The En Masse and the Sequential Retraction Procedures

• In this article, the authors discuss two preeminent notions in orthodontics; those are the approaches of “En Masse Retraction” and “Sequential Retraction” in orthodontic cases. The “Sequential Retraction” is identified by retraction of canines firstly, forming one group of retracted canine and posterior teeth in the respective side, then retraction of the incisors. Besides, the approach of “En Masse Retraction” is identified by retraction of the six anterior teeth “as one group”. Sequential Retraction is called “two-phased retraction”, whereas “En Masse Retraction” termed as “one-phased retraction”. Sequential Retraction has been justified for its characteristic of upholding anchorage, while En Masse Retraction is beneficial in keeping the alignment of the anterior teeth during treatment. Sequential Retraction has two phases: Firstly, canines are moved posteriorly, then canines are congregated with the posterior units of second premolars and first molars (in addition to second molars if they are banded) to form one group. Secondly, the anterior four incisors are retracted. Sequential Retraction may cause temporary spaces especially in between lateral incisors and canines what are unwelcome sometimes.
• In addition, in the first phase of sequential retraction, it is recommended that a “stop” on the mesial of the molar tube be placed, to “maintain the anchorage” by preventing its “burning” (by a potential movement of the first molar mesially). Nonetheless, this stop has its own reaction on the pertinent incisors, consequently the incisors move anteriorly little bit, in the canine retraction phase, what in turn, increases the burden on the anchorage units, during the “phase-two” of incisors retraction. In other word, the conception that sequential retraction is more “harmless” towards the anchorage units is gradually becoming a debatable issue. Furthermore, an advantage of the “En Masse” retraction in maintaining the “Leveling of Alignment” of anterior teeth should be taken into account by clinician. By applying the “theory of Optimal Force Values”, (which depends on using continuous low force, as minimal as available, and simultaneously over the due threshold that is sufficient to cause tooth movement), it is available to achieve canines and incisors “en masse” retracted without such an overload onto anchorage segments. As the standpoint would be to apply optimal forces on the anterior teeth, with least counteracted movements onto anchorage units proposing forces dissipation until be below the sufficient threshold for posterior teeth movement. 

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 “2^nd 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. 

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