Corrosion of orthodontic alloys may releases nickel and chromium ions, resulting contact allergy, asthma, or hypersensitivity. The effect of orthodontic treatment on systemic levels of chromium and nickel is disputed, demonstrating lack of changes or increases. Except one recent study, all previous researches are performed on casting brackets, results of which are not necessarily generalizable to novel orthodontic technologies, MIM brackets, which may corrode in other way. Metal injection molding (MIM) brackets have been designed to eliminate intra-bracket galvanic corrosion through one-piece design, uniform elemental distribution and lack of soldering between the bracket parts. The aim of this study is evaluating the hair concentration of nickel and chromium in hair specimens obtained from 46 orthodontic patients in two groups of casting brackets (AISI 316L, Stratus, Fairfield Orthodontic, United States) and MIM brackets (AISI 316L, Gem Petit, Fairfield Orthodontic) . This measurement will be performed in two travels, immediately before treatment, and 6 months after starting of fixed orthodontic treatment. The inclusion criteria are: having indication of fixed orthodontic treatment, lack of any systemic disease and absence of any hair color or hairdressing. The patients will be divided in two groups of casting (control) and MIM (experimental) brackets (n = 23 in each group) . The randomization will be done by an orthodontist, based on a random number table. The orthodontist is the only person who knows allocation. The laboratory expert and the patients will be blinded about bracket allocation. The hair specimens will be sent to Chemical Analysis Laboratory for atomic absorption spectrophotometry.