Dental Anatomy: Parts Of A Tooth

Each tooth has 3 basic anatomic parts: crown — corona dentis; root — radix dentis and cervix (neck) — collum dentis. If we examine an extracted tooth, we can distinguish an anatomic crown and an anatomic root. The line that separates the anatomic crown from the anatomic root is called the cervical line.

This is also called cement-enamel junction (CEJ), because it separates the crown covered by enamel from the root which is covered by cementum — they both are hard tissues on the surface of the tooth. The root is that part of the tooth which is under the gingiva — the root is usually not visible. The crown is the visible part of the tooth, located in the oral cavity.

The cutting edge (ridge, surface) of anterior teeth is called incisal edge — margo
incisivus. Occlusal surface (facies masticatoria) is the chewing surface of posterior teeth
consisting of cusps, ridges and grooves — or convexities and concavities in general.

The number of roots can be one, two, three or more, depending on the tooth category. Furcation is the place on multi-rooted teeth where the root base divides into separate roots — bifurcation on two-rooted teeth and trifurcation on three-rooted teeth.

The gingiva is that part of the oral mucous membrane that covers the jaw bone, and surrounds the cervical portions of the teeth.

Gingival margin (margo gingivalis) is the occlusal (incisal) border at which the gingiva meets the tooth.

Usually the gingival margin approximately follows the curvature of the cervical line, it is usually at the same level as the cervical line and the neck of the tooth is tightly embraced by the gingival margin.

Anatomic crown is that part of a tooth, visible in the oral cavity, that has an enamel surface. The anatomic root is the part of a tooth that has a cementum surface. The line that separates the anatomic crown from the anatomic root is called the cervical line.

This relationship does not change over a patient’s lifetime. Usually the gingival margin approximately follows the cervical line.

Clinically, when the tooth is in the mouth, this relationship is not always the same. However, the gingival margin is not always at the level of the cervical line because of the eruption process or gingival recession.

The clinical crown is the part of a tooth that is visible in the oral cavity. The clinical crown may be larger or smaller than the anatomic crown. It may include all of the anatomic crown and some of the anatomic roots if it has been proved that there is a recession of the gingiva.

The clinical crown may include only part of the anatomic crown if the cervical part of the crown is still covered by gingiva, for example during the eruption process (especially on newly erupted teeth).

The clinical root is that part of a tooth which is under the gingiva and is not exposed to the oral cavity. A person with considerable recession of the gingiva (i.e. and elderly), the clinical root would be shorter than the anatomic root due to the portion of the root that is exposed. This is considered to be a part of the clinical crown.

The clinical root may be longer than the anatomic root. On newly erupted teeth, any part of the crown not erupted is considered to be part of the clinical root. The crest of curvature is the highest point of a curve or the greatest convexity. The crest of curvature is where this convexity would be touched by a tangent line drawn parallel to the root axis.

Contact areas are the crests of curvature on the proximal surfaces of tooth crowns
where a tooth touches the tooth adjacent to it in the same arch. If we move a pencil parallel to the root axis of the tooth, we shall draw a line called anatomic crest of curvature.

This line divides the tooth surface into two parts — occlusal (above the crest of curvature) and cervical (below the crest of curvature). During chewing, these convexities divert food away from the gingiva that surrounds the neck of the tooth, thus preventing trauma to the gingiva.

The active parts of some retainers for removable dentures, like clasps, are positioned in the cervical part, below the crest of curvature.

The tooth cavity — pulp cavity or cavum dentist in Latin — is positioned in the center part of the tooth and has a similar outline as the tooth itself. The pulp cavity is surrounded by dentin except at a hole near the root apex, called apical foramen.

Pulp is the soft, not calcified tissue in the pulp chamber. It is normally not visible
except on a dental radiograph. The pulp cavity has a coronal portion — pulp chamber
(cavum coronae dentist) and a root portion — pulp canal or canals, depending on the
number of roots. The pulp canals are also called root canals — canalis radicis dentis.