Dental Anatomy Quiz

Surface Anatomy of Permanent Teeth

• Anterior teeth are divided into incisors and canines.
• Incisors consist of four maxillary and four mandibular incisors.
• Central incisors contact each other mesially and lateral incisors distally.
• Lateral incisors contact central incisors mesially and canines distally.
• All anterior teeth (incisors and canines) are formed of four lobes: 3 labially and 1 lingually.
• Enamel organ appearance occurs at 5 months.
• Calcification starts at 3-4 months (except for the 2nd which is 10-12 months).
• Crown is completed by 4-5 years.
• Eruption happens between 6-8 years.
• Root completion is between 10-12 years.

Tooth Description

• For easy descriptions, geometric outlines and surfaces of the crown and root (anatomical landmarks) are important.
• All teeth have five aspects: facial, lingual, mesial, distal, and incisal.
• Maxillary central incisor is the first tooth from the midline.
• The two upper central incisors are widest of all incisors.
• The crown is the longest of all human teeth.
• Facial and lingual aspects of crown feature a trapezoidal outline with the smallest uneven side cervically.
• Cervical outline is convex rootwise, mesial and distal outlines are convex.
• Incisal outline is straightforward and may have mamelons. There is a sharp mesioincisal angle and a rounded distoincisal angle.
• The root has a mesial and distal outline that tapers to a blunt apex.
• The apex is centralized on the long axis, permitting rotation movement during extraction.

Crown Surface Anatomy

• Labial aspect: smooth and convex, with maximum convexity at the cervical third (cervical ridge).
• Shallow developmental grooves may separate mamelons. Root surface is smooth and convex.
• Lingual aspects include marginal ridges (mesial and distal), cingulum (cervically), and incisal ridge.
• Lingual fossa is a depression.
• The lingual surface is smaller than the labial surface due to lingual convergence. This allows for the larger arch size facially compared to lingually.

Proximal Aspects

• Proximal aspects (mesial and distal) have a triangular outline, base cervically, and apex incisally.
• Labial outline is convex with maximum convexity at the cervical third.
• Lingual outline is convex incisally, concave in the middle, and convex cervically.
• Cervical outline curves incisally.

Root Anatomy

• The outlines of the root taper from the cervical line to a blunt rounded apex.

Incisor Aspects

• Incisal aspect outline is triangular-shaped with the base placed labially and apex lingually. Mesiodistal dimensions are greater than labiolingual dimensions. The crown tapers lingually.
• Elevations and depressions in the crown are visible lingually and labially.
• The lingual surface of all teeth is smaller than the labial surface.
• Upper and lower central incisors have similar elevations and depressions but differ in other aspects (e.g., size).

Mandibular Incisors

• Mandibular incisors are smaller than maxillary incisors.
• The width is smaller than the thickness.
• Mamelon's are worn off soon after eruption.
• Incisal ridges are inclined lingually.

Maxillary Lateral Incisor

• Size: The crown is broader than its predecessors.
• Crown: Its broader than other predecessors, and the longest of the anterior teeth.
• Root: Longer than the central incisor. The crown is smaller in all dimensions compared to the central incisor.

Pulp Cavity

• The pulp chamber is wide, conforming to the crown's shape, and has three pulp horns corresponding to the three mamelons.
• The root canal tapers toward the apex. The pulp chamber is pointed incisally and follows the crown's increasing cervical dimensions. The root canal tapers gradually.
• The pulp cavity of the upper lateral incisor is similar but smaller than that of the central incisor. It contains a single root canal and pulp chamber.

Malformations

• Peg-shaped lateral incisors and missing lateral incisors are malformations of upper permanent lateral incisors.

Tooth Differences

• The differences between upper central incisors and upper lateral incisors include size, elevations, depressions, and incisal angles.

Mesial Aspect

• The crown is long and thick labiolingually; the Mesial surface is flat and the contact area is at the I/3 near the MI angle.
• If the crown is shorter and thinner, the surface is flatter. The contact area is near or at the junction of I & M 1/3.

Distal Aspect

• The contact area is more cervically than mesially.
• The cervical curvature is less by 1 mm than mesially.
• The root shows a developmental depression.

Geometric Outline in Crown

• Proximal (mesial and distal) aspects have triangular outlines. The base is cervically, and the apex is incisally.

Elevations and Depressions in Crown

• Elevations and depressions are well-developed in the upper teeth compared to the lower teeth.

Cervical Lines

• Curvature in the cervical lines is less distally compared to mesially. The height of curvature decreases from upper teeth to lower teeth.

Lingual Inclination

• Lingual inclination is a characteristic of lower teeth. The incisal ridge is lingual to the root axis. This facilitates proper occlusion.

Distal Aspect Details

• Contact area is more cervically than mesially.
• Cervical curvature is less by 1mm than mesially.
• Root shows developmental depression.

Incisal Aspect Details

• Outline is diamond-shaped; labiolingual (thickness) is greater than the mesiodistal dimension.
• Incisal ridge in 1 is at right angles to a line bisecting the crown labiolingually.
• Cingulum is centered. Crown tapers lingually.
• Incisal edge may not be at a right angle to the crown labio-lingually.
• Cingulum is displaced distally.
• Cingulum of 1 is more distal. Crown is twisted distolingually on its root allowing its incisal ridge to follow the dental arch curve.

Additional Information

• The root surface shows a longitudinal developmental depression that is deeper distally than mesially.
• The upper teeth have a more pronounced convexity of the labial and lingual outlines than the lower teeth.
• The mesio-incisal angle is sharp, while the disto-incisal angle is rounded.