2.2a teeth

Question 1

what are the 2 set of teeth of humans in their lifetime

Answer 1

deciduous and permanent teeth

Question 2

what does teeth development start with

Answer 2

the focal thickening of the oral epithelium

Question 3

give the full process of teeth development (11)

Answer 3

1. There is a distinct thickening of the oral epithelium form on medial aspect labioginigival band - the dental lamina
2. Mesenchyme underlying each of these laminae condenses
3. Dental lamina invaginates to form the dental bud
4. The dental bud expands and branches to form an enamel organ to surround NCC-derived dental papilla (NCC = neural crest cells)
5. Dental papilla enamel organ complex will form the deciduous tooth
6. The primordium of permanent tooth buds off dental lamina as a small mass of cells
7. Budding off of permanent tooth primordium continues
8. Inner layer of enamel organ (derived from epithelium) differentiates to form ameloblast (makes enamel)
9. Cells in dental papilla (neural crest cell derived) differentiate to form odontoblasts (makes dentine)
10. Dentine surrounds pulp to produce tooth root
11. Later, epithelial cells near distal part of the tooth (cementoblasts) secrete cementum around tooth root

Question 4

what determines the tooth types

Answer 4

mesenchyme

Question 5

what properties does the mesenchyme possess

Answer 5

labile differentiation properties but stable morphogenetic properties

Question 6

does root complete formation before or after eruption of temporary tooth

Answer 6

after

Question 7

process of replacement of temporary teeth by the permanent teeth

Answer 7

1. Migrates into socket of temporary tooth
2. Permanent tooth on lingual side of temporary tooth
3. Growth of permanent tooth, temporary tooth increases pressure
4. Resorption of temporary tooth root leads to loosening
5. Temporary tooth shed and replaced by permanent tooth
6. Premature loss of temporary tooth leads to disorganized permanent teeth

Question 8

how does teeth erupt (by what forces)

Answer 8

• Hydrostatic pressure at tip of developing tooth root to push the tooth gradually into the mouth
• Metabolic activity in periodontal ligament to provide eruptive force pulling tooth upward

Question 9

properties of enamel

Answer 9

• Only in crown
• No repair possible

○ Ameloblasts lost on eruption, hence no repair

• Hardest biological material
• Mineralization requires:
  Enamelins and amelogenins

Question 10

properties of dentine

Answer 10

• Major part of tooth
• Produced continually by odontoblasts
  ○ Rate increases during repair
• Innervated
  ○ Contains nerve endings sensitive to temperature, pain, pressure
• Mineralized matrix
• Odontoblasts recede from newly formed surfaces
  ○ As dentine is produced, odontoblasts move away from the newly formed dentine, leaving the mineralized dentine behind
• Like bones, but acellular

Question 11

properties of gingiva

Answer 11

Adhere to tooth at interface between crown and root

Question 12

properties of pulp cavity

Answer 12

• Nerve and blood supply

○ Superior and inferior alveolar (arteries, nerves and veins)

○ At least one branch in each major elevation of the crown

Question 13

properties of alveolus and PDL

Answer 13

• The alveolus is the bony socket that houses the tooth root. The bone surrounding the alveolus is lined by compact bone
• PL suspends tooth in its alveolar socket
• Lined by compact bone
• PDL have fibres bridge alveolar bone and cementum

Question 14

properties of cementum

Answer 14

• Surrounds define of the root
• Mostly acellular
• Not readily resorbed
• Contains type 1 collagen