orthodontic insight
Mandibular anterior crowding:
normal or pathological?
Alberto Consolaro1,2, Mauricio de Almeida Cardoso3
DOI: https://doi.org/10.1590/2177-6709.23.2.030-036.oin
The teeth become very close to each other when they are crowded, but their structures remain individualized and, in
this situation, the role of the epithelial rests of Malassez is fundamental to release the EGF. The concept of tensegrity is
fundamental to understand the responses of tissues submitted to forces in body movements, including teeth and their
stability in this process. The factors of tooth position stability in the arch — or dental tensegrity — should be considered when one plans and perform an orthodontic treatment. The direct causes of the mandibular anterior crowding are
decisive to decide about the correct retainer indication: Should they be applied and indicated throughout life? Should
they really be permanently used for lifetime? These aspects of the mandibular anterior crowding and their implication at the orthodontic practice will be discussed here to induct reflections and insights for new researches, as well as
advances in knowledge and technology on this subject.
Keywords: Dental crowding, Orthodontic retainer. Dental resorption. Non-erupted teeth. Tensegrity. Dental concrescence.
Os dentes ficam muito próximos quando estão apinhados, mas suas estruturas permanecem individualizadas e, nessa situação, o papel dos restos epiteliais de Malassez é fundamental para liberar o EGF. A tensigridade é um conceito chave para
compreender as respostas dos tecidos submetidos às forças nos movimentos corporais, incluindo os dentes e sua estabilidade
nesse processo. Os fatores da estabilidade de posição de um dente na arcada dentária — ou tensigridade dentária — devem ser considerados quando se planeja e finaliza um caso na prática clínica ortodôntica. As causas diretas do apinhamento
dentário anteroinferior são determinantes para se refletir se a contenção deve ser mesmo indicada e aplicada por toda a vida
e se, necessariamente, deve ser usada de forma permanente. Esses aspectos do apinhamento dentário anteroinferior e suas
implicações na prática clínica serão aqui abordados para induzir reflexões e insights de novas pesquisas, bem como avanços
no conhecimento e tecnologia sobre esse assunto.
Palavras-chave: Apinhamento dentário. Contenção ortodôntica. Reabsorção dentária. Dentes não irrompidos. Concrescência dentária. Tensigridade.
1
Universidade de São Paulo, Faculdade de Odontologia de Bauru (Bauru/SP, Brazil).
Universidade de São Paulo, Faculdade de Odontologia de Ribeirão Preto, Programa
de Pós-graduação em Odontopediatria (Ribeirão Preto/SP, Brazil).
3
Faculdade de Medicina e Odontologia São Leopoldo Mandic, Programa de
Pós-graduação em Ortodontia (Campinas/SP, Brazil.)
How to cite: Consolaro A, Cardoso MA. Mandibular anterior crowding: normal
or pathological? Dental Press J Orthod. 2018 Mar-Apr;23(2):30-6.
DOI: https://doi.org/10.1590/2177-6709.23.2.030-036.oin
» The authors report no commercial, proprietary or financial interest in the products
or companies described in this article.
Contact address: Alberto Consolaro
E-mail: consolaro@uol.com.br
2
© 2018 Dental Press Journal of Orthodontics
Submitted: March 07, 2018 - Revised and accepted: March 12, 2018
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Consolaro A, Cardoso MA
orthodontic insight
tures do not collide.2 And even if a root gets too close
to other, neither inflammatory resorption nor ankylosis occurs, much less dental concrescence. Why does
not this occur?
The periodontal space in which the periodontal ligament is located is maintained thanks to the constant liberation of EGF (Epidermal Growth Factor) by the epithelial rests of Malassez. This peptide is released by this
epithelial web — spatially configured as a “basketball
net” around the root — permeating between the fibers
and the cells, “moistening” the periodontal ligament.
In the periodontal ligament, the EGF has the
function of stimulating the bone resorption at the
periodontal face of the alveolus, if the deposition of
new layers of fasciculate bone gets close to the tooth.
In this way, the periodontal space is always maintained with 0.2 to 0.4-mm thickness.1
The osteoblasts have EGF receptors, but the cementoblasts, do not. Thus, resorption of the hard tissues occurs only on the bone surface of the periodontal ligament and is not visualized on its cementum
surface. That’s how we explain why the alveolodental
ankylosis does not occur with aging, even decades after a strict proximity between the alveolar bone and
tooth root.
