Characteristic Features of Incisor's Crown

Overview and Functions of Permanent Incisors

  • Number and Distribution:

    • Permanent incisors are 88 in total number in the permanent dentition.

    • They are divided equally between arches:

    • 44 Maxillary incisors (located in the upper jaw).

    • 44 Mandibular incisors (located in the lower jaw).


Maxillary and mandibular permanent incisors highlighted in the dental arch

  • Functional Roles:

    • Major Function: To incise or cut food during the mastication process.

    • Lip Support: Play important roles in supporting the lips.

    • Esthetic Appearance: Essential for maintaining a desirable esthetic appearance.

    • Phonetics: Play an important role in speech and phonetics.

Characteristic Features of the Incisor Crown

  • Incisal Ridge vs. Incisal Edge:

    • Incisal Ridge: That portion of the crown which makes up the complete incisal portion.

    • Incisal Edge: The term used when an angle is formed by occlusal wear, which creates a flattened surface linguo-incisally.

  • Mamelons: Presence of mamelons along the incisal margin.

  • Marginal Ridges: Positioned longitudinally along the crown.

  • Lingual Fossa: Presence of a lingual fossa on the lingual surface.

  • Cingulum: Presence of a cingulum at the cervical region of the lingual aspect.


Characteristic morphological features of an incisor crown

Labial Aspect Morphology

  • Mesial Outline:

    • Straight in contour.

    • Crest of curvature is positioned near the mesio-incisal angle.

  • Distal Outline:

    • More convex than the mesial outline.

    • Crest of curvature is located at the junction between the incisal and middle thirds of the crown.

  • Incisal Outline:

    • In newly erupted teeth, features rounded elevations called "Mamelons".

    • With age, mamelons wear off and a straight incisal outline is seen.

  • Cervical Outline:

    • Follows a semi-circular direction with the curvature directed towards the root.

  • Root Morphology:

    • Shape is cone-shaped with a blunt apex.

    • Measures 2−3 mm2-3\,\text{mm} longer than the crown.

  • Center Alignment Line:

    • A line drawn through the center of the root and crown tends to parallel the mesial outline of the crown and root.


Labial aspect outline and anatomical landmarks of an incisor crown and root

Mesial Aspect Morphology

  • Crown Geometry:

    • Triangular in shape, with the base positioned at the cervix and the apex situated at the incisal ridge.

  • Bisection Line:

    • A line which bisects the crown will bisect the root.

  • Labial Outline:

    • Displays a slightly convex profile.

  • Lingual Outline:

    • Convex at the cingulum.

    • Becomes concave at the mesial marginal ridge.

    • Slightly convex at the incisal ridge.

  • Cervical Outline:

    • Curves incisally more than any surface on any tooth, measuring about 3−4 mm3-4\,\text{mm}.


Mesial aspect view showing crown and root contours of an incisor