The Study For Corrosion Resistance Of General Alloy Of Orthodontic

Medical stainless steel,Ni-Ti alloy and titanium alloy with its performance of physical devices,making simple,cheap,and has been widely used in orthodontics. The corrosion of alloy affect the quality of the materials, make the treatment prolonged, corrosion products also cause the body adverse reactions. This behavior has received great attention and many scholars conducted a large number of experiments in vivo and vitro, strive to minimize the harm of alloy to human body.This research indicate the corrosion behaviour of metal brackets in mouthwashes and the corrosion resistance of orthodontic distal end cutters,which is divided into two parts (three experiments).1. Corrosion behavior of metal brackets in mouthwashesIn the process of fixed appliance, brackets and other appliances can be lead to buccal plaque cumulation around the appliances.The patients who is with the decline of patient asself-cleaning ability often occur enameldemineralization, gingivitis and other complications.It is difficult to maintain good oral hygiene relying on conventional brushing,in order to prevent the emergence of these complications,orthodontic patients often choose mouthwashes to be used in conjuction.The stainless steel brackets were soaked in3mouthwashs.To extact the maceration extract after10days.The atomic absorption spectrometer and observe the surface of the brackets before or after immersion by scanning electron microscopy.Potentiodynamic polarization technique was used to depict polarization curve and to measured the electric potential of corrosion(Ecorr) and the current desity of corrosion(Icorr) of three brands of brackets inthe mouthwashs. SEM showed that the three mouthwashes caused changes in the surface structure of the metal brackets. The results demonstrated orthodontic brackets release the ions and led to surface corrosion in kouqiangbao, koujiesu,Colgate mouthwashes. The type and amount of metal ion release in koujiesu is the lowest. Of the three kinds of mouthwashes,the amount of metal ion release in koujiesu was the lowest. The corrosion tendency of brackets in Colgate mouthwash is the largest, but the corrosion rate is the fastest in the kouqiangbao. 2. Corrosion resistance of3stainless steel brackets in mouthwash with fluorideThe most common negative effect of orthodontic treatment with fixed appliances is the evelopment of incipient carious lesions and gingivitis around brackets.The mouthrinses with fluoride for years to prevent enamel demineralization and gingivitis in patients.But according to the resent research,the fluoride cased the corrison of mental surface and ion release. The stainless steel brackets were soaked in Colgate mouthwash(0.02%NaF).To extact the maceration extract after10days.The atomic absorption spectrometer and observe thesurface of the brackets before or after immersion by scanning electron microscopy.Potentiodynamic polarization technique was used to depict polarization curve and to measured the electric potential of corrosion(Ecorr) and the current density of corrosion(Icorr) of three brands of brackets in the Colgate.The conclusion is Colgate mouthwash has much higher influence on the corrosion resistance behavior of ORJ and3B stainless steel brackets,while it as less influence on the xinya brackets.3. Effect of autoclave on the orthodontic distal end cuttersTo investigate the effect of autoclave on two orthodontic distal end cutters comparatively.Tiantian and3M distal end cutters were evaluated in terms of shearing force and corrosion to clarify the effects of autoclave on the two brands (tiantian and3M) of distal end cutters.The results indicated:it was found that with an increase in the number of sterilization cycles, the shear force and extent of corrosion increased in all six groups of distalend cutters, but the situation was worse for Tiantian cutters than for3M cutters. It was found that the difference of shear force between the Tiantian autoclave group and3M autoclave group was statistically significant (p<0.05) after20,40, and60sterilization cycles.And the effect of saliva on the increase in shearing force for the two brands of distal endcutters was negligible.Meanwhile,the metallography showed that different degrees of discoloration and rust spots appeared on the work edges of the two brands of distal end cutters with an increase in the number of sterilization cycles, but the corrosion of the Tiantian distal end cutter was more widespread, and even work-edge defects appeared. The EDS result shows that the element content of two brands of cutters in the beak are different. The use of the autoclave affected the distal end cutters in terms of shearing force and corrosion,but the effect on3M distal end cutters was obviously less than that on Tiatian cutters.