Self-ligating brackets have an inbuilt labial face which can be opened and closed to retain and release engagement of the arch wire.

1. PROF DR MAHER FOUDA
Prepared By HAWA SHOAIB

2. *
The introduction of the self-ligating bracket concept in
orthodontics can be traced back several decade Harradine reports
that the concept of self-ligation is as old as that of the edgewise
bracket itself and was described first by Stolzenberg in 1935.
Although numerous designs were introduced in the following
decades, self-ligation did not become popular until the
introduction of the SPEED appliance (Strit Industries Ltd,
Cambridge, Ontario, Canada) by Hansen in the early 1980s2. In
the 1990s, other companies introduced self-ligating appliances
and, today, almost all major orthodontic companies offer some
form of self-ligating appliance of either the passive or the active
form.

3. *Self-ligating brackets have an inbuilt labial face which can be opened and
closed to retain and release engagement of the arch wire. This labial face is
usually metal but can be ceramic or plastic resin and is usually referred to as a
clip or slide. Brackets incorporating their own ligation system have existed
for a surprisingly long time in orthodontics but they have made a major
impact in orthodontics only in the past decade. New designs continue to
appear, with at least 20 new brackets since 2000. Several earlier designs had
deficiencies, for example the clips or slides were too awkward to open and
close or were prone to distortion or fracture or to inadvertent opening
between visits. There are now some excellent self-ligating brackets available.
Two popular and representative brackets are the Damon MX (Figure 32.1)
and the In-Ovation (Figure 32.2).

6. *
Conventional wire or elastomeric ligatures have significant failings.
Wire ligatures are usually secure and robust but are very slow to
place and remove. Studies have shown that wire ligation is very slow
compared to elastomerics with the use of wire ligatures adding almost
12 minutes to the time needed to remove and replace two archwires.
This difference in speed of use is the largest and very understandable
reason why so few wire ligatures are now used. Elastomeric ligatures,
while being much more rapid to place, have two inherent
deficiencies, inadequate ligating performance and high friction. The
force they provide decays with time and this can lead to loss of full
archwire engagement and consequent loss of tooth alignment.

7. *Figure 32.3 shows failure of elastomeric rings to achieve
full archwire engagement and Figure 32.4 shows loss of
control by elastomeric ligatures later in treatment.
Elastomeric ligatures also have a high coefficient of
friction, which inhibits the majority of desired tooth
movements. Looking at other potential deficiencies, there
is some reason to believe that elastomeric ligatures inhibit
good oral hygiene, while the ends of wire ligatures can
traumatise the oral mucosa.

10. video

11. *
*More certain full arch wire engagement
*Faster arch wire removal and ligation
*Low friction between bracket and arch wire
*Less chair side assistance required
*Better oral hygiene.

12. *
*A self-ligating clip or slide achieves and maintains full arch wire
engagement. The friction between bracket and arch wire has been
clearly demonstrated and quantified in many studies to be much lower
with self-ligation than with elastomerics. This combination of very low
friction and very secure full arch wire engagement is currently only
possible with self-ligating brackets and it uniquely enables teeth to
slide along an arch wire using much lower and more predictable forces
and yet under complete control. This may be particularly beneficial in
the alignment of very irregular teeth. It also reduces the need for
extractions to create space for crowded teeth if that is the desired
treatment goal (Figure 32.5).

14. *
Shivapuja and Berger2 showed a large reduction in time required using
SPEED brackets compared with wire ligation and a smaller but still
significant reduction advantages (approximately 2 minutes per pair of
arch wires) compared with elastomeric ligation. Turnbull and Birnie
found very similar time savings with Damon2 brackets and it is very
probable that more recent bracket types such as the Damon 3MX would
show much greater savings in time for arch wire changes because the
mechanism is so easy and rapid even for a novice. An additional factor
which should be remembered is that arch wire changes using self-ligating
brackets do not require a chair side assistant to speed the process, because
self-ligating brackets require no passing of elastomeric or wire ligatures
to the operator

16. *
*The part of a self-ligating bracket that retains the wire in the slot can
be classified as active or passive. This is an issue which has attracted
heated debate and some misunderstanding. SPEED and In-Ovation,
are examples of brackets which have a flexible spring clip that
encroaches on the slot from the labial aspect, potentially placing an
additional active force on the arch wire. In contrast, Damon and
Vision LP are examples of passive brackets which have a slide that
creates a rigid labial surface to the slot.

17. *The principal intended benefit of an active clip is that a given wire
will have its range of labiolingual action extended and produce more
alignment than would a passive slide with the same wire. A
consequence is that for a given arch wire, the force applied to the
tooth will be higher than with a passive bracket and with thicker
wires, a lingually directed force will remain on the wire even when
the wire is passive. An active clip therefore has higher friction. Hain
et al. and several other authors have demonstrated substantially lower
friction with passive brackets and this may facilitate dissipation of
binding forces and the ability of teeth to push each other aside as they
align. A passive slide requires a slightly larger archwire to achieve full
labiolingual and rotational control. The choice of an active clip or
passive slide is also influenced by other related factors such as
security of ligation or ease of use.

18. *
The studies previously mentioned have
demonstrated a definite and worth while saving in
chair side time with self-ligation. It is also a firm
clinical impression and a very tenable hypothesis
that the combination of good tooth control and low
friction will shorten treatment times and facilitate
high-quality treatment.

19. *It is certainly sensible to exploit the increased
effectiveness of light forces and the better arch wire
control by starting mesiodistal tooth movement on
lighter, more flexible wires and from the first visit in
many instances. This may be expected to shorten
treatment times (Figure 32.6).

22. *
*particularly passive self-ligation – enables tooth-moving
forces to be sufficiently light that forces from the soft tissues
can compete with them and influence the resulting tooth
movement.

23. *Figure 32.7 shows a case where very substantial
alignment has occurred with light forces and without
the significant labial movement of the incisors which
might have been anticipated. This case underwent
orthognathic treatment at a later stage and
proclination of the upper incisors was
contraindicated in that plan.

26. *Statistically greater inter molar expansion associated with self-ligating
appliances arose with SmartClip (Fleming et al. 2009b) and Damon II
(Pandis et al. 2010a) appliances. This finding occurred despite the use of
archwires of uniform dimensions in both groups and the profile of the
bracket types being similar. Additionally, potential confounding factors
including pre-treatment intermolar dimension and the degree of crowding
resolved during treatment were accounted for in the statistical analyses
(Flemingetal. 2009b).
*This outcome indicates that the mechanism of arch
alignment produced by self-ligating systems may be
slightly different from that developing with
conventional appliances.

27. *
*It has been suggested that reduced frictional resistance and the
application of lighter forces with self-ligating brackets would
translate into less deleterious sequelae, for example subjective
discomfort and root resorption.

28. Video