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Dental Press J Orthod. 2021;26(4):e21ins4
https://doi.org/10.1590/2177-6709.26.4.e21ins4
Volume 26 - Number 4 - Online
ORTHODONTIC INSIGHT
Supernumerary teeth in patients with
cleft lip and palate: the tooth germs do
not separate
(1) Universidade de São Paulo, Faculdade de Odontologia de Bauru (Bauru/SP, Brazil). (2) Universidade de São
Paulo, Faculdade de Odontologia de Ribeirão Preto (Ribeirão Preto/SP, Brazil). (3) Oral and Maxillofacial Surgery
department of the Cleft Lip and Palate Service of the “Hospital Infantil Dr. Juvêncio Matos” (São Luís/MA, Brazil).
(4)Universidade Estadual de Feira de Santana, Departamento de Saúde (BA, Brazil).
Submitted: June 07, 2021 • Revised and accepted: July 14, 2021
consolaro@uol.com.br
How to cite: Consolaro A, Medeiros MCM, Miranda DAO, Oliveira IA. Supernumerary teeth in patients with
cleft lip and palate: the tooth germs do not separate. Dental Press J Orthod. 2021;26(4):e21ins4.
Alberto CONSOLARO1,2
https://orcid.org/0000-0002-5902-5646
Maria Carolina Malta MEDEIROS3
https://orcid.org/0000-0002-3659-1848
Dario Augusto Oliveira MIRANDA4
https://orcid.org/0000-0001-7648-6359
Ingrid Araújo de OLIVEIRA3
https://orcid.org/0000-0002-4663-6405
Dental Press J Orthod. 2021;26(4):e21ins4
CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
2
ABSTRACT
Introduction: Supernumerary teeth in cases of cleft lip and
palate do not result from the division of normal germs before
the formation of hard tissue. Deciduous and permanent teeth
odontogenesis begins after the face has formed, either with or
without the cleft.
Discussion: The most acceptable hypothesis to enable un-
derstanding of the presence of supernumerary teeth on one or
both sides of the cleft palate is hyperactivity of the dental lam-
ina in its walls. This hyperactivity, with the formation of more
tooth germs, must be attributed to mediators and genes relat-
ed to tooth formation, under strong influence of local epigene-
tic factors, whose developmental environment was affected by
the presence of the cleft.
Conclusion: The current concepts of embryology no longer
support the fusion of embryonic processes for the formation of
the face, but rather the leveling of the grooves between them.
All human teeth have a dual embryonic origin, as they are com-
posed of ectoderm and mesenchyme/ectomesenchyme, but
this does not make it easy for them to be duplicated to form
supernumerary teeth.
Keywords: Supernumerary tooth. Hyperdontia. Cleft lip and palate.
Dental Press J Orthod. 2021;26(4):e21ins4
CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
3
RESUMO
Introdução: Os dentes extranumerários nas fissuras labiopala-
tinas não são resultado da divisão dos germes normais antes da
formação do tecido duro. A odontogênese dos decíduos e perma-
nentes inicia-se depois de formada a face, com ou sem fissuras.
Discussão: A hipótese mais plausível para compreender a pre-
sença dos dentes extranumerários em um ou nos dois lados da
fissura labiopalatina é a hiperatividade da lâmina dentária em
suas paredes. Essa hiperatividade, com formação de mais ger-
mes dentários, deve ser atribuída aos mediadores e genes rela-
cionados à formação dos dentes, sob forte influência de fatores
epigenéticos locais, cujo ambiente de desenvolvimento foi afe-
tado pela presença da fissura.
Conclusão: Os conceitos atuais da embriologia não fundamen-
tam mais a fusão de processos embrionários para a formação da
face, e sim o nivelamento dos sulcos entre eles. Todos os dentes
humanos têm uma dupla origem embrionária, pois se compõem
de ectoderma e mesênquima/ectomesênquima, mas isso não fa-
cilita sua duplicação para formar dentes extranumerários.
Palavras-chave: Dente extranumerário. Hiperdontia. Dente
supranumerário. Fissuras labiopalatinas.
