Nanodentistry involves the use of nanoparticles (NPs) and nanomaterials to innovate and enhance dental treatment modalities. By modifying materials at the nanoscale, their physicochemical and biologic properties are significantly improved, offering superior antimicrobial, regenerative, and diagnostic capabilities. These advancements have demonstrated their broad utility across preventive and restorative dentistry, periodontics, prosthodontics, orthodontics, and oral cancer therapy. This article highlights key scientifically researched NPs in dentistry, their concerns regarding biocompatibility, and the need for further investigation before these technologies can be widely adopted in clinical practice.
Key points
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Nanotechnology and the application of nanoparticles (NPs) have led to enhanced diagnostic, therapeutic, and preventive care in dentistry.
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Nanotechnology has also enabled the development of improved dental materials with enhanced mechanical properties, antimicrobial activity, and targeted drug delivery systems.
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Among various classes of NPs, metal and metal oxide NPs are primarily experimented and employed for their efficient antimicrobial properties.
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Further research is essential to evaluate the long-term biocompatibility, and safety of NPs and clinical outcomes of employing these materials.
Abbreviations
| AgNPs | silver nanoparticles |
| APDT | antimicrobial photodynamic therapy |
| AuNPs | gold nanoparticles |
| BGNPs | bioactive glass nanoparticles |
| CDHA | calcium-deficient hydroxyapatite |
| CHX | chlorhexidine |
| CNPs | chitosan nanoparticles |
| CPP-ACP | casein phosphopeptide-amorphous calcium phosphate |
| FDA | US Food and Drug Administration |
| FeO NP | iron oxide nanoparticle |
| GCF | gingival crevicular fluid |
| GT | gum tragacanth |
| GTR | guided tissue regeneration |
| HAP | Hydroxyapatite |
| ICMs | intracanal medicaments |
| ISO | International Organization for Standardization |
| MCS NPs | meso calcium silicate nanoparticles |
| MMPs | matrix metalloproteinases |
| MSiO 2 | mesoporous silica |
| NC | calcium carbonat |
| NP | Nanoparticle |
| PCL | polycaprolactone |
| PLGA | poly lactic-co-glycolic acid |
| PMMA | polymethyl methacrylate denture base |
| QDs | quantum dots |
| QPEI | quaternary ammonium polyethyleneimine |
| REPs | regenerative endodontic procedure |
| Res-Nano | nano-formulated version of resveratrol |
| SCAP | stem cells of apical papilla cells |
Introduction
The term “nano” originates from the Greek word “nanos,” meaning “dwarf.” Nanoscience and nanotechnology encompass the study and application of functional materials at the nanoscale, referring to structures and devices measuring approximately a billionth fraction of a meter (10 −9). This advanced technology has gained widespread use in medicine, particularly in imaging and targeted drug delivery to cancer and diseased cells. Considering these medical benefits, nanodentistry evolved, using nanoparticles (NPs) and nanomaterials to overcome major challenges in improving oral health and treatment outcomes.
Modifying materials at the nanoscale optimizes the physicochemical properties, such as increased surface area, enhanced reactivity, size-dependent optical properties, and better mechanical and thermal characteristics, compared with their bulk counterparts. , Improved antimicrobial, bioactive, and regenerative potential of NPs has led to a broad range of applications in dentistry, including oral diagnosis, preventive, restorative, and regenerative dentistry, endodontics, periodontics, prosthodontics, and orthodontics ( Fig. 1 ). Given their broad applications, this article highlights the most extensively researched NPs in dentistry ( Table 1 ).
Implications of nanotechnology and nanoparticles in dentistry.
( Courtesy by Dr Anu Priya Guruswamy Pandian, BDS, MDS.)
