Humans will normally have 32 adult teeth that will erupt during their younger years of life. In order to keep track of all these teeth, they have been assigned numbers. This numbering system can vary in different countries but in the United States, the most common way of tooth numbering is using the numbers from 1-32. The system is sequential and it starts on the upper right side of the mouth. Therefore, #1 will be the last tooth on upper right side. This tooth is also called a 3rd molar or a wisdom tooth. #2 will be directly adjacent to #1 as we move closer to midline. Midline is an imaginary line that divides the mouth into left and right halves. This will then be followed by tooth #3, the #4 and so on. This pattern will continue until we get to the last tooth on the upper left side. This is a wisdom tooth and using our number system, it will be tooth #16. Since we are now at the last tooth on the upper arch, the numbering system will continue but now it will be on the lower teeth. Staying on the patients left side, we drop down to the lower teeth and that 3rd molar will be #17. We can then count all the teeth on the lower, just like we did on top, and eventually end on #32. #32 is 3rd molar on the lower right side. It is important to remember that if a tooth is missing, the number DOES NOT carry over. Every tooth has an assigned number and that will not change. In other words, #6 is ALWAYS an upper right canine and it does not matter if #5 or #7 is present. Finally, baby teeth are counted in the same way but instead of numbers they use letters. The letters are A-T.
What are the letters on adult teeth? There are 5 letters and they represent the 5 surfaces of an individual tooth. Using this lettering system is very helpful in the diagnostic and treatment planning phases of dental care. The top of the tooth, or the biting surface, is called “Occlusal”. This is usually abbreviated with the letter “O”. The surface that is closest to the midline is called “Mesial”, abbreviated by M. The surface that is furthest from the midline is called “Distal”, abbreviated by “D”. The surface closest to the cheek or lips is called “Facial” or “Buccal”, abbreviated by the letters “F” or “B. Finally, the surface closest to the tongue or the palate is called “Lingual”, abbreviated by “L”. With the numbering of teeth and assignment of letters to the 5 surfaces we can now identify which tooth, and what part ofthat tooth is in question. For example, #3 occlusal, abbreviated #3 (O), is the 1st molar on the upper right side, and the occlusal surface is the biting surface.
Dr. Tom Horgan DMD