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.
Comparison of the elastic properties of nickel-titanium and beta titanium arch wires.
The elastic strength, stiffness, and range of two titanium alloys are compared as a function of wire configuration. From the four beta titanium and eight nickel-titanium sizes available, all arch wire permutations were evaluated both in bending and in torsion. Results show that the stiffnesses of the two alloy compositions overlap substantially, except for those wires with the lowest and the highest stiffnesses--that is, the 0.016 and 0.018 inch nickel-titanium and the 0.017 by 0.025 and 0.019 by 0.025 inch beta titanium arch wires, respectively. To conclude, both "variable-cross-section" and "variable-modulus" orthodontics are illustrated within the context of an equivalent wire stiffness chart which includes conventional stainless steel arch wires.
Effect of long-term immersion corrosion on the flexural properties of nitinol.
This study suggests that sporadic failure of nitinol orthodontic wire is due to the presence of surface defects generated during manufacturing and not to the effects of corrosion. The flexural properties were evaluated for both control and corroded samples of nitinol wires and were not found to be statistically different. Fractured surfaces of control as well as corroded samples following bending were examined by scanning electron microscopy to determine the mode of failure.