Etiology of malocclusion

1. Etiology of
malocclusion
Shaimaa Saad Zaki,
Teaching Assistant, Orthodontic Department, Faculty of
Dentistry, Mansoura University.

2. introduction
Classifications of
etiology of
malocclusion
Graber
classification :
• General factors
• Local factors

3. • This question has to be
answered correctly before
any decision can be taken
regarding its prevention or
correction.
• The etiology of most
orthodontic problems are
difficult because several
interacting factors
probably played a role.
WHAT CAUSES A
MALOCCLUSION?

4. Researches have grouped the common etiologic factors associated with
malocclusions and presented various classifications.
The various
classifications
proposed are
• Graber's
classification
• White and
Gardiner's
classification
• Moyer's
classification
• Salzmann's
classification

5. *This was one of the first attempts to classify
malocclusion.

6. DENTAL BASE
ABNORMALITIES
•1. Antero-posterior mal-relationship
2. Vertical mal relationship
3. Lateral mal-relationship
4. Disproportion of size between teeth and basal bone
5. Congenital abnormalities.
PRE·ERUPTION
ABNORMALITIES
•1. Abnormalities in position of developing tooth germ
2. Missing teeth
3. Supernumerary teeth and teeth abnormal in form
4. Prolonged retention of deciduous teeth
5. Large labial frenum
6. Traumatic injury.
POST·ERUPTION
ABNORMALITIES
•1. Muscular
a. Active muscle force
b. Rest position of musculature
c. Sucking habits
d. Abnormalities in path of closure
2. Premature loss of deciduous teeth
3. Extraction of permanent teeth.

7. The division of the etiologic factors into prenatal
,postnatal , functional and environmental or acquired.

8. *PRENATAL
1. Genetic-included malocclusions where the dentofacial
anomaIies may or may not be in evidence at birth.
2. Differentiative-malocclusions that are inborn, engrafted in
the body in the prefunctional embryonic developmental stage.
Can be subdivided into:
a. General-defect the body as a whole
b. Local-effect the face, jaws and teeth only.
3. Congenital-can be hereditary or acquired but
existing at birth. Can be subdivided as:
a. General or constitutional
b. Local or dentofacial.

9. * Postnatal
Developmental
A. General
a. Birth injuries
b. Abnormalities of relative rate of growth in
different body organs
c. Hypo- or hypertonicity of muscles which may
eventually affect the dentofacial development
and function
d. Endocrine disturbances which may modify the
growth pattern and eventually affect dentofaciaI
growth
e. Nutritional disturbances
f. Childhood diseases that affect the growth
pattern
g. Radiation.
B. Local
a. Abnormalities of the dentofacial
complex:
1. Birth injuries of the head, face and
jaws
2. Micro- or macrognathia
3. Micro- or macroglossia
4. Abnormal frenal attachments
5. Facial hemiatrophy
b. Abnormalities of tooth development:
1. Delayed Or premature eruption of the
deciduous or permanent teeth
2. Delayed or premature shedding of
deciduous
teeth
3. Ectopic eruption
4. Impacted teeth
5. Aplasia of teeth.

10. * FUNCTIONAL
A. General
1. Muscular hyper- or
hypotonicity
2. Endocrine disturbances
3. Neurotrophic disturbances
4. Nutritional deficiencies
5. Postural defects
6. Respiratory disturbances
(mouth breathing).
B. Local
1. Malfunction of forces exerted by
the inclined
planes of the cusps of the teeth
2. Loss of forces caused by failure of
proximaI
contact between teeth
3. Temporomandibular articulation
disturbances.
4. Masticatory and facial muscular
hypo- or
hyperactivity
5. Faulty masticatory functions,
especially during
the tooth eruption period
6. Trauma from occlusion
7. Compromised periodontal
condition

11. *Moyer identified etiologic sites, from where the
variations were expected to arise. These sites
included:
a) the craniofacial skeleton, b) the dentition, c) the
orofacial musculature, and d) other 'soft tissues' of the
masticatory system.
* He based his classification on the premise that
various factors may contribute to cause variations at
these sites, more often in groups rather than
individually.

