Evaluation Of Cytotoxicity Of Three Types Of Orthodontic Nickel-titanium Shape Memory Alloy Wire By The Mtt Method

ObjectiveThe nickel-titanium shape memory alloy wire has superior hyperelastic and shape memory function, widely used in orthodontic clinic,however the suitable temperature in the mouth and various chemicals in the saliva will make alloy surface lose luster,and make corrosion. Not only the corrosion reduce strength of the alloy,but also the corrosion products (the metal ions) do harmful for the body to produce adverse effects, such as allergic reaction, shading of the gingival and toxicity. In recent years, some scholars have questioned the biological safety of the nickel-titanium alloy.We made a experiment to study the cytotoxicity and biocompatibility of the three kinds of orthodontic clinic common niti shape memory alloy through the environment in artificial saliva, then compared three alloy's biocompatibility in the view of cytotoxicity.This will provide theory basis for the oral orthodontic clinic nickel-titanium alloy we have chosen, and has certain significance for the safe orthodontic treatment.MethodsSelect the three kinds of commonly used orthodontic treatment brand arch Ni-Ti shape memory alloy wire A, B, C.The A, B, C were divided into three groups, one was extracted extract directly, another group had been added configured artificial saliva to incubate with constant temperature for 4 weeks,then extracted extract. The other had been added artificial saliva for 8 weeks to extract extration. Select L-929 as experimental subjects,to observe the growth of L-929 cell in the extract with inverted phase contrast microscope. The OD value and relative growth rate (RGR) were measured at the 24 hour and 48 hour through MTT test. To make cell toxicity evaluation of the different types of nickel-titanium shape memory alloy wire ResultsAfter immersion in artificial saliva, cell toxicity of three kinds of nickel-titanium arch wires was increased with immersion time gradually increasing (p<0.05); at the same immersion time,the A group had the least cytotoxicity, while the C group had the biggest;the cytotoxicity of three kinds of nickel-titanium arch wires were in normal range.ConclusionArtificial saliva environment has increased the cytotoxicity of the nickel-titanium arch wires and cell toxicity of three kinds of nickel-titanium arch wires was increased with immersion time gradually increasing. Different brands, different soaking time, nickel-titanium orthodontic arch wire had the different cytotoxicity.