Etiology Of Malocclusion: Genetic and Environmental Factors

Etiology Of Malocclusion
www.indiandentalacademy.com

ContentsContents
 Introduction
 Definition of malocclusion
 Types of malocclusion
 Classification of etiologies of malocclusion
 Brief description on various factors
 Conclusion

IntroductionIntroduction
Comprehensive orthodontic management
involves identification of possible etiological factors and
an attempt to eliminate the same. Although it may not be
possible, it is nevertheless of value in preventive and
interceptive procedures.
Rather than having specific “CAUSES” as do
some diseases, malocclusions are usually clinically
significant variations from normal range of growth and
morphology. Etiologic factors contribute to the variance,
more often than they simply cause it

DefinitionDefinition
The arrangement of teeth in a
dentition or their relation in the jaws to each
other, which is not according to the accepted
morphologic configuration of human maxillo-
dentofacial complex

Malocclusions may involve four tissue systems
Teeth
Bones
 Muscles
 Nerves
Malocclusion GroupsMalocclusion Groups

Dental dysplasias
Skeleto dental dysplasias
Skeletal dysplasias
Another way to classify malocclusion isAnother way to classify malocclusion is
to divide them into three groupsto divide them into three groups

Classification Of Etiologic FactorsClassification Of Etiologic Factors
According to Mc coy
 Indirect / Pre disposing causes
 Direct / Determining causes

Indirect / Pre disposing causes includeIndirect / Pre disposing causes include
 Hereditary
 Congenital defects
 Pre natal abnormalities
Acute / chronic infections and deficiency diseases
 Metabolic disturbances
 Endocrine imbalance
 Unknown causes.

Direct / Determining causes includeDirect / Determining causes include
 Missing teeth
 Supernumerary teeth
 Transposed teeth
 Malposed teeth
 Abnormal labial frenum
 Intrauterine pressure
 Sleeping habits
 Posture

Pressure
Abnormal muscular habits
Malfunctioning muscles
Premature shedding of deciduous teeth
Tardy eruption of permanent teeth
Prolonged retention of deciduous teeth
Loss of permanent teeth
Improper dental restorations

ACCORDING TO MOYERSACCORDING TO MOYERS
 Heredity
 Neuro muscular system
 Bone
 Teeth
 Soft parts (other than nerve and muscle)
 Developmental defects of unknown origin
 Trauma
 Prenatal trauma and birth injuries.
 Post natal trauma.

 Physical agents
 Pre natal
 Post natal
 Habits
Thumb and finger sucking, tongue
sucking, lip biting etc
 Disease
 Systemic diseases
 Endocrine diseases
 Local diseases
Malnutrition

According to SalzmannAccording to Salzmann
Salzmann’s diagrammatic representation of the
etiologic factors in malocclusion embodies prenatal and post natal
factors. It clearly shows the genetic, differentiative and congenital
factors that make up the prenatal elements of causation, which can
influence and one or all of the postnatal components-
developmental, functional, environmental.www.indiandentalacademy.com

According to Graber
General Factors
Heredity (The inherited pattern)
Congenital Defects
 Cleft palate
 Torticollis
 Cleidocranial dysostosis
 Cerebral palsy
 Syphilis etc.

 Environment
 Pre natal
 Trauma
 Maternal diet
 Maternal metabolism
 German measles etc.
 Post natal birth injury
 Cerebral palsy
 TMJ injury etc.

Pre disposing metabolic climate and
disease
 endocrine imbalance
 metabolic disturbances
 infectious diseases
Dietary problems
 nutritional deficiency

Abnormal pressure habits and functional
aberrations
 Abnormal suckling
 Forward mandibular posture
 Non physiologic nursing
 Excessive buccal pressures

Thumb and finger sucking
Tongue thrust and tongue sucking
Lip and nail biting
Abnormal swallowing habits
(improper deglutition)
Speech defects

Respiratory abnormalities
(mouth breathing)
Tonsils and adenoids
(compensatory tongue position)
Psychogenic tics and Bruxism
Posture
Trauma and Accidents

Local factors
Anomalies of number
Supernumerary teeth
Missing teeth
 Congenital absence or loss due to
accidents, caries etc
Anomalies of tooth size
Anomalies of tooth shape
Abnormal labial frenum, mucosal barriers

Premature loss
Prolonged retention
Delayed eruption of permanent teeth
Abnormal eruptive path
Ankylosis
Dental caries
Improper dental restorations

