Dental professionals use standardized systems to identify individual teeth, which play specific roles in functions like chewing and speaking. These systems ensure clarity and consistency when discussing a patient’s oral health. Understanding how teeth are identified is beneficial for both dental teams and individuals.
The Universal Numbering System
In the United States, the most widely adopted method for identifying teeth is the Universal Numbering System, sometimes called the “American System”. This system assigns a unique number to each of the 32 permanent teeth in an adult mouth.
It begins by designating the upper right third molar, often known as the wisdom tooth, as tooth number 1. The numbering then proceeds sequentially around the upper arch, moving from right to left, until it reaches tooth number 16, the upper left third molar. After completing the upper jaw, the count drops down to the lower left third molar, which is assigned number 17. The numbering continues from left to right along the lower arch, concluding with tooth number 32, the lower right third molar.
For primary teeth, commonly known as baby teeth, the Universal Numbering System employs uppercase letters from A to T. This letter-based system follows a similar clockwise pattern, starting with the upper right second primary molar as “A” and moving around to “J” for the upper left second primary molar. It then progresses to “K” for the lower left second primary molar and concludes with “T” for the lower right second primary molar. This distinct numbering for primary dentition prevents confusion with permanent teeth in dental records.
Locating Tooth Number 20
Within the Universal Numbering System, tooth number 20 is identified as the permanent mandibular left second premolar. This tooth is located in the lower jaw, on the left side of the mouth. Its position is behind the lower left first premolar and in front of the lower left first molar.
The mandibular second premolar has two or three cusps, with one large cusp on the cheek side and one or two smaller cusps on the tongue side. It assists the mandibular first molar during chewing by grinding and crushing food. While sometimes referred to as a bicuspid, the term “premolar” is more accurate as these teeth can have more than two functional cusps. This tooth erupts around 11 to 12 years of age.
Why Dental Numbering is Used
Standardized dental numbering systems are widely used in the dental profession. These systems facilitate clear and efficient communication among various dental professionals, including dentists, hygienists, and specialists. When discussing a patient’s oral health or treatment plans, using a specific tooth number removes ambiguity and ensures everyone refers to the same tooth.
Dental numbering is important for accurate record-keeping and treatment planning. It allows for precise documentation of conditions, procedures, and changes in a patient’s mouth over time. This consistency is valuable for insurance claims and legal documentation, as it provides an unambiguous reference for specific dental work. These systems help prevent errors and contribute to precise, effective patient care.