Dental Anatomy: Tooth Morphology

Tooth Morphology

Elevations and Ridges

• A cusp is a pyramidal elevation located on the occlusal surfaces of molars and premolars, and on the incisal edges of canines.
• Cusp ridges are linear prominences of enamel that converge toward the cusp tip, forming a four-sided pyramid shape.
• The four cusp ridges are named after the circumferential tooth surface they extend toward: facial, mesial, distal, and triangular.

Cingulum, Marginal Ridges, and Triangular Ridges

• Cingulum is the enlargement or bulge on the cervical third of the lingual surface of the crown on anterior teeth (incisors and canines).
• Marginal ridges are located on the mesial and distal border of the lingual surface on anterior teeth, and on the mesial and distal borders of the occlusal surface on posterior teeth.
• Triangular ridges are located on each major cusp of posterior teeth, extending from the cusp tip toward the depression (sulcus) in the middle of the occlusal surface faciolingually.

Transverse Ridges, Oblique Ridges, and Mamelons

• Transverse ridges are formed when a triangular ridge from a facial cusp joins with a triangular ridge from an adjacent lingual cusp, crossing the occlusal surface in a more or less buccolingual direction.
• An oblique ridge is found only on maxillary molars, crossing the occlusal surface obliquely and made up of one ridge on the mesiolingual cusp joining with the triangular ridge of the distobuccal cusp.
• Mamelons are small tubercles or scallops formed from one of the three facial developmental lobes on the incisal edges of newly erupted incisors.

Depressions and Grooves

• Tooth sulcus is a broad V-shaped depression or valley running mesiodistally on the occlusal surfaces of posterior teeth.
• Developmental grooves are major, sharply defined narrow, linear depressions formed during tooth development, usually separating the lobes or major portions of a tooth.
• Deep developmental grooves are named according to their location, such as central groove, triangular fossa grooves, buccal and lingual grooves.
• Supplemental grooves are small irregular (extra) grooves on the occlusal surface that do not occur at the junction of the lobes or major portions of the tooth.
• A fossa is a small hollow or depression found between the marginal ridges on the lingual surfaces of anterior teeth and at specific locations on the occlusal surfaces of posterior teeth.
• Pits and fissures are caused by the incomplete fusion of enamel during tooth development and are often sites for tooth decay.

Anatomy of Roots

• The apex is the tip or peak at the end of the root.
• The cervix is the slightly constricted region of union of the crown and the root.
• The root trunk is the part of the root of a multi-rooted molar or two-rooted premolar next to the cementoenamel junction.
• The furcation is the place on multi-rooted teeth where the root trunk divides into separate roots, whereas the furcal region is the region or space between two or more roots, apical to the place where the roots divide from the root trunk.

Tooth Surfaces Junctions and Dimensions

• A line angle is the junction line where two tooth surfaces meet, named by combining the names of the two surfaces, changing the “al” ending of the first surface to an “o”.
• Point angles are the junctions of three tooth surfaces at a point, such as a mesiobucco-occlusal point angle.

This quiz covers the anatomical landmarks of teeth, including elevations and ridges, cusp locations, and tooth surfaces.