A Systematic Review on Nano Coated Orthodontic Brackets and its Antibacterial Effects
Correspondence Address :
Suvetha Siva,
Senior Lecturer, Department of Orthodontics, SRM Dental College, Chennai, Tamil Nadu, India.
E-mail: suvetha150992@gmail.com
Introduction: Oral cavity is a natural habitat of bacteria which proliferates when an orthodontic appliance is placed which leads to enamel demineralisation or white spot lesions. In order to reduce the bacterial proliferation, the surface coating of brackets using nano particles came into existence.
Aim: To assess the different surface modifications using nano coating materials and to evaluate the antibacterial properties of these nano coated orthodontic brackets.
Materials and Methods: A systematic review was conducte in September 2021, analysing the microbial adhesion and antibacterial properties of orthodontic brackets after application of nano coating against uncoated brackets was conducted from the available electronic database during January 2000 to June 2021, which included PubMed, Embase, Google Scholar and Medical Literature Analysis and Retrieval System Online (MEDLINE). Due to less number of in-vivo studies, in-vitro studies were also included. An analysis on the microbial adhesion and antibacterial effects of various orthodontic brackets was done. The results were tabulated after performing risk of bias assessment for each study.
Results: Based on the inclusion and exclusion criteria, 13 studies were included in the study. Risk of bias was medium for majority of the selected studies. As per the previous literature, bacterial adherence of Streptococcus mutans, Streptococcus sobrinus, Aggregatibacter actinomycetemcomitans, Lactobacillus acidophilus, Actinomyces viscous and Candida albicans was reported lower in groups of brackets coated with silver nano particles than that in the groups of brackets without the addition of silver nano particles. The corrosion level on the silver or silver platinum (Ag-Pt) coated specimens was lower than that on the non coated specimens.
Conclusion: The stainless-steel orthodontic brackets coated with various nano coating materials like silver, silver-platinum, titanium, Zinc Oxide (ZnO) and Copper Oxide (CuO) exhibited adequate antibacterial effect. This shows that in orthodontic patients, especially the one susceptible to caries, the amount of plaque accumulation is significantly reduced when nano-coated orthodontic brackets are used. They reduce the microbial colony count, prevent enamel demineralisation and white spot lesions. Further clinical trials must be carried out on a large scale to confirm the results.
Antibacterial properties, Microbial adhesion, Nano coating, Nano particles
The oral cavity is a natural habitat for microorganisms like bacteria to proliferate and produce organic acids that demineralise the surface of tooth enamel thus leading to white spot lesions followed by dental caries (1). When a fixed or removable orthodontic appliance is placed in patient's mouth, there will be variation in the microbial flora, decrease in the pH level followed by increased plaque accumulation. This occurs most commonly at tooth surface and bracket interface since these areas are very difficult to access using a toothbrush. There will be adhesion of bacteria and biofilm formation in these areas. The most common type of bacteria that produce significant amount of acid and lead to demineralisation include Streptococcus mutans and Lactobacilli. Streptococcus sobrinus and Porphyromonas gingivalis are also associated with demineralisation (2).
Orthodontic brackets can be classified as metallic and aesthetic brackets based on the material used. Stainless steel orthodontic brackets are the most commonly used metallic brackets in or-thodontic treatment. However, there were reports of enamel demineralisation at the bracket-adhesive-enamel junction, White spot lesions (decalcification of enamel) and dental caries en-countered while undergoing orthodontic treatment due to plaque accumulation around brackets (3). Orthodontic brackets are ideal surface for increased plaque accumulation (4). Because of their complex structure they do not prevent biofilm formation and microbial growth. This leads to decalcification which is the first step to cavity formation (5).
Hence, nano materials can be coated over the brackets to reduce enamel demineralisation, bacterial aggregation, surface roughness and friction (6). Nitrogen doped Titanium dioxide (TiO2), Silver (Ag), Gold (Au), Silica (SiO2), Copper (Cu/CuO) and ZnO nano particles have been used as coating materials to reduce demineralisation. These coatings prevent the bacterial aggregation by changing the antibacterial properties of the metal surface of the appliance before application (3).
Commonly, Ag coatings are used due to its non toxicity and its antimicrobial effect. Silver has superior antibacterial and antibiotic characteristics (5). The antimicrobial effects of silver ion or salts are known well since ancient times. Silver nano particles can be used as antibacterial agents because of their different chemical and physical properties (2). During the silver (Ag) coating process of orthodontic brackets, addition of Palladium (Pd) is done to increase the hardness and wear resistance which will prevent the corrosion caused by chewing food (5).