Table 1
Most commonly experimented nanoparticles and their outcomes in dentistry ,,,
| Nanoparticles Used | Application in Dentistry | Key Experimental Findings |
|---|---|---|
| Silver nanoparticles | Used alone or in combination with endodontic irrigants, medicaments, or sealers | Superior biocompatibility, higher antibacterial activity, and little or no impact on the mechanical properties of dentin |
| Incorporated in dental adhesives | Steady release of silver ions exhibiting long term antibacterial activity | |
| Dental cements |
Enhanced antibacterial activity
Reinforce GIC by improving mechanical properties |
|
| Incorporating into the orthodontics wires, brackets |
Minimizes enamel demineralization
Inhibit adhesion of S mutans to the surfaces of orthodontic appliances |
|
| PMMA denture bases |
AgNPs give the PMMA denture bases a grayish tint
Does not significantly affect the flexibility or strength of the material |
|
| Infused collagen membranes | Kills bacteria linked to periodontitis, specifically Fusobacterium nucleatum and Enterococcus faecalis | |
| Used in combination with antibiotics | Increased antibacterial properties against multi-resistant bacterial strains. | |
| Membranes with 2% AgNPs are used in treating intra-bony defects using guided tissue regeneration (GTR) |
It reduces adherence and inhibits bacteria while supporting the health and growth of human gum cells
Stimulates new collagen synthesis and neovascularization, augmenting wound healing |
|
| Chitosan NPs | Endodontic irrigant and intracanal medicament |
Demonstrates antibiofilm, antimicrobial and chelating properties
Enhanced smear layer removal |
| Aqueous vehicle-carrier for conventional intracanal medicaments such as Ca(OH) 2 |
Enhances the disintegration of Ca(OH)
2
into Ca
2+
and OH
−
ions
Minimize reinfection of dentin by preventing bacterial adhesion and degradation of dentin by bacterial collagenase, thereby stabilizing the dentinal matrix |
|
| Regenerative endodontics |
Local delivery of bioactive molecules
Promotes the adhesion, cellular viability, and differentiation of stem cells of apical papilla |
|
| Used to deliver different drug combinations | Enhanced alkaline phosphatase activity, leading to increased bone formation | |
| Titanium dioxide nanoparticles | Used in PMMA denture bases |
It has built-in antimicrobial properties, as it produces cytotoxic oxygen radicals that help prevent microbial growth
TiO 2 NP offers a good balance of antimicrobial benefits and increased hardness, but it can also make the surface rougher |
| Orthodontic adhesives or acrylic materials | Significantly enhances the antibacterial properties | |
| Nanohydroxyapatite | Implant coating |
Promotes fibroblast proliferation enhancing tissue regeneration and bone growth, leading to more secure implant fixation
Improves osseointegration |
| Dental adhesives | Induces remineralization | |
| Incorporated into glass ionomer cements | Enhances the mechanical and physical properties of set cement | |
| Regenerative endodontics-incorporating into synthetic polymer-based NPs | Mimics dentin matrix, promotes adhesion and proliferation of osteoblast-like cells. | |
| Calcium-deficient hydroxyapatite nanocarriers | Targeted delivery of tetracycline against periodontal bacteria |
Increased the bacterial minimum inhibitory concentration fivefold, making the antibiotic more effective
Improved the attachment of periodontal fibroblast cells augmenting periodontal tissue regeneration |
| Copper oxide | Dental cements and adhesives | Enhances antimicrobial activity without adversely affecting the inherent properties of the dental material |
| Integrated into orthodontic adhesives, brackets | Reduction in biofilm, dental plaque, dental caries, and periodontitis | |
| Zinc oxide | Endodontic procedures | Greater antimicrobial efficacy and amplifies osteoinductive, and vascularization potential |
| Orthodontic materials | Combination of ZnO and CuO nanoparticles provides a synergistic antimicrobial effect that is more effective at inhibiting S mutans and reducing biofilm formation compared with CuO alone |
Definitions
The terms nanoparticle and nanomaterial are often used interchangeably in older literature. However, it is imperative to understand that NPs are a subset of nanomaterials, and they may have different, yet overlapping applications in dentistry. Basic definitions of these terms are listed in Table 2 .
Table 2
Differences between nanomaterial and nanoparticle ,
| Nanomaterial | Nanoparticle |
|---|---|
| Solid particles of natural, incidental, or manufactured origin and at least 50% of their number-based size distribution falls within the range of 1–100 nm- European Commission | A discrete nano-object where all 3 Cartesian dimensions (length, width, and height) are <100 nm- International Organization for Standardization (ISO) |
| Materials that exist at the atomic, molecular, or macromolecular level, typically with at least one of their dimensions within the range of 1–100 nm- US Food and Drug Administration (FDA) | The particles that exist on a nanometer scale (ie, below 100 nm in at least 1 dimension) are known as nanoparticles |
Classification
Nanomaterials are categories based on their dimensionalities ( Fig. 2 ), while NPs are classified based on their origin, composition, and structural configurations ( Fig. 3 ).
Dimensional classification of nanomaterials.
( Courtesy by Dr Abhishek Walhekar, BDS.)
Classification of nanoparticles.
( Courtesy by Dr Abhishek Walhekar, BDS.)
Implications of nanotechnology and nanoparticles in dentistry
Preventive Dentistry
In an attempt to prevent dental caries, NPs have been incorporated into various dental products.
