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Anatomy of Primary Teeth
Steven Chussid D.D.S.
Lecture Overview
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Primary Dentition
General Morphological considerations
Implications of Primary tooth morphology
Primary Dentition
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20 primary teeth as compared to 32
permanent teeth
No premolars in the primary dentition
The primary molars are replaced by the
premolars
The permanent molars erupt distal to the
primary second molars
Eruption Patterns of Primary
Teeth
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Sequence more
important than timing
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Symmetrical pattern
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Mandibular teeth erupt
first
Approximate
Eruption Schedule
“7+4” Guideline
7 Months = First Tooth Erupts
11 Months = 4 Erupted Teeth
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7 months + 4 = 11
months
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0 teeth + 4 = 4 teeth
15 Months = 8 Erupted Teeth
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11 months + 4 = 15
months
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4 teeth + 4 = 8 teeth
19 Months = 12 Erupted Teeth
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15 months + 4 = 19
months
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8 teeth + 4 = 12 teeth
23 Months = 16 Erupted Teeth
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19 months + 4 = 23
months
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12 teeth + 4 = 16 teeth
27 Months = 20 Erupted Teeth
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23 months + 4 = 27
months
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16 teeth + 4 = 20 teeth
General Morphologic
considerations
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Crown
Pulp
Root
Crown of Primary Teeth
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Shorter
Narrower occlusal table
Constricted in the cervical
portion
Thinner enamel and
dentin layers
Enamel rods in the
cervical area directed
occlusally
Broad and flat contacts
Color is usually lighter
Crowns of Primary Teeth
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Prominent mesio-buccal
cervical bulge seen in
primary molars
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Incisors have no
developmental grooves
or mammelons
Primary Crown Anatomy
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Mandibular Central
Incisors
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Symmetrically flat when
viewed from buccal
Crown about 1/3 length of
root
Cingulum present on
lingual surface
Mandibular Lateral
Incisor
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Similar form to central
Usually longer
Incisal edge slopes toward
distal and DI angle more
rounded
Primary Crown Anatomy
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Maxillary Central Incisor
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Only tooth that has a
greater mesiodistal width
than height
Prominent cingulum
Incisal edge straight
Maxillary Lateral Incisor
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Similar form to cental
Smaller and DI angle
rounded
Primary Crown Anatomy
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Maxillary Canine
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Crown constricted at
cervical region
Well developed, sharp
cusp
Root is long, more than 2X
crown
Mandibular Canine
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Similar form to maxillary
Crown shorter and
narrower labiolingually
Primary Crown Anatomy
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Maxillary First Molar
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Unique appearance
Three cusps-MB, DB and
Lingual
Prominent MB cervical
bulge
Mandibular First Molar
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Also unique in appearance
Four cusps-MB, DB, ML
and DL
Prominent MB cervical
bulge
Transverse ridge
Primary Crown Anatomy
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Maxillary 2nd Molar
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Resembles permanent
maxillary first molar
but smaller
Mandibular 2nd
Molar
Resembles permanent
mandibular first molar
but smaller
Pulps of Primary Teeth
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Relatively larger
Pulp horns are closer to
the outer surface
Great variation in size
and location
Mesial pulp horn is higher
Pulp chamber shallow
Form of the pulp follows
the external anatomy
Usually a pulp horn under
each cusp
Pulpal Anatomy
Roots of Primary Teeth
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Roots of anterior teeth
are narrower mesiodistally
Posterior teeth have
longer and more slender
roots in relation to crown
size
Molar roots flare more as
they approach the apex
Apical foramina may be
larger and accessory
canals often larger and
more numerous
Implications of Primary tooth
morphology
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The progress of caries is much faster in
the primary dentition, so incipient lesions
should be restored sooner than later!
 Thinner
enamel and dentin
 Mesial pulp horn higher
Procedures in Primary Teeth
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Restorative Dentistry
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Enamel is thinner, therefore
modifications are necessary in the
cavity prep
Broad contacts need to be restored
Beware of the mesio-buccal pulp horn
May need to do SSC if both proximal
surfaces involved
Preserve the buccal cervical ridge to
obtain mechanical retention for SSC
Procedures in Primary Teeth
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Surgical Procedures
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Conical anterior roots
facilitate easy removal
Flared roots of the molars
- use caution as premolar
buds are located between
the roots
Pulp Therapy
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Pulpotomy- beware of
perforations
Pulpectomy
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Difficult on molars due to
tortuous and irregular
pulp canals
Beware of tooth buds
Summary
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Primary teeth have
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Thinner enamel and dentin layers
Pulp horns closer to the outer surface
Mesial pulp horn much higher
Relatively larger pulps
Enamel rods direct slightly occlusally in the cervical
area
Cervical area is constricted significantly
Roots flare as they approach the apex
More tortuous and irregular pulp canals