Lecture 2
Maxillary central incisor
Generally
 The deciduous tooth appears in the mouth at 3–18 months of
age, with 6 months being the average and is replaced by the
permanent tooth around 7–8 years of age.
 The size of permanent tooth is larger than the deciduous tooth.
 There are gender differences in the appearance of this tooth. In
males, the size of the maxillary central incisor is larger usually
than in females.
 Gender differences in enamel thickness and dentin width are
low.
Maxillary central incisor
 There are some minor differences between the deciduous
maxillary central incisor and that of the permanent maxillary
central incisor.
 The maxillary central incisors contact each other at the midline
of the face. The position of these teeth may determine the
existence of an open bite or diastima. Systemic disease, such as
syphilis, may affect the appearance of teeth.
 Variations of size, shape, and color of teeth exist among people,
as with all other teeth.
 Age differences in the gingival-incisal length of maxillary
central incisors are seen and are attributed to normal attrition
occurring throughout life. Thus, younger individuals have a
greater gingival incisal length of the teeth than older
individuals.
Maxillary central incisor
Development
 The aggregate of cells which eventually form a tooth are derived
from the ectoderm of the first branchial arch and the
ectomesenchyme of the neural crest. As in all cases of tooth
development, the first hard tissue to begin forming is dentine,
with enamel appearing immediately afterwards.
Maxillary central incisor
Development
 The deciduous maxillary central incisor begins to undergo
formation or mineralization 14 weeks in utero, and at birth
5/6ths of the enamel is formed.[The crown of the tooth is
completed at around 1.5 months after birth and erupts into the
mouth at around 10 months of age, making these teeth usually
the second type of teeth to appear. The root completes its
formation when the child is 1.5 years old.
Maxillary central incisor
Development
 The permanent maxillary central incisor begins to undergo
formation or mineralization when a child is 3–4 months of age.
The crown of the tooth is completed at around 4–5 years of age
and erupts into the mouth at 7–8 years of age. The root
completes its formation when the child is 10 years old.
Permanent incisors
 They are eight in number.
 Their major function is to punch and cut food material
during the process of mastication (chewing).
 They play important role in supporting the lips and
maintaining a desirable esthetic appearance and they are
important in phonetics (speech).
Characteristic features of
incisor’s crown
 Incisal ridge and edge.
 The incisal ridge is that portion of the crown which makes up the
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complete. The incisal edge exist on an incisor after occlusal wear
has created a flattened surface linguo-incisally
incisal portion..
Presence of mammelons.
Marginal ridge are longitudinally positioned.
Lingual fossa.
Cingulum.
Permanent maxillary central
incisors
Principal identifying features
 The permanent maxillary central incisor is the widest tooth
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mesiodistally in comparison to any other anterior tooth.
It is larger than the neighboring lateral incisor and is usually not as
convex on its labial surface. As a result, the central incisor appears to
be more rectangular or square in shape.
The mesial incisal angle is sharper than the distal incisal angle.
Straight mesial outline and rounded distal outline.
When this tooth is newly erupted into the mouth, the incisal edges
have three rounded features called mammelons. Mammelons
disappear with time as the enamel wears away by friction.
Well marked marginal ridges, lingual fossa and well developed
cingulum.
Single tapered root.
Labial view
 The mesial outline of the tooth is straight
or slightly convex, whereas the distal
outline is much more convex.
 The crest of curvature is closer to the
mesio-incisal angle on the mesial side,
while it is at the junction between the
incisal and middle thirds.
 The incisal outline in newly erupted teeth
has elevations called mammelons, and
with age they will wear off and result in
straight incisal outline.
Labial view
 The cervical line appears as a
semicircle in shape with the curvature
directed towards the root.
 From this view, the root is blunt and
cone-shaped and is usually 2–3 mm
longer than the length of the crown.
 A line is drawn through the center of
the root and crown tends to parallel
the mesial outline of the crown and
root.
Lingual view
 The crown and the root are tapered lingually, so
the mesio-distal dimension of the lingual surface
is narrower than that of the labial surface.
 Below the cervical line, the lingual side of the
maxillary central incisor has a small smooth
convexity, called a cingulum which is confluent
with raised marginal ridges mesially and distally.
 Incisally, there is the lingual portion of the
incisal ridge. Between this ridge and the
marginal ridges and the cingulum there is a
shallow concavity called the lingual fossa .
 Developmental grooves are found on the
cingulum and lying into the lingual fossa.
Mesial view
 The crown is triangular in shape with the apex
at the incisal ridge and the base at the cervix.
 The root appears cone shaped with a blunt
apex. Unlike most other teeth, a line drawn
through the center of the incisal edge will also
cross through the center of the root apex. This
also occurs in maxillary lateral incisors.
 The crest of curvature for the palatal and labial
surfaces is located directly incisally to the
cervical line.
Mesial view
 The labial surface of the crown is convex from
the crest of curvature to the incisal edge. The
lingual surface of the crown is convex at the
cingulum and slightly convex at the incisal
edge, but it is concave at the mesial marginal
ridge.
 More than any other tooth in the mouth, the
cervical line from this view curves
tremendously, about 3 to 4 mm, toward the
incisal.
Distal view
 This side of the tooth is similar to the
mesial side, with little difference.
 The curvature of the cervical line is less
distally than mesially.
Incisal view
 The incisal edge is centered over the root.
 The labial outline of the crown is broad and flat.
 The incisal edge and incisal ridge are well-
defined.
 The lingual outline tapers lingually to the
cingulum.
 The mesio-distal dimension is greater labially
than lingually.
 The crown has triangular shape, as the root
shape in cross-section.
Permanent maxillary central
incisors
Interproximal contacts
 Contact with adjacent teeth in the same arch is referred
to as interproximal contacts.
 The central incisors contact each other at the incisal third
and contact the lateral incisor nearly at the junction
between the incisal and middle thirds of the crown.
Pulp anatomy
 The pulp is the location of the nerve and blood supply of a tooth.
 In the deciduous maxillary central incisor, endodontic treatment is less
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frequent. In the permanent maxillary central incisor, root canal
treatment can be effective.
There are three pulp horns in this tooth. In nearly all maxillary central
incisors, there is one canal with one apex.
During root canal therapy, access into the pulp is frequently located
centrally on the lingual surface between the incisal edge and the
cingulum.
At the level of the cervical line, the shape of the canal is triangular but
becomes circular at the middle level of the root.
Although the root is generally straight, the most common points of
curvature is near the apex, and their direction is more common toward
the distal and lingual.