Mixed Dentition

Question 1

Dental Arch measurements

4

Answer 1

Arch length
Arch width
Arch perimeter
Intercanine distance

Question 2

Arch length (depth)

Answer 2

Measured at the midline to a tangent touching the distal surfaces of the
second primary molars (Riolo 157)

Question 3

1.Arch length changes (2)

Answer 3

• Lose arch length in the lower arch (lower
incisor eruption)
• Gain arch length in the upper arch (upper
incisor eruption)

Question 4

Arch width (2)

Answer 4

• Measured between the cups of the canines in the
transverse plane
• Measured between the occlusal grooves of the
second primary molars

Question 5

2. Arch width changes (2)

Answer 5

No significant changes from primary to mixed
dentition in the lower arch
Some significant changes from primary to mixed
dentition in the lower arch

Question 6

Arch perimeter

Answer 6

• Measured from the distal surface of the second
primary molar around the arch over the contact
points and incisal edges in a smoothed curve (Riolo p
157)

Question 7

mixed dentition period

Answer 7

• From 6 to 13 years old, the primary dentition is replaced by the
permanent dentition

Question 8

• The permanent first molars erupt to the

Answer 8

distal of the primary dentition

no primary tooth replacement

Question 9

•Primary root resorption to Permanent tooth eruption (4)

Answer 9

Crown of the permanent tooth is formed
Then the root develops and the primary tooth starts
to resorb
When the root is totally resorbed, the primary tooth
exfoliates and the permanent tooth erupts
The permanent tooth will stop erupting when it
reaches the occlusal plane

Question 10

Tooth replacement
Variability in
(4)

Answer 10

Sequence
Timing
Position
Numbers

Question 11

Congenitally missing teeth: rare —% of population

Answer 11

3-5

Question 12

Congenitally missing teeth: rare 3-5% of population (3)

Answer 12

Maxillary lateral incisor: most frequent
Mandibular second premolar
Maxillary central incisor

Question 13

Missing primary tooth =

Answer 13

no permanent successor (dd. Delayed

eruption

Question 14

Example: Ankylosis (2)

Answer 14

Refers to the fusion of the root of a primary tooth to
the underlying bone, which stops the tooth from
erupting
May be due to localized defect during eruption
process in periodontal ligament whereby osseous

Question 15

Ankylosis

Becomes more evident in

Answer 15

mixed
dentition where occlusal level of ankylosed tooth
does not keep up with vertical level of adjacent
teeth (dentoalveolar development keeps the
teeth in contact during growth)

Question 16

Ankylosis

tx

Answer 16

Treatment is usually to simply monitor these teeth (50%
self correction)
If they fail to exfoliate, it may be advisable to extract the
tooth to avoid damages to the permanent dentition

Question 17

Conclusions

4

Answer 17

• The mixed dentition is a very important period in dental development
• Time when succedenous teeth erupt and replace the primary dentition
• High variability among patients
• Understanding the events taking place allow for guided and appropriate
treatments.