12. 7. Diseases:
a. Systemic diseases
b. Endocrine disorders
c. Local diseases:
• Nasopharyngeal diseases and
disturbed
respiratory function
• Gingival and periodontal
disease
• Tumors
• Caries:
- Premature loss of deciduous
teeth
- Disturbances in sequence of
eruption of
permanent teeth
- Early loss of permanent teeth
5. Trauma:
a. Prenatal trauma and
birth injuries
b. Postnatal trauma
6. Physical agents:
a. Premature extraction of
primary teeth
b. Nature of food

13. *Graber divided the etiologic factors as general
or local factors .
*This classification is one of the most detailed
and comprehensive.

15. General factors

16. 1.HEREDITARY
These may or may not be evident at birth, but are likely
to express themselves as the child grows. These can be
those influencing the
• Neuromuscular system
• Skeletal structures
• Soft tissues (other than the neuromusculature).
• Dentition

17. • NEUROMUSCULAR SYSTEM
The anomalies that have been found to possess some
inherited component include deformities in size,
position, tonicity, contractility, and in the neuromuscular
coordination pattern of facial, oral, and tongue
musculature.
It is not possible to differentiate between the origins
of certain habits. Certain tongue and lip habits can be
learned because of imitation, by watching parents and
other siblings of the soft tissue configuration, which
may be inherited or may predispose to the same.
Certain malocclusions may be associated with tongue
size or lip length and tonicity and these may be found
to reoccur within a family over generations and may
be inherited.

18. • SKELETAL STRUCTURES
The underlying basal bone and other associated cranial bone structures
are partially inherited.
This is not to say that they are not influenced by the prenatal and or
postnatal environmental factors, but certain skeletal malocclusions are
definitely inherited. The ClassІІІ skeletal pattern is most commonly
associated with familial tendencies.

19. • SOFT TISSUES (OTHER THAN THE NEUROMUSCULATURE)
These generally include the size and shape of the frenum.
especially the maxillary labial frenum .
Broad flabby frenums are sometimes repeatedly seen in families.

20. • DENTITION
Certain characteristics, especially related to the
dentition are definitely inherited. These include:
1. Size and Shape of the Teeth.
2. Number of Teeth.
3. Primary Position of Tooth Germ and the Path of
Eruption.
4. Shedding of Deciduous Teeth and Sequence of
Eruption.
5. Mineralization of Teeth

21. 1. Size and Shape of the Teeth
Studies on twins have proved that the size and relative
shape of the teeth is inherited .
Peg shaped lateral are the most commonly seen and
noticed abnormally shaped teeth encountered clinically .
 To produce a malocclusion the discrepancy should exist
between the basal bone and the teeth size,or the
associated skeletal structures.

22. 2.Number of Teeth
The number of teeth is a partially inherited characteristic.
It can vary considerably especially in cases with cleft palate and
cleidocranial dysostosis.
 Hypodontia is more widely seen as compared to hyperdontia.
Hypodontia is more commonly seen in the permanent dentition as
compared to the deciduous dentition.
The most frequently missing teeth are the maxillary lateral incisors
(the third molars not being considered).

23. 3. Primary Position of Tooth Germ and the Path of Eruption
The position of tooth germs and the path of eruption are
considered by some researchers to be inherited.
Similar cross-bites or other malocclusions might be a
result of similar jaw structure and tooth size rather
than the position of tooth germs.
 Yet, ectopic teeth have shown to occur more frequently in
some families collaborating the theory that these anomalies
are genetically determined.

24. 4.Shedding of Deciduous Teeth and Sequence of Eruption
These two parameters are not only correlated but are
the ones most commonly mentioned by the parents
themselves.