Likewise, in cases of crowded teeth dangerously
close to each other, there is no root resorption neither
concrescence. Maintenance of the periodontal ligament
also protects the root against inflammatory resorption,
thanks to the epithelial rests of Malassez.1,2
The dental concrescence corresponds to the union
of mature and erupted teeth by cement, which is very
rare. In crowded teeth, this hardly happens, because as
one tooth approaches another, alveolar bone remodeling is directed to where the occlusal forces, neighboring
teeth and soft tissues are moving the tooth. In this bone
remodeling, the periodontal space remains stable, thanks
to the EGF that is continuously liberated by the epithelial
rests of Malassez. As new layers of cement slowly build
up, the periodontal thickness is maintained.
The word crowding is originated from the verb
to crowd, which means: 1. to press closely together;
force into a confined space; cram; 2. to push; shove,
3. to fill to excess; fill by pressing or thronging into;
4. to place under pressure or stress by constant solicitation; 5. to gather in large numbers; throng; swarm;
6. to press forward; advance by pushing.
The present paper focussed on the mandibular anterior crowding in the permanent dentition. The crowding can be classified as primary, secondary or tertiary,
when it affects the mixed dentition in the first transitional period, second transitional period and permanent
dentition, respectively.6,7,8
Crowding represents one of the most frequent
(perhaps the main) complaints of patients seeking orthodontists (Fig 1). Many questions about the mandibular anterior crowding tend to generate incomplete, evasive and reticent answers, since there are still
many doubts about it, although it is a very studied
subject in the literature.
Thus, the objectives of this paper are:
A) To answer the following questions:
1st. Why do teeth become so close to each other, move
from their original position in the arch, but do not contact
each other, even on severe cases of crowding (Fig 1)?
2nd. How are teeth so close, almost in contact, but
with no alveolodental ankylosis, nor inflammatory resorptions?
3rd. Why do not even very close teeth, like crowded
teeth, evolve to concrescence?
B) To discuss the causes of the mandibular anterior
crowding, with its implications in orthodontics practice, in a more inquiring way, in order to lead to reflections and insights. For this, we selected a few questions
to guide this text, such as:
1st. Is mandibular anterior crowding normal or pathological?
2nd. Every patient, throughout life, will have mandibular anterior crowding, as suggested by the vast majority
of orthodontists and the classical orthodontic books?
3rd. What are the causes that directly act on the mandibular anterior crowding?
TENSEGRITY CONCEPT IS THE KEY TO
UNDERSTAND TISSUES ANSWERS
In animal and vegetal bodies, as well in objects, the
supporting systems tend to receive and create forces in
their structures, but, in the end, the forces cancel each
other, with a resultant equal to zero. At the end of the
TEETH ARE CLOSE AND CROWDED, BUT THE
STRUCTURES REMAIN INDIVIDUALIZED
Even in the most severe crowding cases, the teeth
do not touch one another. Their mineralized struc-
© 2018 Dental Press Journal of Orthodontics
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orthodontic insight
Mandibular anterior crowding: normal or pathological?
action of these forces, with internal or external origin,
and resultant equal to zero, the object or the anatomic
structure will remain as it was originally. This indicates
a full and perfect system of forces distribution — a balance —, whose property is called tensegrity.
It is the same to a viaduct, a palace or to the head and
the members of the human body, for example, but even
on very simple things, as a decorative clay pot and the
teeth positioning of the teeth steadily in the dental arch,
by the linked action of tongue, lips, occlusion forces,
neighboring teeth and bone dynamism.
Any structure that returns to its original format
after each applied force is in structural and functional
balance. When this same structure gets modified in its
shape by forces, we can have a new design, provided
a new balance of forces is established, that is, we get
a new tensegrity. If we do not reach a new tensegrity
after all this change, is natural that everything returns
to the original shape, to the normal balance, as if it
were a recurrence to the originality.
Every time that the tensegrity of a cell with its
own cytoskeleton is broken, or from a group of muscles and tendons and/or interrelated bones, the cells
components will release many mediators, so that everything returns to its original shape. For example,
the bones will be reabsorbed or undergo neoformation, vases will get larger, muscles will be sore and
tense, everything to have tensegrity again, since the
new shape gives back the tensegrity and equilibrates
the system.
Tensegrity represents the balance of a system of
forces, in which they cancel each other and the resultant will be zero. The object or organ will thus
remain in a stable shape, just like the bone as well.
