The document discusses the etiology of malocclusion, including general causes like evolution, congenital malformations, endocrine disturbances, and nutritional deficiencies. It also covers local causes such as congenitally missing or supernumerary teeth, teeth of abnormal size/form, abnormal eruption path, abnormal labial frenum, and abnormal pressure habits including thumb sucking, tongue thrusting, nail biting, abnormal swallowing, and mouth breathing.

1. Eighth Lecture
Etiology of
Malocclusion

2. General Causes
1.Evolution:
2. Congenital
malformation:
3. Endocrinal
disturbances:
4. Nutritional
deficiency
5. Pathological
Conditions:
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Local Causes
1. Congenital missing
teeth:
2 Supernumerary teeth:
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3. Continue
B. Local Causes
3.Teeth of abnormal size and form:
Size of teeth is largely determined by hereditary.
This includes:
a. Peg-lateral is the most frequent departure
from normal.
b. Gemination
c. Fusion
Fusion
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4. B. Local Causes
3 Teeth of abnormal size and form:
d. Macro- or microdontism
e. Odontomes, Dens-in-dent,
Hutchinson’s teeth & Mulberry
molars.
Jacket crowning, bridges or space
closing may be necessary.
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L
S
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5. B. Local Causes
4. Abnormal path of
eruption:
This is usually a secondary
manifestation of the following:
a. Severe crowding & totally
inadequate space to accommodate
all teeth, so deflection of the
erupting tooth occurs.
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6. B. Local Causes
4. Abnormal path of eruption:
b. Supernumerary tooth.
c. Retained decid. teeth.
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Supplemental
Teeth
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7. B. Local Causes
4 Abnormal path of eruption:
d. Trauma to decid. Teeth may turn the
developing successor in an abnormal direction.
e. Mechanical interference by early
orthodontic treatment.
f. Eruption cyst.
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8. B. Local Causes
4 Abnormal path of eruption
g. Ectopic eruption: a permanent tooth during
its eruption may cause resorption of
neighboring tooth. The most common is
maxillary first molar may cause abnormal
resorption of maxillary second decid. Molar,
when erupts under the distal convexity of this
tooth (Es).
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9. B. Local Causes
5. Abnormal labial frenum:
Before eruption of teeth, the upper median
labial frenum is continuous with incisive
papilla. As growth proceeds and teeth erupt,
attachment of the frenum recedes to a midway
between the alveolar border and reflection of
lip mucosa (mucolabial fold).
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10. B. Local Causes
5. Abnormal labial frenum:
In the abnormal condition the frenum is
wide and thick and passes between permanent
central incisors into the incisive papilla,
producing a wide space between central
incisors called Median Diastema. Palatal
mucosa blanches on raising upper lip.
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11. B. Local Causes
5. Abnormal labial frenum:
Treatment consists of bringing the central
incisors together orthodontically first, then
excising the frenum (Frenectomy), scar tissue
formed will serve to help in retention.
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12. 6. Abnormal pressure habits:
B. Local Causes
a. Thumb sucking:
It is repeated forceful sucking of the thumb with
associated strong buccal and lip contractions. Clinical
aspect of this problem divided into 3 phases:
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13. B. Local Causes
6. Abnormal pressure habits:
a. Thumb sucking:
Phase I: Normal & subclinically
significant thumb sucking: This
extends from 3 months to 2 years, as
most infants display a certain amount
of thumb sucking during this period.
Particularly at time of weaning.
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14. B. Local Causes
6. Abnormal pressure habits:
a. Thumb sucking:
Phase II: Clinically significant thumbsucking: This extends roughly from 2-4
years, sucking practiced during this time
will result in temporary damage. If the
child drops the habit by end of this period,
he may have no more than reduced overbite
& increased overjet with some spacing in
the maxillary arch, and there may be also
slight crowding of lower anterior teeth.
