developmental abnormalities
TRANSCRIPT
• There are many developmental abnormalities that can affect the teeth and facial skeleton. In most cases, clinicians need little more than to be able to recognize these abnormalities
Classification of developmental abnormalities
1-Anomalies of the teeth
2-Skeletal anomalies.
Missing teeth
• Localized anodontia or hypodontia — usually third molars, upper lateral incisors or second premolars.
• Anodontia or hypodontia associated with
systemic disease — e.g. Down's syndrome,
ectodermal dysplasia.
Additional teeth (hyperdontia)
• Localized hyperdontia — Supernumerary teeth
— Supplemental teeth
• Hyperdontia associated with specific
syndromes, e.g. cleidocranial dysplasia,
Gardener's syndrome.
Genetic defects
• Amelogenesis imperfecta — Hypoplastic type
— Hypocalcified type
— Hypomature type
• Dentinogenesis imperfecta
• Shell teeth
• Regional odontodysplasia (ghost teeth)
• Dentinal dysplasia (rootless teeth).
Acquired defects
• Turner teeth — enamel defects caused by infection from overlying deciduous predecessor • Congenital syphilis — enamel hypoplastic and altered in shape (see below) • Severe childhood fevers, e.g. measles — linear enamel defects Fluorosis — discolouration or pitting of the enamel • Discolouration — e.g. tetracycline staining.
3-Abnormalities in size
• Macrodontia — large teeth
• Microdontia — small teeth, including
rudimentary teeth.
4-Abnormalities in shape
• Anomalies affecting -whole teeth
• Anomalies affecting the crowns
• Anomalies affecting roots andlor pulp canals
Anomalies affecting -whole teeth
• Fusion — two teeth joined together from the fusion of adjacent tooth germs • Gemination — two teeth joined together but arising from a single tooth germ • Concrescence — two teeth joined together by cementum • Dens-in-dente (invaginated odontome) — in folding of the outer surface of a tooth into the interior usually in the cingulum pit region of maxillary lateral incisors.
Anomalies affecting the crowns
• Extra cusps • Congenital syphilis — Hutchinson 's incisors — crowns small, screwdriver or barrel-shaped, and often notched — Moon's/mulberry molars — dome-shaped or modular • Tapering pointed incisors — ectodermal dysplasia.
Anomalies affecting roots and or pulp canals
• Number — additional roots, e.g. two-rooted incisors, three-rooted premolars or four-rooted molars • Morphology, including: — Bifid roots — Excessively curved roots — Dilaceration — sharp bend in the root direction — Taurodontism — short, stumpy roots and longitudinally enlarged pulp chambers Pulp stones — localized or associated with specific syndromes, e.g. Ehlers-Danlos (floppy joint syndrome).
Odontomes
• Enameloma/enamel pearl • Cementoma (see fibro-cemento-osseousmesions in — Benign cementoblastoma (true cementoma) — Periapical cemento-osseous dysplasia — Focal cemento-osseous dysplasia — Florid cemento-osseous dysplasia (gigantiform cementoma) • Composite — Compound odontome — made up of one or more small tooth-like denticles — Complex odontome — complex mass of disorganized dental tissue.
Delayed eruption
• Local causes — Loss of space — Abnormal crypt position — especially 8/8 and 3/3 — Overcrowding — Additional teeth — Retention of deciduous predecessor — Dentigerous and eruption cysts • Systemic causes — Metabolic diseases, e.g. cretinism and rickets — Developmental disturbances, e.g. cleidocranial dysplasia — Hereditary conditions, e.g. gingival fibromatosis and cherubism.
Other positional anomalies
• Transposition two teeth occupying exchanged positions • Wandering teeth, movement of unerupted teeth for no apparent reason (distal drift) • Submersion, second deciduous molars apparently descend into the jaws. Since these teeth do not in fact submerge, but rather remain in their original position while the adjacent Other positional anomalies • Transposition, two teeth occupying exchanged positions • Wandering teeth, movement of unerupted teeth for no apparent reason (distal drift) • Submersion, second deciduous molars apparently descend into the jaws. Since these teeth do not in fact submerge, but rather remain in their original position while the adjacent
Skeletal anomalies
• Abnormalities of the mandible and/or maxilla
• Other rare developmental diseases and
syndromes.
Abnormalities of the mandible or maxilla
• Micrognathia
• Macrognathia (prognathism)
• Other mandibular anomalies
Micrognathia
• True micrognathia — usually caused by bilateral hypoplasia of the jaw or agenesis of the condyles
• Acquired micrognathia — usually caused by unilateral early ankylosis of the temporomandibular joint.
Macrognathia (prognathism)
• Genetic
• Relative prognathism — mandibular/maxillary
disparity
• Acquired, e.g. acromegaly owing to excessive
growth hormone from a pituitary tumour.
Other mandibular anomalies
• Condylar hypoplasia
• Condylar hyperplasia
• Bifid condyle
• Coronoid hyperplasia.
Cleft lip and palate
• Cleft lip — Unilateral, with or without alveolar ridge — Bilateral, with or without alveolar ridge • Cleft palate — Bifid uvula — Soft palate only — Soft and hard palate • Clefts of lip and palate (combined defects) — Unilateral (left or right) — Cleft palate with bilateral cleft lip.
Localized bone defects
• Exostoses
— Torus palatinus
— Torus mandibularis
• Idiopathic bone cavities (see Ch. 25)
— Stafne's bone cavity.
Other rare developmental diseases and syndromes
• Cleidocranial dysplasia
• Gorlin's syndrome (nevoid basal cell
carcinoma syndrome)
• Eagle syndrome
• Crouzon syndrome (craniofacial dysostosis)
• Apert syndrome
• Mandibular facial dysostosis (Treacher Collins
syndrome).
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