S. No.	Author	Study of Title	study Aim	Individuals No.	Study of Results
1	Vano et al., July 2014[6]	“Effectiveness of nHAP toothpaste in reducing DHS: A double-blind RCT”	“To compare the efficacy in reducing DHS of a dentifrice containing nHAP with a fluoride dentifrice and a placebo”	“105 individuals of 20–70 years of age range”	“nHAP toothpastes showed remineralising effects comparable to those of fluoride containing toothpaste”
2	Santos et al., 2014[7]	“A new “Silver bullet” to treat caries in children-NSF: A RCT”	“To investigate the effectiveness of a new anti-caries agent, NSF, applied once a year to arrest caries in children”	“130 teeth in 60 children of 6–7 years of age”	“NSF was demonstrated to be effective in arresting caries when applied once a year. The agent had advantage of not staining the dental tissue black”
3	Pandit et al., 2015[8]	“The use of nanocrystalline and 2 other forms of calcium sulfate in the treatment of infrabony defect: A clinical and radiographic study”	“To evaluate the efficacy of 3 forms of calcium sulfate i.e., Nanogen (nCS) (+), BoneGen (+) and Dentogen (+) in treatment of infrabony defects and to compare their efficacy as bone grafting substitutes”	“45 sites in 16 individuals (age range 20–64 years)”	“Both nanogen and bonegen were found effective in the treatment of infrabony periodontal defect”
4	Hegazy et al., 2016[9]	“Peri-implant outcomes with laser versus nanosurface treatment of early loaded implant- retaining mandibular overdenture”	“To compare peri- implant changes seen with two early loading protocols for modifying surface Treatment of dental implants-one modifying the collar portion (Laser-Lok implant) and the other modifying the implant surface (nanosurface treated implant)”	“36 individuals, age range 47–78 years”	“Both laser collar and nanosurface-treated dental implants found to be reliable with good stability”
5	Wang et al.,2016[10]	“Treatment of DHS using nHAP pastes: A RCT”	“to compare the effect of nHAP pastes indicated for professional (Desensibilise Nano-P) with or without experimental home- care application to Pro-Argin (new technology), and fluoride varnish (already established treatment) on DHS relief after 1 and 3 months of treatment”	“28 individuals”	“The tested formulation was effective in reducing DHS over duration of 3 months”
6	Freire et al., 2017[11]	“AgNPs: The new approach against S. mutans biofilm: A pilot clinical trial and microbiological assay”	“To examine  the antimicrobial properties of a new formulation containing AgNPs, named NSF, to inhibit S. mutans biofilm formation on children’s dental enamel”	“12 individuals of 7–8 years of age”	“NSF treated enamel had lower values of S. mutans viability and therefore can be used for clinical control and prevention of dental biofilm formation”
7	Priyadarshini et al.,2017[12]	“One year comparative evaluation of Ketac Nano with RMGIC and giomer in noncarious cervical lesions: A RCT”	“To evaluate the clinical performance of Ketac Nano (Ketac™N100), RMGIC (Fuji Filling™ LC), and Giomer (Beautifil® II) in NCCLs”	“120 restorations in 20 individuals”	“Ketac nano RMGIC restoration were better retained NCCLs while superior color match and surface finish were observed with Giomer restoration. Marginal discoloration was high with Ketac nano”
8	Amaechi et al.,2018[13]	“Clinical efficacy in relieving dental hypersensitivity of nHAP containing cream: A RCT”	“To compare the effectiveness of Apadent Pro (Sangi) nHAP dental cream to relieve DHS with a positive control cream containing 20% pure silica”	“56 individuals (18–80 years of age)”	“20% nHAP dental cream is an effective method to promote the relief if dental hypersensitivity symptoms when applied daily”
9	Yaberi and Haghgoo 2018[14]	“A comparative study of the effect of nHAP and egg shell on erosive lesion of the enamel of permanent teeth following soft drink exposure: A RCT”	“To compare the effects of nHAP or ES extract on the microhardness of healthy third molar tooth enamel following soft drink exposure”	“20 permanent 3rd molars in 10 individuals”	“nHAP and ES have the potential to remineralise erosive lesions”
10	Tirupathi et al.,2019[15]	“Comparative cariostatic efficacy of novel NSF varnish with 38% SDF varnish a double- blind randomized clinical trial”	“To evaluate the clinical cariostatic efficacy of a concocted 5% NSSF dental varnish with 38% SDF in preventing the progression of dentinal caries of primary molars”	“159 lesions in 50 children (6–10 years)”	“Annual application of 5% NSSF dental varnish with 38% SDF in preventing the dentinal caries of primary molars”
11	Fernando et al.,2019[16]	“Self-assembly of dental surface nanofilaments and remineralisation by SnF2 and CPP-ACP nanocomplexes”	“To demonstrate that SnF2 and CPP-ACP interact to form a nanofilament coating on the tooth surface and that together they are superior in their ability to promote dental remineralisation”	“8 healthy controls, age ranges from 18 to 60 years”	“The combination of CPP-ACP and SnF2 in oral care products may significantly improve their efficiency in prevention and treatment of dental caries, erosion and hypersensitivity”

