Development of the dentition

Question 1

When does the eruption of the deciduous dentition commence and end?

Answer 1

Approximately starts at around 6 months of age, and is completed by around 2.5 to 3 years.

Question 2

What is the characteristic sequence of eruption of the deciduous dentition?

Answer 2

1. Mandibular central incisors erupt first
2. Maxillary central incisors
3. Maxillary lateral incisors
4. Mandibular lateral incisors
5. First deciduous molars
6. Canines
7. Mandibular second molars
8. Maxillary second molars

Question 3

What are the characteristic features of a complete deciduous dentition?

Answer 3

1. Arches are semi-circular in shape
2. Incisors are spaced, upright and associated with a positive overjet and overbite
3. Primate spaces present - mesial to the maxillary canines and distal to the mandibular canines
4. Class I molar and canine relationship
5. The distal edges of the second deciduous molars are flush in the vertical plane

Question 4

Which changes can occur during the deciduous dentition which can affect the way the permanent successors erupt?

Answer 4

1. Occlusal wear of the teeth and more forward growth of the mandible relative to the maxilla - leads to an edge-to-edge incisor relationship and alteration of the molar realtionship
2. Interproximal wear or premature loss of teeth due to caries can also alter the molar relationship
3. Prolonged digit or dummy sucking habit can induce an anterior open bite and posterior crossbites

Question 5

The permanent dentition is established in which 3 phases?

Answer 5

1. Eruption of first molars and incisors
2. Eruption of premolars, canines and second molars
3. Eruption of third molars

Question 6

Which permanent teeth are first to erupt and induce the mixed dentition stage? At what age is this usually seen?

Answer 6

These are the first permanent molars, usually erupting at around 6 years of age.

Question 7

Which permanent teeth erupt after the first permanent molars and at what age?

Answer 7

The first permanent incisors, followed by the second incisors. These usually erupt between the ages of 7-8 years.

Question 8

How is space for the larger permanent incisors acquired?

Answer 8

• Residual spacing between the deciduous incisors
• Permanent incisors erupt more labially to their deciduous predecessors, thus occupying a larger arch perimeter
• Deciduous canines moved distally as the incisors erupt
• Transverse increase in width between the canines

Question 9

Which features associated with maxillary incisor teeth can be present prior to establishing the early permanent dentition?

Answer 9

1. Transient anterior open bite
2. Physiological spacing - ugly duckling stage. In this stage, the central incisors are distally inclined, causing a temporary midline diastema

Cause of the ugly duckling stage is due to the close proximity of the maxillary incisor apices to each other as they are erupting, as well as the lateral pressure coming from the erupting lateral incisors and canines.

Question 10

At what age does the eruption of premolars, canine and second molars occur?

Answer 10

These teeth normally erupt between the ages of 9 and 12

Question 11

What are the general rules of eruption for canines, premolars and second molars?

Answer 11

• In the mandible, the canine erupts ahead of the first premolar, then followed by the second premolar
• In the maxilla, the first premolar erupts first, followed by the second premolar, and finally the canine.

Question 12

Which teeth are most vulnerable for crowding?

Answer 12

Mandibular second premolar
Maxillary canine

Question 13

What is the leeway space?

Answer 13

The leeway space refers to the excess space found between the deciduous canines and molars, which is larger compared to the distance between the permanent canines and premolars.
This space is larger in the mandible, due to the increased size of the permanent second molar.

Question 14

At what age do the second permanent molars erupt?

Answer 14

12 years of age