The 3 Pillars of Orthodontic Passive Self-ligation- Juniper Publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF DENTISTRY & ORAL HEALTH
Abstract
The concept and technique of Self-ligation has
been a hotly debated topic in Orthodontics in recent years. The claimed
advantages of much-reduced or near-zero friction and the resulting light
forces that can lead to more efficient tooth movement are currently
being regularly researched and investigated, and although many of the
proposed effects are not being entirely and consistently corroborated by
clear scientific evidence to date, this treatment modality is certainly
a very tempting proposition to any orthodontist.
Keywords: Self ligation; Malocclusion; Musculature; OrthodonticIntroduction
I’ve tried out various types of self-ligating
brackets throughout my career as a specialist. I started out slowly and
gradually, trying out different types of SL systems as I went along,
however, I had not tried using the recommended self-ligation treatment
mechanics – as opposed to traditional mechanics - until I decided to use
the Damon Q bracket system. Although I had previous experience with
other Self-ligating systems over the years, my research regarding the
Damon system and technique led me to think that the ideas and technique
advocated by Dr. Dwight Damon required a major paradigm shift in the way
I thought about orthodontics in terms of treatment planning and
mechanics, and so I took my time reading, researching, and attending
lectures and courses surrounding the topic until I felt confident with
the this different way of thinking about orthodontic mechanics.
Proposed Advantages of Self-Ligation
Distilling the basic pillars of passive self-ligation
treatment mechanics - as advocated by Dr. Dwight Damon - they can be
simply boiled-down to THREE basic ideas - that equally apply to any
passive self-ligating system:
Variable bracket torques
Dis articulation
Early, (very) light elastics
Variable bracket torques
Dr. Dwight Damon and other passive self-ligation
advocates have always emphasized the need for accurate bracket bonding
from the very start, and often cite it as a major factor in smooth
treatment progression and success. “Begin with the End in Mind” is what
Dr. Tom Pitts preaches. Taking this a step further, Dr. Damon advocates
the use of variable torque prescriptions for anterior teeth right from
the very start in order to maximize efficiency and smooth progression of
tooth movement, with the basic notion that this helps initiate roots
movement into their corrected positions as early as possible and
maintains them in these corrected – or over-corrected – positions for as
long as possible during treatment, thus improving their chances of
post-treatment stability.
This torque selection starts at the treatment
planning stage and depends on the type of malocclusion being treated,
the individual inclinations of specific anterior teeth and the type of
mechanics and elastics to be used during treatment. Indeed, the most
recent Damon Q system comes with High, Standard and Low torque values
for individual upper and lower anterior brackets. The choice for each
individual tooth should be made at the treatment planning stage, whether
using cast study models or computerized digital setups (such as when
using Ormco’s Insignia system for even more precise customization).
Clinical evidence has shown that this notion is
indeed logical and may improve long-term chances of stability, provided
that the required torque prescription is actually fully expressed by the
end of treatment. In practice, and more often than not, the
orthodontist may still need to introduce torque manually through the
arch wire even with variable torque selection at the start, and this may
be due to issues with full arch wire engagement failing to fully
express built-in torque values towards the later stages of treatment, as
expressed by many practitioners of self-ligating systems.
Dis-articulation
The second “pillar” is directly related to the occlusion and
interdigitation of the dentition. In order to facilitate tooth
movement using the very light forces of the initial aligning phase
with PSL, it is recommended to “dis-articulate” the occlusion
in order to minimize interdigitation that could hinder or delay
tooth alignment.
This “Bite Raising” is usually performed either on the
palatal aspects of upper (Class II cases) or lower (Class III cases
with reverse over jet) anterior teeth in Low Angle, deep bite
cases. This helps in holding/intruding the anterior teeth and
maximizing extrusion of posterior teeth thus aiding in correcting
the occlusion. In High Angle, reduced overbite or Open Bite cases,
the bite raising should be positioned on the occlusal surfaces of
posterior teeth, as needed, as this helps prevent or minimize
further extrusion during alignment.
