ETIOLOGY OF

MALOCCLUSIONPrepared by : Dr. Ali Waqar

FCPS – II Resident in OrthodonticsUCMD UOL

Supervised by : Dr. Saad AsadAssociate Professor of Orthodontics

UCMD UOL

DEFINITION Malocclusion is an incorrect

relationship of Maxilla & Mandible

Distortion of normal development

Complex interaction of multiple factors that influence growth & development

CAUSES Malocclusion is said to occur due to the

following factors acting alone or in combination.

Specific causes of malocclusion Genetic Influences Environmental Factors

SPECIFIC CAUSES OF MALOCCLUSION

Disturbances in embryonic development Growth disturbances in fetal period Progressive deformities in childhood Disturbances arising in Adolescence Disturbances of dental development

DISTURBANCES IN EMBRYOLOGIC DEVELOPMENT

Defect in embryo development usually results in death of 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

FETAL ALCOHOL SYNDROME

FAS can be traced to the very early 1st & 2nd stages of craniofacial development

Occurs due to deficiency of midline tissue of the neural plate very early in embryonic development, caused by exposure to 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

FAILURE OF MIGRATION OF NEURAL CREST CELLS

Most craniofacial anomalies are related to neural crest cell origin & migration

Since most structures of face are derived from migrating neural crest cells, interferences with their migration produce facial deformities

TREACHER COLLINS SYNDROME Altered development of

calls derived from neural crest cells has also been implicated in treacher collins syndrome

Characterized by generalized lack of mesenchymal tissue

CRANIOFACIAL MICROSOMIA

Formally called Hemifacial microsomia, is characterized by a lack of development in lateral face areas

Typically there is deformation of external ear and ramus of mandible along with associated soft tissue features

CLEFT LIP & PALATE

Most common congenital defect

Exactely where these clefts appear is determined by the locations at which fusion of various facial processes fail to occur

CROUZON’S SYNDROME Occurs during final stage of facial

development

Arises due to prenatal fusion of the superior and posterior sutures of maxilla alog the wall of the orbit

Characterized by severe under development of mid face & eyes that seem to bulge out from their sockets

GROWTH DISTURBANCE IN FETAL PERIOD

INTRAUTERINE MOLDING

Pressure against the developing face prenatally can lead to distortion of rapidly growing areas

An arm maybe pressed across the face in utero, resulting in severe maxillary deficiency at birth

Fetus head is flexed tightly against the chest in utero, preventing mandible from growing forward normally

Result is an extremely small mandible at birth.

PIERRE ROBIN SYNDROME

Extreme mandibular deficiecy at birth

Reduced volume of oral cavity can lead to respiratory difficulty at birth

1/3rd of patients have a cartilage forming defect along with pierre robin syndrome, known as STICKLER SYNDROME

BIRTH TRAUMA TO MANDIBLE

Use of foreceps to assist in delivery might damage either or both TMJ joints

Heavy pressure in the area of TMJ can lead to internal hemorrhage, loss of tissue and subsequent under development of mandible

PROGRESSIVE DEFORMITIES IN CHILDHOOD

Childhood fractures of Jaws

Muscle Dysfunction

CHILDHOOD FRACTURES OF THE JAWS

Condylar neck is particularly vulnerable & fracture is relatively common

Condylar process tends to regenerate well after early fractures

Early mobilization and resumption of function can work wonders

Problem arises when more severly affected side lags behind in growth or scarring around TMJ restricts translation of condyle

MUSCLE DYSFUNCTION Facial muscles can affect jaw growth in 2

ways :

Formation of bone at points of muscle attachment depends upon muscle activity

Musculature is an important part of total soft tissue matrix whose growth normally carries the jaw downward and forward

Loss of part of musculature is likely to result from damage to motor nerve

Result is under development of that part of face with soft & hard tissue deficiency

Excessive muscle contraction can also restrict growth

Conversely, a major decrease in tonic muscle activity allows the mandible to drop downward

DISTURBANCES ARISING IN ADOLESCENCE

HEMIMANDIBULAR HYPERTROPHY

Unilateral excessive growth of mandible occurs in metabolically normal individuals

Commin in females

Cause is unknown

Proiferation of condylar cartilage is prominent

ACROMEGALY

Release of excessive amounts of growth hormone after the fusion of epiphysial plates

Cause is tumor of anterior pituiary gland resulting in excessive growth of mandible

DISTURBANCES OF DENTAL DEVELOPMENT

Congenitally missing teeth

Malformed & supernumerary teeth

Traumatic dispacement of teeth

CONGENITALLY MISSING TEETH

Results from disturbances during initial stages of formation of a tooth, initiation & proliferation

ANODONTIA : Total absence of teeth

OLIGODONTIA : absence of many but not all teeth ( more than 6 )

HYPODONTIA : absence of only a few teeth

MALFORMED TEETH

Abnormalities in tooth size and shape result from disturbances during the morphodifferentiation stage of development

Most commonly malformed tooth is Maxillary Lateral Incisor

SUPERNUMERARY TEETH Also result from disturbances during

initiation and proliferation stages of dental development

Most commonly appears in Maxillary midline, MESIODENS

Presence of extra tooth disrupts normal occlusal development

Multiple supernumerary teeth are associated with CLEIDOCRANIAL DYSPLASIA

TRAUMATIC DISPLACEMENT OF TEETH

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 root

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