1. Primary Tooth Morphology

Question 1

Issues with primary eruption (4)

Answer 1

Gingival cysts (Epstein’s Pearls/Bohn’s Nodules)
Congenital Epulis
Natal/neonatal teeth
Eruption cysts

Question 2

When do teeth start to form iul

Answer 2

5wks iul

Question 3

When does hard tissue formation begin

Answer 3

13wks iul

Question 4

Features of maxillary central primary incisor development (4)

Answer 4

Calcification begins 13-16wks iul
Crown complete 1.5mths after birth
Eruption 8-12mths
Root complete 33mths

Question 5

Features of maxillary secondary primary molar development (4)

Answer 5

Hard tissue formation 16-23wks iul
Crown formation complete 11mths after birth
Eruption between 25-33mths
Root complete 47mths

Question 6

Calcification of crowns at birth (6)

Answer 6

1/2 of primary central incisors
1/3 of primary  lateral incisors
Tip of primary canines
1/2 of primary first molar
1/3 of primary second molar
Tip of cusps of first permanent molars

Question 7

Reasons for primary dentition defects (3)

Answer 7

Hereditary
Difficult pregnancy
Complications at birth

Question 8

Possible theories behind tooth eruption (4)

Answer 8

Cellular proliferation at apex of tooth
Localised change in BP/hydrostatic pressure
Metabolic activity within PDL
Resorption of overlying hard tissue

Question 9

Why does resorption of overlying hard tissue (bone/tooth) occur

Answer 9

Due to enzymes in dental follicle (dark halo around unerupted tooth radiographically)

Question 10

Function of dental follicle in active tooth eruption (2)

Answer 10

Follicle activated to initiate osteoclastic activity in the alveolar bone ahead of the tooth and clear a path for tooth eruption
Once crystal bone has been breached the follicle is likely to play a lesser role

Question 11

General rules of primary teeth eruption (4)

Answer 11

Lowers before uppers
Sequence - a, b, d, c, e
Teeth of same series normally erupt within 3mths of contralateral tooth
Usually complete by 2.5/3yrs

Question 12

Eruption dates of primary teeth (5)

Answer 12

Centrals (4-6mths)
Laterals (7-16mths)
First molar (13-19mths)
Canine (16-22mths)
Second molar (15-33mths)

Question 13

Differences between primary and permanent central incisors

Answer 13

Primary smaller in both crown and root proportions

Question 14

Differences between primary and permanent lateral incisors

Answer 14

Primary smaller in both crown and root proportions

Question 15

Differences between primary and permanent canines

Answer 15

Primary smaller in both crown and root proportions

Question 16

Differences between primary and permanent first molars (2)

Answer 16

Wider mesiodistally than permanent premolars

Primary crowns more bulbous

Question 17

Differences between primary and permanent second molars

Answer 17

Primary crowns more bulbous

Question 18

Differences between primary and permanent teeth (7)

Answer 18

Primary whiter in colour
Primary roots narrower, longer and slenderer, tend to flare apically
Large pulp chamber in relation to crown
Pulp horns extend high occlusally
Ribbon shaped root canals
Thinner coronal dentine layer
Relatively thin enamel of consistent depth

Question 19

Definition of Leeway space (2)

Answer 19

Extra mesiodistal space occupied by the primary molars which are wider than the premolars which will replace them
Usually equates to 1.5mm per side on the upper arch and 2.5mm per side in the lower arch

Question 20

Definition of anthropoid or primate space (2)

Answer 20

Spacing medial to upper deciduous canine

Spacing distal to lower deciduous canine

Question 21

Features of mixed dentition stage (2)

Answer 21

Begins form the time of the first permanent tooth erupts until the exfoliation of the last primary tooth
Usually between 6 and 11yrs

Question 22

Sequence of eruption of permanent teeth both arches (2)

Answer 22

6, 1, 2, 4, 5, 3, 7, 8

6, 1, 2, 3, 4, 5, 7, 8

Question 23

Identifying primary central incisor (3)

Answer 23

Root may bend distally
Mesial edge of crown tends to be straighter (distal flare)
Lowers are smaller and more triangular labially

Question 24

Identifying primary lateral incisor (2)

Answer 24

Distal flare on crown

Incisal edge of crown slants up distally

Question 25

Identifying primary canine

Answer 25

Mesial edge tends to be straighter with distal flare soon after ACJ

Question 26

Identifying primary first molar (5)

Answer 26

Unique – not like any other tooth
Prominent mesiobuccal tubercle (obvious palatally and mesially)
Upper more square, lower more rectangular
Straight-ish fissure pattern on uppers
Squashed S-shaped fissure pattern on lowers

Question 27

Identifying primary second molar (5)

Answer 27

Prominent transverse ridge, running from the mesiobuccal cusp to the distopalatal cusp and two buccal
Lower second primary molars have three buccal cusps (like first permanent molar – smallest is the distobuccal)
Two buccal roots, one palatal root
C-shaped mesiobuccal fissure; straight distal fissure
Distopalatal cusp slightly separate due to transverse ridge