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Impact of Fluoride Mouthwash on Nickel ion Release from Orthodontic Brackets: An In-vitro Study
Correspondence Address :
Prem Vishva Natarajan,
162, Poonamallee High Rd Velappanchavadi, Chennai, Tamil Nadu, India.
E-mail: drpremvishva@gmail.com
Introduction: In Orthodontic patients, the orthodontic brackets and wires are exposed to the oral fluids for a considerable period of time. Patients use fluoridated mouthwashes to maintain oral hygiene and avoid white spot lesions on their teeth, which can cause release of nickel and chromium from the orthodontic brackets and thus may lead to allergic reactions and cytotoxicity.
Aim: To evaluate the amount of nickel ion release from orthodontic brackets on exposure to different fluoride mouthwash.
Materials and Methods: This in-vitro experimental study was conducted on seventy-five Orthodontic brackets which were divided into three groups of 25 each and immersed in artificial saliva (group A), Amflor mouthwash (group B) and Zero sense (group C) mouthwash respectively in separate beakers. The temperatures of the solutions in the beakers were maintained at 37 degrees to simulate oral temperatures. The 5 mL of the solutions were drawn from the three breakers at 1 hour, 6 hours, 12 hours and 24 hours respectively and the Nickel ion release from each solution was measured using Optima 5300 Dual View (DV) Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). One-way Analysis of Variance (ANOVA) with a post hoc test was performed for comparison between the groups and at different time intervals.
Results: The highest mean value of nickel release was noted in group C (0.32±0.020156 μg/mL) at the 24 hrs peak time followed by group B (0.24±0.014338 μg/mL). Statistical analysis showed a significant difference between the two experimental groups at all time periods except 1 hour (p-value <0.05).
Conclusion: The amount of nickel ion release did not exceed the permissible limit in any of the study groups. However, it can be inferred that Amflor mouthwash can be prefered over Zero sense mouthwash for Orthodontic patients considering the lower nickel ion release.
Corrosion, Metal brackets, Nickel cytotoxicity
Orthodontic brackets are mostly made from American Iron and Steel Institute (AISI) type 316L austenitic Stainless Steel (SS). Such steel contains biomaterials of 18-20 percent chromium, 8-10 percent nickel with a small amount of manganese and silicon with the remainder being iron. They also have very low carbon content (less than 0.03 per cent). Different manufacturers use different types of stainless steel for better corrosion resistance and mechanical properties, including 304 stainless steel, 316 stainless steel, and 17-4 Precipitation-Hardening (PH) stainless steel (1). Nickel in stainless steel stabilizes the austenitic phase of stainless steel and also enhances the alloy’s anticorrosive properties (2). However, Nickel is a potent immunologic sensitizer and the leading cause of allergic contact dermatitis, a type IV delayed hypersensitivity immune response (3). Nickel allergy causes burning sensation, rashes, swelling, and painful erythematous lesions in the mouth and labial mucosa. The allergic reactions also include gingivitis, gingival hyperplasia, lip desquamation, metallic taste, angular civilities, and periodontitis (4). To an orthodontist this is of concern as nickel leeches from the brackets and the wires used in Orthodontics into the saliva (5),(6). Nickel discharge from Nitti orthodontic wires in artificial saliva have been studied and it has been discovered that nickel release increases as the pH increases (4).
Fluoride mouthwashes are being advised for the maintaining good oral hygiene and prevention of White spot lesions (WSLs) by aiding remineralization (7),(8). Fluoride’s effective caries-prevention property is by producing hydrofluoric acid (HF), the fluoride ion of which acts as a bactericidal agent. However HF output has been shown to damage orthodontic wires and brackets. HF corrodes the appliance’s surface by destroying the protective oxide layer (9),(10),(11),(12). Previous research has been conducted to see how fluoride mouthwashes influence nickel release from orthodontic brackets and wires (13),(14),(15). Earlier studies have evaluated the effect of various mouthwashes on the ion release from orthodontic brackets (16),(17). However, there has been no study on the effect of Amflor fluoridated mouthwash on nickel ion release from orthodontic brackets. In this study, the authors assessed the effect of two different fluoride mouthwashes namely Amflor and Zerosence on nickel ion release from orthodontic brackets and compared it with that of artificial saliva.
