Download - Etiology of malocclusion
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ETIOLOGY OF
MALOCCLUSIONPrepared by : Dr. Ali Waqar
FCPS – II Resident in OrthodonticsUCMD UOL
Supervised by : Dr. Saad AsadAssociate Professor of Orthodontics
UCMD UOL
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DEFINITION Malocclusion is an incorrect
relationship of Maxilla & Mandible
Distortion of normal development
Complex interaction of multiple factors that influence growth & development
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CAUSES Malocclusion is said to occur due to the
following factors acting alone or in combination.
Specific causes of malocclusion Genetic Influences Environmental Factors
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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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
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PROGRESSIVE DEFORMITIES IN CHILDHOOD
Childhood fractures of Jaws
Muscle Dysfunction
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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
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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
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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
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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
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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
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DISTURBANCES OF DENTAL DEVELOPMENT
Congenitally missing teeth
Malformed & supernumerary teeth
Traumatic dispacement of teeth
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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
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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
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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
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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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