The concept of tensegrity was established by
Richard Buckminster Fuller (1895-1983),5 an American genius who is considered a designer, an architect and a visionary writer. His main creation was the
“geodesic dome”, which, with its triangular shapes,
cables and balance, brings a very light sphere to protect what is inside it, as weapons, radars, machines
and other activities protected from the weather, even
in inhospitable environments, as deserts and wild valleys, and helped the American government to hide its
radars and missiles.
One of Fuller’s students was Kenneth Duane Snelson (1927-2016),5 an American sculptor and photog-
© 2018 Dental Press Journal of Orthodontics
rapher who created sculptures and artworks based on
tubes and cables, generating forms and structures almost suspended in the air. In many cases, they were
simulations of molecules and microscopic structures.
Snelson brought his work to the extreme of the
tensegrity concept, almost taking for himself the concept of balance and force distribution, spreading it all
over the world. The subject “tensegrity” was treated
very elegantly by Donald E. Ingber in the context of
life architecture, in an article published in the Scientific American5 on January of 1998.
STABILITY FACTORS OF A TOOTH
POSITION IN THE DENTAL ARCH:
THE DENTAL TENSEGRITY
Tensegrity is the term used to describe the concept of balance or stability of any system of forces of
nature or made by humans, including the dental arch.
When a system receives external or internal forces and
the final resultant is equal to zero, it means that there
is a balance in this system, that is, it has tensegrity,
which can be analyzed exclusively in one tooth, one
group of teeth, in the dental arch or across the face.
The systems of forces are dynamic and the external influences tend to modify them, but almost always
temporarily or fleetingly, when they present tensegrity. The teeth on a dental arch should be on tensegrity offered by:
a) The teeth, in the interproximal surfaces.
b) Antagonists teeth in stable occlusion.
c) Forces generated in the functions of the tongue
and other soft tissues, on the lingual side.
d) Cheeks, lips and other soft tissues, on the buccal side.
e) The adaptive and functional dynamism of bone
tissue, constantly remodeling, guided by the dissipation of forces. This process generates forces that tends
to take the tooth to other position, but the occlusion
and all the other forces keep the tooth on the same
position. The countless mitosis, cellular movements
and the constant deposition of tissue matrix generate
forces that add up and increase, while making opposition to other forces from other areas. The result, or
the resulting forces are known as vectors — in this
case, more specifically, as bone growth vectors. Even
after the growth, with the maturation, these vectors
keep existing with less intensity and frequency, with
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orthodontic insight
aptation.3,4 In a situation of balance or tensegrity, its
shape and function remain normal. But the system
may be modified, losing its tensegrity, until a new
shape and balance position is obtained, which may
not be esthetic and functionally convenient, such as
a crowded dental arch in the anterior region.
a much more adaptive nature. In the mandible, this
growth is called later mandibular growth, or residual
mandibular growth.
f) Growth vectors originated by functional and aesthetical adaptations derived from aging, which results
in atrophy, hypertrophy or tissue hyperplasia, as the
vertical dimension reduction caused by attrition, loss
of muscles strength, reduction of soft tissue consistency and reduction of masticatory strength. This process
generates forces that tend to bring the tooth to other
position, but the occlusion and the other forces keep the
tooth at the same position.
When one of these factors decreases, increases or
changes, the balance, or tensegrity, is broken, and the
tendency of the tooth is to slowly and gradually change
its position, spinning within the alveolus, migrating one
of its faces to the other side of the dental arch, which
means that the teeth can become crowded.
The dental arches are one of the parts of the organism under constant movements and loads during
their functions. As the other members, the dental
arches are in constant remodeling and functional ad-
THE DIRECT CAUSES OF MANDIBULAR
ANTERIOR CROWDING
If one of the six determining factors of the dental
tensegrity in the dental arch fails or reduces its effectiveness on stabilization, we may have dental crowding
(from light to severe).
The mandibular anterior crowding in adults can be
explained as a result of the change in the distance between the lower canines, although some retainers bonded to the canines may, eventually, be seen with crowding of the incisors. What could be the reasons for this
intercanine width reduction at the lower arch? It could
be due to a facial aging? Who changes first and is the
cause of the other: the intercanine width or the mandibular anterior crowding?
A
B
Figure 1 - Mandibular anterior crowding, highlighting the proximity of the teeth (roots), maintaining their structures, without inflammatory resorption,
dental ankylosis, nor concrescence.
