Etiology of malocclusion

ETIOLOGYOF
MALOCCLUSION-
GENERAL&LOCAL
FACTORS
MUHSINA T
FINAL YEAR PART1

CONTENTS
 INTRODUCTION
 CLASSIFICATION OF ETIOLOGY OF MALOCCLUSION
 GRABERS CLASSIFICATION
 GENERAL FACTORS
 LOCAL FACTORS
 CONCLUSION
 REFERENCE

INTRODUCTION
• The orthodontic specialty deals with treatment of malocclusion.
• JOHN HUNTER was the first to describe about normal occlusion.
• IDEAL OCCLUSION
• It is a pre conceived theoretical concept of occlusal structural & functional
relationships that include idealized principles & characteristics that an occlusion
should have.

MALOCCLUSION
 “ Malocclusion is defined as any deviation from the ideal occlusion”.
- ANGLE
 Etiology of malocclusion is the study of its cause or causes.
 The preventive and interceptive orthodontic procedures where a possible
malocclusion is prevented or intercepted by timely removal of the cause.

CLASSIFICATION OF ETIOLOGY OF
MALOCCLUSION
1. MOYER`S CLASSIFICATION
2. WHITE & GARDINER`S CLASSIFICATION
3. GRABER`S CLASSIFICATION

1. MOYER`S CLASSIFICATION
HEREDITY
TRAUMA
PHYSICAL AGENTS
HABITS
DISEASES
MALNUTRITION
DEVELOPMENTAL DEFECTS
OF UNKNOWN ORIGIN

2. WHITE & GARDINER`S CLASSIFICATION
DENTAL BASE
ABNORMALITIES
• Antero-posterior
malrelartionship
• Vertical
malrelationship
• Lateral
malrelationship
• Congenital
abnormalities
PRE-ERUPTION
ABNORMALITIES
• Abnormalities in
position of
developing tooth
germ.
• missing teeth
• Supernumerary teeth
• Prolonged retention
of deciduous teeth
POST ERUPTION
ABNORMALITIES
• Muscular
• Premature loss of
deciduous teeth
• Extraction of
permanent teeth
ABNORMALITIES IN
PATH OF CLOSURE
• Premature loss of
deciduous teeth
• Extraction of
permanent teeth

3. GRABER`S CLASSIFICATION
GENERAL FACTORS
• HEREDITY
• CONGENITAL
• ENVIRONMENT
• PRE-DISPOSING METABOLIC CLIMATE &
DISEASE
• DIETARY PROBLEMS
• ABNORMAL PRESSSURE HABITS &
FUNCTIONAL ABERRATIONS
• POSTURE
• TRAUMA & ACCIDENTS
LOCAL FACTORS
• ANOMALIES OF TOOTH NUMBER
• ANOMALIES OF TOOTH SHAPE
• ANOMALIES OF TOOTH IN SIZES
• ABNORMAL LABIAL FRENUM
• PREMATURE LOSS OF DECIDOUS TEETH
• PROLONGED RETENTION OF DECIDOUS TEETH
• DELAYED ERUPTION OF PERMENENT TEETH
• ABNORMAL ERUPTIVE PATH
• ANKYLOSIS

GRABER`S CLASSIFICATION OF ETIOLOGY
OF MALOCCLUSION

GRABER`S CLASSIFICATION
 Graber has classified the etiological factors as
1. General factors
2. Local factors
• the local factors responsible for malocclusion produce a localized effect
confined to one or more adjacent or opposing teeth.
•The general factors on the other hand are those that affect the body as a whole
and have a profound effect on the greater part of dento-facial structures

HEREDITY
 Heredity has for long been attributed as one of the causes of malocclusion.
 The child may inherit conflicting trait from both the parents resulting in
abnormalities of the dentofacial region.
 Another reason attributed for genetically determined malocclusion is the racial,
ethnic and regional inter-mixture, which might have lead to uncoordinated
inheritance of teeth and jaws

According to Lundstrom there exist a number of human traits that are
influenced by the genes that include:
Tooth size:
Abnormalities of tooth size such as microdontia and macrodontia are
attributed to heredity
Arch dimension:
The dental arch length and arch width are believed to be inherited

Crowding or spacing :
Most of these conditions are believed to be a result of uncoordinated
inheritance of arch length & tooth material.
Abnormalities of tooth shape :
Anomalies tooth shape such as peg laterals is another trait shows high
genetic predisposition.

