Nowadays, the demand for orthodontic treatment is increasing, orthodontic treatment has become one of the important dental treatments1. Orthodontic brackets are one of the main components in orthodontic treatment. Generally, orthodontic brackets that are widely used are made of stainless metal whose composition is made of iron (Fe), chromium (Cr), and nickel (Ni). The release of chromium and nickel metals can enter the body or come into direct contact with the tissue.
One of the factors that can cause ion release on stainless orthodontic brackets is the use of this material for a long time in the oral cavity, generally for 2-3 years. The oral cavity provides an environment that affects temperature, microflora, oral enzymes, quality and quantity of saliva, changes in salivary acidity (pH), plaque, protein, physical and chemical properties of food and beverages.
Saliva acts as an electrolyte medium that can trigger electrochemical reactions in which metal ions as the anode and H+ ions from the electrolyte medium as cathodes. Corrosion is the result of the process of interaction between metal materials and the surrounding environment. One of the causes of the corrosion process is an environment with an acidic pH. The release of Ni and Cr from the stainless bracket also have a negative impact on health if it exceeds the body’s normal intake. Ni and Cr are heavy metal groups that can be allergic, cytotoxic, and even carcinogenic to the body. The aim of this narrative review is to describe the release of nickel (Ni) and chromium (Cr) ions in stainless steel orthodontics brackets.
The nickel content in stainless steel has advantages and disadvantages. The most common drawback is an allergic reaction. The prevalence of nickel hypersensitivity has increased steadily, for male patients (38%) while more than 30% for women. However, nickel rarely causes allergic reactions in the oral cavity. Apart from nickel, the stainless-steel bracket also contains chromium. Chromium is an additional component in stainless steel orthodontic wire which serves to increase corrosion resistance. Chromium on metal surfaces reacts with oxygen and forms chromium oxide to resist corrosion.
The corrosion rate is affected by the increase in ambient temperature. In every 10o Celsius increase, the corrosion rate constant increases 2-50 times. The corrosion rate constant increases by 1.1-1.6 times at a reaction temperature of 600 degrees Celsius. The degree of acidity also affects the corrosion process because pH shows the concentration of H + ions in water and results in the release of electrons by the metal in anodic reactions. Saliva contains chloride elements which tend to prevent the formation of a protective oxide layer on the surface of the bracket, thereby accelerating corrosion.
The oral environment is ideal for metal biodegradation, so that corrosion and ionization can occur in orthodontic equipment. The release of nickel and chromium ions has potential carcinogenic, mutagenic and allergenic effects.
This study evaluated the corrosion of titanium and cobalt-chromium alloys immersed in artificial saliva having a pH of 6.5 with and without fluoride over a period of 7, 9 and 11 weeks and with 2g/l NaF for 11 weeks at a temperature constant of 37掳C under static conditions, and evaluates the superficial aspects in scanning electron microscopy and residual components, so that it can be used as an alternative to nickel hypersensitive patient stainless steel. Cobalt-chromium alloys showed the greatest corrosion rates, while pure titanium alloys and steel alloys with low nickel concentrations were the most corrosion resistant. The presence of fluoride causes a greater release in all tested alloys.
Post-immersion measurements in artificial saliva for 30 days with a pH of 6.8 and a temperature of 370C, showing that the release of chromium metal was less than that of nickel metal. This can be due to the composition of the stainless-steel bracket sample containing less chromium metal than nickel metal. Excessive release of chromium and nickel metals can cause changes in the dimensions of the bracket shape which results in the brittleness of the bracket and can affect body health because it is a heavy metal group that can cause type IV hypersensitivity reactions.
Many parameters influence metal ions in the salivary environment, including pH level, oxygen content, temperature, and immersion duration. The increased rate of metal ion release could be attributed to its corrosiveness and subsequently to chlorhexidine mouthwash.
Chlorhexidine mouthwash releases more metal ions (except manganese) than Listerine and Colgate plax mouthwashes. The galvanic corrosion on brackets manufactured by four different companies that were combined with stainless steel (SS) or nickel-titanium (nickel) wire in an artificial saliva solution. The rate and speed of galvanic corrosion also depends on the surface area ratio of the two different alloys in contact.
The cytotoxic effect of nickel ions released from stainless steel brackets was investigated. Allergic reactions can occur in those who are sensitive, even though the amount of nickel and chromium released from the orthodontic appliance is below the average dietary intake of nickel and chromium. Based on this review, the release of nickel and chromium ions in stainless steel orthodontic brackets has an optimum rate, at a certain pH and time. The amount of Cr and Ni ions released in the use of stainless steel brackets in saliva is influenced by the bracket raw material and the mixture of the saliva solution caused by the condition of the mouth and the artificial saliva mixture.
Penulis: Prof. Dr. Ida Bagus Narmada, drg., Sp.Ort(K).
Informasi lebih lanjut: https://www.rjptonline.org/AbstractView.aspx?PID=2023-16-10-70