© 2018 Dental Press Journal of Orthodontics
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orthodontic insight
Mandibular anterior crowding: normal or pathological?
The fact that mandibular anterior crowding is
considered “natural” does not qualify it as “normal”,
although this could lead to many controversial opinions. As an analogy, for comparative purposes, we
could use the alopecia, or baldness, in the men,
which happens with aging: it is natural, but can it be
considered normal?
We can probably find answers for a “natural” tendency to the mandibular anterior crowding in the following observations:
1. The mandible, even after the growth of the entire body has ceased, keeps growing, especially due
to the condyle and its cartilaginous, bony and fibrous
constitution. This would be a residual mandibular
growth that would lead to a bone increase to the anterior region, with a subtle but efficient displacement
of the teeth toward the midline.
2. Chewing promotes occlusal wear, compensated at
the tooth by the continuous deposition of apical cementum, in a process known as passive and continuous dental eruption. Even preserving the height of the clinical
crown, this process promotes changes at the occlusion,
which needs to be compensated.
3. Interproximal contact points gradually turns into
contact facets between the teeth, reducing the mesiodistal width between them as well as the total dental
arch perimeter.
4. These changes micrometrically alter teeth position, and its tensegrity is recomposed from the bone remodeling and the terminal mandibular growth.
The need to keep the contact between teeth in the
dental arch, reducing its perimeter, associated to the
mandibular residual growth, clinically gives the impression that the teeth were “pushed” to the midline.
The quest for tensegrity causes remodeling and mandibular growth to reposition teeth in the dental arch,
constantly and at minimal levels, but on a daily basis.
Any fail on the tensegrity factors can lead to the mandibular anterior crowding.
Even with enough space in the dental arch, can
crowding occur? Maybe just arranging and earning
space will not solve crowding. It would be necessary to
orthodontically correct crowding, aligning teeth and
reestablishing the tensegrity in a new reality, with well
positioned mandibular teeth and in a good relationship
with the maxillary ones and soft tissues.
Crowding should be considered a loss of tensegrity of teeth in the dental arch, and not simply a consequence of the lack of space. It should be identified
which of the stability factors, or tensegrity, in the
dental arch are failing or absent.
© 2018 Dental Press Journal of Orthodontics
FINAL CONSIDERATIONS:
SHOULD WE USE RETAINERS OR NOT?
TEMPORARILY OR PERMANENTLY?
If, after orthodontic treatment, retainers use is mandatory, we must consider that:
1. The system is not in full tensegrity, in the long term.
The teeth that were taken to the crowding did not finish
“locked” by occlusion and other stability factors. There are
still some forces acting in search of a tensegrity that was not
obtained or was lost.
2. In the day to day of bone remodeling and reformatting, as well as in the physiology of the stomatognathic system, forces are generated that can
easily break the obtained dental, bone and facial
tensegrity. The factors of dental stability are not
fully working in space and time.
3. The mandibular anterior crowding should be
considered “normal” in the human being and it is inevitable during the aging process. The term normal is
almost synonymous of “physiological”.
Considering our evolutionary stage, we should recognize that recommending the continued use of retainers in Orthodontics, with all the resulting discomfort,
reflects the need to know more deeply the problem, allowing us to advance, from the technological point of
view, in the purposes of resolution.
How many researches we still need to make to dismiss the use of the retainers in the orthodontic practice?
We’ll get there? Before that, we need to:
1. Recognize that the mandibular anterior crowding is
a result of tensegrity loss in the dental arch.
2. Accept that tensegrity obtained at the beginning
was not stable, permanent and definitive.
3. Understand and explain to the patients that the
dental stability factors, or the dental tensegrity, may be
modified by external factors, including facial aging.
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orthodontic insight
REFERENCES
And the cases of people who naturally, during life time,
do not show mandibular anterior crowding? What are
the factors that lead them to this situation? Is the intercanine width decrease that leads to the mandibular anterior
crowding during aging, or this crowding is the factor that
causes the decrease of the intercanine width?
This matter is not totally clarified in the literature,
but a meticulous study of its evolution in time suggests
that the mandibular anterior crowding represents the
break of tensegrity in the dental arch.
It is very likely that aging will only offer more opportunities in time — increasing the probability — for
the causes that promotes loss of tensegrity in the dental
arch to act, thus promoting the crowding. Let’s make
more researches.
© 2018 Dental Press Journal of Orthodontics
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