Overview of the Dentitions Dental Anatomy Terminology Considerations for Tooth Study

Alveolus

• Each tooth is surrounded and supported by the bone of the tooth socket, or alveolus (alveoli)

• Located in the alveolar process (process is the bone)

• Also referred to as the dental arch

Occlusion

• The way that the teeth of the mandibular arch come into contact with those of the maxillary arch

Midline

• An imaginary vertical plane that divides the arch into two equal halves

• Similar to median or midsagittal

• Midline divide each arch into quadrants

• Maxillary right

• Maxillary left

• Mandibular right

• Mandibular left

Anterior Teeth

• Front teeth

• Closer to the midline

• Incisors

• Canine

Posterior Teeth

• Farther from the midline

• Premolars

• Molars

Parts of the Tooth

• Each tooth consists of a crown and one or more roots

• The tooth may have a single root or multiple roots

• Anterior teeth have one root

• Posterior teeth can have 2-3

• Trifurcation is the joining of 3 roots

• Bifurcation is the joining of 2 roots

• Each root has an apex or terminal end

Root Anatomy

• All roots are widest at the CEJ and taper toward the apex of the tooth (where the crown meets the root)

• Also known as the cervix

• Roots have more bulk on the facial surface than on the lingual surface

• Root concavities are found on root surfaces

• On the side of the tooth there are depressions

Cementoenamel Junction (CEJ)

• Where the cementum meets the enamel

• Separates the anatomical crown and anatomical root

• External line at the cervix, or neck of the tooth

• CEJ is synonymous with the term cervical line

Curvature of the CEJ

• Anterior teeth show greater curvature than posterior teeth

• Usually not straight

• Mesial curvature of a tooth is greater on the same tooth`

Dentinoenamal Junction

• Junction between the dentin and enamel

• CEJ is outside the tooth and DEJ is inside the tooth

Dentinocemental Junction

• Junction between the dentin and cementum

• Inside of the tooth

Dentin is Both Crown and Root But…

• Crown is composed of dentin covered by enamel

• Root is composed of dentin covered by cementum

Tissues

• Tooth is made of four tissues

  1. Enamel

  2. Dentin

  3. Cementum

  4. Pulp

Enamel

• White, protective surface covering the crown

• Hardest substance in the body

• Ameloblasts form enamel

• Doesn’t have a uniform thickness

• Thicker on the biting surface and thinner on the edges of the CEJ

Cementum

• Thin, yellow external layer covering the root

• Similar to bone in hardness

• Cementoblasts form cementum

• Uniform thickness around the root

Dentin

• Hard, yellowish tissue underlying the enamel and cementum

• Forms the largest portion of the tooth

• Odontoblasts form dentin

Pulp (Pulp Cavity)

• Soft tissue in the center of the crown + root

• Contains rich supply of blood and nerves

• Found in both crown and root

• The pulp cavity is within the tooth

• Consists of:

• Pulp chamber (coronal portion)

• Only refer to the part of the pulp in crown and not root

• Pulp canal(s)

• Only refers to the part of the pulp in the root not crown

• Apical foramen (foramina)

• Apex

• Pulp horns

• Top of pulp meets the side of the pulp cavity

Anatomical Crown VS Clinical Crown

• Anatomical crown is only covered by enamel

• Clinical crown is the portion of the anatomical crown that is visible and not covered by gingiva

• Clinical crown of the tooth can change over time due to eruption and gingival recession

• Eruption- movement of the tooth as it emerges through surrounding tissue

• Clinical crown is often shorter

Anatomical Root and Clinical Root

• Portion of the root that is covered by cementum

• Clinical root is the portion of the anatomical tooth that is visible and not covered by gingiva

• The clinical crown and clinical root can change, but the anatomic crown:root ratio must always remain the same

Tooth Orientation

• Each tooth has 5 surfaces:

• Facial (labial/buccal)

• Masticatory (occlusal/incisor)

• Mesial

• Distal

• Lingual (palatal)

• Named according to the direction in which they face

• Lingual- closest to the tongue

• Palatal- lingual surfaces on maxillary arch (you can only say palatal or lingual for the maxillary arch, but only lingual for mandibular arch)

• Facial- closest to facial surfaces (applicable for anterior and posterior teeth)

• Labial- facial surfaces close to the lips (anterior region closest to the face)

• Buccal- facial surfaces close to the inner cheek (posterior region closest to the face)

• Masticatory (occlusal- posterior, incisor -anterior) surface is the chewing surface of posterior teeth

• Incisal edge (ridge) - cutting edge of anterior teeth

• The masticatory surface of anterior and posterior teeth have linear elevations, or ridges

• The masticatory surfaces of canines and posterior teeth have at least one major elevation, or cusp

Tooth Orientation Cont.

• Proximal- faces the neighboring tooth’s surface in the same arch (where teeth touch each other in the same arch)

• Each tooth has two proximal surfaces

• Mesial- closest to the midline

• Distal- faces away from the midline

• The area between adjacent tooth surfaces is called the interproximal space (the space between where two teeth touch)

• Contact area- area where the crowns of adjacent teeth in the same arch physically touch on each proximal surface

• May also be called the “contact”

• Height of contour- greatest elevation of the tooth either incisocervically or occlusocervically

• Aka crest of curvature

• Embrasure- triangular-shaped space formed from the curvatures where two teeth in the same arch contact (broad term interproximal space is an embrasure but tip of teeth embrasure is not interproximal because interproximal must be talking about the space between the gums)

Line Angles

• Formed by the junction of two crown surfaces

• Anterior teeth have 6 line angles per tooth

• Posterior teeth have 8 line angles per tooth

Point Angles

• Formed by the junction of three crown surfaces

• Every tooth has 4 point angles

Dividing the Tooth

• Crown can be divided vertically and horizontally into thirds

• The root can be divided into thirds only horizontally