Tr. Meling et J. Odegaard, SHORT-TERM TEMPERATURE-CHANGES INFLUENCE THE FORCE EXERTED BY SUPERELASTIC NICKEL-TITANIUM ARCHWIRES ACTIVATED IN ORTHODONTIC BENDING, American journal of orthodontics and dentofacial orthopedics, 114(5), 1998, pp. 503-509
Background: Alterations in mouth temperature may lead to changes in th
e force exerted by an activated superelastic wire. It has been assumed
that variations in archwire stiffness associated with short-term cool
ing or heating are transient. This investigation studied the effect of
short-term cooling or heating on the bending force exerted by nickel-
titanium archwire. Material and methods: Six rectangular superelastic
wires and one conventional nickel-titanium wire were tested in bending
at 37 degrees C. The test specimens were deflected 0.5 mm, and the be
nding force was measured continually The activated specimens were subj
ected to cold (10 degrees C) or hot (80 degrees C) water under constan
t deflection, simulating an inserted archwire that is subjected to col
d or hot drinks or food during a meat. Results: The conventional nicke
l-titanium wire was marginally affected by brief cooling or heating. I
n contrast, some of the superelastic wires were strongly affected by s
hort-time application of cold or hot water. Whereas the effect of brie
f heating disappeared quickly, some wires continued to exert sub-basel
ine bending forces (up to 32% less) after short-time application of co
ld water and showed little or no tendencies toward increase even after
30 minutes of postexposure restitution (up to 43% less). Conclusions:
Short-term exposures to hot liquid increased the bending force exerte
d for a given deflection transiently. The effect of short-term exposur
es to cold liquid was not always transient; the bending force remained
sub-baseline for a number of the thermosensitive wires tested for a p
rolonged time.