Mouthwashes
Formulation of antimicrobial mouthwashes with NPs is challenging because of the need for rapid action, safety, and targeted effects without disrupting beneficial oral bacteria. However, promising formulations have been developed. For instance, silver NPs (AgNPs) have been incorporated into alcohol-free mouthwashes, effectively reducing harmful bacteria and dental plaque. Similarly, ferumoxytol, an iron oxide NP (FeO NP), can selectively target and disrupt caries-causing bacteria, such as Streptococcus mutans , without affecting commensal bacteria. Combining ferumoxytol with low concentrations of hydrogen peroxide rinses effectively reduces dental plaque and prevents enamel damage, offering a promising approach to preventing tooth decay. ,
On the other hand, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes help prevent tooth demineralization and promote remineralization by maintaining high calcium (Ca 2+) and phosphate (PO 4 2-) ions levels. CPP-ACP mouthwash significantly increase these ion levels in dental plaque, enhancing the natural repair processes of the oral cavity. Commercial mouthwash containing nanosilver and xylitol was more effective in reducing these lesions than mouthwashes containing 0.05% chlorhexidine (CHX) or fluoride. These findings suggest that incorporating nanotechnology into dental care products, such as CPP-ACP and nanosilver, may offer enhanced protection against tooth decay and demineralization.
Dentifrice
Dentifrice containing 1% nano-sized calcium carbonate (NC) particles increase mineral content in early enamel lesions. High surface area of NC particles allows them to adhere to tooth surfaces and continuously release Ca 2+, promoting the formation of apatite minerals within carious lesions. Dentifrice containing bioactive glass NPs (BGNPs) can repair enamel by reducing mineral leaching and facilitating remineralization.
Novel innovations such as dentifrobots are magnetically controlled robots that are administered by means of mouth rinse or toothpaste. These tiny devices can navigate the gingiva, removing dental plaque and pathogenic microbes, supporting the growth of beneficial oral bacteria to maintain a healthy oral environment. They are currently not employed in clinical practice. Current ongoing research is oriented to explore their application in high precision and minimally invasive dentistry.
Restorative Dentistry
NPs are primarily used in restorative dentistry to enhance the mechanical and physical properties of dental materials. Inorganic NPs have been robustly investigated for these characteristics compared with their organic counterparts. As a result, metal and metal oxide NPs are widely incorporated into restorative dental applications because of their superior physicochemical properties.
Dental adhesives and composites
The most commonly incorporated NPs into composite resins include silica, zirconia, and hydroxyapatite (HAP). They enhance the optical properties of the resin, wear resistance, and polishability, and minimize polymerization shrinkage. Nanohybrid and nanofilled composites are currently being used in dental practice for these properties. In addition, therapeutic effects of NPs include biomineralization and anticaries activity. Metallic NPs of silver, copper, and zinc exhibit excellent antimicrobial activity without adversely affecting the inherent properties of the dental material. Conversely, bioactive NPs such as NACPs, BGNPs, and HAP NPs have been shown to induce remineralization. , These modifications suggest that besides incorporating NPs for improving the strength of the cement, current research is focused on developing smart materials that can respond to pH changes and release therapeutic agents for self-repair.
In dental adhesives, NPs are added to reinforce the resin-dentin bond. Zinc, gold, or platinum NP-incorporated dental adhesives have been studied to inhibit matrix metalloproteinases (MMPs) and minimize collagen degradation. , Various self-etch and universal adhesive systems incorporating AgNPs and silica NPs, among others, are currently used in dental practice for enhancing bond strength, durability, and antibacterial properties.
Glass ionomer cements
Incorporating NPs in GIC has resulted in minimizing porosities and micro-cracks within the set cement, leading to improved strength. Nanoceramics such as HAP NPs and fluorapatite NPs enhance the tensile, compressive, and flexural strength of GIC. In addition to the antibacterial properties offered by metallic NPs, antibiotics have been used in conjunction to improve the compressive strength. Fully commercial nano-GICs remain limited, with promising application in minimally invasive and pediatric dentistry.
Endodontics
Application of nanomaterials in the field of endodontics is primarily aimed at enhancing the antimicrobial activity, improving the mechanical properties of dentin, and regeneration of pulpal and periapical tissues. NP-based applications were experimented in the form of irrigants, intracanal medicaments (ICMs), and as an additive in sealers, obturating and/or restorative materials to enhance the antimicrobial property. Although NPs in endodontic sealers are commercially available for use in current practice, there are no widely adopted commercial irrigants, ICMs, or obturating materials.