ACCORDING TO PROFFITACCORDING TO PROFFIT
Specific causes
Disturbances in embryologic development
(teratogens)
Skeletal growth disturbances
 Intrauterine molding
 Birth trauma to mandible
 Childhood fractures or the jaw
Muscle dysfunction

 Acromegaly and hemi mandibular hyper trophy
 Disturbances of dental development
 Congenitally missing teeth
 Malformed and supernumerary teeth
 Interferance with eruption
 Ectopic eruption
 Early loss of primary teeth
 Traumatic displacement of teeth

Genetic influences
Environmental influences
Equilibrium theory and development of dental occlusion
Functional infuence on dento facial development.

General factors
Heredity
A child may have facial features that markedly
resemble those of his father or mother, or the net result
may be a combination of features from each parent. It is
also to be noted that, a single gene is not responsible for a
particular malocclusion and it may be due to the combined
action of different types of Genes
Heredity could be considered significant in
determining the following characteristics

Tooth size
Width and length of arch
Height of palate
Crowding and spacing of teeth
Overjet
Position and conformation of perioral musculature to
tongue size and shape
Soft tissue peculiarities
Facial asymmetries
Macorgnathia and micrognathia
Macrodontia an microdontia

 Oligodontia and anodontia
 Tooth shape variations
(peg laterals, Carabellis cusps, mamelons etc)
 Cleft palate and hare lip
 Diastemas
 Deep bite
 Rotation of teeth
 Mandibular retrusion
 Mandibular prognathism

Congenital defects
Cleft lip and palate
Congenital defects life cleft lip and palate separately or
in combination are among the most frequent congenital deformities of
mankind. It is not often possible for the dentist to compensate for
residual post surgical abnormalities. In a unilateral cleft, the teeth or
one side are usually in lingual cross bite with the opposing lower teeth.
Many times the premaxilla is displaced anteriorly, or, because of the
tightly repaired lip, the whole pre maxillary structure is forced
lingually. The maxillary incisors in this type are badly malposed with
bizarre axial inclinations. In the area of cleft, teeth are often jumbled.
Maxillary lateral incisors may be missing, atypical in shape or
‘twinned’

Cerebral palsy
Paralysis or lack of muscular co-ordination due to an intra
cranial lesion
Complete lack of motor control resulting in abnormal
muscular function in masticaction, deglutition, speech and
respiration.
Abnormal pressure habits lead to malocclusion

Torticollis
Shortening of the sternocleido mastoid muscle causing
profound changes in the bony morphology of the cranium
and the face
Characterised by “wry neck”
Bizarre facial asymmetries and uncorrectable malocclusions
if not treated early www.indiandentalacademy.com

Cleidocranial dysostosis
Maxillary retrusion and possible mandibular protrusion
Retained deciduous teeth
Retarded eruption of permanent teeth
Short and thin permanent teeth roots
Super numerary teeth

Congenital Syphilis
 Abnormally shaped teeth

Pre natal
Post natal
Environment

Pre natal
Teratogens: Chemical and other agents capable of producing
embryologic defects if given at critical time are called teratogens
Aminopterin
Aspirin
Cigarette smoke (hypoxia)
Cytomegalovirus
Anencephaly
Cleft lip and palate
Microcephaly, hydrocephaly,
microphthalmia
Dilantin
Ethyl alcohol
6-Mercaptopurine
13-cis Rentinoic acid
(Accutane)
Central mid-face deficiency
Cleft Palate
Retinoic acid syndrome: malformations
virtually same as hemifacial microsomia,
Treacher Collins syndrome
Rubella virus
Thalidomide
Microphthalmia, cataracts, deafness
Malformations similar to hemifacial
microsomia, Treacher Collins syndrome
Toxoplasma Microcephaly, hydrocephaly,
microphthalmia
X-radiation
Valium
Vitamin D excess
Microcephaly
Cleft and palate
Premature suture closurewww.indiandentalacademy.com

Intrauterine moldingIntrauterine molding
Pressure against the developing face prenatally can lead
to distortion of rapidly growing areas. Eg: an arm is
pressed across the face in utero resulting in severe
maxillary deficiency.
Other factors that may affect are trauma, maternal diet,
maternal metabolism and German measles

