Nickel ion release from stainless steel brackets in chlorhexidine and Piper betle Linn mouthwash

Background: Orthodontist prescribe mouthwash for their patients especially since most of patients do not have a satisfactory oral hygiene and have high risk of dental caries. Stainless steel brackets that exposed by mouthwash may have nickel ion release. Corrosion and nickel ion release can induced allergic reaction and make more friction during orthodontic treatment. Purpose: This study aimed to measure nickel ion release of stainless steel bracket that immersed in chlorhexidine and Piper betle Linn mouthwash. Methods: Thirty-six stainless steel bracket immersed in artificial saliva, chlorhexidine, and Piper betle Linn mouthwash. All brackets stored in incubator for 1, 3, 5, and 7 weeks. Nickel ion release was measured by Atomic Absorption Spectrophotometry (AAS). Results: The results showed a significant differences of nickel ion release in all groups (p<0.05). Conclusion: In conclusion, among the mouthwash, chlorohexidine has the highest nickel ion release from stainless steel brackets, followed with Piper betle Linn mouthwash.


INTRODUCTION
Orthodontic brackets are an important component in orthodontic appliances.Brackets should have the correct hardness and strength to deliver the exact force from the wire to the teeth.They also should have a smooth archwire slot to reduce frictional resistance and plaque deposition.Orthodontic brackets should be accurately manufactured to reflect the prescription type of each bracket.][3] Brackets are usually placed in oral cavity between two and three years.During this time, brackets are contaminated by substances from the inside and outside mouth.This situation can destroy brackets physically and chemically then leading to corrosion and ion release.Thus, high corrosion resistance metals or alloys are the best choice to prevent orthodontic brackets corrosiveness. 1,2tainless steel bracket is one of metal orthodontic bracket.][3][4] There are some types of stainless steel brackets, such as AISI type 304 L SS, 316 L SS, and 17-4 PH SS.Stainless steeel 304 L consist of 18-20% chromium, 8-10% nickel, and less than 0.03% manganese, silicon, and carbon.Stainless steel 316 L has a higher nickel content than 304 L, 2-3% molybdenum, and consist of lower carbon to improved intergranular corrosion resistance and for better welding results.][3][4] Orthodontic corrosion and ion release in oral environment have two important concerns.First, when corrosion products absorb by body and caused local and systemic toxic effect.Nickel ion release was known as the most common allergic substance that caused contact dermatitis in women and others hypersensitive reaction in 10% of general population.Nickel is a strong medium immune reaction that can cause hypersensitivity reaction, contact dermatitis, gingival enlargement, asthma, hypercytotoxicity, and mutagenic.Cultured human cells study reported that nickel ion release was moderately cytotoxic in cells.Nowadays, there are alternative low-nickel and nickel-free alloys to replace stainless steel.However, the biocompatibility of lownickel alloys have not been accurately evaluated.Second, metal corrosion could affect stainless steel physical and clinical properties.[7][8][9][10][11][12] Good oral hygiene is an essential part of a successful orthodontic treatment.Orthodontist prescribes mouthwash due to most of patients have lack oral hygiene and high risk of dental caries.Mouthwashes are effective to prevent formability of microbial plaques.Among mouthwashes, chlorhexidine has known to be highly effective in prevention of dental plaques and reduction Streptococcus mutans.However, some studies report that chlorhexidine mouthwash could make high ion release due to irrigation effect it self. 13,14ecently, the use of herbal mouthwash is increasing.Natural products that extract from herbal plants are found to be highly efficient to prevent the dental caries/plaque found in fixed orthodontic appliances patients undergoing orthodontic treatment.One of most common herbal plant in Indonesia is Piper betle Linn.This plant has known as traditional medication including to prevent bad breath and dental caries.Piper betle leaves contains several active compounds such as eugenol and its isomers, chavibetol, hydroxychavicol, pentatriacontanol, piperol, piperbetol, carotenes, and ascorbic acid.Hydroxychavicol has been examined as an antimicrobial ingredient, and it shows promising results for several applications as an oral care agent.Antimicrobial profiles of hydroxychavicol are well suited for an active ingredient for oral care products.][16] This study report measured the levels of nickel ion release from stainless steel brackets immersed in chlorhexidine and Piper betle Linn mouthwash.These results should help orthodontist to prescribe the best choice of mouthwash for their patient needs.

