The document discusses the etiology and causes of malocclusion. It identifies general causes such as evolution, congenital malformations, endocrinal disturbances, and nutritional deficiencies. Local causes include factors like congenitally missing or supernumerary teeth, teeth of abnormal size/form, abnormal eruption path, thumb sucking, premature loss of deciduous teeth, prolonged retention of deciduous teeth, delayed eruption of permanent teeth, loss of permanent teeth, trauma, and local pathological factors like cysts and tumors. The document is a lecture on malocclusion causes presented by Dr. Ahmed Basyouni on March 5, 2012.

1. Ninth Lecture
Etiology of
Malocclusion

2. General Causes
1.Evolution:
2. Congenital malformation:
3. Endocrinal disturbances:
4. Nutritional deficiency
5. Pathological Conditions:
March 5, 2012
Dr. Ahmed Basyouni
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3. Continue
B. Local Causes
Local Causes
1. Congenital missing teeth:
2. Supernumerary teeth:
3. Teeth of abnormal size and form:
4. Abnormal path of eruption:
5. Abnormal labial frenum:
6. Abnormal pressure habits:
a. Thumb sucking:
b.Tongue thrusting:
c. Nail biting:
d. Abnormal swallowing:
e. Mouth breathing:
March 5, 2012
Dr. Ahmed Basyouni
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4. Continue
B. Local Causes
 Premature loss
of decid. Teeth:
In general, effects of
premature loss of teeth
depend on dentoalveolar disproportion
& also on muscle
environment.
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Dr. Ahmed Basyouni
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5. B. Local Causes
7. Premature loss of decid. Teeth:
a. Premature loss of decid. Incisors:
In the maxilla, it is not followed by impaction
of the permanent incisors, but will develop
tongue thrust to provide anterior seal during
swallowing.
While in the mandible, it will result in lack of
forward stimulation & crowding of permanent
incisors and deep overbite.
March 5, 2012
Dr. Ahmed Basyouni
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6. B. Local Causes
7. Premature loss of decid. Teeth:
b. Premature loss of decid. canines:
It is frequently followed by interference with
eruption of permanent canine bec. of its later
eruption and longer period allowed for shifting
of adjacent teeth.
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Dr. Ahmed Basyouni
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7. B. Local Causes
7. Premature loss of decid. Teeth:
c. Premature loss of decid. First molar:
Loss, of upp. Ds, rarely followed by impaction
of first premolar, bec. Of relatively their early
eruption and premolars are smaller than their
predecessors.
Loss, of low. Ds, causes collapse of the lower
labial segment.
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Dr. Ahmed Basyouni
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8. B. Local Causes
7. Premature loss of decid. Teeth:
d. Premature loss of decid. Second molar:
Loss of decid. Second molars is the most
serious as there is a forward shift of first
permanent molars & collapse of lower labial
segment.
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Dr. Ahmed Basyouni
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9. B. Local Causes
7. Premature loss of decid. Teeth:
d. Premature loss of decid. Second molar:
Main effects will be:
1. Forward shift and mesial tilting of the lower first
permanent molar & forward shift and mesial rotation
of upp. First permanent molar, resulting in impaction
of second premolars in both arches.
If they are extracted before eruption of first
permanent molars, first permanent molars erupt well
forward with less rotation & tilting.
2. Flattening of lower anterior segment (collapse),
and if unilateral loss, central line may shift toward
affected side. There will be increase in overbite.
There may be crowding of upp. Incisors due to loss of
splinting effect by the lower arch.
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Dr. Ahmed Basyouni
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10. B. Local Causes
7. Premature loss of decid. Teeth:
e. Premature loss of both upper and lower decid.
molars:
It is a predisposing factor in the production of
prenormal occlusion. As the child will try to
bring lower arch forward to be in contact with
upper, so he will protrude the mandible.
This is called false Class III or pseudomesiocclusion.
