11.2. Dental Notation

Humans are born without teeth. A primary dentition is formed by age 6, then the milk teeth are gradually replaced by permanent teeth in a process that completes itself around age 12. Additional teeth erupt up to age 20 when the full permanent dentition is completed.

Nomenclature

Teeth are named by their sets and also arch, class, type, and side. Teeth can belong to one of two sets of teeth: primary (also called deciduous or baby) teeth or permanent (adult) teeth. Teeth of the permanent dentition that replace primary teeth are called succedaneous. Teeth are further named based on the arch on which they are found. Maxillary teeth are found in the upper jaw and mandibular teeth are found in the lower jaw. There are four classes of teeth: incisors, canines, premolars, and molars. Premolars are found only among the permanent teeth; there are no deciduous premolars. Incisors are divided into types: central and lateral incisors. There are first and second premolars, and first, second, and third molars. The side of the mouth in which a tooth is found may also be included in the name. For example, a specific name for a tooth may be "permanent maxillary left lateral incisor."

Dental notation

When working with teeth, it is often necessary to have a faster way of referring to a tooth than, for example, saying “permanent mandibular right second molar”. Several systems for dental notation have been proposed and adopted at various times and locations. Among them, the Universal Numbering System, is most widely used in the United States, whereas the the ISO System is most common in the rest of the world. The American Dental Association (ADA) accepts both systems, while the World Dental Federation (FDI) and the World Health Organization (WHO) use the ISO System.

ISO System

This system, more specifically ISO 3950, is based on the dental notation system previously adopted by the FDI, which was called the FDI System or the International System. It uses two-digits to identify teeth. The first digit represents a tooth's quadrant and the second digit represents the number of the tooth from the midline of the face. For permanent teeth, the upper right teeth begin with the number 1. The upper left teeth begin with the number 2. The lower left teeth begin with the number 3. The lower right teeth begin with the number 4. For primary teeth, the sequence of first digits is 5, 6, 7, and 8, respectively. When speaking about a certain tooth such as the permanent maxillary central incisor, the notation is pronounced “one-one” instead of “eleven”.

Figure 3. Dental notation for the maxillary (left) and mandibular (right) permanent teeth in the ISO System. More details (left, right).

Universal numbering system

Although it is termed "universal numbering system", it is most commonly used in the United States. It is also called the "American system". The uppercase letters A through T are used for primary teeth and the numbers 1 - 32 are used for permanent teeth. The tooth designated "1" is the maxillary right third molar ("wisdom tooth") and the count continues along the upper teeth to the left side. Then the count begins at the mandibular left third molar, designated number 17, and continues along the bottom teeth to the right side. Each tooth has a unique number or letter, allowing for easier use on keyboards.

Directional terms and surfaces

Several specific directional terms are used to locate structures in the mouth and they are commonly used to specify a certain surface on a tooth. Anterior teeth include the incisives and canines, whereas posterior teeth include the premolars and molars. Structures that are nearest the cheeks or lips are referred to as vestibular or facial, They can also be referred to more specifically as buccal, when found near the cheeks (posterior teeth), or labial, when found near the lips (anterior teeth). On the opposite sides of the teeth, structures are called oral. Their position can also be further refined as lingual for mandibular structures, or palatal for maxillary structures. The term lingual is sometimes used referring to all oral structures but this is confusing because the tongue is generally associated with the mandibular portion of the mouth.

The dental midline passes between the central incisors and along the plane of symmetry (sagittal plane) of the face, separating left from right. Mesial refers to a structure that is close to or faces the dental midline. The direction away from the midline toward the furthest teeth is called distal.

At the tooth, the most common landmarks are the apex (tip) of the root, the cervix (neck) of the tooth, its crown, occlusal (biting) surface, and internal tissue types. These are used to form regional and directional terms. At the crown, occlusal indicates at or toward the biting surface whereas cervical is at or toward the neck of the tooth. At the root, apical indicates at or toward the tip whereas coronal or cervical are at or toward the crown or neck, respectively.  Pulpal and dentinal refer to the two tissues that occupy the largest volume in the tooth. Tissues surrounding the apex of the root are called periapical. 

Directional terms are frequently used in pairs combined into a single word, such as distopalatal or buccocervical. This is commonly used to specify the position of a surface on a tooth, or a direction from which the tooth is seen or approached. Two letter abbreviations can be used in conjunction with these terms, as long as the word is spelled out and followed by the abbreviation on the first time that it appears in the text, for example, distolingual (DL).

Summary

Humans have a succedaneous dentition in which a set of primary teeth is replaced once by a set of permanent teeth. All teeth are classified as incisor, canine, premolar or molar. For dental notation, quadrants are numbered clockwise starting with the upper right. Teeth are numbered sequentially or medio-distally depending on the notation system in use. Positional terms and surface landmarks are used to refer to specific locations on each tooth. 

Key terms

Primary dentition, milk teeth, deciduous teeth, permanent dentition, succedaneous teeth, maxillary teeth, mandibular teeth, dental quadrant, dental notation, incisor, canine, cuspid, premolar, bicuspid, molar, wisdom tooth, Universal Numbering System, ISO system, buccal, facial, oral, apical, cervical, coronal, vestibular, lingual.

Figure credits

Figure 1 by Jordan Sparks - Open Dental - Open Source Dental Management Software, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2756634

Figure 2 by Partynia - Own work, modified file of Xauxa: Teeth model front.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27245187

Figure 3a by Partynia, modified file of Xauxa: Upper jaw.jpg - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27199151

Figure 3b by Partynia - Own work, modified file of Xauxa: Lower jaw.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27198809

Figure 4 by DRosenbach (talk). - DRosenbach (talk), Public Domain, https://commons.wikimedia.org/w/index.php?curid=8987930

Figure 5 by DRosenbach at English Wikipedia - Transferred from en.wikipedia to Commons., Public Domain, https://commons.wikimedia.org/w/index.php?curid=3695121