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The Universal Numbering System, which is widely used in the United States, was adopted by the American Dental Association in 1968.

Classification of Permanent and Deciduous Teeth

It is believed that the first dental numbering system was proposed by a Hungarian dentist named Adolf Zsigmondy in 1861. Though more than twenty dental notation or tooth numbering systems have been developed over the years, most dentists use one of the three tooth numbering systems that are given below: ➠ Universal Numbering System (widely used by the dentists in the United States) ➠ Palmer Notation System ➠ FDI World Dental Federation Two-digit Notation (International) In the universal numbering system, the third molar on the right in the upper or maxillary dental arch is assigned the number 1. The teeth are numbered along with upper dental arch from right to left, as 1 to 16, with the last molar tooth back on the top left of the upper dental arch as the number 16. Similarly, in the lower (mandibular) dental arch or jaw, the numbering continues, with the third molar on the left being given the number 17. The teeth in the lower jaw are numbered from left to right, as 17 to 32, with the third molar or the tooth farthest back on the bottom right side of the mouth as the number 32. All the adult teeth are numbered in this manner, even if the third molars or wisdom teeth have not yet erupted, or some of the teeth have been removed due to dental problems. As mentioned earlier, there are a total of 20 primary teeth. In the original system, these were numbered as 1 to 20, as per the method used for adults. The only difference was that a small letter "d" followed each number to suggest that the teeth are deciduous or primary. These days, dentists use another version of the Universal Numbering System for children. Instead of numbering the teeth, each tooth is assigned a letter. Children's teeth are assigned upper case letters from A through T. The second primary molar in the upper jaw on the right is assigned the letter A, and the numbering continues in the alphabetical order, with the second primary molar on the left in the upper jaw being assigned the letter J. Similarly, in the lower jaw, the second primary molar on the left is assigned the letter K, and the numbering continues in the order till T, which is the letter that is assigned to the second primary molar on the right. Mainly used by some orthodontists, pedodontists, and oral surgeons, the Palmer notation method is the method followed by dentists in the United Kingdom. It was earlier called the 'Zsigmondy system', after Adolf Zsigmondy, a dentist from Hungary who came up with this concept of tooth numbering system in 1861. The teeth were divided into four quadrants, and the adult teeth in each quadrant were numbered 1 to 8, whereas the 20 primary or milk teeth were depicted with a quadrant grid using Roman numerals I, II, III, IV, and V to number the teeth from the midline. Corydon Palmer, a dentist from Ohio made changes to this dental notation, replacing the Roman numerals with letters in case of primary teeth. This notation involves the use of a symbol ( ┘└ ┐┌) for each quadrant, with the number or letter assigned to the tooth position from the midline that divides the teeth into four quadrants. While adult teeth in each quadrant are numbered 1 to 8, the five deciduous (milk) teeth in each quadrant are indicated by A to E. Thus, number or letter for a particular type of tooth in the upper and lower jaw would be the same, but the symbol for the quadrant would be different. Right and left quadrants of the upper jaw would be denoted by ┘and└, respectively. On the other hand, the right and left quadrants of the lower jaw would be denoted by ┐and┌, respectively. Though the Palmer method was suggested for the purpose of dental notation earlier in the United States, the American Dental Association adopted the Universal numbering system, as it was easier to type due to the absence of symbols. This is a two-digit system that is used worldwide. For permanent or adult teeth, the mouth is divided into quadrants that are numbered from 1 to 4 in the clockwise direction, starting from the upper-right or the right side of the upper jaw, as seen by the dentist. It must be noted that patient's right would correspond to left side of the dental chart. Every tooth is numbered on the basis of the quadrant and its position. So, in the first quadrant, that is right side of the upper jaw starting from the central incisor, the central incisor will be numbered as 11, the next tooth or the lateral incisor in the first quadrant will be numbered 12. The numbering of the teeth in the first quadrant will continue in this manner, till the third molar that will be numbered 18. Similarly, the teeth in the second quadrant (central incisor to the third molar) or the left side of the upper jaw will be numbered as (21, 22, 23, 24, 25, 26, 27, and 28). The adult teeth in the third and fourth quadrant would be numbered from 31 to 38 and 41 to 48 respectively. In case of the 20 milk teeth, the mouth is divided into four quadrants that are numbered from 5 to 8 in the clockwise direction, starting from the upper-right or right side of the upper jaw (central incisor to second primary molar), as observed by the dentist. Again, the child's right would correspond to the left side of the dental chart. Every tooth is numbered on the basis of the quadrant and its position. So, in the upper-right quadrant, that is right side of the upper jaw starting from the central incisor, the central incisor will be numbered as 51, the next tooth or the lateral incisor in the first quadrant will be numbered 52. The numbering of the teeth in this quadrant will continue in this manner, till the second primary molar that will be numbered 55. Similarly, the teeth in the upper-left quadrant (central incisor to the second primary molar) or the left side of the upper jaw will be numbered as (61, 62, 63, 64, and 65). The teeth in the lower-left and lower-right quadrant would be numbered from 71 to 75 and 81 to 85 respectively.