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Dr. Ahmed Basyouni
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11. B. Local Causes
7 Premature loss of decid. Teeth:
e. Premature loss of both upper and lower decid. molars:
It is distinguished from prenormal occlusion by:
a. Manual retrusion of the mandible.
b. When teeth are occluded, condyles are out of
glenoid fossae.
c. There may be labial inclination of lower
incisors due to pulling action of the muscles to
retrude mandible to its original position.
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Dr. Ahmed Basyouni
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12. B. Local Causes
8. Prolonged retention of decid. Teeth:
Causes:
a. Incomplete root resorption.
b. Ankylosis of decid. Teeth.
c. Absence of permanent teeth.
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Dr. Ahmed Basyouni
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13. B. Local Causes
8. Prolonged retention of decid. Teeth:
Causes:
d. Abnormal path of eruption of permanent teeth.
e. Endocrine disturbances e.g. Hypothyroidism.
f. Cleidocranial dysostosis.
g. Nutritional disturbances.
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Dr. Ahmed Basyouni
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14. B. Local Causes
8. Prolonged retention of decid. Teeth:
In the incisor region, delayed root resorption may
cause lingual eruption of lower incisors, while upp.
Incisors may be displaced either lingually or labially.
Retained decid. Should be extracted after the
presence of permanent successors are confirmed. In
absence of permanent successors, decid. Tooth may
serve some years.
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Dr. Ahmed Basyouni
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15. B. Local Causes
8. Prolonged retention of decid. Teeth:
Ankylosis results in retention of decid. Tooth,
while neighboring teeth will continue to erupt
leaving this tooth behind, this retained tooth
called “submerged” and is seen usually in
decid. Molars. They are causing malocclusion
and stagnation of food, so such tooth should be
removed, or crowned in case of absence of
permanent successor.
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Dr. Ahmed Basyouni
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16. 9. Delayed eruption
of permanent teeth:
B. Local Causes
Causes:
a. Presence of
supernumerary or
Odontomes.
b. Eruption cyst.
c. Retained decid. Teeth.
d. Malformation of the tooth
e.g. dilaceration.
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Dr. Ahmed Basyouni
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17. B. Local Causes
9 Delayed eruption of permanent teeth:
Causes:
e. Ectopic position of the tooth.
f. Infection of tooth germ.
g. Systemic diseases such as dietary,
metabolic, or endocrine disturbances.
Removal of cause before closure of root
apex would be followed by eruption. If not,
tooth has to be exposed surgically & brought
down by appliance.
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Dr. Ahmed Basyouni
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18. B. Local Causes
10. Loss of permanent teeth:
a. Incisor teeth:
Loss of upp. Central & lateral incisors will
result in collapse of anterior part of the
dental arch (space being closed by adjacent
teeth).
Loss of a lower incisor is followed by a
similar collapse and loss of intercanine
width.
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Dr. Ahmed Basyouni
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19. B. Local Causes
10. Loss of permanent teeth:
b. Canine teeth:
Loss of an upp. Canine tooth may affect
appearance of the face (Lack of canine
eminence) and if unilateral will produce an
asymmetry.
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Dr. Ahmed Basyouni
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20. B. Local Causes
10. Loss of permanent teeth:
c. Premolar teeth:
First premolars are the teeth most frequently extracted
to relieve incisor crowding and in the treatment of
Angle’s Class II & III malocclusions.
Second premolars are not so often chosen bec.
Resulting contact between first premolars and first
permanent molars is not usually so good as that
between canines and second premolars.
Unilateral loss of a premolar may cause a shift of the
midline.
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Dr. Ahmed Basyouni
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21. B. Local Causes
10. Loss of permanent teeth:
d. First molars:
The most commonly lost teeth by caries are the
first permanent molars.
i. Effects of early loss of upper first molars:
1.The space is filled most by forward
movement of second molar and also to a less
extent by distal movement of second premolar
and teeth in front of it. This tends to reduce the
incisor overbite.
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Dr. Ahmed Basyouni
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22. B. Local Causes
10. Loss of permanent teeth:
d. First molars:
2. If unilateral there may be a shift of the
midline to the affected side.
