A malocclusion is an incorrect relationship between the upper and lower jaws or misaligned teeth. It can result from genetic factors, environmental influences, and disturbances during craniofacial development. Several craniofacial anomalies like cleft lip/palate are related to errors in neural crest cell migration. Conditions like fetal alcohol syndrome are caused very early in development by ethanol exposure. Childhood injuries and muscle dysfunction can also influence jaw growth and cause malocclusions.

2.  A malocclusion is an incorrect relationship
between the maxilla (upper arch) and the
mandible (lower arch), or a general
misalignment of the teeth.

3.  Malocclusion is said to result due to the
following factors occurring alone or in
combination:
1. Specific causes of malocclusion
2. Genetic influences
3. Environmental influences

4.  Disturbances in embryologic development
 Growth disturbances in fetal period
 Progressive deformities in childhood
 Disturbances arising in adolescence
 Disturbances of dental development

5. Defect in embryologic development usually .
result in death of the embryo
Although most defects are of genetic origin, effects
from environment are also important
Chemicals and other agents capable of producing
embryologic defects are called teratogens.

7. Stages of Embryonic Craniofacial Development
Stage
Time in humans
(post-fertilization) Related syndromes
Germ layer formation and
Initial organization of structures
Day 17 Fetal alcohol syndrome (FAS)
Neural tube formation Day 18-23 Anencephaly
Origin, migration and interaction of
cell populations
Day 19-28 Craniofacial microsomia
Mandibulofacial dysostosis
Limb abnormalities
Formation of organ systems
Primary palate
Secondary palate
Day 28-38
Day 42-45
Cleft lip and/or palate, other facial
clefts
Cleft palate
Final differentiation of tissues Day 50-birth Achondroplasia
Synsostosis syndromes (e.g. crouzon’s)

8.  FAS can be traced to the very early first and second
stages of craniofacial development.
 Occurs due to deficiencies of midline tissue of the
neural plate very early in embryonic development
caused by exposure to very high levels of ethanol.
 Although extreme intoxication is required, the
resulting facial deformity and developmental delay
occur frequently enough to be implicated in many
cases of mid-face deficiency.

10.  Most craniofacial anomalies
are related to neural crest cell
origin and migration.
 Since most structures of the
face are derived from
migrating neural crest cells,
interferences with their
migration produce facial
deformities

11.  Altered development of
cells derived from neural
crest cells has also been
implicated inTreachers-
Collins syndrome
 It is characterized by
generalized lack of
mesenchymal tissue

12.  Formerly called hemifacial
microsomia is
characterized by a lack of
development in lateral
facial areas.
 Typically there is
deformation of external
ear and ramus of the
mandible alongwith
associated soft tissues.

13.  Most common congenital defect involving
the face and jaws
 Exactly where these clefts appear is
determined by the locations at which fusion
of various facial processes fail to occur

15.  Occurs during the final stage of facial
development
 Arises due to prenatal fusion of the superior
and posterior sutures of maxilla along the
wall of the orbit.
 Characterized by severe underdevelopment
of midface and eyes that seem to bulge from
their sockets.

17.  Pressure against the developing face prenatally can
lead to distortion of rapidly growing areas.
 For instance, an arm may be pressed across the face
in utero, resulting in severe maxillary deficiency at
birth.
 Occasionally, a fetus’ head is flexed tightly against
the chest in utero, preventing the mandible from
growing forward normally.
 Result is an extremely small mandible at birth.

18.  Extreme mandibular
deficiency at birth
 Reduced volume of the
oral cavity can lead to
respiratory difficulty at
birth
 One-third of the patients
have a cartilage forming
defect alongwith pierre
robin syndrome, this is
known as Stickler
syndrome.

19.  Use of forceps to assist in delivery might
damage either or both of temporomandibular
joints.
 Heavy pressure in the area ofTMJ can cause
internal hemorrhage, loss of tissue and a
subsequent underdevelopment of the
mandible.

20.  Childhood fractures of the jaw
 Muscle dysfunction

21.  Condylar neck is
particularly vulnerable and
fracture of this area is
relatively common
 Condylar process tends to
regenerate well after early
fractures.
 Problem arises when the
more severely affected side
lags behind in growth or
scarring aroundTM joint
restricts translation of
condyle.

22. Facial muscles can affect jaw growth in two
ways:
1.Formation of bone at points of muscle
attachment depends upon muscle activity
2.musculature is an important part of the total soft
tissue matrix whose growth normally carries the
jaw downward and forward

23.  Loss of part of musculature is
most likely to result from
damage to motor nerve
 Result is underdevelopment
of that part of face with a
deficiency of both soft and
hard tissues
 Excessive muscle contraction
can also restrict growth
 Conversely, a major decrease
in tonic muscle activity allows
the mandible to drop
downward

24. Occasionally, unilateral excessive growth of the
mandible occurs in metabolically normal
individuals. Proliferation of condylar cartilage is a
prominent feature.
Release of excessive amounts of growth hormone
from an anterior pituitary gland tumor resulting in
excessive growth of mandible.

26.  Congenitally missing teeth
 Malformed and supernumerary teeth
 Traumatic displacement of teeth

27.  Results from disturbances during the initial stages of
formation of a tooth, that is, initiation and
proliferation.
Total absence of teeth
absence of many but not all teeth
absence of only a few teeth

29.  Abnormalities in tooth size and shape result
from disturbances during the
morphodifferentiation stage of development.
 Most commonly malformed tooth is maxillary
lateral incisor

31.  Supernumerary teeth also result from disturbances
during the initiation and proliferation stages of
dental development
 Most common supernumerary tooth appears in the
maxillary midline and termed as mesiodens.
 Presence of an extra tooth disrupts normal occlusal
development
 Multiple supernumerary teeth are associated with
Cleidocranial dysplasia, a congenital syndrome.

33.  Trauma to teeth during their formative phase occurs
very commonly in children.
 Trauma to primary tooth displaces the underlying
permanent tooth bud.
 If trauma occurs during the stage of crown
formation, a permanent tooth with defective crown is
formed.
 If trauma occurs after the completion of crown, the
crown is displaced relative to the root.