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The Etiology of
Orthodontic Problems
Prepared by
Dr Hana Omar Al
Balbeesi
Malocclusion and Dentofacial
deformities result not only
from some pathological
processes, but also by
moderate distortions of
normal development.
Causes of Orthodontic Problems
Either from
•Environmental influences
Eg. Mandibular deficiency secondary to jaw fracture
during childhood
Or
•Genetic influences accompanied some rare genetic
syndromes.
However
Orthodontic problems seem to arise from
environmental and hereditary influences
interaction.
Etiologic Factors for
malocclusion are
1. Specific causes of
malocclusion.
2. Hereditary influences.
3. Environmental influences.
1.Specific causes of
malocclusion:Disturbances in Embryologic
Development.
Skeletal Growth
Disturbances .
Disturbances of Dental
Development .
Disturbances in
Embryologic
Development
Defect in embryologic development usually
result in death of the embryo,20 % of such
defects cause early abortion.
Causes
genetic disturbances ,
specific environmental influences
teratogenic influences (i.e chemicals &other
agents) .
Drugs
are either teratogenic or non
teratogenic. Teratogenic
drugs can cause specific
defects with low doses ,or
death in high doses.
This table lists the teratogens known to
produce orthodontic problems
 Skeletal Growth
Disturbances
1. Fetal Molding & Birth Injures.
2. Childhood fractures of the
jaws.
3. Muscle dysfunction.
4. Acromegaly and Hemi
mandibular Hyper trophy.
1.Fetal Molding and Birth
injures :
Injures at birth have two major
categories:
A. Intra uterine molding.
B. Trauma to the mandible
during birth
from the
forceps that used in delivery.
A. Intra uterine Molding :
• Any pressure against the
developing face lead to
distortion of rapidly
growing areas.
• Its not a true birth injury
such as maxillary
defeciency due to arm
pressure
• flexing of head against chest
leading to abnormal mandibular
growth (Pierre Robin Syndrome)
accompanied with cleft palate .
• If cartilage formation defect is
present with (PRS) this will be
called Stickler Syndrome .
• Child can recover if the source
is stopped ,so early treatment
should be avoided.
• Some others need surgical
interference to catch up with
future growth.
B. Birth Trauma to the
Mandible :
• Facial deformities that are not caused
by birth injures but referred by parent
like birth injury such as Treacher Collins
Syndrome & Crouzons Syndrome .
• Facial deformities caused by forceps
usage lead to tempro-mandibular joints
damage (due to internal hemorrage ,loss
of tissue &a subsequent
underdevelopment of the mandible).
2. Childhood Fractures of the Jaw :
•
•
•
•
•
Fractures of the condylar neck .
Trauma to maxilla & mandible .
Rheumatoid arthrities lead to
asymmetric mandibular
defeciency.
Hemi facial microsomia.
Asymmetric mandibular growth.
3. Muscle Dysfunction :
Facial muscles can affect jaw growth in
two ways:
1. formation of bone at muscle
attachments point.
2. musculature is an important part of
the total soft tissue matrix whose
growth lead to jaw growth. Also damage
to the motor nerve causes muscle
atrophy.
• Excessive muscle contraction
(torticollis) can restrict growth like
scaring after injury (especially
sternocliedomastoid muscle).
• Treatment is surgical detachment of
the muscle.
Muscular dystrophy ,cerebral
palsy ,muscle weakness
syndromes lead :
• to increased anterior facial height.
• distortion of facial proportions &
mandibular form.
• excessive eruption of the posterior
teeth
• narrowing of the maxillary arch.
• anterior open bite.
4. Acromegaly and Hemimandibular Hypertrophy :
• Acromegaly caused by anterior
pituitary tumor secretes excessive
growth hormone lead to excessive
growth of the mandible (Cl III
malocclusion).
• Tx is an orthognathic surgery though
tumor is removed or irradiated .
• Hemi-mandibular hypertrophy or
condylar hyperplasia occur mostly in
10 yrs old females or at 30 yrs on both
sexes .
• When condylar cartilage proliferation
& body of the Mandible growth stop
the affected area will be removed &
reconstructed .
• Cause is unknown.
 Disturbances
of Dental Development
It may accompany major congenital
defects but it is more significant with
Cl I malocclusion.
Significant
Disturbances Include:
1. Congenitally Missing teeth.
2. Malformed & Supernumerary
teeth.
3. Interference with Eruption.
4. Ectopic Eruption.
5. Early loss of Primary teeth.
6. Traumatic Displacement of
Teeth.