MATERIALS AND METHODS
Thirty six brackets (first premolar bracket, stainless steel, 0.018-in, Roth prescription, Mini-Gamma SD Orthodontic, USA) were used for this study.The brackets divided into 12 groups.Each group immersed for 1, 3, 5, and 7 weeks in different solutions.Group 1-4 is a control group that immersed in artificial saliva.Group 5-8 immersed in chlorhexidine mouthwash 0.2%.Group 9-12 immersed in Piper betle Linn mouthwash 3%.
Direction of use mouthwash is usually rinse for about one minute twice a week, and after having mouthwash, patient should not be eating food, drinking, and rinsing their mouth to ensure that its components remain present for period of time.To calculate the presence of mouthwash active ingredient on mouth especially on brackets, we estimated that, if an individual followed this regime, the mouthwash components would be present in a patient's mouth for 6 hours (twice a week for 24 months is equal 69.000 minutes).Therefore, on this study the immersion and incubation time of brackets was 49 days (49 days being almost equivalen to 69.700 minutes). 16Each bracket was placed in individual glass tube containing 10 mL of immersion solution and incubated at 37° C for 1, 3, 5, and 7 weeks.After incubation, the immersion solution was measured with atomic absorption spectrophotometer (AAS) (Shimadzu AA-7000).
AAS is spectroanalytical procedure to measuring the ion concentration in immersion solution using energy absorption from certain wavelength of light (commonly 190-900 nm).AAS typically include a flame burner to atomize the sample (in this research we used a hollow cathode lamp as a flame burner), a monochromator and a photon detector.Wavelength to measured nickel ion is 232.10 nm.First, we have to make standard solutions of three different concentrations, determine the absorbance then make a calibration curve from the values.Fitting nickel light source lamp to the lamp housing to measure the absorbance then switch on the instrument.Switch on the source lamp and set at nickel's wavelength (232.10 nm).Ignite the mixture of these gases.Adjust the gas flow rate and pressure, and make the zero adjustment after nebulizing the solvent into the flame.The absorbance for the sample was measured then determined concentration from the previous curve of calibration. 171 showed nickel ion release mean levels in the groups.Therefore, to look the presence of different nickel ion release we need to tested data with Kruskal-Wallis test in Table 2.
This research not only report based on type solution but also based on immersion time (Table 3).Kruskal-Wallis test reported nickel ion release statistically significant differences in artificial saliva, chlorhexidine, and Piper betle Linn for 1 week p=0.023(p<0.05), 3 weeks p=0.020 (p<0.05), 5 weeks p=0.017 (p<0.05); and 7 weeks p= 0.015 (p<0.05).commonly recommended mouthwash for their patients to decrease the risk of plaque and caries formability.However, lack of study reported the effects of various mouthwashes on ion release of orthodontic brackets. 18his study reported nickel ion release from stainless steel brackets that immersed in artificial saliva, chlorhexidine, and Piper betle Linn.mouthwash increased over time.This result relevant with Amini's study that measured chromium and nickel concentration in gingival crevicular fluid before treatment, 1 month, and 6 months after using orthodontic appliance from 24 patients using AAS.The nickel levels were increased over time same with this study. 19mong various mouthwash solutions, chlorhexidine showed the maximum level of nickel ion released, the next highest being in Piper betle Linn mouthwash, and the lowest in artificial saliva.This result relevant with Danaei et al. study that immersed 160 stainless steel brackets divided randomly in four solution groups (chlorhexidine, oral-B fluoride, persica mouthwash, and distillated deionized water) and incubation time for 45 days at 37° C. Nickel, chromium, iron, copper, and manganese ion release were measured by inductively coupled plasma spectrometer.The highest nickel ion release showed in chlorhexidine solution compared with the other mouthwash. 20t reported on a fixed appliance simulator that described full upper arch.The samples were measured at 1, 7, 14, 21, and 28 days by flame atomic absorption spectrophotometer.The highest levels of metal ion release at day 7, and all releasing ion is finished within 28 days.This results is not relevant with our study. 21orrosion occurs from either dissolve of metal ions into solution or progressive release of a protective layer, usually an oxide or a sulphide.The corrosion and metal ion release mechanism from stainless steel alloy started from dissolved the protective film that consist of chromium oxide and chromium hydroxide, and then forms on contact with oxygen on the stainless steel's surface. 20orrosion made from two simultaneous reactions: oxidation and reduction (redox).For example we were using iron in a weak acid.Oxidation (anodic) reaction results

