Biomedical Engineering Reference
In-Depth Information
(A)
(B)
FIGURE 12.3
(A) Large-scaled LIPUS device and (B) future nanofabricated intraoral LIPUS device.
12.5
Nanomechanical sensors for orthodontic forces
and moments measurement
Orthodontic forces and moments are an undetermined force system due to many factors that are
involved, including the orthodontic wire materials (that affect its modulus of elasticity) and geome-
try (that affects its stiffness). Both modulus of elasticity and geometry are important in determining
wire stiffness according to the following equation:
K
ð
stiffness
Þ
5
E
3
I
ð
E is the modulus of elasticity and I is the area moment of inertia
Þ
For round wire (
Figure 12.4
). Where d is the diameter of the round wire
d
4
I
5
πð
Þ
=
64
For rectangular wire (
Figure 12.5
). Dimensions of the rectangular wire where (b) is the wire
base in the in-out direction; and (h) is the wire height in the up-down direction
h
3
ð
Þ
=
I
5
b
12
In addition, wire stiffness is also dependent on the wire length, which is determined intraorally
by the interbracket distance. The smaller the bracket width, the greater the interbracket distance
and lower the wire stiffness according to the following equation:
L
3
K
ð
stiffness
Þα
1
=
where L is the interbracket distance or wire length (
Figure 12.6
).
All the above factors affect the stiffness of the wire and consequently the force applied to the
teeth. Since any small changes in wire length or diameter/cross section can change the wire stiff-
ness and consequently the applied force by this wire, it is almost impossible to predict the
exact amount of force applied by the same wire to two different patients due to the difference in
