Development of the Dentition and Occlusion

Question 1

Eruption dates for the permanent dentition

Answer 1

1| 2| 3| 4| 5| 6| 7| 8
7| 8| 11| 10| 11| 6| 12| 18
6| 7| 10| 10| 11| 6| 12| 18

Question 2

Eruption dates for the primary dentition

Answer 2

A| B| C| D| E
10| 11| 19| 16| 24
7| 12| 19| 16| 24

Question 3

How are the neonates gum pads positioned in relation to each other

Answer 3

at birth the lower gym pad lies distal to the upper to a variable degree

Question 4

What is the overbite like in neonates

Answer 4

OB is increased but reduces over the next 4 years until the incisors are edge to edge which can result in marked attrition

Question 5

How can the absence of lower arch crowding be assured in the permanent dentition when looking at the deciduous dentition?

Answer 5

The deciduous dentition is spaced by more than 6mm

Question 6

What determines where the 6s guided into their respective position during eruption?

Answer 6

• If the Es are flush, the 6s are guided into a cusp-to-cusp relationship by the distal surfaces of the Es
• If the lower arch has moved forward, the 6s will erupt into full intercuspation

Question 7

What is leeway space? What are the values for maxillary and mandibular leeway space?

Answer 7

• The combined width of the deciduous C, D, E is greater than that of their permanent successors, the surplus space is called leeway space
• 1-1.5mm in the maxilla
• 2-2.5mm in the mandible

Question 8

What is seen when the upper labial segment erupts?

Answer 8

• Teeth in upper labial segment develop on the palatal aspect of the roots of predecessors
• When the upper 1s erupt, a midline diastema is normally present
• the upper 2s develop in a more palatal position than the 1s
• diastema usually closes as 3s erupt
• The upper labial frenum should no longer be attached to the crest of the alveolar proves but to its labial surface

Question 9

How is space made for the 1s? (3 points)

Answer 9

• 1s are larger than predecessors
• Deciduous incisors are spaced
• Permanent incisors erupt more proclined
• Increase in the inter canine width at this time ~3mm

Question 10

When does the transition to the stepped Class I molar relationship occur?

Answer 10

• When all the deciduous teeth have been replaced

- When the upper 6 moves mesially LESS THAN the lower 6

Question 11

How much does the inter canine width increase by during the primary and then mixed dentition?

Answer 11

• Increase of 1-2mm seen during primary dentition

- Increase of 3mm in mixed dentition which is complete by 9 yrs

Question 12

How does arch width change?

Answer 12

• Increase of 2-3mm between 3-14 yrs

- Determined by measuring distance between lingual cusps of Es or 5s

Question 13

How does arch circumference change?

Answer 13

• Determined by measuring around the buccal cusps and incisor edges of the teeth to the distal aspect of Es or 5s
• Maxilla there is little change
• But in mandibular arch it decreases by 4mm due to leeway space