Other Anatomical Structures Defined

A. Crown Elevations:

1. Cusps - Elevated and usually pointed projections of various sizes and shapes on the crowns of teeth. They form the bulk of the occlusal surfaces of posterior teeth, and the incisal portion of canine crowns. Incisors do not possess cusps, while canines normally exhibit one cusp, premolars two or three cusps, and molars usually four or more.

2. Tubercles - Rounded or pointed projections found on the crowns of teeth. Tubercles are not a normal finding, although they are not rare. They are also variable in size and shape, but are usually smaller than cusps. Tubercles are often thought of as minicusps, and their most likely location is on the lingual surface of maxillary anterior teeth, especially deciduous canines. The Cusp of Carabelli. a tubercle, is a normal finding on the mesial part of the lingual surface of permanent maxillary first molars.

3. Cingulum (Plural - cingula) - A large rounded eminence on the lingual surface of all permanent and deciduous anterior teeth, which encompasses the entire cervical third of the lingual surface.

4. Ridges - Linear and usually convex elevations on the surfaces of the crowns of teeth, which are named according to their location. Several specific types of ridges can be identified as follows:

a. Marginal ridges - The linear elevations which are convex in cross section and are found at the mesial and distal terminations of the occlusal surface of posterior teeth. They are also found on anterior teeth, but are less prominent. Their location also differs, since on anterior teeth they form the lateral (mesial and distal) margins of the lingual surface.

b. Triangular ridges - Linear ridges which descend from the tips of cusps of posterior teeth toward the central area of the occlusal surface. In cross-section, they are more or less triangular, hence their name.

c. Transverse ridge - The combination of two triangular ridges, which transversely cross the occlusal surface on a posterior tooth to merge with each other. Thus a transverse ridge is simply a union of two triangular ridges of a posterior tooth, one from a buccal cusp and the other from a lingual cusp and also is composed of two triangular ridges.

d. Oblique ridge - A special type of transverse ridge, which crosses the occlusal surface of most maxillary molars of both dentitions in an oblique direction from the distobuccal to mesiolingual cusps.

e. Cusp ridges - Each cusp has four cusp ridges extending in different directions (mesial, distal, facial, lingual) from its tip. They vary in size, shape, and sharpness. Normally, the cusp ridge which extends toward the central portion of the occlusal surface is also a triangular ridge. They are named by the direction they extend from the cusp tip.

f. Inclined plane - The sloping area found between two cusp ridges. Planes are named by combining the names of the two cusp ridges between which they lie. Normally, each cusp exhibits four inclined planes.

5. Mamelons - Small, rounded projections of enamel which are found in varying sizes and numbers on the incisal ridges of recently erupted incisors. They - are normally worn away rather soon after eruption, if the tooth contacts its antagonist(s) in the opposite arch when in function.



Central Fossa Oblique Ridge Marginal Ridge Supplemental Groove
Developmental Groove Triangular Ridges Transverse Ridge Central Pit

Marginal Ridge


Marginal Ridge



Groove (Cross Section)


Groove (Cross Section)

B. Crown Depressions:

1. Fossa (Plural - fossae) - An irregular, usually rounded depression, or concavity, on the crown of a tooth. There is normally a rather large, shallow fossa on the lingual surface of anterior teeth, while posterior teeth exhibit two or more fossae of varying size and shape on the occlusal surface.

2. Developmental (primary) groove - A groove, or line, which usually denotes the coalescence of the primary parts, or lobes, of the crown of a tooth.

3. Supplemental (secondary ) groove - An auxiliary groove which branches from a developmental groove. Its location is not related to the junction of primary tooth parts, and it is normally not as deep as a primary groove.

4. Pit - A small, depressed area where developmental grooves often join or terminate. A pit is usually found in the deepest portion of a fossa.

C. Miscellaneous Structures:

1. Contact area - The area on a proximal surface of the crown that contacts the adjacent tooth in the same arch, and is thus named mesial or distal by location. All teeth in each quadrant normally have two contact areas, except the most distal tooth which, of course, has no distal contact area.

2. Lobe - One of the primary anatomical divisions of the tooth crown, often separated by identifiable developmental grooves.

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