Part 1 - anomalies involving number, size and shape of teeth Flashcards
List the stages in tooth development (8 stages)
Stages of tooth development:
1–4 = Growth (bud, cap, bell)
4–6 = Eruption (apposition and calcification, pre- and post-emergence)
6–8 = Attrition (early and later signs)
- Initation (bud stage) at 6 weeks
- Proliferative (cap stage)
- Morphodifferentiation and histodifferentiation (bell stage)
- Aposition and calcification
- Pre-emergence
- Post-emergence
- Early signs of attrition
- Later signs of attrition
Describe the abnormality which may occur due to disrupted dental lamina formation
Abnormality in number of teeth
Describe the abnormality which may occur due to disrupted morphodifferentiation
Abnormality in tooth size and shape
Describe the abnormality which may occur due to disrupted matrix deposition and mineralisation
Abnormality in tooth structure
Define anodontia
No teeth (very rare)
Define hypodontia (or partial anodontia/oligodontia)
Fewer than normal number of teeth
Define hyperdontia
More than the normal number of teeth
Recall the rate and pattern of hypodontia in the permanent dention
Rate of hypodontia in permanent dentition (2-10%)
Most likely third molars (35% < 1), then maxillary lateral incisors followed by lower second premolars.
Familial tendency
Recall the national tendency of hypodontia
National tendency (Japan / Sweden – L1’s)
Recall the formation of tooth bud for deciduous and permanent teeth
Successional tooth bud:
Tooth germ (bud) of permanent incisors, canines and premolars form as a result of proliferative activity within the dental lamina, lingual to the deciduous tooth germ (ABCDE)
If the developing permanent molars have no deciduous predecessor (i.e. permanent molars 678), their tooth germs originate directly from the dental lamina.
Recall the most common clinical signs of hypodontia (3 points)
- Retained deciduous teeth, well after the date of normal exfoliation
- Spaces
- Infraoccluding deciduous teeth
Recall the X-ray investigations required for suspected hypodontia
Radiographic images required for assessment of missing teeth (e.g. suspected hypodontia) are:-
- OPG X-Ray
- Upper occlusal X-ray
(If no upper occlusal X-rays are available P/A’s will be an alternative – but not the ideal)
Describe this case and name one differential diagnosis
Retained deciduous teeth - ?hypodontia:
Spacing
Infraoccluded deciduous teeth
Missing maxillary lateral incisors
Describe the buccal segment teeth and list 8 possible aetiological factors
The teeth are infraoccluded teeth. Aetiological factors:
- Ankylosis
- Impaction
- Absence of a permanent successor
- Trauma causing damage to Hertwigs epithelial root sheath
- Infection, chemical or thermal irritation
- Failure in bone growth
- Abnormal tongue pressure.
- A genetic aetiology has also been suggested as observed in siblings
Name of differential diagnosis from this radiograph
Hypodontia - more than normal number of teeth missing
What are some clinical considerations of infraocclusion?
- Orthodontic assessment (IOTN = 5s)
- Extractions
- Ankylosed
- Impacted
- Advanced restoration?
Name 3 conditions associated with missing teeth (hypodontia)
- Hereditary ectodermal dysplasia
- Cleft lip and palate
- Down’s syndrome (3rd molars absent 90% cases)
Describe hereditary ectodermal dysplasia and the tissues affected
- Hair (absent / thin and sparse)
- Small, conical teeth (sometimes missing but rarely 100% missing)
- Reduction in/absence of sweat glands (dry smooth skin)
- Decreased skin pigment/colour
- Abnormal fingernails
- Small maxilla (maxillary hypoplasia)
- Poor hearing and vision, decreased tear production
Name this condition
Hereditary ectodermal dysplasia
Name this condition
Hereditary ectodermal dysplasia
Describe the possible inheritance patterns of hereditary ectodermal dysplasia (3 points)
- X-linked recessive
- Autosomal dominant
- Autosomal recessive
Recall the incidence of cleft palate
Boys vs girls (freqency and severity)
Unilateral vs bilateral
Left side vs right side
Europe vs Africa
Boys are more commonly affected than girls 3:2
More boys experience the more severe cleft lip and palate 2:1
75% of clefts unilateral
The left side is more than right side
Europeans 1:750
Less frequent in African populations 1:2000
Recall the aetiology (causes) of cleft lip and palate
Unknown what causes defects – many factors suggested:-
- Genetics (4% increase of CL&P if sibling or parent has CL&P)
- Environment
- Drugs (corticosteroids, phenytoin)
- Infections in pregnancy (e.g. rubella)
- Alcohol consumption/ smoking / some dietary deficiencies (e.g. folic acid / vitamin A)
- Maternal age
List 10 dential issues associated with cleft lip/palate cases
- Can be hypodontia OR in rare cases hyperdontia.
