The Occlusal Anatomy Of Teeth

The Occlusal Anatomy Of Teeth

Basic Forms Of Occlusal Surfaces The Occlusal surface is the chewing surface of posterior teeth consisting of a number of specific details. The basic groups of details (forms) are convexities and concavities, or in general - grooves and ridges. In the study of tooth morphology, the grooves and ridges on the various surfaces are described and named. A knowledge of the character and location of these ridges, grooves, convexities and concavities on teeth is invaluable in describing and identifying teeth in regard to arch, class, type and side of the mouth.

Convexities Cusp, tubercle (tuberculum) is a point or peak on the chewing surface of molar and premolar teeth, and on the incisal edge of canines.

Cusp Cusp ridges (cusp slopes) are the inclined surfaces that form an angle at the cusp tip when viewed from the facial or lingual aspect. These cusp slopes may also be called cusp arms. All cusps are basically a gothic pyramid with 4 ridges: mesial cusp ridge, distal cusp ridge, buccal cusp ridge (labial ridge on canines), triangular ridge on posterior teeth (lingual ridge on canines).

Cingulum Cingulum is the enlargement or bulge on the cervical third of the lingual surface of the crown of anterior teeth - incisors and canines.

Labial Labial ridge (margo labialis) - a ridge running cervico incisal in approximately the centre of the labial surface of canines.

Buccal Buccal ridge, cusp ridge (margo buccalis) - a ridge running cervico occlusal in approximately the centre of the buccal surface of premolars.

Cervical Cervical ridge (margo cervicalis) is a ridge running mesiodistally on the cervical one-third of the buccal surface of the crowns, found on all primary teeth but only on the permanent molars.

Marginal Marginal ridge - it is located on the mesial and distal border of the lingual surface. For posterior teeth - on the mesial and distal border of the occlusal surface.

Triangular Triangular ridge (margo triangularis) - on the occlusal surface of posterior teeth, It is the ridge from any cusp tip to the centre of the occlusal surface. Some cusps have more than one triangular ridge - the mesiolingual cusp on maxillary molars has two triangular ridges.

Oblique Oblique ridge (margo obliquus) - a ridge found only on maxillary molars. Crosses the occlusal surface obliquely and is made up of the triangular ridges of the mesiolingual and the distobuccal cusps.

Transverse Transverse ridge - this is a ridge crossing the occlusal surface of most posterior teeth in a buccolingual direction. This ridge is made up of connecting triangular ridges.

Example: between the mesiolingual and mesiobuccal or between the distolingual and distobuccal cusps on molars. The transverse ridge is also running between buccal and lingual cusps on premolars.

Depressions & Grooves Sulcus A broad depression or valley on the occlusal surfaces of posterior teeth, the inclines of which meet in the central groove and extend outward to the cusp tips - developmental grooves - this is a sharply defined, narrow and linear depression, short or long, formed during tooth development and usually separating lobes or major portions of a tooth. The major grooves are named according to their location (central, mesial, distobuccal, mesiobuccal, etc.).

Fissure This is a narrow channel (cleft, crevice), formed at the depth of a developmental groove, extending inward toward the pulp. NB! Decay (dental caries) often begins in a deep fissure.

Supplemental Grooves Small, irregularly placed grooves, not at the junction of lobes or major portions of a tooth, found usually on occlusal surfaces. They can be named for the part of the tooth on which they are found - mesiobuccal supplemental groove, distolingual supplemental groove, etc.

Fossa (Fossae in plural) A depression found on the lingual surfaces of some anterior teeth (particularly maxillary incisors) and on the occlusal surfaces of all posterior teeth - central fossa, mesial triangular fossa, distal triangular fossa, etc.

Pits Just like fissures, often occur at the depth of a fossa where two or more grooves join. Similar to fissures at the depth of grooves, pits are areas where dental decay may begin.