“RCT=Randomized controlled trial, S. mutans=Streptococcus mutans, CPP-ACP=Casein phosphopeptide-stabilized amorphous calcium phosphate, HA=Hydroxyapatite, nHAP=Nano-HA, NSF=Nano silver fluoride, NCCLs=Noncarious cervical lesions, DHS=Dentin hypersensitivity, ES=eggshell, SDF=Silver diammine fluoride, NSSF=Nano-silver incorporated sodium fluoride, RMSIC=Resin-modified glass ionomer cement, nCS=Nanocalcium sulfate, AgNPs=Silver nanoparticles”

Figure 1: Application of Nanotechnology in different aspects in dental sciences

Figure 2: Basic structure of teeth

Introduction

Due to lack of dental care, millions of people have been suffering with dental problems. The most common problem is; dental carries or tooth decay which eventually leads to permanent tooth loss due to acids formation by bacterial infection. Food debris and sugar are the primary energy source for the bacteria. Free sugar is the most common risk factor for dental carries [1,2]. The cause of cavities are due to formation of acid through cariogenic bacteria such as Streptococcus mutans (S. mutans) and Lactobacillus species found in dental plaque biofilms, dissolving the teeth of hard tissues (enamel, dentin and cementum)[3,4]. Dental carries engage an interaction between hard tissues of teeth and microbial biofilm which is an irreversible process. Females are more prone to tooth decay or carries as compare to male of same age group [5]. Different approaches have been applied to cure dental carries; such as adhesives, restorative and denture bases used for treatment shows poor retention, non-bactericidal and toxic to the surroundings [6]. In a conventional approach different material i.e., silver, gold, Zinc, cupper, steel, ceramics, and amalgam have been extensively used in dentistry. Amalgam is a mercury-based alloy which is used to treat or fill carries worldwide but the mercury concentration may be toxic for human health [7]. Some people are very sensitive to mercury therefore they want to avoid this approach [8]. Nanomaterials has emerged as the most promising approach to treat plaque and biofilm. Tailored nanoparticles have the potential to target biofilms with less toxicity. Nanoparticles can be tuned with different sizes, shape and surface charge by adjusting the chemical compositions or adding different functional groups to it. Nanoparticles produce excellent results for drug delivery on very specific site to treat oral diseases [9].Various approaches for the application of nanotechnology have been epitomized in Figure 1. Utilization of different nanoparticles in dental sciences have been summarized in Table 1 [10].

Figure 1

Table 1

visible portion of our tooth is just a part of whole tooth which is called crown. The remaining part is completely buried into the jaw bone known as root. Basically, a tooth is comprised of enamel, dentin and dental pulp [11] as shown in Figure 2. Enamel is a thin translucent covering layer on dental crown that guards tooth against any physical and chemical damage[12]. Dentin is a hard, pale-yellow layer of mineralized tissues immediately after the enamel. Dental pulp is an oral tissue comprising of soft connective tissue, blood and lymph vessels and nerve fibers [13]. Pulp supplies essential nutrients to the Dentin.

Figure 2

Remineralization

Tooth enamel is the hardest tissue present in our body to guard our teeth against the damage. Tooth enamel is made up of calcium Phosphate. To avoid the demineralization of hard tissues of teeth, fluoride has long been used to boost the dental health [14]. Fluoride is helpful to remineralize tooth enamel and reverse the process of cavity at early stage [15]. Fluoride collaborates with calcium and phosphate to create a powerful defense system to maintain the oral health.  Toothpastes having different concentrations of fluoride are found helpful to prevent carry or tooth decay [16]. Fluoride varnish is also being used in primary oral health care [17, 18]. Fluoridation  programmes to prevent dental carries, have been endorsed officially by WHO [19].  Fluoridation of drinking water is also one of the greatest achievements for public oral health in America in 20th century [20, 21]. The doping with fluorine may offer feasible means of tuning physical and mechanical properties enhancing antimicrobial dental adhesives, dental implants, aesthetic restorative materials and denture bases increase the efficiency of dental materials [22-24].

