Transcript The Primary Dentition MORPHOLOGY

The Primary Dentition
MORPHOLOGY
The Primary Dentition
The Primary Dentition
• The primary dentition consists of twenty teeth: ten
maxillary and ten mandibular.
• There are four incisors in each arch, two canines, and four
molars.
• The primary dentition begins formation at fourteen weeks
in utero
• Enamel formation is complete on all primary teeth by 12
months.
• The primary teeth begin their eruption in the mouth of the
infant at an average age of 6 months, and are completely
erupted (on average) at 24 months.
• The primary dentition is in complete occlusion by age three.
• Primary teeth were formerly referred to as deciduous
teeth.
Universal Coding System
The Maxillary Arch
Mandibular Arch
Eruption Schedule and
Sequence*
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Mandibular Central Incisor:
Mandibular Lateral Incisor:
Maxillary Central Incisor:
Maxillary Lateral Incisor:
Mandibular First Molar:
Maxillary First Molar:
Mandibular Canine:
Maxillary Canine:
Mandibular Second Molar
Maxillary Second Molar
6
7
7 1/2
9
12
14
16
18
20
24
Months
Months
Months
Months
Months
Months
Months
Months
Months
Months
* Dates are averages with standard deviations. The mandibular
teeth usually precede the maxillary in eruption. Time of
arrival of the teeth is of no particular significance unless it
deviates significantly.
Exfoliation Schedule and
Sequence
(Tooth Fairy Visits)
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Mandibular Central Incisor
Maxillary Central Incisor
Mandibular Lateral Incisor
Maxillary Lateral Incisor
Maxillary First Molar
Mandibular First Molar
Mandibular Canine
Maxillary Canine
Mandibular Second Molar
Maxillary Second Molar
6-7 Years
6-7 Years
7-8 Years
7-8 Years
9-11 Years
9-11 Years
9-12 Years
10-12 Years
10-12 Years
10-12 Years
Developmental Schedule
Developmental Schedule
Developmental Schedule
Developmental Schedule
Developmental Schedule
Developmental Schedule
Characteristics
• There is usually
generalized spacing among
the anterior teeth.
• Spacing ranges from 0-10
mm in the maxillary arch,
with an average of 4 mm.
• Spacing ranges from 0-6
mm in the mandibular arch
with an average of 3 mm.
• Spacing is normal and
desirable, as it helps
overcome the significant
size differential between
the primary and
permanent incisors.
Characteristics
• Typically there is a larger
space mesial to the
maxillary primary canine
and distal to the
mandibular canine.
• This space is referred to
as the primate space, as it
is characteristically found
in the dentitions of all
primates.
• The primate space is that
space into which the canine
of the opposing arch
interdigitates.
Characteristics
• The arches are ovoid in
shape and there are few
variations to this.
• The “crooked” teeth of
the permanent dentition,
that is rotations, lingual
and labial versions, etc.
are generally not
observed in the primary
dentition.
Characteristics
• Interdigitation of the primary
arches occurs by age three.
• The primary teeth have
relatively flat occlusal
surfaces and the primary
dentition does not develop the
stable cusp-fossa relationship
seen in the permanent
occlusion.
• Bruxism, with attrition of the
teeth, is common due to the
continual searching for
maximum intercuspation.
• The primary teeth are smaller
in size and lighter in color
than the permanent teeth.
Maxillary Central Incisor
• From the facial the maxillary
central incisor is wider mesiodistally than it is long incisocervically.
• It is convex in the mesiodistal dimension.
• The disto-incisal edge is more
rounded than the mesio-incisal
edge.
• Lingually, the tooth features
mesial and distal marginal
ridges, a lingual fossa and a
cingulum.
• The root is conical-shaped.
Maxillary Central Incisor
• The mesio-distal width of
the facial of the maxillary
central incisor is greater
than the inciso-cervical
length, giving the tooth
this “squatty” appearance.
• This appearance is
characteristic of all the
primary anterior teeth, and
makes them dissimilar to
their permanent analogues.
Maxillary Central Incisor
• The root, and the
root canal, of the
central incisor are
evenly tapered
from the coronal
to the apical.
• The root, and the
root canal, are
circular in cross
section.
Maxillary Central Incisor
Maxillary Lateral Incisor
• The maxillary lateral incisor is
smaller both mesio-distally and
inciso-cervially than the central
incisor.
• In contrast to the central
incisor, it has a greater
dimension inciso-cervically than
mesio-distally.
• Lingually, the marginal ridges
are more prominent, making the
lingual fossa deeper.
