Professor,  Department of Orthodontics, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Science (SIMATS), Saveetha University,  Chennai Tamilnadu, India

Corresponding author email: aravindkumar@saveetha.com

Article Publishing History

INTRODUCTION

Nanoparticles are currently used in dental practice for several applications  in the field of orthodontics  nano particles is applied as nano-coatings in arch wires and brackets to reduce friction , Fabrication of hollow wires , orthodontic brackets, as antimicrobial agent to prevent white spot lesion. Direct bonding with resin adhesives has become the most popular method for orthodontic bonding. One of the most important considerations for a good orthodontic adhesive is to have adequate bond strength which is able to withstand both occlusal and orthodontic forces. An orthodontic bonding agent must possess high bond strength balanced with the ability of the material to leave little or no residue on enamel upon removal. The bonding material must be inexpensive and accessible. At present, most orthodontic cements available in the market already have these features, however, finding a bonding agent that may also prevent white spot lesions (WSLs) is a challenge. An obstacle on the crown level during fixed orthodontic procedures (FOP) are white spot, enamel demineralization and tooth decay, ( Bishara et al 2007, Uysal, 2010, Panchali, 2016, Florence 2020).

Nanoparticles are incorporated into orthodontic adhesives/cement and can be coated on the surfaces of orthodontic appliances to prevent dental plaque  or enamel demineralization during the treatment . Various literature studies showed that the addition of antimicrobial NPs to orthodontic adhesive agents and resin-modified glass ionomers cements (RMGICs) might prevent plaque accumulation and bacterial adhesion, (Gunes 2008) This review provides a useful insight into the antimicrobial effects and orthodontic adhesives incorporated with  zinc oxide and hydroxyapatite nanoparticles.

Antimicrobial Activity Based on Literature Review

Dental disorders have  affected over  3.47 billion individuals in the world and is one of the three most common reasons for worldwide infections. Among the oral disorders, the most common were dental caries and periodontitis. Together, they contribute to the most widely recognized irresistible human ailment in the world. Regardless of whether caries and periodontitis are multifactorial ailments, the primary etiological factor is the occurrence of pathogenic microorganisms. These microbes are composed inside an extracellular framework to shape a bacterial biofilm, ( Frencken et al .2017). In the biofilm, the microorganisms are amassed to shape a hindrance that opposes anti-toxins furthermore, advances incessant fundamental diseases. Additionally, microorganisms are multiple times progressively impervious to hostile to microbial treatment. Additionally, in biofilms, microbes can escape the resistant framework by delivering super antigens. To battle these bacterial contaminations, metal, metal oxide, and different NPs give off an impression of being promising choices due to their particular physio-synthetic properties, ( Seil and Webster,2012 ;Valm, 2019)

Sodager et al (2013) investigated the antibacterial properties of ordinary orthodontic composite containing silver/hydroxyapatite nanoparticles. In his investigation antibacterial properties of the composite groups were tested against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus sanguinis. Plate dissemination strategy was followed to discover the zone of hindrance. Antibiofilm activity showed that silver/hydroxyapatite nanoparticles indicated zone of inhibition  against all the microorganisms tested. NiTi orthodontic wires were covered with ZnO nanoparticles utilizing the chemical deposition activity. Coating characteristics  just as the physical, mechanical and antibacterial properties of the wires were researched. The covered wires introduced up to 21% decrease in the frictional powers and antibacterial action against Streptococcus mutans, ZnO nano coating fundamentally improved the surface nature of NiTi wires (Kachoei et al  2016).

A recent study by Scribante et al (2020) demonstrated  the utilization of remineralizing solution which initiated decrease of demineralized areas .Bond quality characteristics  were essentially diminished for the two sections and connections subsequent to remineralizing treatment. His investigation additionally indicated higher grip esteems brackets in both conditions tested. Remineralized enamel showed significantly higher micro hardness values than demineralized enamel and lower values than intact enamel, Ohtsu et al (2017) in their examination called attention to the antibacterial viability of ZnO/HAP These discoveries proposed that the coatings utilized in the investigation assumes critical job for the surface adjustment of Ti inserts, with a capacity to consolidate the avoidance of irresistible sicknesses with osteogenic action. In a study involving pure and ZnO (0% – 43%) in various forms doped with nano Hydroxyapatite powders .Sol gel method is used to synthesise the nanoparticles. The characterisation of  this nanoparticles were performed using XRD, FTIR assay (Deepa.,2013)

In vitro Antimicrobial assay was carried out against gram negative bacteria in which pure and doped nHAp samples were observed irrespective of the ZnO content.Another study was performed focussing on  the antimicrobial efficacy of silver, titanium dioxide and zinc oxide nanoparticles against Streptococcus mutans (Reddy  et al .,2018) Viable bacterial count is determined in the study which showed a significant difference in the colony forming units among all three concentrations of silver (Ag), titanium dioxide (TiO2) and zinc (ZnO) nanoparticles  .The study further proved that the Silver, Zinc oxide and Titanium dioxide which showed  significant antimicrobial effects were found to be  concentration dependent .

