9. Dental Anomalies Flashcards
The 4 types of Amelogenesis Imperfecta are..
- Hypoplastic type
- Hypomaturation type
- Hypocalcification type (more common than hypoplastic type)
- Hypomaturation with Taurodontism
Which genes mutate in AI?
- Amelogenin (AMELX)
- Enamelin (ENAM)
- Enamelysin (MMP20)
- Kallikrein (KLK4)
- no need to be able to regurgitate but must be able to have recollection
How is AI transmitted?
- due to genetic anomalies arising from mutations
- in autosomal dom or rec manner
- or X-linked pattern
- not related to any time/period of enamel development or any clinically demonstrable alteration in other tissues
- affects all/almost all teeth in both dentitions
Clinical features of hypomaturation type AI:
Appearance:
1. Enamel of normal thickness
2. Motteld appearance (spots/smears)
3. Softer than normal, as dense as dentine
=> may easily break away from crown
Colour:
- enamel appears clear/cloudy white/yellow/brown
- can have snow-capped appearance
Radiographic features of hypomaturation type AI:
Enamel n dentine of same radiolucency
Clinical features of hypoplastic type AI
Appearance:
- reduced thickness => no contact between adj teeth
- may have abnormal surface (rough/smooth, pitted/glossy)
- undersized crowns w roughly square shape
- attrition of low, not fully formed cusp tips => flat occlusal surface of posterior teeth w low/absent cusps
Radiographic features of hypoplastic type AI:
- anterior teeth have ‘picket fence’ appearance
- normal density BUT pitted enamel appears as localised areas of mottled density
Key stuff: thin layer of enamel, absence of interprox contacts, square shape & ‘picket fence’ appearance
Clinical features of hypocalcification type AI:
Appearance of enamel
- normal thickness
- softer than normal, poorly mineralised, less than dentine => fractured away shortly after funciton
- enamel & dentine wear down rapidly => worn down tooth
- explorer point under pressure can penetrate enamel
- crowns of normal size & shape upon eruption
However,
- caries in worn teeth is unusual
Radiographic features of hypocalcification type AI:
- enamel more radiolucent than dentine
- w advanced attrition/abrasion, obliteration of pulp chambers may complicate recognition of image
Note: reduced radioopacity of enamel & abrasion of crowns
How is DI inherited?
- autosomal dominant
- equal freq in both sexes
- affects both dentitions
What are the types of DI?
Type I
- associated w osteogenesis imperfecta
- mutation of genes involved in collagen synthesis
Type II
- similar to type I but only affects dentine, no skeletal defects
- mutation of genes DSP & DSPP
Type III
- mutation of genes DSP & DSPP
Which genes are mutated in type I DI?
- Collagen type I, alpha 1 (COL1A1)
- Collagen type I, alpha 2 (COL1A2)
What are the genes mutated in type II & III DI?
- Dentin sialoprotein (DSP)
- Dentin sialophosphoprotein (DSPP)
Clinical features of DI:
- enamel fractures easily => crowns wear rapidly => exposed dentine stained dark brown/black
- may observe anterior open bite (AOB)
Tooth colour:
- high degree of amber-like translucency
- variable colour, yellow to blue-grey (changes when observed under transmitted/reflected light
Radiographic features of DI:
- Crowns normal in size
- Bulbous appearance of crown, due to constriction at cervical portion
- Roots short & slender
- Pulp chambers:
- appear large early in development
- partial/complete obliteration by deposition of dentine => root canals absent/threadlike - Microscopic communicationi btw residual pulp & oral cavity => areas of rarefying osteitis, in seemingly sound teeth & w/o pulp involvement (but more freq in DD)
- Normal bone architexture in max & mand
TLDR: bulbous crowns, constriction at CEJ, short roots, decreased size of pulp chamber & root canals
Type I DI patients display.. (systemically)
Due to osteogenesis imperfecta
1. Blue sclera
2. Skeletal deformaties
3. Workman bones (bowing of legs)
4. Progressive osteopenia (loss of bone mineral density)
How is DD transmitted?
- autosomal dominant
- less frequent than DI
Clinical features of type I (radicular) DD:
- normal shape & colour in both dentitions
- occasional slight bluish brown transparency
- teeth misaligned in arch, drifting/spontaneous exfoliation w little/no trauma
Radiographic features of type I (radicular) DD:
TLDR: short roots, obliterated pulp chambers & root canals (half-moon shaped chambers), PA rarefying osteitis
- roots short/abnormally shaped/absent
-> Molar roots present in shallow “W” shape
-> primary dentition: thin spicules - pulp chambers & root canals COMPLETELY obliterated B4 eruption
- microscopic commuincations btw residual pulp & oral cavity => areas of rarefying osteitis, seen w non-carious teeth (more freq in DD than in DI)
** the only type of AI, DI & DD that we need to be able to via radiograph!!
Difference between hypodontia and oligodontia.
Hypodontia: missing less than 6 teeth
Oligodontia: missing more than 6 teeth
Which teeth are commonly missing in hypodontia cases?
More common in permanent dentition
- wisdom teeth
- maxillary laterals
- mandibular 2nd premolars
- mandibular central incisors
- rmb theres a rs between missing teeth and microdonts (laterals and wisdom commonly)
What are mesiodens?
- extra tooth located between 2 central incisors
Common cases of hyperdontia:
- mesiodens
- behind wisdom tooth e.g. #19
- mandibular premolar region
Microdontia occurs most commonly in..
- maxillary laterals => peg shaped deformity
- maxillary wisdoms => max 3M microdontia
