초내식성 스테인리스강의 교정용 브라]켓에의 적용

Abstract

Esthetic has become an indispensable factors to consider when choosing a orthodontic fixed appliances. However, most of the brackets used on orthodontics are made of metallic materials because those esthetic alternatives showed several controversies like brittleness, deformation and discoloration. The AISI austenitic classes, 303, 304, 316 and 317 type of stainless steels are frequently used for orthodontic metallic brackets fabrication. The composition of this type of alloy is 18 wt% of chrome, 8 wt% of nickel, 2 to 3 wt% of molybdenum and low carbon contents. They seemed to show relatively good characteristics to fabricate the orthodontic brackets in previous study. But in hostile condition such as low pH containing chlorine ion like saliva they might to be attacked by localized corrosion. The purposes of this study were to evaluate the microstructure, microhardness, corrosion resistance, frictional resistance and cytotoxocity of 316L(MD), AISI 304(AC) and experimentally produced super stainless stell bracket(SS). The results from this study were as follows; 1. MD and AC showed (Cr, Fe)23C6 precipitating in austenite matrix. SS showed small ferrite island forming in matrix. 2. SS showed the highest polarization resistance(Rp). SS seemed to have the highest corrosion resistance since SS showed 0.9 ×10-3 MPY, MD showed 3.7 ×10-3 MPY and AC showed 7.4×10-3 MPY. 3. The friction resistance decreased from 3 days to 4 weeks for SS(p<0.05). MD showed significant differences for the measurement of 3 days, 2 weeks and 4 weeks. AD did not showed significant differences to 3 days but increased at 2 weeks(p<0.05). 4. SS seemed to have the best biocompatibility since SS showed response index of 0/1 (mild), AC showed 1/2 (mild+) at cytotoxicity test. According to these results, SS seemed to have sufficient characteristics to fabricate the orthodontic brackets and superior corrosion resistance compare to AISI 300 type stainless steel which could lower the chance of nickel allergic reaction.