Some other works investigated by Grenho et al (2015) about the development of three dimensional and inter connected porous granules of nanostructured hydroxyapatite .In vitro and In vivo experimental models were performed in this study .In the In vitro model ,when the granules exposed to staphylococcus aureus and staphylococcus epidermidis showed antibacterial activity cytocompability assay  towards osteoblast cell line showed inflammatory response .In vivo models also showed antibacterial effects .Altogether these nano HA-ZnO porous granules possess significant antibacterial activity and employed in orthopaedic and dental applications.

Nanoparticle Based Dental Fillers

HA-NPs have been incorporated into oral care products, for example, dentifrices and mouthwash to decrease or erase dental affectability by hindering open dentinal tubules on the outside of the dentin also, associated with the mash, or to advance the remineralization of lacquer by supplanting calcium and phosphate particles in the regions from which minerals dissolved, restoring its integrity and shine, (Jena et al.,2017 ;Vano.,2014)

Hydroxyapatite nanoparticle is one of the  commonly metal nanoparticle  for the teeth filling but the literature regarding its efficacy for filling in infectious mouth is still not clear .study conducted by Konar et al (2019) using Graphene oxide ,hydroxyapatite ,zirconia nanoparticles against Enterobacter ludwigii  and Escherichia coli .field emission scanning electron microscopy (FESEM), fluorescence microscopy and zeta potential techniques. The findings revealed that Zirconia nanoparticles are not efficient dental filler, whereas graphene oxide nanoparticle  is the best filler followed by hydroxyapatite nanoparticles, that can  reduce the bacterial load significantly.

Sheer Bond Strength

Influence of silver (Ag), zinc oxide (ZnO), and titanium dioxide (TiO2) nanoparticles on shear bond strength (SBS) was investigated by Reddy et al .In the study he observed that there was a significant difference between control  , Ag, ZnO, and TiO2  with SBS at 5% level of significance. The Scanning electron microscopic examination confirmed homogenous distribution of nanoparticles in the adhesive in all three groups. Further to mention in the study,  it was concluded that the incorporation of various nanoparticles in to adhesive materials in minimal amounts may decrease SBS and may lead to the failure of bracket or adhesive (Reddy et al.,2016).

The addition of silver, zinc oxide or titanium dioxide nanoparticles into orthodontic bonding agent at a concentration (1%) did not show any  effect on bond strength. These nanoparticles  have shear bond strength values above the minimum for clinical routine use. The findings in the study  suggest significant differences is observed  in ARI, considerably more adhesive remains on the enamel surface following bracket removal in Ag, ZnO, and TiO2 groups compared to the control group. In an experimental study 80 extracted human pre molars were used and divided in to 4 groups, the study was conducted to evaluate the SBS of resin-modified glass ionomer cements. (RMGICs) modified by nano-zinc oxide (NZnO) and nano-hydroxyapatite (NHA) in comparison with composite resins. Findings of the study showed that the amount of SBS was similar among all groups and addition of NZnO and NHA particles had no negative effect on SBS of RMGIC (Sari et al.,2015).

Similar study was based on the addition of silver and Hydroxyapatite nanoparticles on the shear bond strength (SBS) of an orthodontic adhesive. SEM and EDAX analysis showed significant changes between the study groups and the control .Incorporation of silver/HA nanoparticles containing 5% and 1% silver maintains and increases the SBS of orthodontic adhesives, whereas increasing the amount of particles to 10% has an undesirable effect when compared to the control group (Baratali et al.,2015).

Saffarpour et al (2016) suggested that the incorporation of Zincoxide nanoparticles in to the dental adhesives increased the antimicrobial effects without affecting the bond strength properties .Adhesive system with hydroxyapatite nanoparticles as load, characterizing it and evaluate the effectiveness of its bond to dental structure. Evaluating with  microshear test and characterization technique. It was found that the nanoparticles showed statistically significant difference between the groups. It has been observed that Combined effect of Zinc oxide and CuO has also been studied and it has been observed that CuO and ZnO/CuO nanoparticles coated brackets have better antimicrobial effect on S.mutans than brackets coated with Zinc oxide or CuO alone (Sarah 2018; Dumont et al 2013).