Birth trauma
In some difficult births use of forceps to the head to
assist in delivary might damage either or both TMJ.
Heavy pressure in the area of TMJ could cause internal
haemorrhage, loss of tissue and a subsequent under
development of the mandible
Childhood fractures: Falls that produce condylar
fractures may cause marked facial asymmetries
Extensive scar tissue, from a burn may also produce
malocclusions
Post natal

Some specific endocrinologic diseases may be potent
makers of malocclusion. Diseases with a paralytic effect,
such as poleomyelitis are capable of producing
malocclusions.
Disease with muscle malfunction, such as muscular
dystrophy and cerebral palsy also have deforming effects
on dental arch
Pre disposing metabolic climate and diseases

HypothyroidismHypothyroidism
Abnormal resorption patterns
Delayed eruption pattern
Gingival disturbances
Retained deciduous teeth

AcromegalyAcromegaly
Which is caused by an anterior pituitary
tumor that secrete excess amounts of GH, excessive growth
of mandible may occur, creating a skeletal class III
malocclusion in adult life. Also multiple root resorption
may be found.

Nutritional deficiencyNutritional deficiency
Disturbances such as rickets, scurvy and berry-berry
can produce severe malocclusions. Main problem is upsetting of the
dental developmental time tables. The resultant premature loss,
prolonged retention, poor tissue health and abnormal eruptive paths
lead to malocclusion

Non nutritive sucking habits, Includes all
sucking habits
Thumb sucking
Finger sucking
Pacifiers etc.
Abnormal pressure habits andAbnormal pressure habits and
functional aberrationsfunctional aberrations

Dento facial changes associated with prolonged
non nutritive sucking habits are
Increased proclination of upper incisors
Increased maxillary arch length
Increased clinical crown length of max incisiors
Increased atypical root resorption in primary
central incisors

Increased retroclination of mandibular incisors
Increased overjet
Decreased over bite
Increased unilateral and bilateral class II occlusion
Increased lip incompetence
Tongue thrust
Speech defects, especially lisping

Lip biting
 Involves the lower lip which is turned inwards and
pressure is exerted on the lingual surfaces of
maxillary anteriors
 Proclined upper anteriors and retroclined lower
anteriors
 Hyper trophic and redundant lower lip
 Cracking of lips
Lip habitsLip habits

Nail bitingNail biting
Does not produce gross malocclusion. But minor
local tooth irregularities like
Rotation
Wear of incisal edge
Minor crowding.

Tongue thrustTongue thrust
 Defined as a condition in which the tongue makes contact with any
teeth anterior to the molars during swallowing
 It has to be remembered at this time that there is a controversy
regarding Tongue thrust as an etiologic factor of anterior open bite.
According to Graber and Moyers, Tongue thrust definitely leads to
anterior open bite. Proffit contradicts this fully and according to him,
it is an already existing anterior open bite that leads to Tongue
thrusting habit
 Proclination of anterior teeth
 Anterior open bite
 Bimaxillary protrusion
 Posterior open bite in case of
lateral Tongue thrust
 Posterior cross bite

Mouth breathingMouth breathing
Mouth breathing can result in altered jaw and tongue posture which
could alter the oro-facial equilibrium there by leading to malocclusion
Long and narrow face
Short and flaccid upper lip.
Contracted upper arch with possibility of
posterior cross bite
Increased overjet as a result of flaring of the incisors.
Dryness of the mouth predisposes to caries.
Anterior open bite

BruxismBruxism
Grinding of teeth for non functional purposes
Occlusal wear facets
Fractures of teeth and restorations
Mobility of teeth.
Tenderness and hypertrophy of masticatory muscles
TMJ pain

Tongue size as well as function is an important
consideration. Aglossia can result in narrowing of the
upper dental arch with severely malpositioned teeth and
crowding. Where as Macroglossia can lead to widening of
dental arches, spacing and open bite.

Anomalies in number of teeth
 Super numerary teeth
 Missing teeth
Local factorsLocal factors

Super numerary teethSuper numerary teeth
The presence of extra tooth obviously has great potential to disrupt
normal occlusal development. Early intervention and to remove it is
usually required to obtain reasonable alignment and occlusal
relationships. Most common-mesiodens.

