A COMPARATIVE EVALUATION OF EFFECTS OF DIFFERENT KINDS OF STERILIZATIONS ON LOAD DEFLECTION CHARACTERISTICS , TENSILE PROPERTIES OF COPPER NITI WIRES-AN INVITRO STUDY 1
Copper NiTi wires were introduced by Sachdeva R and Miyasaki S in 1994. This latest innovation in the evolutionary scale gives us the opportunity of choosing the force level by choosing the temperature at which the wires will deliver its optimum force level. With so many advantages and their ability to return to their original form coupled with the high cost of copper NiTi many clinicians started reusing the wire. This raises concern about disinfecting/sterilizing the wire before using in another patient for prevention of cross infection. Hence, various sterilization procedures like cold sterilization using 2% acidic glutaraldehyde, dry heat sterilization and autoclaving were used to prevent this cross infection..Aim: The main aim of this study is used to evaluate the effects of different kinds of sterilization on load characteristics and tensile properties of copper Ni Ti wire. Materials and Methods: In the present study, selected mechanical properties like load deflection characteristics, ultimate tensile strength of the 0.016 copper NiTi wires were studied before and after sterilization procedure. Three point bending test was performed to evaluate the load deflection characteristics and tensile test were evaluated to determine other mechanical properties. Pretreatment and post treatment values were statistically analyzed by one way ANOVA test. Results: On the load deflection characteristics, even though there was an increase in the loading and unloading forces, statistically significant changes in the forces are seen only when the wires were subjected to two cycles of sterilization with autoclave and dry heat. No detrimental changes were detected in tensile properties of copper NiTi were after single cycle of sterilization with any of the stated sterilants. Very minimal non significant changes occurred during the second cycle of sterilization procedure. Conclusion: Pronounced changes in load deflection characteristics have been found in the wires which have undergone two cycles of sterilization with either dry heat or autoclave implying that there was loss in pseudoplastic and pseudoelastic properties of wires and increase in stiffness of wires.
Effects of clinical recycling on mechanical properties of nickel-titanium alloy wires.
The purpose of this investigation was to determine the effects of clinical recycling on the load-deflection characteristics and the surface topography of nickel-titanium alloy wires. Thirty wires each of Nitinol and NiTi were subjected to a three-point bending test in an as-received condition (T0) and after clinical exposure of one cycle (T1) and two cycles (T2). Ten wires made up the sample at each of these time points. One cycle was defined as 8 weeks, plus or minus 1 week, of clinical use. Wires undergoing two recycles were cold sterilized after their first clinical exposure. Statistical analyses were done by one-factor repeated measures ANOVA and Scheffe F test. Recycling produced significant changes in both the loading and unloading characteristics of NiTi wires, but only with the loading forces associated with nitinol wires. Representative scanning electron micrographs demonstrated increased pitting of both nitinol and NiTi wires. Several areas were also observed to be smoothened on nitinol wires and scored on NiTi wires.
Study the characteristics of magnetic finishing with gel abrasive
Abstract Given the flexible polishing effect in magnetic abrasive finishing (MAF), the precise and mirrorlike surface can be obtained during this process. However, the abrasives are easily flown away from the working area regardless of what abrasives are used in MAF; this situation will reduce the polished efficiency and induce the pollution problem in the environment. Besides, the abrasives cannot recycle after the finishing process. Therefore, a novel abrasive medium, using the silicone gel to mix the ferromagnetic particles and abrasive, was developed to enhance the disadvantages in MAF. Magnetic finishing with gel abrasive (MFGA) was utilized in this study to polish the cylindrical rod of mold steel; furthermore, this cylindrical rod was fixed in a horizontal chuck that could rotate and vibrate in the axial direction. This study focused on the finishing efficiencies and the surface roughness of the workpieces after MFGA. Moreover, recycling times of gel abrasive were also the main effects that need to be approved. The results demonstrated that surface roughness of the cylinder part was reduced to 0.1 μm Ra from an initial value of 0.677 μm Ra within 10 min, and surface roughness could decrease to 0.038 μm Ra after 30 min in MFGA. Surface roughness reduction in MFGA was 3 times of surface roughness reduction in MAF using the unbonded magnetic abrasive as medium. Roughness improvement rate still remained at a high level of 90% when the same abrasive medium (35 g) was used 15 times to finish 15 workpieces; therefore, this result proved that the gel abrasive had excellent ability for recycling.