Abnormalities of tooth number :
This includes condition such as anodontia & oligodontia.
Over jet :
The horizontal overlap of the upper & lower dentition referred to genetically
influenced

Inter arch relationship :
Discrepancies in the transverse, sagittal & vertical planes between the upper
and lower jaws can be inherited
Frenum :
The malocclusions such as midline diastema that may be due abnormalities of
the frenum are to a large to be determined genetically

According to Harris & Johnson a number of craniofacial parameters showed significant
genetic influence.
These includes the following distances :
1. Sella- gnathion
2. Sella-point A
3. Sella- gonion

4. Nasion- anterior nasal spine
5. Articulare- progonion
6. Bizygomatic width
7. Anterior facial height.

CONGENITAL DEFECT
 Congenital defect or developmental defect are malformation seen at the time of birth.
 They may be caused by a variety of factors including genetic, radiologic, chemical,
endocrine, infections, and mechanical factors.
 The congenital abnormalities that cause malocclusion can be broadly classified as
1. General congenital factors
2. Local congenital factors

General congenital factors
• Abnormal state of mother during
pregnancy
• Malnutrition
• Endocrinopathies
• Metabolic and nutritional
disturbances
• Accident during pregnancy and
child birth
• Intrauterine pressure
• Accidental traumatization of the
foetus by external forces
Local congenital factors
• Abnormalities of jaw
development due to intrauterine
position
• Clefts of the face and palate
• Macro and microglossia
• Cleidocranial dysostosis

The following are some of the congenital conditions
CLEFTS OF THE LIP AND PALATE
• Clefts involving the lip and palate are the most commonly seen developmental
defects that occur as a result of non- fusion between the various embryonic
processes.
• Cleft patients may exhibits a number of dental problems including missing
teeth, mobile teeth , rotations, crossbite etc..

Cleft lip
Cleft lip with cleft palate

CONGENITAL SYPHILIS :
 Syphilis of congenital origin is transmitted from infected mother to the child.
 The child exhibits on or more of the following features:
1. Hutchinson`s incisors
2. Mulberry molars
3. Enamel deficiencies
4. Extensive dental decay
5. The maxilla may be smaller in size relative to the mandible
6. Anterior crossbite

MATERNAL RUBELLA INFECTIONS
• Maternal rubella infection during pregnancy is believed to cause widespread
congenital malformations in the child
• Features are
1. Dental hypoplasia
2. Retarded eruption of teeth
3. Extensive caries

CLEIDOCRANIAL DYSOSTOSIS
 This is a congenital condition characterized by unilateral or bilateral, partial or
complete absence of clavicle
 Features includes
a) Maxillary retrusion and possible mandibular protrusion
b) Over retained deciduous teeth and retarded eruption of permanent teeth.
c) Presence of supernumerary teeth
d) Presence of short and thin roots

CEREBRAL PALSY
o This is a condition where in the patient lacks muscular coordination.
o It is usually due to birth injuries.
o The uncontrolled and aberrant muscle activity upsets the muscle balance
resulting in malocclusion.

Malocclusion associated with
cerebral palsy

ENVIRONMENT
 Various prenatal and post natal environmental factors can cause malocclusion.
PRENATAL FACTORS
There are certain factors, the presence of which can result in abnormal growth
of the oro-facial region there by predisposing to malocclusion.
Abnormal fetal position during gestation is said to interfere with symmetric
development of the face.

The other prenatal influences include maternal fibroids, amniotic lesions,
maternal diet and metabolism.
Maternal infections such as German measles and use certain drugs during
pregnancy such as Thalidomide can cause gross congenital deformities including
clefts

Congenital deformities caused by
thalidomide

POSTNATAL FACTORS
The following are some of the postnatal factors that can cause malocclusion.
Forceps delivery can result in injury to the temperomandibular joint area, which can
undergo ankylosis. Such patient shows retarded mandibular growth and thus have a
hypoplastic mandible.
Cerebral palsy is a condition characterized by muscle incoordination. this may occur
due to birth injuries. The patient can exhibits malocclusion due to loss of muscle
balance.

Traumatic injuries that cause condylar fracture can cause growth
retardation resulting in marked facial asymmetry.
Presence of scar tissue such as those caused by burns or as a result of cleft
lip surgery may produce malocclusion due to their restrictive influence on
growth.
Milwaukee brases are used for treatment of scoliosis. Prolonged use of
these braces can cause marked mandibular growth retardation.