Titanium coatings are used due to its biocompatibility properties (5). The bracket coated with the TiO2-xNy thin film strongly prevents the adherence of S. mutans. It shows high antimicrobial activity against S. mutans, L. acidophilus, A. viscous, and C. albicans. Enamel demineralisation and gingivitis occurring during orthodontic treatment can also be prevented effectively. Nano titanium films are not suitable for friction reduction (6),(7). Studies showed that the brackets coated with ZnO and CuO nano particles have excellent antimicrobial properties and after a period of time the bacterial count was reduced to zero (8),(9),(10),(11). Orthodontic brackets coated with Silver (Ag) and Platinum (Pt) also provide antimicrobial property and prevent the biofilm formation (3). Nano coating process was done by using physical vapour deposition system (1).
The aim of this systematic review is to assess the different surface modifications using nano coating materials and to evaluate the antibacterial properties of these nano coated orthodontic brackets.
This systematic review was done in SRM Dental College, Ramapuram, Chennai in the month of September 2021, using four investigators under the registration ID SRMU/M&HS/SRMDC/2021/S/032 (SRM Dental College). A computerised search of the database was done from January 2000 to June 2021. The following databases were searched: Pubmed; Google Scholar, MEDLINE, MEDLINE In-process, Embase using the keywords like Microbial Adhesion; Nano coating; Nano Particles; Orthodontic Brackets and the articles were included in the systemic review based on the search criteria.
PICO Question: Population, Intervention, Comparison and Outcome
Can the incorporation of nano particle coating increase the antibacterial properties of orthodontic brackets and reduce the occurrence of dental caries?
PICO Analysis
Population (P): Orthodontic brackets
Intervention (I): Brackets coated with Nano particles
Comparison (C): Uncoated brackets
Outcome (O): Increase or decrease in the antimicrobial properties and its effect on enamel demineralisation or dental caries.
Inclusion criteria: Those publications of studies in English language with full text articles and studies on nano coated brackets and their antibacterial properties, from the year 2000 were included in the review.
Exclusion criteria: Articles published in language other than English, those studies which do not assess antibacterial properties of nano coated brackets and case reports were excluded from the review.
Data Extraction and Synthesis
Articles abstracts were read thoroughly to determine the eligibility of articles. Two researchers independently completed the selection process. If a discrepancy arose, a third researcher helped in making the final decision. Articles for which the abstracts did not present enough relevant information to make a final decision regarding their inclusion were rejected. The reference lists of the selected articles were also searched for additional relevant publications that may have missed in the database searches.
All the articles from the selected abstracts were evaluated independently and conclusion regarding which articles included in the review was drawn. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flowchart of article selection is given in (Table/Fig 1).
Google Scholar and PubMed had the greatest diversity of abstracts. All of the selected abstracts from PubMed were included in Google Scholar and vice versa. After completing the review of the selected abstracts, the reference lists of the selected articles were included are displayed in (Table/Fig 2) (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13).
Based on quality analysis; (National Institute of Health (NIH) quality assessment tool for risk of bias} (14), the quality of research and methodology was low for only one study, medium for eleven studies and high for one study (Table/Fig 3).
When orthodontic treatment is done using fixed appliances, occurrence of plaque and microbial accumulation followed by white spot lesions around the bracket base area is very common. This will lead to frequent debonding of the brackets or bracket failure and also gingival inflammation because of increased bacterial count. In order to avoid this, the surface of the brackets is coated with different nano coatings (15). The main objective of this systematic review was comparison of different nano-coated brackets with uncoated brackets to prevent the bacterial accumulation and antimicrobial property.
The different microorganisms that are present in the oral cavity will lead to the formation of enamel demineralisation by releasing certain acids. The most commonly associated bacteria with enamel demineralisation are Streptococcus mutans and Lactobacilli. These bacteria release lactic acid into the oral cavity thus leading to the formation of white spot lesions. The other bacteria that are associated include Streptococcus sobrinus, Porphymonas gingivalis and Aggregatibacter actinomycetemcomitans. The orthodontic brackets do not have the ability to prevent plaque accumulation or formation of white spot lesions because of its complex structure. An idea of nano coatings on orthodontic brackets has been introduced to prevent enamel demineralisation. The various coating materials that are used include Nitrogen doped Titanium dioxide (TiO2), Silver (Ag), Gold (Au), Silica (SiO2), Copper (Cu/CuO) and ZnO nano particles (16).
