2. Maxillary Incisor
Principal Identifying Features
The maxillary central incisor is the tooth in each maxillary
quadrant of the permanent dentition which is on each side of the
midline.
Normally, the max central incisors are the most prominent teeth
in the oral cavity and so they are most noticeable in the dental
arch, hence they contribute a focal point for the eye of the
observer. In general, the labial outline of the crown conform to
the general outline of the face.
The max central incisor (MCI) is the widest tooth mesio-distally
(MD), the labial surface is less convex than lateral incisor and
canine that give the tooth a rectangular appearance. It is the first
tooth from the midline. It has a slightly straight incisal edge.
4. Maxillary first incisor[FDI: right=11, left=21]
Principal Identifying Features
One tapering root which, when looked at in cross-section, is roughly triangular
with rounded angles.
There is only one root canal but two pulp horns (cornua), one mesial and one
distal.
The crown, when viewed vestibular, has a smooth surface and is usually slightly
convex.
The mesio-incisal angle sharp and the disto-incisal angle rounded.
The lingual surface is concave with mesial and distal marginal ridges which meet
at the neck (cervix) of the tooth forming a convex cingulum.
When viewed mesially or distally, the crown appears wedge-shaped and leans
lingually.
5. Chronology
Appearance of enamel organ 5 m.i.u
Initial calcification 3-4 months
Crown completion 4-5 years
Eruption into occlussion 7-8 years
Root completion 10 years
6.
7. Maxillary central incisor in millimeters
Crown
Length
Root
Length
M.D.at
contact
area
M.D.at
cervical
line
L.L.at
crest of
curvature
L.L.at
cervical
line
Curvature
of C.L.
M D
10.5 13.0 8.5 7.0 7.0 6.0 3.5 2.5
19. Variations and anomalies
a) Of all the crown surfaces, the lingual exhibits the greatest
variation. As previously mentioned, a pit may occasionally be
present, and the depth of the fossa has a considerable range.
b) When viewed from the labial or lingual aspects, a wide variation
occurs in the amount of convergence of the mesial and distal
surfaces toward the cervical. When there is little convergence, the
outline of the surface resembles a rectangle, but when great
convergence is present, it is more nearly triangular.
c) Root length may vary considerably, but deflections of the root are
relatively rare. When the root is exceptionally short, in conjunction
with an abnormal contour of the crown, this anomalous condition is
referred to as dwarfed root, and the lack of root support may
endanger the tooth's longevity in the mouth.
20. a) Hutchinson's incisors: Congenitalsyphilis sometimes manifests
itself in the central incisorbyproducing a screwdrivershaped
crown,whenitisviewed fromthe labial aspect.
b) Talon cusp: Alargeaccessorycuspon thelingual surface of
maxillaryincisors characterizesthis anomaly.Involvedteethoften
bear a resemblance toaPhillipsscrewdriver.
c) The alveolar bone between the roots ofthe two centralincisorsis
occasionallythesiteof supernumerary teeth or extra teeth,
known as mesiodens.Cysts mayalsobe found in this area.