- Presence of natal and neonatal teeth
- Microdontia
- Fused teeth
- Enamel hypoplasia
- Poor periodontal support
- Gemination and dilacerations
- Anterior and posterior cross bite
- Class III tendency
- Spacing and crowding
Which chromosome is most commonly associated with Down’s Syndrome (95% of cases)?
Trisomy 21 (3rd copy of chromosome 21) most common cause (95%).
Recall the incidence of Down’s Syndrome
1 in 700 births but closely associated with the maternal age
(it increases to 1 in 25 of mothers over the age of 45yrs.)
Recall 7 developmental issues leading to oral complications in Down’s Syndrome
- Hypoplasia of the mid-face - an underdeveloped maxilla means that most are Class III – and also have a protrusive tongue
- Poorly developed paranasal sinuses are common due to the small maxilla – and breathing can be difficult.
- Often have an anterior open bite and in many cases the lateral incisors are missing
- Teeth can appear smaller (microdontia) and can also be missing (hypodontia)
- Delayed eruption
- Relatively low incidence dental caries, however often rapidly progressing periodontal disease is associated
- They have a heavily fissured and enlarged tongue
Recall the clinical considerations of hypodontia for a patient with Down’s Syndrome
- Do nothing
- Direct restoration (disguise)
- Orthodontics with or without restoration
- Restoration of spaces with:-
- Implants
- Removable prosthesis (consider types)
- Fixed prosthesis (consider design/types)
Define hyperdontia
More than the normal number of teeth
Recall the incidence hyperdontia
Relatively common (1.5 to 3.5% in UK)
Male : Female ratio = 2:1
Jaws:
- Maxilla – 90% with 98% in pre-maxilla (anterior teeth)
- Mandible 10%
Recall the classification of hyperdontia
Classified by tooth shape:
- Supplemental (resembles normal shape often in line with other teeth in the arch)
- Supernumerary
- Conical (inverted / everted) shape
- Tuberculate shape (like a barrel)
- Odontome - irregular mass (unerupted and can impede eruption of other teeth)
Describe supplemental teeth
- Same structure as normal
- Erupt normally
- Caused by excessive but organised growth of dental lamina
- Usually tagged onto series.
- CAN BE MISSED WHEN EXAMINED!
Describe supernumerary teeth (e.g. shape, eruption)
- Conical or tuberculate or odontome (malformed)
- Can prevent eruption of other teeth
- Inverted or everted
Recall the common patterns of hyperdontia in the maxilla
Most common in maxilla are:-
- Mesiodens
- Paramolars (4th molars)
- Maxillary lateral incisors
Recall the patterns of hyperdonita in the mandible
Common in mandible are:-
- Premolars
- 4th molars (paramolars)
- Extra incisors
What radiograph investigations would you require to investigate hyperdontia
Radiographic examination:-
- OPG
- Upper occlusal X-ray
Similar to hypodontia!
Idfentify an anamoloy in this radiograph
Supplemental ‘third’ molar LLQ
Idenfy this pre-maxillary anomoly
Mesiodens - conical positioned in line of the arch between UR1 and UL1
Define ‘mesiodens’
A supernumerary tooth present in the midline (hence ‘mesio’) between the two central incisors
Describe the radiographs below (left and right)
Left radiograph: mesiodens conical shaped supernumerary teeth
Right radiograph: mesiodens tuberculate supernumerary teeth
Identify this rare syndrome associated with supernumerary teeth
Cleidocranial dysplasia
Also has characteristic:-
- Aplasia or hypoplasia of one or both clavicles
- Delayed ossification of fontanelles
- Short stature
- Increased number of supernumerary teeth
- Delayed eruption
- Dentigerous cysts
- Frontal bossing
Recall the inheritance pattern of cleidocranial dysplasia
Hereditary either autosomal dominant or as a spontaneous mutation.
Which chromosomal defect is associated with cleidocranial dysplasia
Short arm of Chromosome 6
What are the clinical considerations for suplemental and supernumerary teeth?
Supplemental teeth:
- Do nothing
- Plaque traps / aesthetics
Supernumerary teeth:
- Diagnosis crucial! (Often unerupted)
- Affect on rest of dentition i.e. prevention of eruption.