1. Congenitally missing teeth
It results from disturbance during
initial stages of tooth formation
,initiation and proliferation.
Missing of teeth can be:a. Complete (Anodontia).
b. Many teeth (oligodontia).
Both are rare & are associated
with ectodermal dysplasia
(systemic abnormality).
C. Few teeth (hypodontia) is more
common.
• Missing of primary teeth lead to
missing of its permanent
successor.
• The sequence of missing teeth are
3rd molars, lateral insicors,2nd
premolars, and rarely Canine.
2. Malformed and supernumerary
teeth
Abnormalities in tooth
size and shape will be
due to disturbances
during morpho & histo differentiation
stages of its development.
Most common abnormality is seen in
lateral incisors & 2nd premolars .
Abnormalities are :Malformation
supernumerary
Gemination
Fusion
• Multiple numeraries can be
seen in cleidocranial
Dysplasia.
• Supernumeraries (mesiodens,
lateral incisors, premolars, &
3rd molars ).
Fusion:is teeth with separate pulp chambers
joined at dentin .
Gemination:is teeth with common pulp chamber.
They are almost similar ,so you should
count no of teeth.
3. Interference with eruption
•
•
•
•
Eruption of permanent teeth can be
impaired due to :Supernumerary.
Sclerotic bone.
Heavy fibrous gingiva.
All the previous can be seen in
cleidocranial dysplasia .Tx is removal
of the cause.
Drifting of teeth. Ex. ankylosed
deciduous molar
4. Ectopic eruption
It occurs as a result of a
permanent tooth bud malposition.
Ex:1. Mesial drifting of maxillary first
molar.
2. Mandibular 2nd premolar erupt
distally.
3. Impacted Maxillary canines
5. Early loss of primary
teeth
Early loss of teeth will lead to dental
arch collapse, but it’s not the only
cause for crowding & Malalignment.
Collapse will be due to :
1. Mesial drifting of posterior teeth.
2. Distal drifting of incisors a/f canine &
1st decidious molar loss.
Distal drifting caused by 2
sources :• Active contraction of transseptal
fibres in the gingiva.
• Pressure from lips and cheeks.
If loss of teeth is present only on one
side a symmetry & crowding will be
present .
6. Traumatic displacement of
teeth
Dental trauma can lead to
development of malocclusion in 3
ways:
1. Damage to permanent tooth buds
from injury to primary teeth.
2. Drift of permanent teeth a/f
premature loss of primary teeth.
3. Direct injury to permanent teeth.
Trauma to primary tooth lead
to 2 results: Trauma to the permanent tooth crown
& disturbances in enamel formation
&defect on tooth .
The crown may be displaced relative to
the root causing less root formation &
short root or dilacerations .
What is dilaceration
?
• Dilaceration is formation of root at an
angle to the traumatically displaced
crown.
• It will be due to trauma especially in
incisors, or to ankylosed primary tooth
resulting in mechanical interference with
eruption.
• Sever trauma can lead to dilaceration &
projection of root outside the bone. Tx is
extraction of severely dilacerated tooth.
What
is the treatment
of displaced tooth
?
•
Displaced tooth bud in children should be
repositioned as early as possible to minimize
root distortion.
• If a permanent tooth is displaced by trauma
labially or lingually ,the root may be damaged ,
accompany alveolar process fracture.
• Tx is replacement of traumatized tooth
immediately a/f the accident to its original place.
• After healing (2-3 weeks ) it is difficult to
reposition the tooth and ankylosis may develop.
2.Genetic Influences :
It is apparent that certain types
of malocclusion runs in families
Inheritance can affect malocclusion
in 2 ways:
1. Inherited disproportion b/w size of
teeth & jaws lead to either crowding
or spacing .
2. Inherited disproportion b/w size or
shape of the upper & lower jaws
cause improper occlusal
relationships
Why primitive population has
less malocclusion than modern
groups ?
1. They are characterized by genetic
isolation & uniformity.
2.
Absence of processed food & better
masticatory function .
3.
No out breeding b/w the originally
distinct human population .
What is the main cause of
malocclusion ?
• It is the great increase in out breeding b/w
human populations. Eg Chinese ,Japanese,
Europeans ,Polynesian, and Hawaiian.
• Many studies were conducted on humans as
well as animals to confirm that inheritance
plays major role in malocclusion.
• On animals such as mixing b/w different types
of dogs resulting on achondroplasia Which is
very rare in humans.
What are the characteristic
features of achondroplasia ?
• Short limbs.
• deficient cranial base length (due to
deficient growth of synchodrosis).