Milwaukee brases are used for
treatment of scoliosis

PREDISPOSING METABOLIC CLIMATE
AND DISEASE
A number of endocrinal disorders, infectious conditions and metabolic
disturbances can predispose to malocclusion.
ENDOCRINAL DISTURBANCES
o Certain endocrinal disorders result in malocclusion
o The following are some of the endocrinal disturbances that can cause
malocclusion.

Hypothyroidism
It is characterized by the presence one or more of the following features :
a) Retardation in rate of calcium deposition in bones and teeth
b) Marked delay in tooth bud formation and eruption of tooth
c) Delayed carpel and epiphyseal calcification

d) The deciduous teeth are often over retained and permanent teeth are slow to
erupt
e) Abnormal root resorption
f) Irregularities in the tooth arrangement and crowding of tooth occur

Hyperthyroidism
oThis condition is characterized by increase in the rate of maturation, and an
increase in metabolic rate.
oThe patient exhibits premature eruption of deciduous teeth, disturbed root
resorption of deciduous teeth and early eruption of permanent teeth
oThe patient may have osteoporosis which condra-indicates orthodontic
treatment

Hypoparathyroidism
This endocrinal disorder is associated with changes in calcium metabolism.
It can cause delay in tooth eruption, altered tooth morphology, delayed
eruption of deciduous and permanent teeth and hypoplastic teeth

Hyperparathyroidism
oProduces increase in blood calcium
oThere is demineralization of bone and disruption of trabecular pattern.
oIn growing children, interruption of tooth development occurs.
oThe teeth may become mobile due to loss of cortical bone and resorption of the
alveolar process

METABOLIC DISTURBANCES
oAcute febrile diseases are believed to slow down the pace of growth and
development.
oThese conditions may cause disturbance in tooth eruption and shedding
thereby increase the risk of malocclusion.
oDisease affecting the oro- facial muscles can have a profound effect on the
dento-alveolar complex predisposing to the malocclusion.

DIETARY PROBLEMS (NUTRITIONAL
DEFICIENCY)
Nutritional deficiencies during growth may result in abnormal development,
causing malocclusion.
These diseases are more common in the developing countries than in the
developed.
Nutrition related disturbances such as rickets, scurvy and beriberi can produce
severe malocclusion and may upset the dental developmental timetable

POSTURE
oPoor postural habits are said to be cause for malocclusion.
oThey may be associated with abnormal pressure and muscle imbalance thereby
increase in the risk of malocclusion.
o Children who support their head by resting on their hand and those who hang
their head so that the chin rests against the chest are observed to have
mandibular deficiency.

ACCIDENTS AND TRUAMA
oChildren are more prone to injuries of dento-facial region during the early years
of life when they crawl, walk or during play.
o Most of these injuries go unnoticed and may be responsible for non vital teeth
that do not resorb and deflection of erupting permanent teeth abnormal
positions

ANOMALIES IN NUMBER OF TEETH
Presence of extra teeth or absence of one or more teeth predisposes to malocclusion.
Supernumerary teeth
Teeth that are extra to the normal complement are termed supernumerary teeth.
These teeth have abnormal morphology and do not resemble normal teeth.
75% of supernumerary teeth remain impacted in the bone are only diagnosed
radiographically.

 Multiple supernumerary teeth are seen in cleidocranial dysplasia, oral-facial-
digital syndrome type 1, Gardener syndrome.
 A frequently seen supernumerary tooth is the mesiodens that occurs in the
maxillary midline. Unerupted mesiodens causes midline spacing.

PROBLEMS ASSOCIATED WITH SUPERNUMERARY TEETH
Failure of eruption :
the presence of supernumerary tooth is the most common cause for the failure
of eruption of central incisors.
Supernumerary tooth in other region causes failure of eruption of adjacent teeth.
It may also cause retention of the primary incisor.

Displacement or rotation of permanent teeth
 The presence of supernumerary teeth may cause displacement of a permanent
tooth, it may vary from a mild rotation to complete displacement
 Displacement of the crown of the incisor teeth is a common feature in the
majority of cases associated with delayed eruption.
 The presence of supernumerary tooth between the roots of adjacent teeth
may prevent root approximation and result in formation of a diastema.

Crowding
 Erupted supplemental teeth most often cause of crowding.
 The problem may be resolved by extracting the most displaced/deformed
tooth
 Incomplete space closure during orthodontic treatment
 The presence of an undiagnosed supernumerary tooth, particularly a late
forming premolar , may prevent orthodontic space closure.

