3. Introduction
1- Numbers.
• TWO teeth in mouth (upper dental arch).
• One tooth in each quadrant.
2- Eruption time.
• Upper Central incisor (7-8) year.
3- Numbering System
a- Universal
Upper Right 8
Upper Left 9
b- Palmer
1 in upper right quadrant
1 in upper left quadrant
c- FDI
Upper Right 11
Upper Left 21
4. Crown Geometrie
•TRIANGLES
A. Mesial aspect
B. Distal aspect
•TRAPEZOIDS
• Trapezoid with longest uneven side toward
incisal aspect.
A. Labial aspect
B. Lingual aspect
5. Surfaces
1- Labial surface
• The mesial outline of the crown is slightly convex.
• The crest of curvature (contact area) near the mesioincisal
angle (within incisal third).
• The distal outline of the crown is more convex.
• The crest of curvature higher toward the cervical line
(at junction between incisal and middle third).
• The mesioincisal angle sharp.
• The distoincisal angle is round.
• The incisal outline is usually regular and straight in a
mesiodistal direction.
• The crown length is greater at the center.
• The cervical outline of the crown follows a semicircular
direction with the curvature rootwise (Convex towards apex).
6. 2- Lingual surface
•The lingual outline is the reverse of the labial aspect.
•The lingual aspect has convexities and a concavity.
•The outline below the cervical line has a smooth
convexity called the cingulum.
•Mesially and distally con
fl
uent with the cingulum are the
marginal ridges.
•Between the marginal ridges, below the cingulum, a
shallow concavity is called the lingual fossa.
•The crown and root taper lingually.
Surfaces
7. 3- Mesial Surface
•The crown is wedge-shaped, or triangular, with the base of the
triangle at the cervix and the apex at the incisal ridge .
•The incisal ridge of the crown is on a line with the center of the
root.
•Labially and lingually, ; crest of curveture within cervical third.
•The labial outline of the crown from the crest of curvature to the
incisal ridge is very slightly convex.
•The lingual outline is convex at the cingulum then becomes
concave at the mesial marginal ridge and slightly convex again
at incisal ridge.
•The cervical line outlining the cementoenamel junction (CEJ)
mesially on the maxillary central incisor curves incisally.
•The root of this tooth from the mesial aspect is cone- shaped.
•The apex of the root is bluntly rounded.
Surfaces
8. 4- Distal surface
• When looking at the central incisor from the distal
aspect, it may be noted that the crown gives the
impression of being somewhat thicker toward the
incisal third.
• Because of the slope of the labial surface
distolingually, more of that surface is seen from the
distal aspect.
• The curvature of the cervical line is less in extent on
the distal than on the mesial surfaces.
Surfaces
9. Incisal Aspect
• The crown has a triangular outline.
• The labial face of the crown is
fl
at especially toward the incisal
third.
• The Labial arc is broad
• The cervical portion of the crown labially is convex
• The incisal ridge seen clearly.
• There are two Incisal edge :
A- Labioincisal edge.
B- Linguoincisal edge.
• The outline of the lingual portion tapers lingually toward the
cingulum.
• The cingulum of the crown makes up the cervical portion of
the lingual surface.
• The lingual portion : a line drawn from the mesioincisal angle
to the center of the cingulum lingually will be longer than one
drawn from the same point on the cingulum to the distoincisal
angle.
• The root is not visible.
10. Root
• The root of the central incisor:
• Cone-shaped.
• Blunt apex.
• The outline mesially and distally is regular.
• The root is usually 2 or 3 mm longer than the crown.