• mid face deficiency (due to lack of
maxillary growth) .
Many classical studies were conducted on
humans such as :
1.Monozygotic (identical ) twins & dizygotic (fraternal)
twins. It was concluded that 40 % of dental & facial
variation that lead to malocclusion are hereditary factors.
2.Studies on family members.
They show that skeletal (craniofacial) characteristic is
hereditary, while dental (occlusal) characteristic are
environmental.
The influence of inherited tendencies is particularly strong for
mandibular prognathism ,then long face pattern of facial
deformity.
3. Environmental Influences :
Function of teeth and jaws must adapt to
the environment. Ex :
1. Chewing and swallowing pressures can
affect jaw growth & eruption.
2. Changes in body form although it has
minimal effect ,but individual who does
heavy physical work has both stronger
muscles & a sturdier skeletal system than
the one who is sedentary.
Equilibrium Theory and
Development of the Dental
Occlusion
Although teeth are subjected to a
variety of forces such as
masticatory forces, swallowing &
speaking, they do not move to a
new location. But when they tend
to move they move to a static
equilibrium.
Equilibrium effects on the
dentition
To understand equilibrium you
should observe the effect of
various pressure types.
Forces are not coming from
mastication only but also from
lips ,cheeks ,& tongue at rest &
at function.
Mechanism of bone
response to occlusal
forces :
• The duration of force is more important
than its magnitude .
• When chewing forces are applied to
the teeth ,the fluids in the periodontal
ligament acts as a shock absorber to
stabilize the tooth in its socket while the
alveolar bone bends ,so the tooth will be
displaced for a short distance along the
bone.
• If heavy pressure is maintained for more
than a few seconds sever pain will result
,so the biting force is released quickly.
• This type of heavy intermittent pressure
has no impact on tooth position as long as
periodontal ligament is intact.
• On the other hand, heavy occlusal
contacts may cause pain & mobility of the
teeth.
Contributors for equilibrium
theory :
1. The chewing forces.
2. The pressure from lips, cheeks &
tongue are very light but with greatest
duration/cause movement of them.
Ex:
• Scaring of lips or soft tissue / lingual
tooth position.
• Large tongue / labial displacement of
teeth.
3. The external forces such as habits &
orthodontic appliances.
1. Bilateral expansion to align teeth.
2. Thumb sucking .
3. Playing of musical instrument.
4. The periodontal fiber system.
1. Space closure a/f teeth loss due to forces
exerted from transseptal fibres in the
gingiva.
2. Eruption of teeth due to eruption forces from
gingiva.
It is very important to consider the effect of
forces against teeth in 3 planes of space:
• Anteroposteriorly.
• Transversely.
• Vertically.
Equilibrium Effects on Jaw size
& shape
The functional processes of bone will be
altered if the function is lost or changed
such as :.
1. Tooth presence or absence (extraction or
impaction).
2. Muscle attachments & growth change the
shape of the jaw (particularly coronoid
process & angle of the mandible).
3.
Condylar process of the mandible articulate
the mandible with the rest of the facial
skeleton .Any alteration in the position of the
mandible may alter mandibular growth.
• Many studies suggest that size of
tongue & forces from the lips &cheeks
may affect shape of the jaw.
• However, from the perspective
equilibrium theory , it’s concluded that
the intermittent pressures or forces
have little if any effect on either the
position of teeth or size and shape of
the jaws.
Functional Influences on
Dentofacial Development
1.
•
•
2.
3.
4.
Masticatory Function.
Function & Dental Arch Size.
Biting Force & Eruption.
Sucking &Other Habits.
Tongue Thrusting.
Respiratory Pattern.
1. Masticatory Function
The pressure generated by chewing
activity potentially could affect
dentofacial development in 2 ways:
a. Prolonged biting force & greater use
of jaws can increase jaw dimensions
& dental arches .
b. Decreased biting force could affect
eruption of teeth thereby affecting
lower facial height ,over bite/deep
bite relationships .
Function & Dental arch
size
•
The size & shape of the muscular
processes of the jaws should reflect
muscle size & activity.
ex:Enlargement of mandibular gonial
angles in humans can be seen with
hypertrophy of the mandibular
elevator muscles.
• Coronoid process form changes in children
will be seen when temporalis muscle
altered its function a/f injury.
• Dietary consistency affects dental arch size
and the amount of space for the teeth early
in life as an individual develops ,ex
Eskimos.
• We can conclude that muscular processes of
the jaws are affected by muscle function in
human.
