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.
Interview with an innovator: SureSmile Chief Clinical Officer Rohit C. L. Sachdeva.
Robert P. Scholz: You have an interesting educational and work background. Where did you get started, and how did you end up with SureSmile? Rohit C. L. Sachdeva: I was born in Kenya and completed my dental education at the University of Nairobi in the mid 1970s. I took a position as a registrar in orthodontics at the Royal Dental Hospital, University of London, under Dr Bill Houston. There, I was exposed to many orthodontic philosophies, including both functional and Begg. I moved to the United States in the early 1980s and completed my orthodontic residency at the University of Connecticut Health Sciences Center under Dr Charles Burstone. I learned the segmental approach to orthodontics and also developed an interest in the bioengineering aspects of orthodontics. I joined the University of Connecticut faculty and then moved to Canada and joined the faculty at the University of Manitoba, which also had a strong focus on bioengineering research in orthodontics. In the late 1980s, I joined the faculty at Baylor College of Dentistry, Texas A and M University, in Dallas. This was a unique opportunity, since the entire department was being transformed after Dr Moody Alexander resigned. The environment was rich in clinical faculty participation and was strongly influenced by the Alexander discipline. The segmental approach to orthodontics was the polar opposite of the Alexander method in terms of philosophy of care; with time, I recognized the value of both, driven by the patient’s needs. So, in many ways, I was fortunate to be groomed by the best in terms of my clinical background. While in Connecticut, through sheer serendipity, friends introduced me to Professor Marv Wayman of the University of Illinois at
Nitinol arch wire in a simulated oral environment: changes in mechanical properties.
Changes in the mechanical properties of a nickel-titanium orthodontic alloy, nitinol (0.016-inch arch wires), were studied in a simulated oral environment across time, at various levels of acidity, and at different amounts of static deflection. Significant decreases in specific mechanical properties were observed in these incubated wires compared with a group kept dry and unstressed. Ultimate tensile strain, modulus of elasticity, and 0.2% yield strength each decreased. Acidity (pH 3 to 7) and amount of deflection (0 to 4 mm in a 10-mm span) did not affect the wire, but there was a significant, monotonic decrease in yield strength with time in the simulated oral environment. By 4 months this measure of susceptibility to permanent deformation increased by 15%. Consequently, long-term use (or reuse) of a nitinol wire may be associated with a modest, but statistically significant, degradation in performance, notably in the limit of the wire's elasticity.