3. Upper second molar tends to rotate forward
rather than tilt. It rotates around palatal root.
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Dr. Ahmed Basyouni
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23. B. Local Causes
10. Loss of permanent teeth:
d. First molars:
ii. Effects of early loss of lower first molars:
1. The space is filled by mesial tilting of second
molar and distal moving second premolar. There is a
lack of forward development of anterior teeth which
may cause collapse and result in a class II incisor
relationship (increased overjet & overbite).
2. If unilateral the lower midline will shift to the
affected side.
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Dr. Ahmed Basyouni
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24. B. Local Causes
10. Loss of permanent teeth:
d. First molars:
3. lower second molar tends to tilt rather than
rotate forwards.
4. If lost before eruption of lower second
premolar, this tooth drift backwards or fail to
develop forwards leaving large space between
it and the lower first premolar.
5. Opposing maxill. First permanent molars
may overerupt.
The earlier the loss of the first molars, the less
the tilt or rotation of the second molars, when
they erupt forward.
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Dr. Ahmed Basyouni
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25. B. Local Causes
10. Loss of permanent teeth:
e. Second molars:
These teeth are sometimes extracted in the
treatment of certain malocclusions. The third
molars must be present on radiographs and of
good size and position.
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Dr. Ahmed Basyouni
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26. B. Local Causes
10. Loss of permanent teeth:
f. Third molars:
Third molars will be extracted by the
oral surgeon if they become
impacted.
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Dr. Ahmed Basyouni
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27. B. Local Causes
11. Trauma:
Children are prone to accidents and upp. &
low. Incisors are most likely affected from
blows on the mouth.
Generally, direct trauma to jaws and
associated parts may cause:
1. Loss of decid. Teeth & effects will be
similar to those arising from premature loss.
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Dr. Ahmed Basyouni
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28. B. Local Causes
11. Trauma:
2. Permanent incisors may be:
a. Dilacerated.
b. Displaced in the alveolus which may be
fractured.
c. Fractured.
d. Completely lost.
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Dr. Ahmed Basyouni
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29. B. Local Causes
11. Trauma:
3. Trauma to TMJ may result in damage &
limitation of its movement.
4. Malunion that may follow fractured jaws
result in severe degree of malocclusion.
Trauma
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Dr. Ahmed Basyouni
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30. B. Local Causes
12. Local pathological factors:
Cysts, Odontoms, Tumors
These include:
a. Cysts or tumors in jaws may displace
neighboring teeth creating malocclusion.
b. Scar tissues resulting from burns of lips &
cheeks may contract & upset balance of
musculature.
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Dr. Ahmed Basyouni
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31. B. Local Causes
12. Local pathological factors:
c. Inflammatory conditions causing ankylosis
of TMJ may cause damage of condylar
cartilage (main growth center), mandible
become deficient in affected side, ascending
ramus become short & resulting malocclusion
is severe.
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Dr. Ahmed Basyouni
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32. Summary
General Causes
1.Evolution:
2. Congenital malformation:
3. Endocrinal disturbances:
4. Nutritional deficiency
5. Pathological Conditions:
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Dr. Ahmed Basyouni
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33. B. Local Causes
Summary
Local Causes
1. Congenital missing teeth:
2. Supernumerary teeth:
3. Teeth of abnormal size and form:
4. Abnormal path of eruption:
5. Abnormal labial frenum:
6. Abnormal pressure habits:
a. Thumb sucking:
b. Tongue thrusting:
c. Nail biting:
d. Abnormal swallowing:
e. Mouth breathing:
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Dr. Ahmed Basyouni
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34. B. Local Causes
Summary
7. Premature loss of decid. Teeth:
8. Prolonged retention of decid. Teeth:
9. Delayed eruption of permanent teeth:
10. Loss of permanent teeth:
11. Trauma:
12. Local pathological factors:
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Dr. Ahmed Basyouni
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35. March 5, 2012
Dr. Ahmed Basyouni
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