Tooth morphology Flashcards
When does deciduous dentition begin to form and complete?
- begin forming ~7weeks in utero
- complete ~3 years old postnatally
What are the types of teeth in primary/ deciduous dentition?
1) Maxillary
- 4 incisors
- 2 canine
- 4 molars
2) Mandibular
- 4 incisors
- 2 canine
- 4 molars
When does the first succedaneous or permanent teeth erupt in the mouth?
- ~3 years old
When does mixture/ transition period begin?
- ~3 years old, when the first succedaneous or permanent teeth emerge.
How long is the mixture/ transition?
- 6 to 12 years
When does the the transition period end?
- 14/15 years old, with exception of 3rd molar, which erupts around 18 to 25 years old.
What are the two types of crown?
1) anatomical crown
- part of the tooth that has enamel surface & situated above the neck of the tooth
- can be observed on extracted tooth
2) clinical crown
- part of the tooth that is visible in the oral cavity
- located above the margin
- maybe shorter or longer than the anatomic crown, depending on the gingival.
What is the neck of the tooth?
- circumferential constricted line that separates the anatomic crown from anatomic root
- line = cements-enamel junction or cervical line
What are the two types of root?
1) anatomic roots
- part of the tooth below the cervical line
- has cementum surface
2) clinical roots
- part of the tooth that is under the gingival and not exposed to the oral cavity.
Which teeth has single roots, two roots & three roots?
1) single roots
- anterior teeth
- mandibular premolars
2) two roots
- maxillary first premolars
- mandibular molars
3) three roots
- maxillary molars
What is enamel?
- inorganic calcified tissue
- brittle
- develops from ectoderm
What is the composition of enamel?
- 95% calcium hydroxyapatite
- 4% water
- 1% enamel matrix
What is dentine?
- hard, but elastic structures
- inorganic calcified tissue
- developed from the dental papilla -> mesoderm
What is the composition of dentine?
- 70% calcium hydroxyapatite
- 12% water’
- 18 organic matter
What are 2 microscopic structures in dentine?
1) Dentine tubules
- S-shaped canals (crown) or straight canals (roots) that run through the dentine.
2) Inter-tubular
- ground substance that binds tubules together.
What is cementum?
- dull yellow surface that covers the dentine of the anatomic root.
Where does the cementum develop from?
- dental sac (mesoderm)
Where is cementum most thin?
- cementoenamel junction
What is the composition of cementum?
- 65% calcium hydroxyapatite
- 23% organic material (collagen fibres)
- 12% water
What is the pulp?
- the cavity in the centre of the crown and roots
- crown portion = pulp chamber
- radicular portion = root canals or canals
- contains soft non calcified tissue and is developed from dental papilla mesoderm.
What are these features:
- pulp horn
- root canals
- apical foramen
1) pulp horns = elongations of the pulp chamber corresponding to the cusps or lobes
2) Root canals = extended to spices of the roots through apical foramen
3) apical foramen = hole at the bottom of the tooth that allows entry of blood vessels.
What is another name for the cementoenamel junction?
- cervical line
What is the equation for deciduous dentition?
I(2/2) C(1/1) M(2/2) = 10
- the equation refers to one quadrant, but there are 10 teeth in each arch.
What is the equation of the permanent dentition?
I(2/2) C(1/1) P(2/2) M(3/3) = 16
