EFFECT OF HEAT TREATMENT ON STAINLESS STEEL ORTHODONTIC WIRE
The purpose of this in vitro experimental study was to study the effects of heat treatment on the direct tensile strength and maximum strain (at breakage point) of stainless steel orthodontic wires.
The prepared specimens were 180 mm long chunks of 1.13 mm diameter stainless steel wire were heat treated in a furnace at three temperature variables of 500, 600 and 700C and four time variables of 30, 60, 90, and 120 s. Heat treated specimens as well as a control group with no treatment were tested on a tensometer for direct tensile strength following which the broken pieces were assembled to measure the maximum strain at the breaking point.
The results showed that maximum strain at the point of breakage increased when time and / or temperature of annealing were increased while the direct tensile strength decreased when the same variables of time and temperature are increased.
It was concluded from the present study that heat treatment of stainless steel orthodontic wires does affect their mechanical properties as their direct tensile strength decreases and the maximum strain (at the breaking point) increases.