Pathology and other complications
 Resorption of roots adjacent to a supernumerary may occur rarely
 Dentigerous cyst formation associated with supernumerary teeth
 Migration of supernumerary tooth into the nasal cavity, maxillary sinus or hard
palate is rare complication.

MISSING TEETH
o Congenital missing teeth are far common than the supernumerary teeth and
can occur in either of the jaws.
o Congenital absence of teeth is referred to as hypodontia if some teeth are
missing from the arch or anodontia if all of the teeth are absent.
o If six or more permanent teeth are missing , the term oligodontia.

The following are some of the commonly missing teeth in decreasing order of
frequency :
• Third molars
• Maxillary lateral incisor
• Mandibular second premolars
• Mandibular incisors
• Maxillary second premolars.

Hypodontia or anodontia can be classified as:
1. Isolated or non syndromic hypodontia
2. Syndromic hypodontia

COMPLICATIONS
 Absence of one or more teeth predispose to spacing in the dental arch.
 Adjacent teeth migrate and there fore cause abnormal location and axial
inclination of teeth.
 Absence of permanent teeth often results in over-retained deciduous teeth.

ANOMALIES OF TOOTH SIZE
MACRODONTIA
o Any tooth or teeth larger than normal for that particular tooth type.
o True macrodontia involving the all dentition is extremely rare.
o Generalised macrodontia is observed in cases pituitary gigantism, and
individuals with a small jaw.
o Affects most often upper central incisors, second premolars and lower third
molars.

MICRODONTIA
Refers to teeth that appear smaller in size compared to normal.
It is important to note that the teeth affected are usually the ones that
are also most often congenitally absent.

o Generalized microdontia is rare, and may be associated with congenital
hypopituitarism or exposure to radiation or chemotherapy during dental
development.
oMicrodontia is frequently seen association with Downs syndrome and various
types of ectodermal dysplasia.

Fusion
refers to the union between the dentine and/ or enamel of two or more
separate developing teeth.
Fusion most often leads to a reduced number of teeth in the dental arch,
although occasionally a normal and supernumerary tooth may be fused.

Gemination
Refers to the partial development of two teeth from a single tooth bud following
incomplete division.

Concrescence
Refers to the roots of one or more teeth united by cementum alone after
formation of the crowns

Complications
oMacrodontia may results in crowding while, smallersized teeth or microdontia
predispose to spacing.
oFusion between two adjacent teeth or between asupernumerary tooth and a
normal tooth may predispose to malocclusion.

ANOMALIES OF TOOTH SHAPE
Anomalies of tooth size and shape are very often interrelated. Abnormally shaped
teeth predispose to malocclusion.
The following are some of the examples of frequently seen tooth shape anomalies:
a. The presence of peg shaped maxillary lateral incisors is often accompanied by
spacing and migration of teeth.
b. Another anomaly of tooth shape is the presence of an abnormally large
cingulum on a maxillary incisor. The presence of an exaggerated cingulum
prevents establishment of normal overbite and overjet.

c. The mandibular second premolars may rarely have an additional lingual cusp,
thereby increasing the mesiodistal dimension of the tooth.
d. Congenital syphilis is often associated with presence of abnormal tooth form.
Peg shaped laterals and mulberry molars are classical findings in such patient.
e. Anomalies of shape can occur as a result of developmental defect like
amelogenesis imperfect, hypoplasia of teeth, fusion and gemination.

f. Dilaceration is described as a condition characterized by an abnormal
angulation between the crown and root of a tooth or angulation within the root.
It usually occurs due to blow to a deciduous tooth, which is transmitted to the
underlying permanent tooth bud. Dilacerated teeth fail to erupt to normal level
and can thus cause malocclusion.

ABNORMAL LABIAL FRENUM
Abnormalities of maxillary labial frenum us associated with the midline
spacing.
The heavy band of fibrous frenum is attached to interdental papilla region,
which prevents the approximation of 2 central incisors
This condition is diagnosed by a positive blanch test. When the upper lip is
stretched for a period of time , a noticeable blanching occurs over the
interdental papilla.