Clinical Significance: Various research has been published in the application of Nanotechnology in the form of metallic nanoparticles like silver, gold, titanium ,nickel, Copper oxide, zinc oxide, hydroxyapatite coated in the orthodontic adhesives as bonding agent to evaluate the sheer bond strength, nano fillers, enamel remineralising agents, fabrication of brackets. This nanoparticle application in the field of orthodontics is in a growing stage ,although several studies were done in orthodontics incorporating the nanotechnology but they are mostly in the in vitro phase and in future several in vivo research to be carried out in order to investigate the antimicrobial ,anti-inflammatory ,cytotoxicity efficacy  to use in the clinical treatment for the patients.

CONCLUSION

Nanotechnology has carried enormous changes to the field of Orthodontics. As of now, these improvements are found for an enormous scope in different field identified with oral prophylaxis. Right now, oral care products like toothpastes and mouthwash which contain NPs with anti-microbial, mitigating, and remineralizing properties. In view of promising outcomes and changed, diversified properties, nanomaterials contain various possibilities, and their uses brief numerous points of view that make it workable for them to be compelling. In any case, the advantages of NPs include similar reasons that make them Safe—Properties like small particle size , surface properties, quantum state, movement, conglomeration, change, and the formation of free radicals. In this manner, Incorporation of NPs is as of now one of the most contemplated component of dentistry, because of the practically boundless fields of utilization, furthermore, subsequently administrative and well being concerns must be considered and addressed, particularly concerning the utilization of hydroxy /Zinc oxide NPs in oral care products.

Conflict of Interest : Nil

REFERENCES

Baratali Ramazanzadeh ., Arezoo Jahanbin ., Masoud Yaghoubi ., Nasser Shahtahmassbi ., Kiarash Ghazvini .,  Mohammadtaghi Shakeri ., Hooman Shafaee (2015).  Comparison of Antibacterial Effects of ZnO and CuO Nanoparticles Coated Brackets against Streptococcus Mutans. J Dent Shiraz Univ Med Sci.,16(3): 200-205.

 Bishara ,SE., Ajlouni ,R., Soliman, MM., Oonsombat, C., Laffoon, JF., Warren J (2007). Evaluation of a new nano‑ filled restorative material for bonding orthodontic brackets. World J Orthod ., 8:8-12.

Deepa,C .,Nishara Begum , A .,Aravindan,S., (2013).Preparation and Antimicrobial Observations Of Zinc Doped Nanohydroxyapatite. Nanosystems: Phys. Chem. Math. 4(3);370-77

Dumont, V., Silva, R., Almeida-Júnior, L., Roa, J. , Botelho, A. and Santos, M (2013).Characterization and Evaluation of Bond Strength of Dental Polymer Systems Modified with Hydroxyapatite Nanoparticles. J Mat Sci Chem Eng.1, 13-23.

Florence Carrouel  , Stephane Viennot  , Livia Ottolenghi  , Cedric Gaillard , Denis Bourgeois (2020) Nanoparticles as Anti-Microbial, Anti-Inflammatory, and Remineralizing Agents in Oral Care Cosmetics: A Review of the Current Situation. Nanomaterials  10, 140;1-32. doi:10.3390/nano10010140

Frencken, J.E.; Sharma, P.; Stenhouse, L.; Green, D.; Laverty, D.; Dietrich, T(2017). Global epidemiology of dental caries and severe periodontitis—A comprehensive review. J. Clin. Periodontol.  44, S94–S105.

Grenho ,L., Salgado,C L., Fernandes,M H., Monteiroand,F J.,Ferraz ,M P (2015).Antibacterial activity and biocompatibility of three-dimensional nanostructured porous granules of hydroxyapatite and zinc oxide nanoparticles – An in vitro and in vivo study. Nanotechnol. 26; 315101 .

Gunes, S., Jana, C (2008). Shape memory polymers and their nanocomposites: a review of science and technology of new multifunctional materials. J Nanosci Nanotechnol. 8(4):1616-1637.

Jena, A.; Kala, S.; Shashirekha, G.(2017)Comparing the effectiveness of four desensitizing toothpastes on dentinal tubule occlusion: A scanning electron microscope analysis. J. Conserv. Dent.  20, 269–272 .