This in-vitro experimental study was conducted in a Saveetha Dental college and hospital in Chennai in August, 2021. Ethical approval was obtained from the institutional review board (IHEC Ref NO: IHEC/SDC/ORTHO-2002/22/375). This study consisted of 75 orthodontic metal brackets (3M-Abzil kiriumR) which were divided into three groups of 25 brackets each:
• (Group A-artificial saliva,
• Group B-Amflor mouthwash,
• Group C-zero sense mouthwash).
Procedure
These brackets were immersed in 50 mL of their respective solutions that were kept in separate beakers for 24 hours. The fluoride mouthwashes used for the study namely Amflor Mouthwash and Zero sense mouthwash were commercially purchased and were not diluted for the study. The artificial saliva used in Group A was prepared according to study by Levine MJ et al., (18).
The temperature of the solutions in the beakers were maintained at 37 degrees to simulate oral temperatures. At intervals of 1 hour, 6 hours, 12 hours and 24 hours, 5 mL of the solutions were drawn from the three breakers and tested for nickel ion using Optima 5300 DV ICP – OES.
Statistical Analysis
The statistical software International Business Management (IBM) Statistical Package for Social Sciences (SPSS) statistics version 23.0 was used for statistical analysis. The data on the amount of nickel ions released from the orthodontic brackets in the different solutions at various time intervals were then distributed into google spreadsheet. The mean and standard deviation of each group were obtained. To check for significant differences between the three groups involved, a one-way Analysis of Variance (ANOVA) was performed with a post hoc test to find significance at difference time intervals between the groups. Level of significance was set at 95%.
The amount of nickel ion released was highest at 12 hour time period in both the Amflor and Zero sense mouthwash groups. The mean values of nickel ions released for each group at various time intervals are given in (Table/Fig 1). One-way ANOVA was used for finding statistically significant differences between all the time intervals was shown in (Table/Fig 2). Statistically significant nickel release was seen between the three groups in all the time intervals studied; hence a post hoc test was conducted to determine the statistical significance at various time intervals (Table/Fig 3).
When Group B (0.052±0.002754) was compared with Group A (0.031±0.009129) and Group C (0.064±0.002944) at 1-hour intervals, there was no significant difference (p>0.05); but, when group A(0.031±0.009129) was compared with group C(0.064±0.002944) at the same hour, there was a significant difference in the amount of ion released (p=0.002). There was a substantial difference in ion release across the groups at 6-hour, 12 hour and 24 hour time intervals. Based on the mean values, study can conclude that zero sense mouthwash had a higher amount of ion release than the other two at all time intervals which was significant at all time intervals from 6 to 24 hours (p<0.05).
The study aimed to evaluate the amount of nickel ion release from the orthodontic brackets when immersed in fluoride mouthwashes at different time interval. When the three groups were compared, Amflor mouthwash showed no significant difference when compared to artificial saliva and zero sense mouthwash, but when artificial saliva was compared with zero sense mouthwash, there was a significant difference in the amount of ion released at 1 hour interval. However, there was a substantial difference in ion release across the groups from 6-hour time intervals with Zero sense causing the maximum release.
Nickel ions are often the major concern among various ions released by stainless steel due to its ability to cause allergic, toxic, or carcinogenic reactions (19),(20),(21). The recommended maximum limit of nickel ion release that would not cause any negative reactions is 200-300 μg/day by WHO (World Health Organization) (22). Clinicians should be aware that the release of metal ions can result in local hypersensitivity reactions, such as mild erythema or redness with or without edema, at oral soft-tissue sites. Acute gingivitis can also appear as a hypersensitivity reaction when associated with poor oral hygiene (23),(24),(25). These symptoms can be severe for a short time or mild for a longer time, and some can be treated while others can become a persistent problem (26).
Patients are recommended to use mouthwash twice a day for around 2 minutes. It is advised that the patient does not eat, drink, or rinse after mouth washing, since the components of mouthwash remain in the mouth for a long time. It is difficult to establish the exact period of contact between brackets and mouthwashes as it depends on a lot of factors like oral temperature, pH of saliva, which differs when reacting with food substances, concentration of mouthwash solution and other beverages (23),(27),(28). The study also evaluated for how much nickel ion is released from stainless steel brackets during the treatment period and whether it reaches the toxicity level during the treatment period. On an average, if a patient uses mouthwash once a day for around 2 minutes, it works out to 60 mins (2mins x 30 days) for a month. With an approximate orthodontic treatment period of 24 months, the total time that the brackets and wires would be exposed to the mouthwash would be 1,440 mins (60mins x 24month =1,440) or 24 hours. Hence the exposure of the brackets to the mouthwashes/artificial saliva was 24 hours in the study (29).
