Dental Anomalies I

Question 1

How are teeth formed?

Answer 1

Ectoderm of facial process and mesenchymal cells from neural crest lead to differentiation, forming ameloblasts and odontoblasts
Advanced specialisation of cells

Question 2

Stages of tooth development?

Answer 2

Initiation
Morphodifferentiation
Cytodifferentiation

1. Crown formed 1st
2. Then root formation

Question 3

What occurs in tooth initiation?

Answer 3

Starts tooth formation and ensures the right number of teeth in the correct location in the jaws

Question 4

What occurs in tooth morphodifferentiation?

Answer 4

Formation of teeth of the correct shape

Question 5

What occurs in tooth cytodifferentiation?

Answer 5

Differentiation of cells to produce specific dental tissues

Question 6

Types of dental anomalies impact what?

Answer 6

Structure
Shape/form
Size
Number

Question 7

Aetiology of dental anomalies?

Answer 7

Genetic

• Genetic component - polygenic and environmental component
• Chromosomal anomalies e.g. down syndrome
• Single gene syndromes =e.g. ectodermal dysplasia
• Single genes of localised effect - maxillary lateral incisors
• Environmental insults e.g. rubella, irradiation

Environmental

• Localised (trauma, infec)
• Generalised (infec, drugs)

Question 8

Cellular response to stimuli

Answer 8

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

Question 9

Anomalies regarding tooth number?

Answer 9

1. Hypodontia (oligodontia = absence of more than 6 teeth primary or 2ndry)
2. Supernumerary teeth (hyperdontia)
3. Anodontia

Question 10

Hypodontia features for primary teeth?

Answer 10

B more common
Maxillary > mandibular
F = M
0.1 - 0.9% caucasian

Question 11

Hypodontia features for secondary teeth?

Answer 11

8 most common
Max = mandibular
8>5>2>4 
F:M 4:1
3.5-6.5%
Mild, moderate, severe (oligo)

Question 12

Aetiology of hypodontia?

Answer 12

Obscure
Polygenic, plus intrauterine systemic factor
Frequency increased with low birth weight, multiple births, increased maternal age
Single gene mainly for 2
PAX9, MSX1

Question 13

What can hypodontia occur with?

Answer 13

Down syndrome

Rubella, thaliodomide embryopathy

Question 14

What is severe hypodontia and microdontia linked with?

Answer 14

X linked hypohidrotic ectodermal dysplasia
AR chondroectodermal dysplasia
Cleft lip/palate

Question 15

Types of supernumerary teeth?

Answer 15

Supplemental - normal series
Accessory - atypical form
Location - mesiodens (adjacent to midline structure)

Question 16

What percentage of supernumerary teeth erupt?

Answer 16

25%

Question 17

Where are supernumerary teeth most common?

Answer 17

Premaxilla

Question 18

What can supernumerary teeth do?

Answer 18

Prevent eruption

Question 19

Supernumerary teeth prevalence - primary and permanent?

Answer 19

Primary 0.2-0.8%
Permanent 1.5 - 3.5% unilateral
M:F 2:1
Maxilla:mandible 5:1

Question 20

If someone has a primary supernumerary tooth premaxilla, how likely is it to occur in the permanent dentition?

Answer 20

30-50% of primary in premaxilla followed by permanent

Question 21

Implications/associations of supernumerary teeth?

Answer 21

Invaginated teeth
Palatal clefts
Syndromes:
- Cleidocranial dysplasia
- Oral-facial-digital syndrome
- Gardner syndrome

Question 22

Who has smaller teeth?

Answer 22

Females have smaller teeth than males

Question 23

Mirodontia and megadontia - define?

Answer 23

Micro = smaller teeth
Megadontia = larger teeth

Question 24

Tooth size anomalies?

Answer 24

Microdont
Megadont/macrodont (1, 5)

Whole tooth, crown or root
Isolated teeth, multiple, uni or bi-lateral

Question 25

Microdontia features?

Answer 25

Unusual form, tapering
Primary teeth - uncommon 0.2-0.5%
Permanent 2.5%
F>M

Question 26

Megadontia/macrodontia

Answer 26

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

Question 27

Aetiology of megadontia/macrodontia?

Answer 27

Mutlifactorial - polygenic and environment

For microdontia - single gene inheritance described, associated with Down, Ectodermal dysplasia

Question 28

What can go wrong with tooth form?

Answer 28

Double teeth - fusion, gemination
Labial segment mand>max (primary)
1>2 (0.5-1.6%)
F = M

Question 29

Why do abnormalities occur in tooth form?

Answer 29

Mode of development unclear
Genetic?
Minor notch to almost separate crowns
Common pulp space, root canal 
Concrescences = fusion of 2 teeth due to excess cementum, occurs after tooth development

Question 30

Chance of permanent anomalies in tooth form following double primary teeth?

Answer 30

30-50% caucasian

70% japanese

Question 31

What can primary double teeth cause?

Answer 31

Delayed eruption due to retarded root resorption

Question 32

Tooth form anomalies - accessory cusp features?

Answer 32

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

Question 33

Tooth form anomalies - invaginated tooth (odontome) features?

Answer 33

• 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 or incomplete
Dentine missing

Question 34

Tooth form anomalies - evaginated tooth (odontome) features?

Answer 34

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

Question 35

Tooth form anomalies - root size features?

Answer 35

1. Large - 3’s
   M > F (5 : 1)
2. Small - primary and permanent, dentine dysplasias

Irradiation - shortened roots
Racial variation

Question 36

Tooth form anomalies - what is taurodontism?

Answer 36

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

Question 37

Tooth form anomalies - accessory roots?

Answer 37

Carabelli tubercle
Paramolar tubercle
Enamel pearls
Trauma or genetic

Question 38

Tooth form anomalies - pyramidal roots?

Answer 38

Mutlirooted (fused)