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Dr. Ahmed Basyouni
Phase II
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15. B. Local Causes
6. Abnormal pressure habits:
a. Thumb sucking:
Phase III: Active thumb-sucking:
Child continuation of this habit
after 4 years will develop
malocclusion. Type of
malocclusion is dependent upon
the position of the thumb,
associated musc. Contraction of the
cheeks and position of the
mandible during sucking.
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16. B. Local Causes
6. Abnormal pressure habits:
a. Thumb sucking:
Effects:
1. Protraction of maxillary anterior
teeth & mandibular retraction.
2. Anterior open bite.
3. Contraction of the maxillary arch
and high vault.
4. Hypotonic upper lip and lower lip is
usually caught beneath maxillary
incisors, forcing them further forward.
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17. b.Tongue thrusting:
B. Local Causes
6. Abnormal pressure habits:
It is usually of two types:
1. Simple: in which tongue thrust is associated with a
normal or teeth together swallow. This usually
accompanies thumb sucking habit, as it is necessary
for the tongue to thrust forward through the open bite
to maintain anterior seal with lips during swallowing.
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18. B. Local Causes
6. Abnormal pressure habits:
b.Tongue thrusting:
2. Complex: is originating from tonsillitis, or
pharyngitis. When tonsils are swollen & sore,
the root of the tongue encroaches on the
enlarged pillars. This causes pain and reflexly
the mandible is dropped down, teeth become
separated and tongue is thrust between them
during last stage of swallowing.
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19. B. Local Causes
6. Abnormal pressure habits:
b.Tongue thrusting:
Anterior tongue thrust is an etiologic factor
of anterior open bite as tongue will prevent
normal vertical development of the dentoalveolar structures anteriorly.
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20. Habit breaking appliance
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21. B. Local Causes
6. Abnormal pressure habits:
c. Nail biting:
Nail biting is mentioned as a cause of tooth
malposition. It is absent under 3 years, there is
a rapid increase at 6 years of age. The
incidence of nail biting drops sharply after 18
years. Clinical examination may reveal
crowding, rotation and attrition of the incisal
edges of the incisor teeth. Most commonly is
seen in excitable children.
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22. B. Local Causes
6. Abnormal pressure habits:
d. Abnormal swallowing:
Teeth are often separated, tongue thrusts
forward into the excessive overjet and dorsum
of the tongue drops away from the palatal
vault. Enlarged tonsils may accentuate tongue
thrust habit .
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23. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Mouth breathers seem to have high incidence of
malocclusions.
Mouth breathing is prevented by 3 sphincter
mechanism:
1. Anterior sphincter: formed by the lips.
2. Intermediate sphincter: formed by tongue and hard
palate.
3. Posterior sphincter: formed between the soft palate
& the dorsum of the tongue.
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24. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Causes:
1. Partial nasal obstruction: due to
a. deviated septum
b. narrow nasal passages.
c. Inflammatory reaction of nasal
mucous membrane.
d. Allergic reaction of nasal
mucosa.
e. Obstructive adenoids in
postnasal space.
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25. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Continu. Causes of mouth breathing:
2. Habit: formed during presence of
one or more of the obstructive
causes, and persisted after removal
of the cause (habitual mouth
breathing).
3. An increased free way space: in
rare cases tongue falls away from
the palate and therefore lips do not
form an anterior seal. This type
found in complete absence of any
upper respiratory obstruction (True
mouth breathing).
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26. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Continu. Causes of mouth breathing:
4. Air hunger e.g. in children with heart
disease and as a normal behaviour during
exercise.
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27. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Effects:
Typical mouth breathing
syndrome characterized by:
1. Contracted maxillary arch.
2. Protrusion of upper incisors.
3. Crowding of anterior teeth in
both arches.
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28. B. Local Causes
6. Abnormal pressure habits:
e. Mouth breathing:
Effects:
lip.
4. Hypertrophy of the lower
5. Hypotonic and short upper lip
& frequently increased over bite.
6. The molar relationship may be
normal or distocclusion.
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29. Summary
General Causes
1.Evolution:
2. Congenital malformation:
3. Endocrinal disturbances:
4. Nutritional deficiency
5. Pathological Conditions:
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30. Continue
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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