Abnormalities of tooth number, tooth size, tooth shape

Question 1

Tooth development - revise

Answer 1

Tooth development - revise

Question 2

Tooth development in stages (3)

Answer 2

• Initiation
starts tooth formation and ensures the right number of
teeth in the correct location in the jaws
• Morphodifferentiation
formation of teeth of the correct shape
• Cytodifferentiation
differentiation of cells to produce specific dental tissues

Question 3

Tooth development phases (2)

Answer 3

1. crown formed first

2. then root formation

Question 4

Aetiology of dental anomalies (2)

Answer 4

Genetic

Environmental

Question 5

Environmental factors - Localised (2)

Answer 5

Trauma

Infection

Question 6

Environmental factors - generalised (2)

Answer 6

Infection

Drugs

Question 7

Aetiology of dental anomalies - multifactorial determination (2)

Answer 7

Genetic component - polygenic

Environmental component

Question 8

Occasional major influences on dental anomalies (4)

Answer 8

• Chromosomal anomalies e.g. Down syndrome
(Chromosomal gain, loss)
• Single gene syndromes e.g. Ectodermal dysplasia
• Single genes of localised effect e.g. maxillary lateral incisors
• Environmental insults e.g. rubella, thalidomide, irradiation

Question 9

Cellular response to stimuli (4)

Answer 9

1. Developmental stage
2. Adaptive range
3. Stimulus severity, duration, interaction
4. Individual’s response capacity

Question 10

Anomalies involving tooth number (3)

Answer 10

1. Hypodontia (oligodontia, -6)
2. Supernumerary teeth (hyperdontia)
3. Anodontia

Question 11

Primary hypodontia stats (4)

Answer 11

B most common
Max > mand
F = M
0.1-0.9% Caucasian

Question 12

Secondary hypodontia stats (6)

Answer 12

8 most common (practical)
max = mand
8 > 5 > upper 2 > 4 (Europeans)
F : M 4 : 1
3.5 - 6.5% (9-37%)
mild, moderate, severe (oligo)

Question 13

Aetiology of hypodontia (5)

Answer 13

• Obscure
• Polygenic, plus intrauterine systemic factor
• Increased frequency of 
-low birth weight
-multiple births
-increased maternal age
• Single gene mainly for 2
• PAX9, MSX1

Question 14

Hypodontia occurs with (3)

Answer 14

Down Syndrome
Rubella, thalidomide embryopathy
Cleft lip/ palate

Question 15

Severe hypodontia and microdontia occur with (2)

Answer 15

X-linked hypohidrotic ectodermal dysplasia
AR chondroectodermal dysplasia
(Ellis–van–Creveld Syndrome) i.e. syndromes

Question 16

Supernumerary teeth types (3)

Answer 16

Supplemental - normal series
Accessory - atypical form
Location - e.g. Mesiodens
adjacent to midline suture

Question 17

Most common regions of supernumararies (3)

Answer 17

Premaxilla - most common region
75% not erupt - chance finding
May prevent eruption - e.g. mesiodens

Question 18

Epidemiology of supernumeraries (4)

Answer 18

• 1° - 0.2 - 0.8%
• 2° - 1.5 - 3.5% unilateral
M : F 2:1
• maxilla : mandible 5:1
• 30-50% of primary in premaxilla followed by permanent

Question 19

Associations with supernumerary teeth (3)

Answer 19

• Invaginated teeth
• Palatal clefts
• Syndromes
-cleidocranial dysplasia
-oral-facial-digital syndrome
-Gardner syndrome

Question 20

Tooth size anomalies (2)

Answer 20

1. Microdont

2. Megadont/macrodont ( upper 1, 5 )

Question 21

Microdontia stats (4)

Answer 21

• 1° - uncommon (0.2 - 0.5%)
• 2° - 2.5%
• F > M
• Unusual form, tapering

Question 22

Megadontia / macrodontia (3)

Answer 22

• 1.1% permanent dentition
• Generalised
-pituitary gigantism
-unilateral facial hyperplasia
• Isolated megadont -hereditary gingival hyperplasia
-hypertrichosis

Question 23

Aetiology of megadontia (3)

Answer 23

• Multi-factorial - polygenic + environment
-for microdontia
• Single gene inheritance described
• Associated with Down, Ectodermal dysplasia

Question 24

Tooth form - double teeth - what can go wrong (5)

Answer 24

• fusion, gemination…
• labial segment mand > max (1°)
• incisors frequent (2°)
• 1° > 2° (0.5 - 1.6%)
• F = M

Question 25

Tooth form - double teeth - why? (5)

Answer 25

• Mode of development unclear
• ?Genetic
• Minor notch to almost separate crowns
• plus/ minus common pulp space, root canal
• Concrescences

Question 26

Accessory cusps that exist (3)

Answer 26

• Carabelli (6s)
• Talon (1s + 2s)
• Buccal cusp (paramolar tubercles)
(4s + 5s and molars)

Question 27

Double teeth - what are the implications (2)

Answer 27

• Permanent anomalies follow double primary teeth
-30 - 50% Caucasian
-70% Japanese
• Delayed eruption due to retarded root resorption

Question 28

Invaginated tooth (odontome) stats (4)

Answer 28

• Permanent (1 - 5%), maxillary incisors
• enamel epithelium into dental papilla
• dens in dente, invaginated odontome
• deep cingulum pit ........
• M : F 2 : 1
• Bilateral symmetry (plus supernumeraries)
• Enamel complete
incomplete
• Dentine missing

Question 29

Evaginated tooth (odontome ) stats (4)

Answer 29

• Premolars
• Enamel epithelium or focal hyperplasia of
ectomesenchyme
• Rare in Caucasians
• Enamel, dentine, pulp

Question 30

Root size (4)

Answer 30

1. Large - 3’s
M > F (5 : 1)
2. Small - 1., 2.
dentine dysplasias
• Irradiation - shortened roots
• Racial variation

Question 31

Root form anomalies - taurodontism (4)

Answer 31

Multi-rooted
Crown elongated corono-apically
ACJ constriction (cervix) absent
Syndromes + polygenic inheritance

Question 32

Root form anomalies - accessory roots (4)

Answer 32

Carabelli tubercle
Paramolar tubercle
Enamel pearls
Trauma or genetic

Question 33

Root form anomalies - pyramidal roots (1)

Answer 33

Multi-rooted (fused)

Question 34

Root form anomalies

Answer 34

Taurodontism
Accessory roots
Pyramidal roots