Dental professionals use standardized notation systems to identify specific teeth for accurate record-keeping and clear communication. These systems ensure there is no ambiguity when referring to a particular tooth. While the United States primarily uses one system, international dentistry often relies on others, leading to different designations for the maxillary first molars.
Universal Numbering System for Permanent Molars
The Universal Numbering System (UNS) is the primary method of tooth identification used by dentists throughout the United States. This system assigns a unique number, from 1 to 32, to each permanent tooth. Numbering begins with the upper right third molar and moves clockwise, continuing sequentially across the upper arch and down to the lower arch.
The permanent maxillary first molars are designated by specific numbers reflecting their position in the upper arch. The permanent first molar on the upper right side is assigned the number 3. Moving across the upper arch to the opposite side, the permanent first molar on the upper left side is identified as tooth number 14. This systematic assignment allows for easy verbal communication and is compatible with computer-based record systems.
International and Quadrant Notation for Permanent Molars
Outside the United States, the FDI World Dental Federation Notation (ISO 3950 standard) is the most globally recognized system for identifying permanent teeth. This method uses a two-digit code. The first digit indicates the quadrant, and the second digit identifies the tooth type and position within that quadrant. The quadrants are numbered 1 through 4, with 1 representing the upper right and 2 representing the upper left.
For the permanent maxillary first molars, the second digit is always 6, as it is the sixth tooth from the midline in each quadrant. Consequently, the upper right first molar is designated as 16, and the upper left first molar is designated as 26. These two digits are pronounced separately (e.g., “one six” and “two six”) to prevent confusion with the single numbers used in the Universal System.
The Palmer Notation Method is another quadrant-based system that uses a number combined with an angle symbol to denote the tooth and its quadrant. Permanent teeth are numbered 1 through 8, starting at the central incisor, making the first molar number 6 in both upper quadrants. The upper right first molar is represented by the number 6 with a right-angle symbol (┘). The upper left first molar uses the number 6 with a left-angle symbol (└).
Identifying Primary Maxillary First Molars
Primary teeth (deciduous or baby teeth) have distinct identifiers across notation systems to differentiate them from permanent teeth. In the Universal Numbering System, uppercase letters A through T are used for the primary dentition. The count begins in the upper right quadrant with letter A and proceeds clockwise around the mouth.
Specifically, in the UNS, the primary maxillary first molars are identified by the letters B and I. Letter B represents the primary first molar on the upper right side, and letter I represents the primary first molar on the upper left side. The FDI system uses a two-digit code for primary teeth, but the quadrant numbers are 5 through 8, starting with 5 for the upper right. Under this system, the primary maxillary first molars are designated 54 (upper right) and 64 (upper left), where the number 4 indicates the first molar’s position from the midline.