Pm. Clifford et al., The effects of increasing the reverse curve of Spee in a lower archwire examined using a dynamic photo-elastic gelatine model, EUR J ORTHO, 21(3), 1999, pp. 213-222
This paper describes the development and testing of a dynamic in vitro phot
oelastic model for evaluating the effects of orthodontic mechanics on an en
tire arch of teeth. A model of a mandibular arch was made and the teeth wer
e embedded in a gelatine material with a high level of mechanical creep whi
ch permitted tooth movement in response to orthodontic forces. The excellen
t photo-elastic properties of this material also facilitated the analysis o
f the stress distribution around the roots of the teeth. The model of a man
dibular arch was used to investigate the tooth movements and stress distrib
utions produced by increasing the reverse curve of Spee in a 0.018 x 0.025-
inch stainless steel archwire.
The results revealed that a l-mm reverse curve of Spee increased the arch l
ength by 1.6 mm, but increasing the reverse curve of Spee to 5 mm did not i
ncrease arch length further. Photo-elastic analysis showed an increased str
ess distribution around the roots of the incisors and molars as the reverse
curve of Spee was increased in the archwire.