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CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
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The most frequent supernumerary teeth are the mesiodens,
mandibular premolars and Bolk’s fourth molars. When they
resemble the group of origin, they are denominated eumor-
phic supernumerary teeth, and when they have an undefined
shape, they are said to be dysmorphic. In cleft lip and palate
patients, the frequency of supernumerary teeth reaches up
to 43.5% of cases1-5 (Fig 1).
FORMATION OF THE FACE DOES NOT OCCUR BY FUSION
The formation of the face does not occur by fusion of embry-
onic processes, which was an older way of understanding how
facial development takes place. All evidence has shown that the
face is formed by leveling of the embryonic processes, except
at a very specific and central point of the hard palate, from
which anterior and posterior leveling is also established.6
These concepts, of face formation mechanisms, and their
evolution — from the fusion to the leveling — have been
meticulously reviewed, described and presented in an arti-
cle published in 20176 (Figs 2 and 3).
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5CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
Figure 1: Example of a super-
numerary tooth (red arrow) in
front of the canine and at the
margin of the cleft palate (white
arrow) in tomographic images
(Source:Freitas20, 2007).
tooth #23
Cleft
supernumerary
tooth #26
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6CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
Figure 2: Diagram of the leveling of facial embryonic processes, on the left; and when fa-
cial cleft occurs due to lack of leveling, on the right (Source: Consolaro et al.6, 2017).
Etiopathogenesis of some cystic diseases and lesions based on
the non-fusion of processes is no longer accepted. Many of
these diseases continue to be considered clinical entities, as
their true etiopathogenesis has been discovered; others were
diseases such as the odontogenic keratocyst, which develops
in areas where fusions of embryonic processes supposedly
occurred, and were not fissure lesions or cysts.7-11
Two embryonic processes
Ectoderm
Mesoderm
Proliferating cells
Stable cells
Increased proliferation in the
mesoderm below the sulcus
Leveling = formed structure Without leveling = facial cleft
Absence of increased proliferation in the
mesoderm below the sulcus
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7CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
Figure 3: Diagram of palate formation: the two lateral palatal processes ( LP ) meet in the mid-
line at a certain point ( red arrows ), the only point where the disappearance of the ectoderm
is present, with integration or fusion of the two mesoderms. After this point, leveling ( blue
arrows ) for anterior and posterior occurs, ending the secondary palate and complementing
the primary palate (Source: Consolaro et al.6, 2017).
WHEN THE DENTAL LAMINA AND TOOTH GERMS BEGIN
The anterior part of the primitive mouth, or stomodeum, has
an ectodermal lining of the external part that invaginates. This
lining joins with the lining at the back of the mouth — which,
in the embryo, is called the embryonic pharynx.12 When the
buccopharyngeal membrane is broken, the two cavities join to
form the final mouth. The exact site in the oral mucosa where
this membrane adheres is still controversial.
LP
Primary palate Primary palate
Secondary palate
Leveling
LP LP
LP
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The first sign of deciduous human dentition occurs around the
eighth week of embryonic life, with a linear thickening in the
lining and a horseshoe-shaped contour at the location of the
future dental arch.13 This thickening will form the dental lamina
that descends vertically as it enters the space that will be the
mandible and maxilla. Underlying this thickening, there is an
increase in the concentration of mesoderm and ectomesen-
chymal cells derived from the neural crest, that will later form
the dental papilla and dental follicle.
This thickening of the ectodermal lining initially occurs at the
region of the incisors and molars in each quadrant, which will
unite, as they grow towards the anterior and posterior direc-
tions, and become equal in the region that will be the canines.
These two areas are influenced by the same mediators and
tooth-related genes (Fgf-8, Pitx-2, Shh, Msx-1, Pax-9, Bmp-4),
without specific differences between one and the other, as
shown by Kriangkrai et al.14 At a certain point, the fact that
these two areas have not yet become equalized or met does
not mean that there was no fusion,15,16,17 because the face is
formed by the leveling of embryonic processes by a prolifera-
tive phenomenon.
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CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
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All these above-mentioned characteristics and occurrences are
relative to the deciduous lateral incisor, and not the permanent
lateral incisor. From the deciduous lamina, sprouts or buds will
form, which will give rise to the germs of the deciduous teeth
and to another lamina that arise by lingual, and will give rise
to the permanent teeth — which is also called the successional
lamina, and is continuous around the entire dental arch.