Jasso-Ruiz I et al., had concluded that the nano silver coated orthodontic brackets exhibit significant antibacterial properties against microorganisms and reduce their colony count. There is less adherence of microorganisms (Streptococcus mutans) to the brackets that were nano silver coated (1). A study was done by Ryu HS et al., to compare the antibacterial properties and corrosion level of Silver-Platinum (Ag-Pt) coated orthodontic brackets with uncoated brackets. It was found out that the bacterial growth was significantly reduced in coated brackets (approximately 60%). Level of corrosion was also lower in Ag-Pt brackets when compared to the uncoated brackets (3).
A report by Ghasemi T et al., on the brackets coated with nano films of silver and titanium oxide coating was done. The four coated groups with silver and titanium oxide reduced the S. mutans count. Another important requirement during orthodontic treatment is the biocompatibility of the appliance. It has been found out that Nano costed Ag/TiO2 brackets have good biocompatibility other than the antibacterial effects (6). A study was done by Fatani EJ et al., to compare the antibacterial and antiadherent properties of Titanium oxide mixed with silver coated brackets against the uncoated brackets. The type of bacteria that was used in the study included Streptococcus mutans and Porphyromonas gingivalis. It was concluded that the antiadherent and antibacterial properties of coated brackets was significantly higher than that of uncoated brackets (5).
Many studies have reported on the antimicrobial assessment of brackets coated with nitrogen doped titanium dioxide coating. The studies showed that the N-doped TiO2-xNy surface coated bracket have significantly higher antimicrobial activity because of fewer bacterial adherence. Since the bacterial count was less, there was a reduction in colony forming units. The bactericidal effects of TiO2 coated brackets against L. acidophilus, which cause dental caries was also significant (4),(7),(12),(13). In a study done by Ramazanzadeh B et al., 4 groups were compared for the antibacterial properties against Streptococcus mutans. Group 1 included brackets coated with CuO, Group 2 included ZnO brackets, Group 3 included CuO- ZnO coated brackets and Group 4 included uncoated brackets. They found that the coated brackets have significant antibacterial properties than uncoated brackets (8). In groups with CuO, coated brackets and CuO-ZnO coated brackets, the bacterial count was reduced to zero within two hours. But in ZnO coated brackets group, the antimicrobial properties were less when compared to other two groups.
Limitation(s)
Even though there are many studies to prove that the nano coated brackets have antibacterial properties, 11 out of 13 studies were only in-vitro studies. Only 2 out of 13, studies were in-vivo which accounts to about 15% of total studies. It might seem logical to think that the results of in-vitro studies would be more reliable, since it is done under controlled environment without the factors affecting the interpretation of results. But the in-vitro studies have its own drawbacks such as the variability encountered during the human experiments/in-vivo studies and it is impossible to replicate the exact intraoral environment such as medium, temperature and pH, etc. (17). Further in-vivo studies are required to check the reliability of the results.
The stainless steel orthodontic brackets coated with various nano coating materials like silver, silver-platinum, titanium, ZnO and CuO were evaluated, and they exhibited adequate antibacterial effect by decreasing the adherence of Streptococcus mutans on the orthodontic brackets. This indicates that in patients susceptible to dental caries and undergoing orthodontic treatment, there was a significant reduction in plaque accumulation when nano coated brackets are used. They reduce the microbial colony count, prevent enamel demineralisation and white spot lesions. Further clinical trials must be carried out on a large scale to confirm the results.
DOI: 10.7860/JCDR/2022/52649.16020
Date of Submission: Oct 05, 2021
Date of Peer Review: Nov 09, 2021
Date of Acceptance: Dec 21, 2021
Date of Publishing: Feb 01, 2022
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? NA
• For any images presented appropriate consent has been obtained from the subjects. NA
PLAGIARISM CHECKING METHODS:
• Plagiarism X-checker: Oct 06, 2021
• Manual Googling: Dec 13, 2021
• iThenticate Software: Dec 20, 2021 (16%)
ETYMOLOGY: Author Origin
- Emerging Sources Citation Index (Web of Science, thomsonreuters)
- Index Copernicus ICV 2017: 134.54
- Academic Search Complete Database
- Directory of Open Access Journals (DOAJ)
- Embase
- EBSCOhost
- Google Scholar
- HINARI Access to Research in Health Programme
- Indian Science Abstracts (ISA)
- Journal seek Database
- Popline (reproductive health literature)
- www.omnimedicalsearch.com