PREMATURE LOSS OF DECIDUOUS TEETH
This refers to loss of a tooth before its permanent successor is sufficiently
advanced in development and eruption to occupy its place.
Premature loss of deciduous teeth can cause migration of adjacent teeth into
the space and can therefore prevent the eruption of the permanent successor.
Loss of deciduous second molar can cause a marked forward shift of the
permanent first molar thereby blocking the eruption of the second premolar,
which either impacted or is deflected to an abnormal position.

Loss of deciduous second
molar can cause a marked
forward shift of the
permanent first molar
thereby blocking the eruption
of the second premolar

The severity of malocclusion caused due to early loss of a deciduous tooth
depends on the following factors
a) Premature loss of deciduous molars predispose to malocclusion due to
shifting of adjacent teeth into the space.
b) The earlier the deciduous teeth are extracted before the successional teeth
are ready to erupt, the greater is the possibility of malocclusion.
c) In a person having arch length deficiency or crowding the early loss of
deciduous teeth may worsen the existing malocclusion.

PROLONGED RETENTION OF DECIDUOUS
TEETH
This refers to the condition where there is undue retention of deciduous teeth
beyond the usual eruption age of their permanent successors.
Prolonged retention of deciduous anteriors usually results in lingual or palatal
eruption of the permanent successors
Prolonged retention of buccal teeth results in eruption of the permanent teeth
either buccally or lingually or may remain impacted

Prolonged retention of deciduous
anteriors

The following are some of the reasons for prolonged retention of deciduous
teeth:
a) Absence of underlying permanent teeth
b) Endocrinal disturbances such as hypothyroidism.
c) Ankylosed deciduous teeth that fail to resorb.
d) Non- vital deciduous teeth that do not resorb.

DELAYED ERUPTION OF PERMENENT TEETH
There are number of reasons that can delay the eruption of permanent teeth.
The following are some of them:
a. Congenital absence of the permanent tooth.
b. Presence of supernumerary tooth or pathology such as odondomes can block
the erupting permanent tooth
c. Presence of a mucosal barrier can prevent the tooth from emerging into the
oral cavity.

d. Premature loss of deciduous teeth can result in delayed eruption of the
underlying permanent teeth due to formation of bone over the erupting
permanent tooth
e. Endocrinal disorders such as hypothyroidism can cause delay in eruption of the
permanent teeth
f. Presence of deciduous root fragments that are not resorbed can block the
erupting permanent teeth

ABNORMAL ERUPTIVE PATH
•One of the causes of malocclusion is an abnormal path of eruption, which could
be due to arch length deficiency presence of supernumerary teeth, impacted
tooth, retained root fragments, or formation of a bony barrier.
•The maxillary canine develop almost near the floor of the orbit and travel down
to their final position in the oral cavity. Thus they are most often found erupting
in an abnormal position.

ANKYLOSIS
•Ankylosis is a condition wherein a part or whole of the root surface is directly
fused to the bone with the absence of the intervening periodontal membrane.
•This most often occurs as a result of trauma to the tooth that perforates the
periodontal membrane.

•Ankylosis can also associated with certain infections, endocrinal disorders,
disturbed local metabolism, chemical or thermal irritation and congenital
disorder such as cliedocranial dyostosis.
•Sometimes teeth are totally submerged within the jaw and therefore cause
migration of adjacent teeth in to the space.

DENTAL CARIES
Caries can lead to premature loss of deciduous or permanent teeth therby
causing migration of contiguous tooth, abnormal axial inclination and supra-
eruption of opposing tooth.
Proximal caries that has been not restored can cause migration of adjacent
teeth in to the space leading to a reduction in arch length.

IMPROPER DENTAL RESTORATIONS
•Improper dental restorations may predispose to malocclusion.
•Over-contoured occlusal restorations cause premature contacts leading to
functional shift of the mandible during jaw closure.
•Under-contoured occlusal restorations can permit the opposing dentition to
supra erupt.
•Proximal restorations that are under-contoured invariably result in loss of arch
length due to drifting of adjacent teeth to occupy space

CONCLUSION
 Developmental of normal dentition and occlusion depends on a number interrelated
factors that include the dentoalveolar, skeletal and the neuromuscular factors.
Malocclusion can occur due to number of possible causes.
Comprehensive orthodontic treatment involves identification possible etiologic factors
and attempt to eliminate the same.
The preventive and interceptive orthodontic procedures where a possible malocclusion is
prevented or intercepted by timely removal of the cause.

REFERENCE
Text book of Orthodontics arts and science S.I bhalaji 7th edition

Etiology of malocclusion

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