But there is a most important point: the first signs of forma-
tion of this successional lamina that will give rise to perma-
nent teeth only begin to appear after the eleventh week of
embryonic life.6,13 As mentioned before, the deciduous teeth
odontogenesis begins after the eighth week, when the forma-
tion of the face and palate has been completed. The non-lev-
eling of the processes and establishment of the cleft occurs
before odontogenesis begins.
The lack of closure by leveling and the formation of the cleft
represent local epigenetic factors very important in the gener-
ation of dental anomalies in the region, including the supernu-
merary teeth. The chronology of formation of the deciduous
and permanent teeth can be retrieved in the studies conducted
by Massler, Schour and Poncher,18,19 in 1941 and 1946, with still
up to date figures, tables and illustrative diagrams.
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HYPOTHESES TO EXPLAIN SUPERNUMERARY TEETH,
INCLUDING IN CASES WITH CLEFTS
The cause of supernumerary teeth is unknown. There are the-
ories or hypotheses to explain them, highlighting the following:
1. The hyperactivity of the dental lamina, represented by
excessive induction for this laminar and continuous tissue
to form more tooth buds than the normal number. Thiscan
occur due to an excessive quantity of growth factors or
mediators, especially in the areas of clefts, which lead to
more teeth appearing than were originally programmed
by the genes.
2. Atavism, or phylogenetic reversal, which represents current
manifestations of distant ancestral characteristics — as a
possible occurrence of third dentition, which has never
been described or observed in primates and predecessors
of the human race. This theory represents a theoretical
and very imaginative presumption.
3. The sectioning, into two or more parts, of a tooth germ
prior to the formation of hard or mineralized tooth tissue,
but due to an unknown cause that has never been demon-
strated in vivo.
4. Some cases of supernumerary teeth are familiar, but hered-
ity is not necessarily linked to the etiopathogenesis in the
majority of cases. Heredity as a factor in supernumerary
teeth still needs to be further investigated, but random-
ness does occur in almost all cases.
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CConsolaro A, Medeiros MCM, Miranda DAO, Oliveira IA — Supernumerary teeth in patients with cleft lip
and palate: the tooth germs do not separate
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CLEFT LIP AND PALATE DO NOT OCCUR CONCOMITANTLY
WITH THE BEGINNING OF ODONTOGENESIS
On the lateral walls of cleft palate, there is frequent presence
of supernumeraries in the form of a extra lateral incisor on the
side corresponding to the premaxilla or as a tooth similar to the
lateral incisor on the maxillary side of the cleft, also identified
as precanine.1-5 These teeth may also be dysmorphic, as they
do not have the morphology of the dental group that gave rise
to them, but their tissues are microscopically indistinguishable
from eumorphic and normal teeth.
An explanation often given for these supernumerary teeth in
clefts is that the supposed lack of fusion — an event that could
never be demonstrated, even in a rudimentary way — would
cleave the tooth germ into two parts, thus giving rise to two
independent teeth, with one of them being supernumerary.
In the formation of clefts, no cleavage occurs, and there is no
external force that separates the structures, such as the maxilla
and the teeth, which have already been formed. In this period,
the teeth have not yet been formed.
It is difficult to imagine this occurring, as the formation of the
face by leveling, or even if it was by fusion, occurs between the
fourth and eighth week of embryonic life, while the first traces
or tissue changes for the formation of the band and dental
lamina that will give rise to permanent teeth occur from the
eleventh week.
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12
The phenomena of formation of the face and the cleft lip and
palate, and the presence of tooth germs — even the germs of
deciduous maxillary lateral incisors — do not occur concomi-
tantly. In the case of permanent teeth, the formation of germs
occurs much later than the occurrence of clefts, which occurs
at a much earlier stage than the formation of the dental lamina
of permanent teeth, called the successional lamina.
The leveling of embryonic processes means their gradual
increase by proliferation of the mesoderm at the bottom of
the grooves, depressions and valleys formed between them,
thereby leveling the surfaces. Embryonic processes are pro-
tuberances and elevations that level out at the top of their
projections (Figs 2 and 3). Hyperactivity of the dental lamina is
suggested to be the explanation for the supernumerary teeth,
which could be increased by the accentuated epigenetic fac-
tors in the cleft palate area.