Metal corrosion could
Dental Journal (Majalah Kedokteran Gigi) p-ISSN: 1978-3728; e-ISSN: 2442-9740.Accredited No. 32a/E/KPT/2017.Open access under CC-BY-SA license.Available at http://e-journal.unair.ac.id/index.php/MKGDOI: 10.20473/j.djmkg.v51.i1.p5-9 in dissolution of the iron as ferrous ions are produced (Fe Fe 2+ + 2e -).Reduction occurs at the cathode, with hydrogen ions reduced to hydrogen gas (2H + + 2e -H 2 ).This reaction will continue until all of the metal consumed, unless the metal can form a protective surface layer (passivation), or until the cathodic reactant is consumed (exhaustion of dissolved oxygen in solution). 22,23orrosion levels of any metal depends on chemical reaction of the immersion solution (Figure 1).The formation of passive oxide film can delay the corrosion process on the orthodontic appliances.However, this protective layer can dissolve mechanically and chemically.This passive oxide films can slowly dissolve (passivation) without chemical or mechanical abrasion only to reform (repassivation) as the metal surface is exposed to oxygen from the air or the surrounding medium.The passivation reaction could accelerated by chloride ions and acidic environment that happen because of sodium chloride, acidic carbonated drinks intake, and fluoride-containing products, such as toothpaste and mouthwash.][24][25] The orthodontic metal alloy risk of corrosion depends on the oral environment, which is determined by mechanical and chemical factors.Mechanical factors including foods, liquids, and tooth brushes abrasion.Chemical factors including quantity and quality of saliva, and pH of food and beverages.Corrosion will occur continuously in the mouth over time. 27ome factor that effect different results betwen studies are study design, measuring system, immersion time, and immersion solution.Moreover, same products on different manufacturers have been shown different results.Surface area of the bracket is one of an important factor to determine the amount of corrosion and ion release, but calculating orthodontic bracket's comprehensive surface area was on our exclusion criteria in this study because of their complex shape and geometry.
The corrosion of brackets could influence the process of orthodontic treatment.Nickel ion release can result allergic reactions and cytotoxicity.Since the nickel allergic reaction is one of our concern, orthodontist should be aware that nickel ion release might cause some allergic reaction including contact allergy and gingivitis.Contact allergy clinically seems at oral soft tissue that contact with brackets.In orthodontic patient, severe gingivitis not only related to lack of oral hygiene but also to nickel allergic reaction from stainless steel brackets.We also need to determine patient history of hypersensitivity by anamneses the patient. 20arameters that affect the corrosion and ion release of metals in saliva including immersion time, presence of oxygen, pH, and temperature.Metal ion released into the oral environment with saliva as the medium.High level of chloride contain in saliva, various intake of foods and drinks with a low pH could lead to acidic condition that increase the amount of corrosion and ion release.][24] In this study, mouthwash was used in a static environment.However, in real life, mouthwash were used in dynamic environment.Increasing metal ion release could happen in dynamic condition not only because of the saliva fluidity and pH but also abrasion by tooth brushing and mastication mechanism.A large number of metal ion release after using an oral functioning simulator apparatus to describe the dynamic condition of oral environment. 28In this study, we did not use adhesive resin to coverage base of brackets so the involved bracket surface was larger than clinical conditions. 29,30verage nickel intake a day from foods are 5-100 mg and 300-500 mg, respectively.Nickel ion intake in beverages is commonly under 20 mg per liter.The amount of nickel ion released from in this study is lower than daily food and water nickel intake.However, patient with nickel intolerant reacted even with a small amount of nickel ion release. 20his study clearly identifies the risk of corrosion and nickel ion release when mouthwashes are used.Corrosion could make some clinical problems when orthodontic treatment occurs including allergic reaction and uncomfortable sliding movements.It also could negatively impact the aesthetic result of orthodontic treatment.Patients who have metal ion hipersensitivity especially nickel is recommended not having mouthwash for a long period of time.It seems to be a need for a new type of mouthwash containing both anti-caries and corrosion inhibitors which could be used without restriction by patients undergoing orthodontic therapy.In conclusion, among the mouthwash, chlorohexidine has the highest nickel ion release from stainless steel brackets, followed with Piper betle Linn mouthwash.

Table 1 .
Mean levels of the ions released in all groups

Table 2 .
Kruskal-Wallis test of nickel ion released in the artificial saliva, chlorhexidine, and Piper betle Linn.

Table 3 .
Kruskal-Wallis test in immersion time groups