Molars are the large, flat teeth located in the back of the mouth, designed primarily for crushing and grinding food. Dental professionals use standardized numbering systems to identify each of the up to twelve molars in an adult mouth for accurate diagnosis and record-keeping. These systems assign a unique code to every tooth, eliminating ambiguity.
Understanding Dental Charting Systems
Dental numbering systems establish a clear, universal language among practitioners, insurance providers, and laboratories. Three major notation methods exist globally, with the choice often depending on geographic location.
The Universal Numbering System (American system) is the standard in the United States, using a continuous sequence of numbers from 1 to 32 for permanent teeth. The FDI World Dental Federation Notation is the international standard, employing a two-digit code. The Palmer Notation, which uses symbols and numbers, is primarily utilized in specialized fields like orthodontics.
Molar Identification in the Universal Numbering System
The Universal Numbering System assigns a unique number to each of the 32 permanent teeth, starting with the upper right third molar (tooth 1). The count continues sequentially around the upper arch, then drops to the lower left, and progresses across the lower arch.
Permanent Molars
The upper right molars are numbered 1 (third molar), 2 (second molar), and 3 (first molar).
The upper left molars are 14 (first molar), 15 (second molar), and 16 (third molar).
The lower left molars are 17 (third molar), 18 (second molar), and 19 (first molar).
The lower right molars are 30 (first molar), 31 (second molar), and 32 (third molar).
For primary, or “baby,” teeth, the Universal system uses uppercase letters A through T instead of numbers. The primary molars are lettered A, B (upper right), I, J (upper left), K, L (lower left), S, and T (lower right).
Molar Identification in the FDI World Dental Federation System
The FDI World Dental Federation System (ISO 3950 standard) is the international standard, using a two-digit code. The first digit identifies the quadrant, and the second digit specifies the tooth type, counting from the midline outward.
Quadrant Numbering
- Quadrant 1: Upper right
- Quadrant 2: Upper left
- Quadrant 3: Lower left
- Quadrant 4: Lower right
In this system, the second digit for permanent molars is 6 (first molar), 7 (second molar), or 8 (third molar).
Permanent Molars
- Upper right molars: 16, 17, 18
- Upper left molars: 26, 27, 28
- Lower left molars: 36, 37, 38
- Lower right molars: 46, 47, 48
For primary teeth, the FDI system uses quadrant numbers 5, 6, 7, and 8. The primary molars are designated as ‘4’ (first) and ‘5’ (second) within those quadrants.
Biological Roles and Different Types of Molars
Molars are structurally adapted for mastication, the mechanical breakdown of food. Their broad, flat occlusal surface features cusps and depressions that effectively crush and grind food particles.
First Molars
First molars, often called “six-year molars,” are the first permanent teeth to erupt, typically around age six. They are the largest and most anchored teeth, with upper molars having three roots and lower molars having two roots.
Second Molars
Second molars erupt several years later, usually between ages 11 and 13. They share the same general function and root structure as the first molars but are typically slightly smaller.
Third Molars (Wisdom Teeth)
Third molars, or wisdom teeth, are the last to emerge, often appearing between 17 and 21 years of age. Their presence is variable, and they are frequently removed due to impaction or lack of jaw space. Deciduous (baby) molars are succeeded by permanent premolars, while permanent molars erupt into previously empty space behind them.