ALL TEETH ARE OF DUAL EMBRYONIC ORIGIN
The formation of sprouts or buds that will form tooth germs
at each point corresponding to a tooth occurs by cell differ-
entiation that is induced by mediators such as growth factors,
which are peptides that have this function in an organism in the
process of formation. These mediators activate odontogenesis
genes in the ectoderm and mesenchyme.14
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13
The lack of leveling of the medial nasal process with the maxil-
lary process leads to the occurrence of cleft between the max-
illa and premaxilla. The initial foci of this differentiation, in the
incisor and molar region, as previously mentioned, continue to
expand forwards and in a posterior direction, even if there is a
previously established cleft.
In the region of the cleft palate, the two separate parts will
continue to receive stimuli from the mediators to give rise to
tooth germs. On both sides of the dental lamina and both sides
of the future maxillary lateral incisor germ, the embryonic ori-
gin is the same. The topography and location of a structure
does not determine its embryonic origin, but rather to which
embryonic layer those cells belong. All teeth will always have
an ectodermal and mesenchymal origin.
The fact that the maxillary lateral incisor is derived from the site
where the medial nasal process was leveled, and the canine
is derived from the area that was topographically derived
from the maxillary process, does not imply that lateral inci-
sor and canine have a distinct or different embryonic origin.
Theembryonic origin or nature has to do with being derived
from the ectoderm, mesoderm and endoderm, and even being
of ectomesenchymal origin, as in the case of all human teeth.
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14
The fact that the deciduous maxillary lateral incisor arises
from one or another facial embryonic process does not distin-
guish or modify its embryonic origin or its nature, especially
if we consider that the mechanism of fusion of embryonic
processes is not scientifically supported: There is no evidence
of these fusions, obtained by means of any analysis or meth-
odology.6 All evidence shows that leveling of embryonic pro-
cesses takes place, not fusion. Unfortunately, many studies,
although recent, have tried to explain the embryonic phe-
nomena of the face and teeth based on the theoretical model
of the fusion of processes.
Probably, the activity on each side of the cleft, or hyperactivity
of the dental lamina, explains why an supernumerary maxillary
lateral incisor is sometimes formed on the side of the premaxilla,
and, at the same time, another supernumerary lateral incisor in
the region anterior to the canine — which has, therefore, been
called the pre-canine supernumerary. In many cases of cleft lip
and palate there are no supernumerary teeth, and in others only
one of these two types of supernumerary teeth occurs.
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FINAL CONSIDERATIONS
The location and organization of dental buds in the dental lam-
ina occur by induction of mediators called growth factors, which
act and activate the genes of odontogenesis.14 Hyperactivity
represented by more mediators and an increased response to
them may plausibly explain the formation of supernumerary
tooth buds and germs, irrespective of whether they occur in
cleft areas or not.
As the times of formation of the face and the chronology of odon-
togenesis do not occur concomitantly, this does not allow us to
affirm that the formation of a cleft lip and palate cleaves or severs
the germ of the maxillary lateral incisor, in order to give rise to
supernumerary teeth that are so common in these cases. Onboth
sides of a cleft lip and palate, mediator induction continues nor-
mally and may induce supernumerary formation, by local lamina
hyperactivity at these separate ends or interfaces.
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AUTHORS’ CONTRIBUTION
Alberto Consolaro (AC)
Maria C. Malta Medeiros (MCMM)
Dario A. Oliveira Miranda (DAOM)
Ingrid Araújo de Oliveira (IAO)
Conception or design of the study:
AC, IAO.
Data acquisition, analysis or
interpretation:
AC, MCMM, DAOM, IAO.
Writing the article:
AC, MCMM, DAOM, IAO.
Critical revision of the article:
AC, MCMM, DAOM, IAO.
Final approval of the article:
AC, MCMM, DAOM, IAO.
Overall responsibility:
IAO.
The authors report no commercial, proprietary or financial interest in the products or
companies described in this article.
Dental Press J Orthod. 2021;26(4):e21ins4
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