Nanoparticles in root canal disinfection
Silver nanoparticles
The antimicrobial, antibiofilm, and antifungal properties of AgNPs make them a potential alternative to conventional irrigant NaOCl. , They are more widely used as an ICM than as an irrigant for enhanced antibacterial efficacy. , Combination of AgNPs and conventional calcium hydroxide (Ca(OH) 2 ) demonstrated greater antibiofilm action against E faecalis , functioning as a potential vehicle. , In addition, this combination also enhanced the anti-inflammatory and antioxidant properties of Ca(OH) 2 . ,
Chitosan nanoparticles
Chitosan NPs (CNPs) exhibit both antibiofilm and antimicrobial properties. As an irrigant, the chelating action of CNPs results in better smear layer removal characteristics than conventional agents. Their application as an ICM is attributed to their ability to minimize re-infection of dentin by preventing bacterial adhesion and degradation of dentin by bacterial collagenase. , The antibiofilm and dentin-stabilizing aspects can be further enhanced by photoactivation of CNPs. ,
Metal and metal oxide nanoparticles
Metal oxide NPs have gained attention in endodontics for their antimicrobial potential. Although zinc oxide (ZnO) NPs possess bactericidal properties similar to that of AgNPs, studies have shown inconsistent results regarding their antibacterial effectiveness and biofilm disruption when used as an endodontic irrigant. , Magnesium oxide, titanium dioxide (TiO 2 ), and iron oxide NPs exhibit antimicrobial activity, but research on their use in endodontics remains limited.
Nanoparticles in antimicrobial photodynamic therapy
NPs are effective carriers for photosensitizer molecules in antimicrobial photodynamic therapy. They act as photosensitizers (eg, TiO2 and ZnO) or serve as carriers by combining, encapsulated, or loading photosensitizers to enhance the antimicrobial efficacy of APDT. Poly(lactic-co-glycolic acid) (PLGA) NPs are widely used carriers for methylene-blue photosensitizer in APDT.
Drug delivery in endodontics
Biodegradable NPs are widely used as carriers for targeted drug delivery in endodontics. Among various biodegradable NPs, CNPs and polyester-based NPs exhibit excellent biocompatibility and low cytotoxicity. CNPs being an aqueous vehicle enhances the disintegration of Ca(OH) 2 into Ca 2+ and OH − ions, when used as carrier for Ca(OH) 2 . This leads to greater reparative and antibacterial properties of Ca(OH) 2 . ,
Another highly effective approach for incorporation and sustained release of biomolecules, such as antibiotics and antibacterial agents, is mesoporous NPs. Meso calcium silicate NPs (MCS NPs) induce hard tissue formation by precipitating appetite crystals. Their ability to occlude dentinal tubules by depositing these crystals can be used for the management of dentin hypersensitivity. When used alone or as a carrier for antibiotics, they effectively inhibit bacterial growth. Owing to their high viscosity, MCS NPs have also been used to fill the apical-third of root canals. The current and upcoming literature seems to point in the direction of definitive advantages of using NPs and nanotechnology for drug delivery in endodontics.
Nanoparticles in regenerative endodontic procedures
Nanofibrous scaffolds have been developed with enhanced mechanical properties for controlled and sustained release of embedded bioactive molecules. Among the different forms and shapes of polymeric NPs, nanospheres and nanocapsules are used in regenerative endodontic procedures (REPs) as drug carriers. In addition, various types of nanofibers have been experimented to enhance the proliferation of dental pulp stem cells and subsequent odontogenic differentiation. Further, the adverse impact of NaOCl irrigation on stem cells of apical papilla cells (SCAP) can be counteracted by conditioning dentin with CNPs, promoting their adhesion, cell viability, and differentiation. The adhesion and proliferation of osteoblast-like cells can be facilitated by incorporating HAP NPs into synthetic polymer-based NPs mimicking dentin matrix. Moreover, metallic NPs, such as graphene oxide, strontium, magnesium, zinc, and copper ions also exhibit osteoinductive and vascularizing potential.
Nano-based endodontic sealers
Endodontic sealers incorporate various bio-ceramic NPs, such as zirconia, glass-ceramics, and bioglass to enhance their adhesion to dentin while facilitating the release of Ca 2+ and PO 4 2- ions. CNPs incorporated in zinc oxide eugenol cements and/or resin sealers could inhibit bacterial biofilm formation at the sealer-dentin interface. Owing to the osteogenic and bioactive potential of MCS NPs, they were used as sealers. In addition, the minimal artifacts formed by these sealers may help in better analysis of abnormalities in the quality of root canal obturation.
The antibacterial efficacy of epoxy resin-based sealers was found to be improved when quaternary ammonium polyethyleneimine (QPEI) NPs were incorporated. , Further, incorporation of QPEI into commercially available root canal sealers has minimal or no impact on the physicochemical properties of the latter.
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