Dentin Hypersensitivity

Dentin is composed of tiny dentinal tubules. Any kind of loss to these tubules may lead to hypersensitivity of dentin. Hypersensitivity of dentin is a very basic problem and has been reported with a higher prevalence [25]. DH can be prevented by reversing demineralization or blocking the exposure of tubules. Bioactive elements (BE) are one of these elemental agents which have oxides metals like calcium, sodium, and non-metals like phosphorus, silica, in respective ratios of bioactivity [26]. Streptococcus mutans (S. mutans) is the prime cariogenic bacteria which lead to dental carries [27-29]. Fluoride-based BG and ZnO nanoparticles composites have better tubule  occlusion potential for treatment of DH [30]. Novel nanocomposites by incorporating fluoride-doped nano bioactive glass and ZnO nanoparticles were synthesized successfully and have shown multi-benefit approach to prohibit plaque and bacterial growth [31]. Our emphasis has been targeted on calcium phosphates (CaP) nanoparticles for restorative of polymer materials because these demonstrate excellent remineralization and bacterial reduction capabilities [32-35]. Carboxymethyl chitosan and lysozyme nanogels with encased amorphous calcium phosphate have showcased increased effectiveness for dentinal tubule occlusion [36].

nti-bacterial

Silver (Ag) and zinc oxide nanoparticles have been used in the medical field for many years ago due to its bioavailability, biocompatibility and antimicrobial activities[37-39]. Ag ions react with microorganisms cell membrane to inhibit the enzymatic activity to lead DNA damage [39].

It has been reported that the smaller silver nanoparticles have better contact and antibacterial activity with the surface of the bacteria in comparison to larger particles. Some forms of nanosilver-fluorideproducts have been examined so far. Nano-silver-diamine-fluoride is one of these products that possess useful properties in caries inhibition despite some draw backs such as tooth staining [23]. Antibacterial activity of Ag nanoparticles has been posed to occur via two main mechanisms first one is by free Ag ions toxicity arising from the dissolution of the metals fromthe surface of these nanoparticles and second one is due to oxidative stress generation via reactive oxygen species (ROS) on surfaces of the nanoparticles [23,40]. Polymeric silane conjugated hafnium oxide nanoparticles are synthesized which prohibits bacteria growth significantly. Simultaneously they have used target-specific X-ray imaging of pathogen S. mutans. This unique study appreciates HfO2 nanoparticles for its diagnosis and antibacterial characteristics [41]. Zirconia surfaces, functionalized with gold and silver nanoparticles, have applied in dental implants for improved antibacterial activity [42]. Multiple oral species growth has been inhibited by Zinc oxide (ZnO) [43]. Zinc oxide nanoparticles have been  found effective against gram negative and gram positive bacteria [44]. Zinc oxide nanoparticles exhibit strong anti-bacterial property against S. mutansat 0.53μg/mL. These ZnO nanoparticles have shown anti-biofilm, anti-oxidant and anti-caries characteristics as well [45]. ZnO nanoparticles have shown excellent antibacterial activity, biocompatibility and low toxicity [46,47]. ZnO nanoparticles can be functionalized, tuned and doped easily via simple synthesis process [48]. “Nanoparticles of different sizes, shapes, and functionality can be synthesized to meet the specific pathways. Researchers are potentially exploring thesebenefits to overcome both the physical and chemical limitations by incorporatingbioactive compounds in dental polymeric compounds”. Therefore, synthesis fluoride doped silver and zinc oxide based CaP nanocomposites have been appreciated intensively for dental carries prevention.

Teeth whitening

Basically, teeth whitening are a procedure in which natural tone of teeth is diminished as per the requirement. Hydrogen Peroxide is commonly used as a whitening agent[49, 50] which acts as an oxidizing agent and produces unstable free radicals while diffusion into the tooth. These free radicals bind to organic color which leads to lighter pigmented compounds which eventually gives a whiter effect. Whitening of teeth is directly related to the intensity and location of stain [51].Concentration and exposure time of a bleaching agent will decide the end point of tooth whitening [52]. Carbamide peroxide nanoparticles have also been used for teeth whitening for better efficacy and stability [53]. A piezo-catalytic technique using BaTiO2 nanoparticles, have been reported less-destructive and harmless to enamelas compare to H2O2 based tooth bleaching [54].

Conclusion

This review has shown that how application of different nanoparticles can cause a paradigm shift in dentistry. Use of these nanoparticles is quite fruitful to face different challenges in dentistry. Fluoride have shown an excellent property to remineralize the enamel whereas various nanoparticles are helpful to cure dentin hypersensitivity. Silver and Zinc oxide NPs have possessed strong anti-bacterial property against S. mutans. Calcium phosphate nano composites have shown significant prevention rate against dental carries. Toxicity of NPs is the only concern which needs to optimize and further detailed study. Overall nanotechnology has the potential to improve the current pattern of dentistry to provide advanced oral health treatment.

Conflict of Interest

No conflict of interest.

Acknowledgements

The authors would like to acknowledge the Department of Biochemistry, Faculty of Dentistry, Jamia Millia Islamia, New Delhi.

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