscale, enabling the detection of salivary biomarkers at femtomolar concentrations – levels previously unattainable with conventional diagnostic tools.^[49] Graphene-based sensing platforms have further advanced diagnostic applications by offering ultra-sensitive detection of inflammatory biomarkers, such as cytokines associated with periodontitis. The exceptional conductivity, large surface area, and biocompatibility of graphene enhance the signal transduction of biosensors, facilitating the detection of even trace amounts of disease-specific proteins and inflammatory mediators.^[50] Such engineered surfaces are capable of performing nano-biopsies – techniques designed to isolate and analyze individual cells or cellular components at the nanoscale. These platforms allow for the precise extraction of single oral cancer cells, enabling detailed molecular and genetic analysis that can guide targeted therapy and improve prognostic accuracy.^[51] Exosome-based diagnostics using magnetic nanoparticles are emerging for non-invasive detection of oral cancer and systemic diseases.^[52] Systematic reviews confirm nanobiosensors’ potential for rapid, point-of-care diagnostics.^[53]

FUTURE DIRECTIONS IN NANODENTISTRY

Nanotechnology is advancing toward next-generation applications aimed at personalized, responsive, and highly precise care. Smart biomaterials capable of responding to pH, temperature, or enzymatic activity are under development, promising targeted drug delivery and adaptive restoration properties. Meanwhile, computationally simulated nanorobots have been proposed for site-specific plaque removal, localized antimicrobial therapy, and regenerative microsurgery.^[53,55] Therefore, table 3 summarizes the future directions in dentistry.

Nanorobotics stands at the forefront of futuristic concepts in nanodentistry, offering a vision of unparalleled precision in diagnostics, treatment delivery, and minimally invasive procedures. Although predominantly theoretical at present, the field has garnered considerable scientific interest due to its potential transformative impact on dental care. Pioneering work by Freitas conceptualized the use of nanorobots designed to perform complex tasks within the oral cavity – including targeted drug delivery, precise plaque removal, and execution of minimally invasive surgical interventions at the cellular or subcellular level.^[11,53] Computational models simulate nanorobots navigating periodontal pockets for localized antibiotic delivery.^[54,55] However, challenges regarding navigation, biocompatibility, and regulatory pathways remain significant obstacles to clinical adoption [Table 4].^[56] Table 5 shows the nanomaterials across dental specialities.

Despite significant benefits, nanotechnology poses potential risks:

• Cytotoxicity to oral fibroblasts and other cells^[57]

• Systemic toxicity with potential accumulation in organs^[58]

• Environmental persistence and bioaccumulation.^[59]

AgNPs show dose-dependent cytotoxicity, although surface modification can mitigate toxicity.^[60] Regulatory frameworks from agencies such as the European Medicines Agency and Food and Drug Administration are evolving to address the unique challenges of nanomaterials in dental products.^[61-63] Green synthesis techniques using plant extracts may reduce toxicity and environmental impact.^[64,65] A systematic review emphasized the importance of long-term human trials to confirm nanomaterial safety in dental applications.^[66] Patient education remains essential to promote acceptance of novel technologies.^[67] Table 3 summarizes the potential risks.

CONCLUSION

Nanotechnology holds significant promise in dentistry, offering innovative solutions across materials science, preventive care, diagnostics, and potential nanorobotic interventions. While laboratory advances are encouraging, clinical translation demands rigorous safety evaluations, standardized regulations, and long-term outcome studies. Future directions involve smart, responsive materials and personalized approaches tailored to individual patients, potentially transforming the landscape of dental care.