Article Type : Case Report
Authors : Mhd. Azhar Ibrahim Kharsa
Keywords : En masse retraction; Sequential retraction; Extraction cases; Optimal forces
Orthodontists had followed sequential Retraction for
decades, depending on a hypothesis presumes that two-phased retraction protects
more the anchorage. As anchorage fortification has been always the sought after
target, sequential retraction technique has been mistakenly related with such
an objective. On the other hand, a trend in orthodontics starts to float that
believes such a correlation in between sequential retraction and anchorage
maintenance a sort of “Pathetic Fallacy”.
The reasons for revitalization of the notion of “En
Masse Retraction” are:
1.
The advent of
miniscrews and relevant temporary anchorage devices.
2.
The perception of
“Optimal Forces Application” takes part in giving a new lease of life into the
“En Masse Retraction” approach.
3.
The application of
contemporary biomechanics principia could support “one-phased retraction”
approach (Figure 1).
As translation movement helps (in case of en masse
retraction) in conserving the leveling and alignment of anterior teeth and in avoiding
the high “moment-values” effects, (High moments may affect the anchorage units,
as a reaction, to counteract the moments of the anteriors) [1-5].
Nonetheless, En Masse Retraction is not indicated in all cases, nor it
is a panacea. In other world, there is no magic potion in orthodontics, thus
contraindication of En Masse Retraction should also be respected.
Figure 1: The force vectors in case of translation movement of the anterior teeth.
Clinician
is encouraged to discern in between cases, consequently en masse retraction,
maybe applied when:
·
Anterior teeth are
in order with good alignment.
·
Crowding is either
moderate or mild.
·
Protrusion is
either moderate or mild.
·
The arch wire
should not be sectional.
·
The least friction
and absence of notching is preferable to fiddle with the notion of Optimal
Force.
·
The Cases where
burning of anchorage forms a part of treatment plan.
·
Cases when
Miniscrews are used.
The Optimal Force notion in the en masse retraction
approach depends on the ability to apply low forces slightly above the
thresholds to retract the anterior teeth, simultaneously such forces are
counteracted and dissipated in the posterior teeth without remarkable anchorage
loss (Figure 2).
In short: The “optimal force” here: is the “minor
force” which is slightly above the “threshold” force, (The threshold force: is
least available force to move a tooth).
Figure 2: Case of En Masse Retraction in lingual technique.
Figure 3: A case where in mass retraction has been used to retract the anterior teeth depending on increasing anchorage and using optimal force values.
Clinically, En masse retraction is an easy approach,
as it is available to be applied when anchor units are the posterior teeth “2nd
premolars, 1st molars and second molars if included” (Figure 2) [6-12].
In spite of the belief which most of orthodontists have regarding sequential retraction (as they think that it conservers more the anchorage units in extraction cases), the clinical views show sometimes-contradictory paradigms to such a notion (Figure 5).
Figure 4: A case of “En Masse Retraction”, Using
Stainless Steel Retraction Springs to adjust Optimal Forces.
Figure 5: An example of an anchorage burned in a sequential retraction case, the first molar and 2nd premolar are shifted and inclined mesially, closing and consuming the previous extraction space of the first premolar.
Sequential Retraction is an indispensable must sometimes, especially when teeth are misaligned, severely protruded and severely crowded (Figure 6). Openbites may support also the sequential retraction approach, not only because of teeth protrusion, but because of tongue thrusting that usually accompanies such cases what makes optimal forces adjustment a sort of impossible “Utopian Deed” (Figure 7). Ectopic eruption of canines may lead the orthodontist to follow the sequential retraction; as it impossible to retract the anterior teeth as a group when canines are highly leveled (Figures 7 and 8). Besides, it is imperative that en masse retraction be avoided when sectional archwires, Utility arches (Figure 7) notched archwires and high friction fixed appliances are to be used.
Figure 6: A case of severe crowding, where en masse retraction in not indicated.
Figure 7: An open bite, ectopic maxillary canines’ eruption and severe tongue thrusting case. In such cases “En Masse Retraction” is contraindicated.
Figure 8: Sequential Retraction within sectional archwires.
The Canine Retraction NiTi Closed Coil Spring
transmits low and continuous forces (Figures 9-11).
Figure 9: A case with open bite with anterior teeth misaligned.
Figure 10: The same case after extraction and retraction springs are installed. An example of Sequential Retraction.
Figure 11: A retraction NiTi closed coil spring installed.
Figure 12: A case where “Molars Mesialization” forms a part of treatment plan.
Figure 13: A case where the First Molar Mesial Stops protrude the anterior teeth what alleviate the anterior crowding, align anterior teeth in their proper positions and help in enhancing patient’s profile.
Figure 14: an example when Molars Mesialization “or Burning of Anchorage”, is an essential part of treatment plan. P.S.: left side required retraction of canine and first premolar, whereas right side required only molars mesialization movement.
1.
The sequential
retraction is not always a time consuming procedure. Besides, the en masse
retraction is not always the rapid and “short-cut” approach. The time “required
for each treatment” depends on several factors not only on the technique used.
2.
When a stop is
added on the mesial side of the first molars it may cause a protrusion of the
anterior teeth as a reaction “which is in fact a side-effect”, unless light
forces are applied. Also, it is highly recommended to add the stop on the
mesial side of the second molars instead of the first molars, unless the case
is class II Division 2 “when the incisors are retruded”. In such cases the stop
added on the mesial side of the first molars will produce a beneficial reaction
onto the incisors.
3.
The theory of
“optimal force level” has now clinical evidences in a lot of parts of
“orthodontic world”, where light forces application technique is being applied
successfully regardless of whether lingual or labial orthodontic techniques are
followed. Consequently, it is necessary to apply such a concept on both
techniques: Sequential and En Masse Retraction. Besides, to have a successful
retraction, the total amount of roots surface in the anchorage unit must be
higher than the total amount of roots surface in the anterior six, if not,
other supportive approaches should be sought after “as microimplants, for
instance”.
4.
To apply optimal
forces it is highly recommended to use NiTi coils instead of stainless steels
coils due the superelastic properties within the NiTi alloys. The forces
provided by the stainless steel coils are so much higher than the NiTi coils
mainly in the beginning of the coil activation. However, they decrease
gradually and progressively, what may incite the clinician either to change or
to reactivate the SS coil more frequently.
5.
Choosing the
appropriate technique depends on the clinical needs of the respective case. In
other word, it is not an option that is chosen freely by the practitioner. It
is imperative that orthodontist be aware when to use “En Masse Retraction” and
when to use “Sequential Retraction” depending on each individual case, per se.
6.
It is recommended
that all the teeth be bonded “or banded”, as to have more control over the
teeth and dental movements. Such a recommendation is not conditional whether
archwire is continuous or segmental “sectional”. The point is that orthodontist
should handle properly which tooth/teeth to be the Reaction Unit(s) and which
to be moved, on the basis of the objective purpose of treatment plan. Furthermore,
anterior tooth/teeth retraction and/or posterior tooth/teeth protraction are
not conditional to be symmetric in between right and left sides of the
respective case, therefore clinician is encouraged to peruse and scrutinize
each tooth and each group of teeth, to determine the best approach for each
unit, per se.
Finally, the more orthodontist is aware of
biomechanical principles, the more he/she is successful in discerning the best
plan of treatment and the best way to harness that plan.