The release of metals into the oral cavity by saliva can be affected by a high chloride content in saliva or due to consumption of low-pH foods (28),(30). Hence artificial saliva was used to mimic an optimum oral environment. The fluidity of saliva in the mouth and the removal of oxide layers by tooth brushing will further cause metal release that could occur in real life (28). The present study tested the mouthwashes in a static setting so as to obtain the ion release effect of mouthwashes/artificial saliva without being influenced by tooth brushing or any other means.
The amount of nickel released in artificial saliva during 24 hours in the present study sample were lower than Jamilian A et al., and Shruthi DP et al., (13),(31). Variations in ion release between brackets of different manufacturers and different solutions have been reported by Grimsdoittir MR et al., (32). In this study, when comparing Amflor mouthwash and Zero sense mouthwash to artificial saliva, the findings showed that at 1 hour, the difference in ion release was not significant. However, based on the values obtained, it can be inferred that Amflor mouthwash resulted in lesser ion release when compared to Zero sense mouthwash. The artificial saliva had the least nickel ion release as expected thus confirming that fluoride mouthwashes stimulate increased nickel ion release from orthodontic brackets and wires.
Similar research evaluating nickel ion release in orthodontic brackets/orthodontic wires in mouthwash solutions has been table/figured (Table/Fig 4) (16),(29),(33). Two studies (29),(16), compared three mouthwashes over a 45-day period and found that the nickel ion release was higher in the chlorhexidine group compared to the persica mouthwash, oral B mouthwash, Piper beetle Linn mouthwash and deionized water group. The present study was done over 24 hours and hence cannot be directly compared. However, if the data has been multiplied from 24 hour values to 45 days, the authors got 1.44 μg/mL and 1.08 μg/mL for Zero sense and Amflor respectively. These values were similar to the values for chlorhexidine 1.19 μg/mL. Mirhashemi A et al., (33) observed the nickel ion release in orthodontic wires and found that the quantity of ion release with listerine mouthwash was greater during a 24-hour time interval when compared to all other mouthwashes (Oral B, Oral B white luxe and Listerine advanced white). Though the fluoride mouthwashes used in the study had values comparable to nickel ion values with that of chlorhexidine in other studies, fluoride mouthwashes have a therapeutic effect of preventing and remineralization of white spot lesions that occur with orthodontic treatment (34). Hence fluoride mouthwashes are preferable in orthodontic patients. Among the two mouthwashes, Amflor mouthwash can be preferred as it had lesser nickel release when compared to Zero sense mouthwash.
Limitation(s)
Firstly, the bracket bases would be coated with adhesives in an actual clinical setting hence the exposed surface for ion release in this study would be more than that of clinical conditions. The arch wire and brackets should ideally be subjected to a brushing stimulator so as to enable oxide layer removal when reacting to artificial saliva and fluoride mouthwash so as to mimic the actual oral environment. Secondly, the effect of oral temperature, pH of saliva, which differs when reacting with food substances, concentration of mouthwash solution and its reacting time with brackets, could be major factors that could increase the ion release from brackets and arch wires. All the above factors might have a greater influence on ion release from brackets and wires and could give varying results were not considered in this study.
Zero sense mouthwash was found to cause greater nickel ion release followed by Amflor mouthwash and artificial saliva respectively. The toxicity level of ions emitted in a given period of time in this study did not exceed the permissible limits (200-300 μg/day). However, as per the mouthwash use is concerned, it can be inferred that Amflor mouthwash can be prefered over Zero sense mouthwash for Orthodontic patients considering the lower nickel ion release. Further studies with different mouthwashes and different research settings need to be done to accurately determine the ion release from orthodontic appliances and its effects on the oral cavity.
DOI: 10.7860/JCDR/2022/55175.16635
Date of Submission: Jan 27, 2022
Date of Peer Review: Feb 28, 2022
Date of Acceptance: Apr 22, 2022
Date of Publishing: Jul 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
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• Plagiarism X-checker: Jan 29, 2022
• Manual Googling: Apr 19, 2022
• iThenticate Software: Jun 23, 2022 (11%)
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