Abnormalities of Tooth Structure and Development Flashcards
What is Anodontia?
- Total failure of development of a complete dentition - rare
- If the permanent dentition fails to form, the deciduous dentition is retained for many years
- If the teeth survive caries, attrition will eventually destroy the crowns
- Lack of alveolar bone growth may make implant placement difficult
What is isolated oligodontia (hypodontia)
- Failure of development of 1 or 2 teeth is relatively common and often hereditary
- Most frequently: 8s, 5s, U2s
- Absence of 8s only a problem when 6/7s been lost (otherwise only orthodontic problems of alignments and space loss)
- Absence of 2s can be noticeable because large pointed canines erupt beside centrals (almost impossible to prevent loss of space and difficult to make space and disgusting canines is destructive)
What disorders can cause oligodontia or anodontia with systemic effects?
Anhidrotic (hereditary) ectodermal dysplasia
- Major features: hypodontia, peg-shaped or conical teeth, hypotrichosis (scanty hair), anhidrosis (inability to sweat), thin dry skin, koilonychia (spoon nails)
- Severe cases: anodotnia, alveolar process without teeth to support fails to develops and can’t support implants
Down’s syndrome
- There are many rare syndromes in which oligodontia is a feature, but only common one is Down’s
Incidence of supernumerary teeth?
- 0.5% deciduous, 2.5% permanent
- Deciduous supernumeraries are usually followed by permanent successors
- > 90% supernumeraries are in the maxilla
Types of supernumerary
Supernumerary (conical/malformed)
- Mesiodens
- Small torpedo shaped tooth that forms in midline
- Forms early, at same time as permanent incisors
- Often compete with upper centrals for space
- Often erupts or causes midline diastema - Tuberculate
- May have incisor or cusped crown pattern
- Forms later and usually has no root at presentation
- Forms to one side of midline and competes for the space of one central incisor
Supplemental teeth
- Normal morphology
- Commonest = deciduous incisor
What are the effects of supernumerary teeth
Failure of eruption
- Most common reason for failure of U1
- Management involves removing supernumerary and ensuring that there is sufficient space to accommodate unerupted tooth
Displacement or rotation of erupted tooth
- Removal of supernumerary and fixed appliance
Crowding
- Caused by supplemental tooth is treated by removing most poorly formed or displaced tooth
No effect
- Occasionally chance finding on radiograph
- Usually symptomless and can be left in situ
- Remove: if signs of enlargement of follicle with potential cystic formation around crown OR if orthodontic tooth movement is required
Which syndromes are associated with hyperdonita?
- Rare
- Best known association is cleidocranial dysostosis
- Cleft palate is sometimes associated with lateral incisor each side of the cleft
What is the aetiology, incidence, features and associated conditions of microdontia?
Aetiology
- Polygenic or single gene defect
Incidence
- Deciduous 0.2%, permanent 1-2%
Features
- May be one tooth or generalised
- Teeth affected are usually the ones that are most often congenitally absent
- Typically upper 2s (peg laterals), 5s, 8s
- Conical or tapering shape
Associated conditions
- Frequent finding in cleft lip and palate
- Down’s
What is the aetiology, incidence, features and associated conditions of Macrodontia?
Aetiology
- Polygenic or single gene defect
Incidence
- Rare in deciduous, permanent 1.1%
Features
- One or two teeth more common
- Do not confuse with fusion
Associated conditions
- Usually occurs alone
- Rare syndromes (pituitary gigantism, facial hemihypertrophy) associated with large teeth but are proportionate with size of body
What is the aetiology, incidence, features of fusion?
Aetiology
- Unknown but likely to be genetic
Incidence
- Deciduous 1%, permanent 0.1%
Features
- Upper anteriors common
- Often bilateral
- If deciduous is affected, permanent successor usually isnt
- Union between dentine and/or enamel of two or more separate developing teeth
- Often leads to reduced number of teeth although occasionally a normal and supernumerary may be fused
What are the features of tooth gemination?
- Refers to partial development of two teeth from a single tooth bud following incomplete division
- Features
Commonly anterior teeth
Usually one root canal is present
How to tell if double tooth is fused or geminated?
- if double tooth is in place of one tooth, it is probably a result of germ splitting (gemination)
- If replaces two (i.e. another tooth is missing), it is the result of fusion of two germs
- The pulp chambers may be entirely separate, joined int he middle of the tooth or branched, with the pulp chambers of separated crowns sharing a common root canal
What does a concrescence refer to?
- Roots of one or more teeth united by cementum alone after formation oft he crowns
- Does not have nay clinical significance except in cases where extractions are needed
- Affects maxillary 7s and 8s
- Rare
What is the aetiology, incidence, features and associated conditions of dens invaginatus (dens in dente)?
Aetiology
- Unknown, may be familial, commoner in some races
Incidence
- 0.1% deciduous, 3-4% permanent
Features
- Commonest: lateral incisors > centrals > premolars > canines
- Exaggeration of the process of formation of a cingulum pit
- Dentine and enamel-forming tissue invaginate into the pulp to appear radiographically as a tooth within a tooth
- In the full dens invaginatus, the invagination extends the whole length of the tooth, and sometimes through the widely dilated apex
- Often invagination has incomplete walls allowing the exterior to communicate with the pulp and devitalising it
- Alternatively, food debris lodge in the cavity to cause caries which penetrates pulp
Associated conditions
- Commoner in supernumerary lateral incisors
What does dens evaginatus refer to?
Refers to an enamel-covered tubercle projection from the occlusal surface of affected teeth
- Evaginations contain enamel, dentine and pulp
- Affects premolars and molars, usually bilaterally