The key for alignment and crowding of
incisors is the inter canine distance
which increases after primary canines
eruption
decreases
eruption.
at
age
after
of
two
years
permanent
and
canines
Biting force and eruption
The biting force is not a major
determinant of either dental arch
size or vertical dimensions ,if
syndromes is not present .
2. Sucking & other habits
If the child continue the habit beyond the
eruption time of the permanent teeth ,it
may lead to malocclusion (such as flared &
spaced maxillary incisors, lingually
positioned lower incisors, anterior open
bite, and constricted maxilla .
The magnitude of pressure and
prolonged duration can cause
significant malocclusions :.
1. Anterior open bite is resulting from
excessive eruption of posterior teeth
and impeding of anterior teeth.1 mm
elongation posteriorly can opens the
bite 2 mm anteriorly .
2. Maxillary constriction during
sucking the tongue will be lowered
and buccinator muscle will contract
so a negative great pressure will be
produced b/w the tongue & cheeks
that lead to constriction of the
maxillary arch.
Tx: Stop the habit and expand the
arch.
3.Tongue Thrusting:• Placement of the tongue tip forward b/w
the incisors during swallowing.
• Individual swallows about 800 times per
day , which lasts for few minutes ,and its
not enough to produce a tremendous
effect either for teeth or equilibrium.
• But if the patient has a continuous
forward resting posture of the tongue
this could affect tooth position vertically
or horizontally.
4.Respiratory Pattern:Respiratory needs are the primary determinants
of the posture of the jaws and tongue.
Therefore ,mouth breathing changes posture of
head, jaws ,and tongue.
If this posture is maintained it leads to increase
lower facial height, super eruption of posterior
teeth , narrow maxillary dental arch ,increased
over jet and anterior open bite .
• It is called the adenoid face .
Nasal obstruction can be due
to many causes:1.
2.
3.
4.
Chronic respiratory obstruction.
Large adenoids and tonsils.
Common cold .
Total nasal obstruction (rare in humans).
When this obstruction is removed ,the
original posture immediately returns ,but
if persists it causes 3mm increase in
facial height , over jet /over bite, &
constricted maxilla.
Researches on respiration
established 2 opposing
principles :
1. Total nasal obstruction alter the
pattern of growth & lead to
malocclusion in humans (esp long –
face population)& animals .
2. The majority of long-face individuals
have no nasal obstruction & may
have some other etiologic factors.
Etiology in Contemporary
Perspective
Changing Views of Etiologic
Possibilities :
• Edward Angle & his contemporaries
influenced the finding that
malocclusion is a disease of
civilization .
• While, Mendelian developed a different
view which was that malocclusion is
primarily the result of inherited
dentofacial proportions which may be
altered by developmental variations,
trauma ,or altered function.
Etiology of Crowding and
Malalignment :
Causes of skeletal
problems:
1.
2.
3.
4.
5.
Disproportion b/w jaw &
tooth size.
Increased out breeding
b/w population.
Environmental factors.
Mouth breathing alter
the tongue-lip/cheek
equilibrium.
Hereditary factors.
Therefore the conclusion
is that Cl I problems
,especially non skeletal
cross bite ,often are
caused by alterations in
function, On the other hand
major problems usually
have an additional genetic
or developmental
component.
Etiology of Skeletal
Problems:Skeletal orthodontic
problems resulting
from malposition or
malformation of the
jaws rather than
irregularity of the
teeth
can arise from
number of causes : .
Causes of skeletal
problems:
1. Inherited patterns.
2. Defects in
embryologic
development &
genetic syndromes
(rare).
3. Trauma (common
cause).
4. Functional
influences.
Egs :1. Cl II malocclusion 15-20 % of U.S &
European population have tendency toward
(retrognathic mandible) due to heredity.
The more sever the case is probably due
to hereditary & environmental effects.
2. Mandibular prognathism or Cl III
malocclusion . There is a definite familial &
racial tendency.
It is caused by:
1. Excessive mandibular growth due to constant distraction of
the condyle from the fossa .
2. Large tongue
3. Respiratory needs .
4. Pharyngeal dimensions.
5. Hereditary factors (major cause).
6. Functional mandibular shifts (affect teeth more than jaws).
3. Open bite can be due to :
•
•
•
•
Sucking habit .
Tongue posture accompany nasal
obstruction.
Excessive eruption of posterior teeth.
Hereditary factors.
Findings shows that anterior open
bite is more common in blacks than
whites ,whereas deep bite is more
common in whites.
Conclusion
• Whatever the malocclusion is it
will be always stable a/f growth has
been completed.
• Malocclusion ,after all is a
developmental problem.
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