25. 5.Mineralization of Teeth
Inherited defects of the tooth structure differ from
exogenic-induced defects in mineralization :
as they are present in both the deciduous dentition
as well as permanent dentition and are localized in
the enamel or the dentine.
 These may result in malformed teeth and
contribute towards producing a malocclusion

26. 2.CONGENITAL FACTORS
Congenital defects include those malformations that are seen
at the time of birth. These are generally maldevelopments of
the 1st and the 2nd branchial arches.
The most frequently associated malformations are:
*MICROGNATHISM:The congenital variety is often seen associated
with congenital heart disease and the Pierre Robin syndrome.
*OLIGODONTIA :Also known as hypodontia, Different teeth seem
to be affected in raring degree with the third molars being
involved most frequently.
*ANODONTIA:True anodontia is extremely rare and may be
associated with hereditary ectodermal dysplasia.
*CLEFT LIP AND PALATE :This is relatively more frequently seen
anomaly. It can be identified as early as the 18 to 20th week of
pregnancy. It is generally associated with under developed
maxilla and related dental disorders.

27. 3. Environment:
a. Prenatal (trauma, maternal diet, German
measles, material maternal metabolism, etc).
b. Postnatal (birth injury, cerebral palsy, TMJ
injury)

28. 4.PREDISPOSING METABOLIC CLIMATE AND DISEASE
Under this three separate conditions need to be
stressed upon:
a. Endocrine imbalance
b. Metabolic disturbances
c. Infectious diseases.

29. a) ENDOCRINE IMBALANCE
The usually encountered anomalies include:
Hypo/hyperpituitarism, Hypo/hyperthyroidism,
Hypo/hyperparathyroidism
b) METABOLIC DISTURBANCES
Acute febrile diseases are capable of affecting not only
the general health of the child but might also affect the
dentition and its surrounding hard and soft tissues.
Temporarily they are capable of slowing down growth and
may cause delayed tooth eruption.

30. c) INFECTIOUS DISEASES
The effects of infectious diseases are dependent not only on
the severity and duration of the disease but also at what age it
affects the child of the mother.
The frequently seen diseases are:
• Bacterial infections:
Osteomyelitis, Congenital syphilis, Tuberculosis.
• Viral infections:
Mumps, Measles Rubella, Chickenpox

31. Riboflavin deficiency (vitamin B12): Cleft lip and palate.
Folic acid deficiency : • Cleft lip and palate
• Mental retardation
• Nutritional imbalances in the pregnant mother have been associated
with certain malformations in the child
• as:
Protein deficiency: • Delayed eruption
• Decreased radicular osteocementum
Vitamin A deficiency:
• Calcification of teeth is affected
• Retarded eruption
• Thickened-mandibular processes and zygoma
• Periodontal tissues might be disturbed • General growth is slow
• In a growing child nutritional imbalances can further accentuate an
existing problem or may by themselves be capable of producing
certain malformations,which may lead to malocclusions. These
include:
5. DIETARY PROBLEMS (NUTRITIONAL DEFICIENCY)

32. 6)ABNORMAL PRESSURE HABITS AND FUNCTIONAL
ABERRATIONS
These are possibly the most frequently encountered
causes of malocclusion. These include:
a. Abnormal sucking
b. Thumb and finger sucking .
c. Tongue thrust and tongue sucking .
d. Lip and nail biting.
e. Abnormal swallowing habits (improper deglutition)
f. Speech defects
g. Respiratory abnormalities (mouth breathing, etc.)
h. Tonsils and adenoids .
i. Psychogenic habits and bruxism.

33. 7)POSTURE
Though not directly. They may be associated with other
abnormal pressure or muscle imbalances increasing the risk of
malocclusion.

34. 8)TRAUMA AND ACCIDENTS
Trauma and accidents can be further subdivided into three
categories depending upon the time at which the trauma
occurred, as:
• Prenatal trauma
• Trauma at the time of delivery
• Postnatal trauma

36. Local factors

37. 1)ANOMALIES OF NUMBER
However, if the number of teeth present increases, or size
of teeth is abnormally large, it can cause crowding or
hamper the eruption of succedaneous teeth in their ideal
positions.
The anomalies in the number of teeth can be of two
types
(i) increased number of teeth or supernumerary teeth
and, (U)less number of teeth or missing teeth.

