Biomedical Engineering Reference
In-Depth Information
NO
BI
BI
FR
FR
FR
θ
c
θ
z
Angulation,
θ
(degree)
Active
Configuration
Passive
Configuration
FIGURE 13.2
Schematic diagram showing the partition of the resistance to sliding (RS) into classical friction (FR), elastic
binding (BI), and physical notching (NO) within the passive and active configurations with important
boundary conditions (
θ
c
and
θ
z
) delineated
[6]
.
Following are the number of factors that may influence the RS components directly and
indirectly:
1.
The archwire: size, shape, material, surface roughness.
2.
The bracket: material, size, and shape of the slot and its edges, surface of slot and the angle
formed between the wire and the slot.
3.
Ligation of the wire in the slot: elastic module, metal wire ligature, and self-ligating brackets.
4.
Intraoral factors: saliva, plaque, and corrosion.
5.
Other factors: distance between teeth and direction of the applied force.
Over the years, attempts have been made by researchers and manufacturers to reduce the
friction. The problem was approached from different aspects:
1.
A method for ligating the wire to the slot can theoretically reduce the friction. This was shown
to be true with the self-ligating brackets at a 0 angle (clinically not relevant), but higher friction
was recorded once the wire contacted the slot walls
[7
9]
.
The massive advertisement campaign by most orthodontic manufacturers during the last
decade in favor of the self-ligating brackets to reduce friction and reduce treatment time was
not scientifically and clinically proven
[9,10]
.
2.
Surface modification like ion implantation at the wire
bracket interface can minimize friction
during tooth movement. However, limited studies to date have evaluated the frictional
characteristics of wires and brackets which have received this surface treatment
[11]
.
3.
Recently, diamond-like carbon (DLC) coatings showed a significant reduction in friction
forces
[12]
. Such DLC coatings have been also applied on orthodontic wires and brackets,