Mojgan Kachoei .,Azin Nourian .,Baharak Divband .,Zahra Kachoei .,Sajjad Shirazi (2016). Zinc-oxide nanocoating for improvement of the antibacterial and frictional behavior of nickel-titanium alloy. Nanomedicine .11(19).

Monidipa Konar., Nibedita Nayak., Subhashree Priyadarsini., Monalisa Mishra .,Harekrushna Sahoo (2019). Antimicrobial activity of nanoparticle-based dental fillers on novel chromogenic bacteria Enterobacter ludwigii. Mater Res Express, 6 (8); Article id. 085407

Naofumi Ohtsu .,Yuko Kakuchi .,Tsubasa Ohtsuki (2017).Antibacterial effect of zinc oxide/hydroxyapatite coatings prepared by chemical solution deposition. Applied Surface Science . 445.

Panchali, B., Anam, M., Jahirul, M., Meryam, SR., Ragini, M (2016).Nanoparticles and their Applications in Orthodontics. Adv Dent & Oral Health.  2(2): 555584.

Reddy AR .,Prabhuraj B Kambalyal., Karpagavalli Shanmugasundaram., Rajesh V., Sowjanya Donthula., Santosh R Patil (2018).Comparative Evaluation of Antimicrobial Efficacy of Silver, Titanium Dioxide and Zinc Oxide Nanoparticles against Streptococcus mutans. Pesquisa Brasileira em Odontopediatria e Clinica Integrada . 18(1):e4150

Reddy, AK., Kambalyal, PB., Patil, SR., Vankhre, M., Khan, MY., Kumar, TR (2016). Comparative evaluation and influence on shear bond  strength  of  incorporating  silver,  zinc  oxide,  and  tita-nium dioxide nanoparticles in orthodontic adhesive. J Orthod Sci. 5(4):127-131.

Saffarpour M., Marjan Rahmani., Mohammadreza Tahriri., Amir Peymani (2016). Antimicrobial and bond strength properties of a dental adhesive containing zinc oxide nanoparticles. Braz J Oral Sci.  (15)1 ;66-69

Sarah Y. Hailan .,Mustafa M. Al-Khatieeb (2018). The Effects of Incorporating some Additives on Shear Bond Strength of Orthodontic Adhesive (An In-vitro Study). International Journal of Medical Research & Health Sciences .7(11): 11-18.

Sari MN  ., Nafiseh Rahmani., Mehdi Araghbidi Kashani., GHolamreza Eslami Amirabadi ., Ali Akbari Sari ., Elahe Seyedtabaii (2015). Effect of Incorporation of Nano-Hydroxyapatite and Nano-Zinc Oxide in Resin Modified Glass Ionomer Cement on Metal Bracket Debonding Spring . J Islam Dent Assoc Iran .27(2);70-76.

Scribante A .,Mohammad Reza .,Dermenaki Farahani., Giorgio Marino., Claudia Matera., Ruggero Rodriguez y Baena .,Valentina Lanteri., Andrea Butera (2020). Biomimetic Effect of Nano-Hydroxyapatite in Demineralized Enamel before Orthodontic Bonding of Brackets and Attachments: Visual, Adhesion Strength, and Hardness in In Vitro Tests. Biomed Res Int.Article ID 6747498 ;Vol-2020 .1-9  .

Seil, J.T.; Webster, T.J (2012). Antimicrobial applications of nanotechnology: Methods and literature. Int. J. Nanomed.  7, 2767–2781.

Sodagar, A., Bahador ,A., Khalil, S., Shahroudi ,AS., Kassaee, MZ., (2013). The effect of TiO2 and SiO2 nanoparticles on flexural strength of poly (methyl methacrylate) acrylic resins. J Prosthodont Res 57(1): 15-19.

 Uysal ,T., Yagci ,A., Uysal, B., Akdogan, G (2010). Are the nano‑ composites and nano‑ ionomers suitable for orthodontic bracket bonding? Eur J Orthod.  32:78- 82.

Valm, A.M. (2019)The Structure of Dental Plaque Microbial Communities in the Transition from Health to Dental Caries and Periodontal Disease. J. Mol. Biol.  431, 2957–2969.

Vano, M.; Derchi, G.; Barone, A.; Covani, U. Effectiveness of nano-hydroxyapatite toothpaste in reducing dentin hypersensitivity: A double-blind randomized controlled trial. Quintessence Int. Berl. Ger. 2014, 45, 703–711