|
Dentition
Dentition is a term that describes all of the upper and lower teeth collectively.
Clinically, there are three types of dentitions:
The primary dentition consists of 20 teeth in all: ten upper and ten lower. Primary teeth are also called 'baby teeth, deciduous, or 'milk' teeth. Primary teeth begin to appear at about six months and are entirely replaced by permanent teeth by 12 to 13 years of age.
The mixed dentition is the stage from ages 6 to 12 and is composed of both primary and permanent teeth.
The permanent dentition is composed of 32 teeth in all, 16 upper and 16 lower.
Types of dentition
Homodont - Teeth that differ from each other only in size. All of the teeth in the dentition look alike; for example, alligators!
Heterodont - Most mammals, including humans, develop distinctive classes of teeth that are specialized based on their location in the mouth.
Anodontia - Anodontia is the developmental absence of teeth; for example, anteaters (zot! zot!). In humans, anodontia occurs as a pathological condition.
Monophyodont - Some mammals, such as seals and walruses have a single set of teeth.
Diphyodont - Most mammals, including humans, have two sets of teeth.
Polyphyodont - Describes the continual generation of teeth. Most reptiles and fish fall into this category.
Classes of Teeth
Anterior Teeth
Incisors - Four uppers and four lowers.
Canines - Two upper and two lower. They function with the incisors to support the lips, cut or shear food, and as guideposts in occlusion. Essentially, they're the cornerstones of the dental arch.
Posterior Teeth
Premolars - Also known as bicuspids. There are four in the upper arch and four in the lower arch. They function with the molars in the mastication of food and in maintaining vertical dimension (the height of the face).
Molars - There are six in the upper arch and six in the lower (designated as first, second, or third). Molars are important in the mastication of food and in maintaining vertical dimension. Upper molars have three roots ; lower molars have two roots.
Parts of the Tooth
Crown - The anatomical crown is the portion of a tooth covered by enamel. The clinical crown is the portion of the tooth actually visible in the mouth.
Root - The anatomical root is the portion of the tooth that is covered with cementum. The clinical root is that part of the anatomical root that is actually embedded in the jaw.
Layers of a Tooth
Enamel - The protective outer surface of the crown. It’s the hardest substance in the body.
Dentin - Located in both the crown and root, it makes up the bulk of the tooth; it lies beneath the enamel and cementum and provides the outer lining of the pulp chamber.
Cementum - Covers the surfaces of the root.
Pulp - The central, innermost portion of the tooth.
Dental Orientation
Median line - an imaginary line that bisects the dental arch at the center.
Mesial - toward the center (median) line of the dental arch.
Distal - away from the center (median) line of the dental arch.
Occlusal plane - A plane formed by the cusps of the teeth (the chewing surfaces).
Mesial surface - toward the midline.
Distal surface - away from the midline.
Proximal - the surface of a tooth that's adjacent to another tooth in the arch.
Facial - toward the cheeks or lips.
Buccal - facial surface of posterior teeth (toward the cheeks).
Labial - facial surface of anterior teeth (toward the lips).
Lingual - toward the tongue.
Incisal - cutting edge of anterior teeth.
Occlusal - the biting surface of a tooth.
Apical - toward the apex, the tip of the root. |