 Also lateral incisors, extra premolars, fourth molars multiple super
numerary teeth are found in cleidocranial dysplasia and other
congenital deformities like cleft lip and cleft palate

Missing teethMissing teeth
Congenital absence
Due to accidents / caries
Order of frequency
 Max and mandibular 3rd
molars
 Max laterals
 Mandibular 2rd premolars
 Mandibular incisors
 Maxillary second premolars
Anodontia–complete absence
Oligodontia–congenital absence of many, but not all teeth
Hypodontia – absence of only a few teeth

Quite frequently it has been noted
that, one maxillary lateral incisor will be of
normal size and configuration while the
other is small. Anomalies of size are
relatively frequent in the mandibular pre
molar area
Anomalies of tooth sizeAnomalies of tooth size

Anomalies of Tooth ShapeAnomalies of Tooth Shape
Most frequent – “Peg Lateral”
Leads to excessive spacing. Anomalies of shape occur as a
result of developmental defects like amelogenesis
imperfecta, hypoplasia, Gemination, Dens in Dente,
Odontomas, Fusions, Congenital syphilitic aberations such
as Hutchinson’s incisors and mulberry molars.

Abnormal labial FrenumAbnormal labial Frenum
If the frenum is thick, it prevents the closure of
diastema (which is normal during mixed dentition prior to the
eruption of canines)
In these cases a frenectomy is indicated

Premature loss of deciduous teethPremature loss of deciduous teeth
The early loss of permanent teeth should be
considered as a “Malocclusion Maker”
Deciduous teeth not only serve as organs of
mastication, but as space savers for permanent teeth.
Loss of a deciduous 2nd
molar will lead to mesial drift
of the 1st
permanent molar and blocking of erupting
2nd
premolars. In this cases appropriate space
maintainers should be given

Prolonged retention and abnormal Prolonged retention and abnormal
resorption of deciduous teethresorption of deciduous teeth
If the roots of the deciduous teeth are not resorbed
properly, uniformly or on schedule, the permanent
successors may be either withheld from eruption,
or they may be deflected into malposition

Delayed eruption of Permanent teethDelayed eruption of Permanent teeth
 Endocrine disorders like hypothyroidism
 Presence of supernumerary teeth or
deciduous root
 Mucosal or Bony barrier

This is usually a secondary manifestation of a primary
disturbance
Severe crowding
Super numerary tooth
Retained deciduous tooth / root fragment
   Bony barrier
   Dentigerous cysts
Another form of abnormal eruption is referred as ectopic
eruption.  Most common form is a permanent tooth
erupting through the alveolar process causing resorption on
a contiguous deciduous tooth or permanent teeth , rather
than its predecessor.  Eg; maxillary first molar, causing
resorption of maxillary deciduous second molar.
Abnormal eruptive pathAbnormal eruptive path

AnkylosisAnkylosis
Ankylosis or partial ankylosis occurs relatively frequently
during 6-12 year age period. Ankylosed deciduous teeth
should be identified and treated by removal or building up
or surgical subluxation along with space maintainers.
Permanent teeth can also be found to be ankylosed can be
due to
 Accidents / trauma
 Congenital diseases like cleidocranial dysostosis

Dental cariesDental caries
Dental caries should be considered as one of the local
factors causing mal occlusion. Caries which leads to
premature loss of a deciduous or permanent tooth may
cause drifting, axial inclination, over eruption, bone loss
etc.

Improper dental restorationsImproper dental restorations
Silver mercury alloy restorations have a tendency
to “flow” under pressure. Large proximal restorations change
gradually under the assault of occlusal forces, and arch length is
increased. This may result in the creation of broken contacts,
rotations, crossbite conditions and functional prematurities. Lack
of anatomic detail in restoration of cuspal areas of a tooth can
permit elongation of opposing tooth.
Loose contacts also leads to food packing, teeth
tend to move apart and also leads to bone loss

Knowledge about the various etiological factors of malocclusion will
help us to plan the various interceptive and preventive orthodontic
procedures.
It also helps in eliminating the etiological factor if it is of a
environmental type.
The recognition and reporting of a malocclusion or a condition that
could lead to a malocclusion is the most important service that a
dentist can provide to his patients. Malocclusion has an important
impact on the function and esthetics of the entire dentition. In fact,
malocclusion has a detrimental effect on the self esteem of many
children, adolescent and adult. If a malocclusion is not recognized by
either the dentist or the patient, it cannot be assessed and treated
A sound knowledge about the various factors that lead to
malocclusion, will definitely help is to render excellent treatment for
our patients with good retention and stability
Conclusion

Etiology Of Malocclusion: Genetic and Environmental Factors

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