Overview
This lecture covers the dental anatomy of the permanent maxillary central incisor, with emphasis on shape, structure, identifying features, and comparative trends.
Maxillary Central Incisor Anatomy
- Maxillary central incisors are teeth numbers 8 and 9 in the universal notation.
- The facial view shows a trapezoidal shape—wider at the proximal contacts and narrower at the neck.
- The inciso-cervical (IC) dimension is greater than the mesio-distal (MD) dimension for all permanent anterior teeth.
- It has the second tallest crown (after the mandibular canine) and is the widest anterior permanent tooth.
- The incisal edge is nearly perpendicular to the tooth’s long axis.
Developmental Features
- The facial surface develops from three developmental lobes; the lingual from one (forming the cingulum).
- Three facial lobes appear as bulges with depressions in between, resulting in mamelons (incisal edge bumps).
- Mamelons typically wear away by age 10.
- The mesial incisal angle is sharper (~90°); the distal is more rounded and convex.
- Root tends to be curved and points distally.
Surface Characteristics
- Perikymata (cervical ridges) and imbrication lines (grooves) are most noticeable on the cervical third near the gum line.
- Cervical third is the most convex region; other areas are relatively flat.
- Mesial height of contour and contact: incisal third; distal: junction of incisal and middle third.
- Proximal contacts and heights of contour move cervically as you go posteriorly around the arch (incisors = incisal, molars = middle).
Lingual & Side Views
- Tooth is narrower lingually; only one lingual developmental lobe.
- Cervical line (CEJ) is deeper on lingual than facial sides; always convex toward apex on both.
- Mesial marginal ridge, distal marginal ridge, and cingulum are visible lingually.
- Crown is wedge/triangular shaped from the mesial view, tapering from CEJ to incisal edge.
- Height of contour is in cervical third on both facial and lingual surfaces.
- Cervical line is concave toward apex on mesial and distal; more pronounced mesially.
Pulp and Root Structure
- Pulp chamber usually has three pulp horns corresponding to facial developmental lobes.
- Almost always has one pulp canal and is least likely among non-molars to have a bifurcated root.
- Cross-section of root at mid-root is triangular.
- Shows the greatest natural axial inclination among all teeth (crown leans facial to root).
Key Trends & Summary
- IC > MD > facio-lingual (FL) dimension.
- Trapezoidal facial view; triangular side, incisal, and cross-sectional views.
- Four lobes, three pulp horns, one pulp canal.
- Moving posteriorly: proximal contacts move cervically, cervical lines flatten, and axial inclination decreases.
Key Terms & Definitions
- Inciso-cervical (IC) dimension — Height of crown from incisal edge to cervical line.
- Mesio-distal (MD) dimension — Width of crown from mesial to distal side.
- Cingulum — Bulge on lingual surface, formed by lingual developmental lobe.
- Perikymata — Cervical enamel ridges.
- Imbrication lines — Grooves between perikymata.
- Cervical line (CEJ) — Junction of crown and root.
- Axial inclination — Tilt of the crown relative to the root axis.
- Pulp horn — Protrusion of pulp chamber corresponding to a developmental lobe.
Action Items / Next Steps
- Review and memorize distinctive features and trends of the maxillary central incisor.
- Prepare for the next lecture on maxillary lateral incisors and their lingual variations.