• The root is longer than the
maxillary central incisor.
Maxillary Lateral Incisor
• Note that the maxillary
lateral (1) is not as
wide, mesio-distally as
the maxillary central
(2)
• The central incisor is
slightly larger in terms
of its inciso-cervical
relationship.
Maxillary Lateral Incisor
• The root and root
canal structure
between the maxillary
central incisor (1) and
the maxillary primary
incisor (2) are
essentially the same.
Maxillary Incisors
Maxillary Incisors
Mandibular Central Incisor
• The mandibular central
incisor is smaller than the
maxillary central incisor.
• It is more convex at the
cervical than at the incisal.
• The lingual surface is
smooth making the marginal
ridges and cingulum
indistinct and the lingual
fossa shallow.
• The root is single, slender
and long.
Mandibular Central Incisor
• The mandibular central incisor is smaller in
relationship to the maxillary central incisor.
Mandibular Lateral Incisor
• The mandibular lateral incisor
is larger than the mandibular
central incisor.
• This is true in both the
incisor-cervical dimension and
in the mesio-distal dimension.
• Lingually, the marginal ridges
are more convex, making the
lingual fossa deeper.
• The root is longer an thicker
than the mandibular central
incisor.
Mandibular Lateral Incisor
• The mandibular lateral
incisor has a longer incisocervical length than the
mandibular central incisor.
• The mandibular lateral
incisor is wider mesiodistally than the
mandibular central incisor.
Mandibular Lateral Incisor
• The mandibular lateral incisor (2) has a longer root than
the mandibular central incisor (1).
Mandibular Incisors
Mandibular Incisors
Maxillary Canine
• The maxillary canine is larger
inciso-cervically than mesiodistally.
• The mesio-incisal cusp ridge
has a greater slope than the
disto-incisal, that is, the cusp
tip is distally located.
• The tooth is thicker faciallingually than the incisors.
• Lingually, there is a prominent
lingual cingulum and lingual
ridge. Mesio-lingual and distolingual fossa are present.
• The root is similar to the
maxillary incisors, except
longer.
Maxillary Canine
Maxillary Canine
• The cusp tip of the canine divides the incisal into the mesial
cusp ridge and the distal cusp ridge. The mesial cusp ridge is
longer.
Maxillary Canine
• The root of the maxillary canine is longer than the root of
the maxillary lateral and central.
Mandibular Canine
• The disto-incisal edge of the
mandibular canine is longer
than the mesio-incisal--the
opposite of the maxillary
canine.
• The mandibular canine is
narrower mesio-distally than
the maxillary canine.
• The lingual features are less
distinct on the mandibular
versus the maxillary.
• The root is more tapered
than the maxillary.
Mandibular Canine
• The mandibular canine (2) has essentially the same
features and characteristics as the maxillary canine (1),
except on the mandibular canine the distal incisal edge is
longer than the mesial--the opposite of the maxillary.
Canines
Maxillary First Molar
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The mesio-distal dimension is greater
than the occluso-cervial height.
The mesio-facial cusp has a greater
occluso-cervial length than the distofacial cusp, giving rise to a skewed
cervical line.
The lingual surface is narrower than
the facial.
There is on oblique ridge on the
occlusal. Typically three cusps are
present, mesio-facial, disto-facial,
and lingual; with two fossa, the
mesial and distal.
There are three roots--largest to
smallest: lingual, mesio-facial, distofacial.
Of the three pulp horns, the mesiofacial is the largest.
Maxillary First Molar
Maxillary First Molar
• The maxillary first molar
is triangular in shape;
with the facial mesiodistal dimension being
larger than the lingual.
• There is a prominent
oblique ridge connecting
the mesio-buccal and
lingual cusps.
Maxillary First Molar
• The three roots are the mesio-facial (C), disto-facial
(A), and the lingual (B).
Maxillary First Molar
Maxillary Second Molar
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This tooth resembles the maxillary
first permanent molar.
There are five cusps present: mesiofacial, disto-facial, mesio-lingual, distallingual, and cusp of Carabelli.
An oblique ridge extends from the
disto-facial to the mesio-lingual cusp.
It has the same groove and fossa
pattern as the first permanent molar.
The is facial groove and an lingual
groove.
There are three roots, from largest to
smallest: lingual, mesio-facial, and
disto-facial
There are three root canals, with the
mesio-facial pulp horn being the most
prominent.
Maxillary Second Molar
• The maxillary second molar is rhomboid in appearance. Note
the the facial-lingual dimension is greater than the mesialdistal one.
