Dental practitioners rely on a system of precise identification to manage patient care, assigning a unique designation to every tooth in the mouth. This standardized method is a fundamental tool for accurate communication between members of the dental team, ensuring clarity in diagnosis and treatment planning. Instead of using long anatomical names, a numerical or alphabetical label provides a quick and unambiguous reference for any specific tooth. Utilizing these established systems helps dentists maintain consistent and reliable patient records across different offices and over many years of care.
Decoding the Universal Numbering System
The system commonly used in the United States to identify adult teeth is the Universal Numbering System (UNS), which assigns a number from 1 through 32 to the permanent teeth. This methodology works by dividing the mouth into four quadrants and then following a sequential path to label each tooth. The numbering sequence begins with tooth number 1, which is the third molar, or wisdom tooth, located in the upper right quadrant of the mouth.
From the upper right, the count continues along the upper arch, moving toward the front and wrapping around to the upper left side, ending with tooth number 16. The system then drops down to the lower jaw, starting with tooth number 17, the lower left third molar. The final tooth in the sequence is number 32, which is the third molar located in the lower right quadrant.
Identifying Tooth Number 20
Following the established sequence of the Universal Numbering System, tooth number 20 is specifically identified as the mandibular left second premolar. This means the tooth is located in the lower jaw, on the left side of the mouth, positioned toward the back of the dental arch. It is situated between the canine tooth and the first molar, acting as a bridge between the front cutting teeth and the large grinding surfaces in the rear.
The second premolar is sometimes also referred to as the second bicuspid, a term that describes the presence of two cusps, or points, on its biting surface. Its function is to engage in the initial stages of crushing and grinding food after it has been torn by the canines. The tooth’s shape provides a transitional surface, breaking food down into smaller pieces before it reaches the larger molars.
Its position in the dental arch is important for maintaining the overall integrity and structure of the bite. Along with its counterpart, the first premolar, tooth number 20 helps to support the cheek and guides the alignment of the molars during chewing. The loss or damage of this tooth can affect both the efficiency of mastication and the stability of adjacent teeth. In a complete set of permanent teeth, this premolar is one of eight total premolars, two in each quadrant of the mouth.
Categories and Function of Adult Teeth
A typical adult mouth contains four distinct classes of permanent teeth, each shaped to perform a specialized role in the process of eating.
- Incisors: These eight flat, chisel-shaped teeth at the very front of the mouth are designed for biting and cutting food cleanly.
- Canines: The four pointed and strong canines flank the incisors, serving to tear tough or fibrous foods.
- Premolars: These transitional teeth have a broader surface that incorporates features of both canines and molars, responsible for the initial crushing and mashing of food particles.
- Molars: The largest teeth at the back of the mouth, molars feature wide, ridged surfaces that exert the heavy forces needed for the final grinding of food.