Many long time self-ligation practitioners have demonstrated
that it is entirely possible to achieve excellent results without disarticulation
in every single case. However, dis-articulation right
from the beginning is a more efficient way of operating as one
would often end up performing this bite raising at later stages on
many occasions, especially in the presence of cross-bites, if it is
not done from the very start.
Early, (very) light elastics
One of the most intriguing – and indeed, anxiety-ridden –
shifts from traditional orthodontic thinking and mechanics that I
had personally faced was the advocated use of early elastics right
from the first visit with light, round, flexible Nickel Titanium
arch wires in place! Conventional wisdom and teaching with preadjusted
appliance treatment mechanics was built on the idea
that elastics are used towards the later stages of treatment once
heavier, more rigid arch wires are reached, as using them early
on when very light Nickel-Titanium wires are in place would
produce all kinds of unwanted tooth movements, rotations and
overall occlusal imbalances. Once that rather huge mind block
was overcome, this single “pillar” alone would prove to be the
defining strong point for my decision to continue my use of PSL.
Valuable and unique research done by Badawi H [1] in Canada
has shown the effect of force distribution on different teeth along
the dental arch using PSL and conventional bracket systems. In
PSL systems, the effect of a certain local force does not extend
beyond a couple of teeth either side of the location of application,
and even then, the effects were minimal. In contrast, the force
distribution in conventional appliances had a more far-reaching
effect all the way to teeth on the opposing side of the arch; hence,
the unwanted tooth movements due to any force application
were at a maximum most of the time. This notion, when extended
to the use of early light elastics, helps explain how the use of such
light forces even as early as the first visit and on flexible Nickel-
Titanium arch wires does not – in general – have a detrimental
effect on the rest of the arch. On the contrary, the light forces
seem to gently help in guiding the involved teeth as they level and align, without overpowering the surrounding musculature
to any measurable extent.
Clinically, It seems there is a very reasonable clinical validity
to such claims. The main noticeable issue faced at the aligning
phase is the incomplete – or delayed – correction of rotations
which is most probably due to the increased “play” between the
small initial arch wires and the 0.022” slot of the Damon Q bracket,
where full engagement against the slot base is non-existent due
to the nature of the locking mechanism’s “passive” construction.
Full rotational correction does not actually occur until later in
treatment when –at least – an 0.016”×0.25” or 0.018”×0.25”
rectangular arch wire is in place. This probably explains the
findings of a study by Miles et al. [2] and others that have shown
no measurable statistical difference in alignment speeds between
self-ligating appliances in general and conventional appliance. In
fact, some studies noted that alignment was actually faster with
conventional appliances in many instances (Figure 1 & 2).
Discussion
It is true that further clear evidence is needed to backup
many of the claims related to passive self-ligation, as a review
by Padhraig and O’Brien [3] comprehensively investigated.
However, clinical experience is clearly showing the potential in overcoming many of conventionally ligated fixed appliances’
issues we’ve had for decades now. Considering we still lack solid
evidence for many aspects of even our current conventional
fixed appliance treatment modalities, it may be a bit hasty to
dismiss self-ligating systems and techniques simply because of
the findings of currently available research, although indeed, the
marketing approach for many such systems can only be described
as Over-the-top Hype, often directly aimed at consumers, rather
than orthodontic professionals [4].
Conclusion
Our minds and way of thinking have been locked for too long
in a certain “mold” surrounding conventional fixed appliances,
and I believe that in order for the research to be able to accurately
determine the Cons and Pros of Self-ligation, we need a Paradigm
Shift in the way we approach future research in the first place,
as old ways of thinking and solving problems may not always be suitable to properly judge newer ways. Until then, an open eye
and an open mind are key.
The author would like to clearly point-out that he has no
“invested interest“in any self-ligating appliance or system. This
is simply a statement of personal experience and brief review on
the use of this particular appliance system.
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