Maxillary Second Molar
• The maxillary second molar (1) is larger than the
maxillary first molar (2).
• Note the rhomboid shape to the second molar in
comparison to the triangular shape of the first.
Maxillary Second Molar
• The second molar has five
cusps:
– A: mesio-facial
– B: mesio-lingual
– C: cusp of Carabelli
– D: disto-lingual
– E: disto-facial
• There are three pits in the
occlusal surface:
– mesial pit
– central pit
– distal pit
Maxillary Second Molar
Maxillary Second Molar
• Similar to all maxillary molars, both primary and
permanent, the maxillary second primary molar has
three roots: mesiol-facial, disto-facial, and lingual.
Maxillary Second Molar
Maxillary Second Molar
• The maxillary second molar
has one pulp horn that
corresponds to each cusp,
and one root canal that
corresponds to each root;
Therefore it has five pulp
horns and three root canals.
• The pulp cavity
demonstrates more
development facially and
mesially (2) than it does
facially and distal (1);
therefore the largest and
longest pulp horn is the
mesio-facial.
Maxillary Molars
Mandibular First Molar
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The crown is larger mesio-distally than
facial-lingually.
The four cusps are the mesio-facial,
disto-facial, mesio-lingual, and distallingual; with the mesial cusps being the
largest.
A transverse ridge exists between the
mesio-facial and mesio-lingual cusps.
There are three pits: the mesial, the
distal and the central.
The mesial is distinctive due to a large
cervial ridge.
There are two roots, the mesial and
distal, which are wider facial-lingually
than mesio-distally.
The number of pulp horns correspond
to the number of cusps (four), with the
mesio-facial being the largest. There
may be two root canals in the mesial
root.
Mandibular First Molar
• Because of the extreme occlusal convergence of the facial
surface, the occlusal table of the mandibular first molar is
narrow facial-lingually.
Mandibular First Molar
• In cross section the mandibular first molar presents a very
prominent facial bulge at the cervical (A); a characteristic
unique to this tooth.
Mandibular First Molar
Mandibular First Molar
• The facial view of the mandibular first molar is unusual as
well. Note the occlusal-cervical length of the tooth at the
mesial versus the distal, as a result of the cementoenamel junction being positioned more apically.
Mandibular First Molar
Mandibular First Molar
• The tooth has four cusps:
– mesio-facial
– mesio-lingual
– disto-facial
– disto-lingual
• The mesial aspect of the
tooth is marked by a
distinct transverse ridge,
which runs across the
tooth between the mesiofacial and mesio-lingual
cusps.
• The tooth has three pits:
– mesial
– central
– distal
Mandibular First Molar
• Similar to permanent molars the mandibular first primary
molar has two roots; a mesial and a distal.
• The mesial and distal roots of the tooth are narrow and
convex in the mesio-distal directions (1), but broad and
facio-lingual (2).
Mandibular First Molar
• Corresponding the to
number of cusps, the pulp
chamber has four pulp
horns.
• While the tooth has two
roots, the mesial root (the
larger of the two roots)
has two root canals, which
correspond to the two
largest cusps the mesiofacial and the mesio-lingual.
Mandibular Second Molar
• The primary second primary
molar closely resembles the
permanent mandibular second
molar.
• Five cusps are present: mesiofacial, disto-facial, mesio-lingual,
disto-lingual, and distal.
• All five cusps can be seen from
the lingual.
• The two roots (mesial and distal)
are larger than the mandibular
first primary molar.
• There are five pulp horns, and
commonly three (sometimes four)
root canals: mesio-facial, mesiolingual and distal.
Mandibular Second Molar
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The second molar has five cusps:
– A: mesio-facial
– B: distal-facial
– C: distal
– D: mesio-lingual
– E: distal-lingual
The second molar has five major
grooves:
– mesial
– mesio-facial
– distal-facial
– lingual
– distal
The second molar has three pits:
– mesial pit
– central pit
– distal pit
Mandibular Second Molar
Mandibular Second Molar
• The mandibular second
molar has two roots, a
mesial and a distal
• As with all primary molars
the roots are flared to
provide space for the
developing succedaneous
permanent tooth bud to
develop.
Mandibular Second Molar
Mandibular Second Molar
Mandibular Second Molar
• A suggested by the number of
cusps, the pulp chamber has
five pulp horns.
• The tooth has either three or
four root canals. The mesial
root has two canals.
• The distal root may have one
or two canals.
Mandibular Molars