Normal Dental development Flashcards
How many permanent teeth are there?
32
How many primary teeth are there?
20
When do a’s erupt?
6-9 months (lower then upper)
When do b’s erupt?
7-10 months (lower then upper)
When do d’s erupt?
12-16 months (all similar time)
When do c’s erupt?
16-20 months (lower then upper)
When do e’s erupt?
23-30 months (lower then upper)
In which order do the primary dentition erupt?
a -> b -> d -> c -> e
By which age do we have most of our primary teeth?
2.5 y/o
How long after eruption of the primary dentition does root formation complete?
12-18 months
Which teeth erupt at 6-7 y/o?
Lower 1’s and 6’s
Upper 6’s
Upper 1’s
Which teeth erupt at 7-8 y/o?
Lower 2’s
Which teeth erupt at 8-9 y/o?
Upper 2’s
Which teeth erupt at 9-11 y/o?
Lower 3’s
Which teeth erupt at 10-12 y/o?
All 4’s then all 5’s
Which teeth erupt at 11-13 y/o?
All 7’s
Which teeth erupt 17-25 y/o?
All 8’s
In which order do the permanent dentition erupt?
Lower 1's and 6's Upper 6's Upper 1's Lower 2's Upper 2's Lower 3's Upper 3's All 4's All 5's All 7's All 8's
How long after eruption of permanent teeth does root formation complete?
2-3 yrs
What is the leeway space?
The difference between the combined mesiodistal width of the primary canine and molars and the permanent canine and premolars
What is the leeway space in the maxillary arch?
1.5mm
What is the leeway space in the mandibular arch?
2.5mm (due to larger second molar)
What is the occlusion like at birth?
Gum pads occlude distally
Anterior oval opening = suckling
Fleshy labial frenum
What is the occlusion like at 6-10 months?
Maxillary incisors erupt labial to the mandibular
Incisors are more upright than permanent ones
What is the occlusion like at 36 months?
Dentition is complete
Incisors vertical and spaced
Deep overbite
Anthropoid spaces mesial to maxillary canine and distal to mandibular canine
Flush terminal plane
Distal edges of the maxillary and mandibular e are matched
What is occlusion like at 6 years?
Overbite decreases
Spacing of anterior teeth
Attrition of incisors
Eruption of first permanent molar
Mesial migration of primary molars = closure of anthropoid spaces
Permanent molars = class I or half class II relationship
What is the class I relationship?
Where mesiobuccal cusp of U6’s is in line with the fissure of L6’s
What is occlusion like at 7-8 years?
Maxillary central incisors erupt spaced and more proclaimed than primary predecessors
Maxillary lateral incisors are often more distally inclined
Maxillary incisors labial to mandibular
What is occlusion like at 9-12 years?
Primary canines and molars exfoliate, permanent molars drift mesially into leeway space to form class I relationship Maxillary permanent canines should be palatable buccal at 10 y/o unless gone astray (often erupt buccally)
What is occlusion like at 11-12 years?
Incisal spacing reduced by eruption of canines
What is occlusion like at 11-13 years?
All primary teeth have exfoliated
1st permanent molars in class I relationship
2nd permanent molars erupting
What are the different deviations from normal/ideal occlusion (7)?
Anterior open bite Deviation of eruption sequence Attrition Natal/neonatal teeth Ectopic canines Early tooth loss Delayed tooth loss
What is an anterior open bite?
Where front incisors do not touch = vertical gap between them
Due to thumb sucking/ tongue thrust or skeletal
Depends on child (if old tell them to stop sucking thumb)
What is the significance in deviation of eruption sequence?
Dates may vary but sequence should not
Concern if contralateral counterpart not erupted 6 months later (won’t erupt at same time)
What is attrition?
Normal
But significant tooth loss and pulp exposure is not (causes should be addressed)
What are ectopic canines?
Canines in wrong place
- often not palpable buccally at age 10
- can do damage and cause resorption of roots of permanent teeth if in palate etc.)
What are natal/neonatal teeth?
Teeth present at birth or soon after (usually the lower incisors)
Should be removed if cause aspiration risk/ interfering with feeding or traumatising the soft tissue
n.b. usually part of normal sequence but occasionally can be supernumerary teeth
What is the consequence of early tooth loss?
Can delay permanent tooth eruption (gum heals over)
Can accelerate eruption of the successor (if comes out very close to natural tooth eruption)
Cause of space loss and crowding in the permanent arch
What is the consequence of delayed tooth loss?
May be because successor is missing
Common that permanent tooth starts erupting before the primary is lost but if fails to resorb on further eruption can be extracted
Why may an orthodontist be required?
Crowding / spacing in late dentition Increase/reverse overjet Increase or reverse overbite or overbite Crossbite Rotation of teeth Unerupted / ectopic canines
