Development of the dentition Flashcards
List the ideal features of the primary dentition
- Spacing of incisors
- Anthropoid spaces
- Midline diastema
- Upper and lower Es are in the same terminal plane
- Lower incisors occlude on cingulum of upper incisors
What is the ideal incisor relationship in the primary dentition?
- Deep overbite at first which then reduces over 3-4 years
- At 5 there is edge to edge occlusion which may cause marked dentition
Why is the primary incisor occlusion initially a deep overbite?
At birth, the lower gum pad is slightly distal to the upper gum pad
What can change the incisor relationship in the primary dentition?
- Digit sucking resulting in an asymmetrical increased overbite and overjet
What is the ideal amount of spacing of incisors in the primary dentition?
> 6mm spacing of primary incisors to allow permanent incisors to align (Leighton)
What happens if there is crowding in the primary dentition?
The permanent dentition will be severely crowded
What is the ideal E relationship in the primary dentition? Why?
Flush terminal plane - as it will result in a class I occlusion in the permanent dentition
What happens if there is a mesial step in the primary E relationship?
Is this common?
- Can lead to class III or class I (HOWEVER THIS IS RARE AS THE MANDIBLE IS LAGGING BEHIND MAXILLA)
What happens if there is a distal step in the primary E relationship?
Class II molar relationship
Where are the anthropoid spaces located?
Mesial to the upper C
Distal to the lower C
List some things that can go wrong in the primary dentition
- Incisor protrusion from digit sucking habit
- Posterior crossbite due to sucking habits
- Abnormalities in tooth number - supernumeraries or premature loss of primary tooth
- Tooth to tissue ratio causing predilection for crowding
- Anteroposterior discrepancy
What are the 3 stages of the permanent dentition development?
Stage 1 (age 6-8) - eruption of the 6s and incisors
Stage 2 (age 11-12) - eruption of canines, premolars and 7s
Stage 3 (18-25) - eruption of 8s
Where does extra space come from when the permanent incisors erupt?
- Spacing in the primary dentition
- Permanent incisors are proclined (gives 1-2mm extra space)
- Increase in intercanine width
- Leeway space
How much space is provided from the increase in intercanine width in the maxilla and mandible
Maxilla - 3mm
Mandible - 2.5mm
Where is extra space provided in the mandible for the permanent teeth?
- Transitory lower incisor crowding from ages 8-9
- Distal shift of lower 3 when the D is exfoliated giving 1mm of space
What issues can occur at stage I in permanent dentition development?
- Premature loss of E causing drift of the 6 causing impaction of the 5s
- Missing central (impaction)
- Missing laterals - hypodontia
- Abnormal form (peg lats, microdontia)
- Loss of permanent teeth from trauma
- Crossbites
If an E is retained but the 5 is present radiographically, what should be done?
Leave it, the 6 is present therefore the E will exfoliate with eruption of the 6
If >6 months - then extract the E
What is the management of a patient in the mixed dentition who is digit sucking?
Needs to be stopped asap as there is still chance for spontaneous improvement in this stage
How does leeway space arise?
The combined width of the primary canines, first molar and second molar (CDE) is more than the width of the permanent successors
What is leeway space?
Surplus of space provided for the permanent teeth to erupt in alignment
What is the width difference between lower E and lower 5s
Lower E is 2mm larger than lower 5
What is the space difference between lower D and lower 4
Lower D is 0.5mm larger than lower 4
What is the space difference between upper E and upper 5
Upper E is 1.5mm larger than upper 5
What is the space difference between upper D and upper 4
Upper D slightly larger than upper 4