39. 2)ANOMALIES OF TOOTH SIZE
Only two anomalies of tooth size are of interest to an
orthodontist-microdontia and macrodontia, involving one or
more teeth.
The most commonly seen form of localized microdontia
involves the maxillary lateral incisors. The tooth is called a
'peg lateral"

40. 3)ANOMALIES OF TOOTH SHAPE
Anomalies of tooth shape include true fusion,
gemination, concrescence, talon cusp, and 'dens in dente'.
Dilaceration is also an anomaly of the tooth shape in which
there is a sharp bend. or curve in the root or crown.

41. 4)ABNORMAL LABIAL FRENUM
Midline diastema may persist even after the "ugly duckling stage"
or close simultaneously
depending upon the amount of fibers crossing over interdentally. A
midline diastema can exist due to various causes:

42. 5)PREMATURE LOSS OF DECIDUOUS TEETH
The premature loss of a deciduous tooth can lead to
malocclusion only if the succedaneous tooth is not
sufficientlly close to the point of eruption.
This can lead to a decrease in the over all arch
length as the posterior teeth have a tendency to
migrate mesially. This might cause the permanent
successor to erupt malpositioned or get impacted
or cause a shift in the midline

43. 6)PROLONGED RETENTION OF DECIDUOUS TEETH
they have a significant impact on the
dentition.
1. Buccal/labialor palatal/lingual deflection in its
path of eruption; or
ii. Impaction of the permanent tooth

44. 7)DELAYED ERUPTION OF PERMANENT TEETH
As a result the tooth whose eruption has been delayed might
get displaced or impacted.
*Most commonly impacted tooth is the maxillary canine (third
molars not taken into account). The reasons for this include:
i. It is the last anterior tooth to erupt
ii. Space occupied by the deciduous canine is less than the
mesiodistal width of the permanent canines
ill. The premolars might migrate mesially leaving limited space
for the canines to erupt
iv. It has the longest path of eruption
v. Controversially, as it may seem, it is the only tooth to erupt
after root completion.

46. 8)ABNORMAL ERUPTIVE PATH
It can deviate from this eruption path because of many
reasons.:
1. Tooth bud facing and/or placed or displaced from it ideal
location
2. Presence of a supernumerary looth may divert a tooth from
its eruptive path
3. Presence of odontomas or a cyst or tremor may divert it if
not altogether prevent its eruption
4. Unresorbed or retained deciduous teeth might force a tooth
to erupt along a path of least resistance rather than in place of
the deciduous tooth
5. Retained root fragments (especially of deciduous molars) may
deflect an erupting permanent tooth
6. A true arch length deficiencies or excess of tooth material
may cause one or more teeth to deviate from their eruptive
path .The tooth that most frequently erupts in an abnormal
location is the maxillary canine.

47. 9)ANKYLOSIS
Ankylosis of teeth is seen more commonly associated
with certain infection endocrine disorders and
congenital disorders, e.g. Cleidocranial dysostosis, but
these are rare occurrences.
Ankylosis should generally be suspected in cases
where there is a past history of trauma, or a mobile
tooth has regained stability or apicoectomy has been
performed.

48. 10)DENTAL CARIES
Proximal caries are especially to blame for the
reduction in arch length.
This might be brought about by migration of
adjacent teeth and/or tilting of adjacent teeth
into the space available and/or supra-eruption
of the teeth in th opposing arch.

49. 11)IMPROPER DENTAL RESTORATIONS
Under contoured proximal restoration can lead to a significant
decrease in the arch length especially in the deciduous molars. Over
contoured restorations might bulge into the space to be occupied by a
succedaneous tooth and result in reduction of this space.
Premature contacts on over contoured occlusal restoration can cause
a functional shift of the mandible during jaw closure, undercontoured
occlusal restorations can lead to the supra-eruption of the opposing
dentition.

50. Reference