S Spring Dental Orthodontic Appliances Medical stainless steel
Palatal finger springs are often used in removable orthodontic
appliances to tip teeth in a mesiodistal direction.
There is general consensus that a force of 30-50 g is required to
tip a single-rooted tooth, with an activation of about 3 mm for a
spring with a load/deflection rate (LDR) of 15 g/mm.
The purpose of this report is to establish the magnitude of forces
for finger springs made from different types of wires (i.e. those
from different manufacturers and of different diameters and
The findings were that springs made from ordinary 18/8 stainless
steel wire showed a lower LDR than previously reported. The 18/9
stainless steel springs gave yet a lower LDR. Definite
specifications are given for forming springs.
For example, a Unitek 0.51 x 17 mm spring can be used when the
traditional activation of 2-4 mm is applied, but should increased
activation be required (advocated in this report), the spring
length would have to be increased to 20 mm to keep the force within
the specified range.