- Possible resorption of adjacent teeth
- Aesthetics
Define microdontia
One or more teeth that are smaller than normal
Can be generalised or localised
Define macrodonita
One or more teeth that are larger than normal
Can be generalised or localised
Recall the differences between true generalized and relative generalized microdontia
True generalised:
- Uncommon – pituitary dwarfism
Relative generalised:
- Jaw size larger than normal, but teeth normal size – so teeth spaced (illusion)
- Spaced due to strong tongue (Down Syndrome)
Describe localized microdontia
Most common presentations of localized microdontia:-
- Lateral incisors (peg laterals)
- Maxillary third molar (not second premolars)
Often both smaller and conical
Recall the differences between true generalized, relative generalized, and regional macrodontia
True generalised
- Uncommon – pituitary gigantism
Relative generalised (illusion)
- Jaw size smaller than normal, but teeth normal size – so teeth crowded (illusion)
Regional macrodontia (illusion)
- Hemifacial hypertrophy
- Segmented odontomaxillary dysplasia
What is rhyzomegaly?
Rhizomegaly (radiculomegaly) – uncommon – roots of teeth are longer than normal (normally mandibular canines)
Type of localised macrodontia
Rare – and should not be confused by the fusion of two teeth.
Identify this condition
Localized macrodontia
Abormality in the shape of a tooth may occur following disruption of which tooth development stage?
Bell stage:
Morphodifferentiation and histodifferentiation
Define this condition
Dilaceration - a sharp bend or angulation involving the root of a tooth
Recall 3 common causes of tooth dilaceration
1. Trauma to a developing tooth
2. Disrupted root formation along a tortuous path, can cause the root to form at an angle to the normal axis of the tooth.
3. Odontogenesis disrupted
Define taurodontism
A molar with an elongated crown and apically placed furcation of the roots, resulting in an enlarged rectangular coronal pulpal chamber.
Identify this condition
Dens invaginatus
Define dens invaginatus
Developmental anomaly with deep enamel-lined pit extending to varying lengths into the underlying dentine, often displacing the pulp, and often altering the root shape.
List 3 types of supernumerary cusps
- Carabellis cusp
- Dens evaginatus
- Talon cusp
Identify this condition
Cusp of carabelli - found on mesiopalatal cusp surface of maxillary first molars (upper 6’s)
Define this condition
Dens evaginatus - a developmental anomaly characterised by a cusp-like supernumerary focal enamel protrusion (spur) on the occlusal or lingual surface of the crown.
Affects mainly premolar teeth
Describe dens evaginatus (4 points)
- Affects mainly premolar teeth
- Abnormal globe-shaped projection of enamel in central groove
- More common in Chinese, Japanese, Filipino and American Indian populations. In Singapore/Malaysia – Leong premolar
- If fractured can expose the pulp.
Define this condition and identify one risk associated with reducing this anomoly
Talon cusp
- Uncommon
- Lingual aspect maxillary lateral (or central) incisors – looks like an eagles talon
- Can extend to incisal edge.
- Deep lingual pits – need restoration/ F-S
- Prominent pulp horn, so easily exposed if reduced
Risk - prominent pulp horn, so easily exposed if reduced!
Recall two types of ‘double’ teeth
Fusion
Gemination
(Both more common in deciduous dentition)
Define fusion of a tooth
A developmental anomaly characterised by abnormally shaped tooth with either a wide crown and one root, or a normal crown with an additional root (or a combination)
Describe tooth fusion
Combination of two adjacent tooth germs united by dentine
Deciduous and permanent
Some hereditary link
Pulp can be separate or fused
If fused one less tooth in the arch
Vulnarable to periodontal disease, caries, aesthetics compromised
Define tooth gemination
A developmental dental anomaly single rooted tooth and unusually wide, partly divided crown or two separate crowns.
Describe tooth gemination
Partial division or twinning of a single tooth germ
Developmental anomaly – perm or deciduous
Microscopically same as fusion, but different developmental pathways.
Define hypercementosis
An apposition of excessive amounts of cementum
Recall 5 causes of hypercementosis (including one systemic disease)
- Aging
- May be caused by inflammation.
- Functionless and unerupted teeth
- Can be in association with resorption
- As a consequence of Paget’s Disease – may produce an irregular mass of cementum with a histological “mosaic” pattern.
Define concrescence
Union of roots caused by confluence of cementum only.
Describe this condition (3 points)
Concrescence
- Type of fusion
- May be as a result of trauma / crowding with interseptal bone loss
- Can occur before OR after tooth eruption.
Describe this anomoly
Ectopic droplets of enamel that primarily occur in the bifurcation or trifurcation areas on roots of molar
- Uncommon
- Radiographically 1-3 mm radiopacities
- May have a central core of dentine
- Treatment avoided as may create root caries, external resorption or pulpitis
What can cause the formation of enamel pearls?
Caused by ameloblasts displaced below the cementoenamel junction
