Gráfico de Numeración Dental - Sistemas de Notación

Three tooth numbering systems are in common use, and they do not agree. A dentist in the United States saying "number 30" and a dentist almost anywhere else saying "46" are describing the same tooth. Knowing which system a chart or treatment plan uses is the difference between reading it correctly and misreading it entirely.

The three systems

The Universal Numbering System is standard in the United States. The FDI two-digit system is the international standard and is used almost everywhere else, as well as in most research. The Palmer notation, using a bracket symbol plus a number, remains common in orthodontics and in the United Kingdom.

• Universal numbering runs continuously: it starts at the upper right third molar as 1, runs left across the top to 16, drops to the lower left third molar as 17, and runs back to 32 at the lower right third molar.
• FDI numbers are read as two separate digits, not as a number in the twenties or forties. Tooth 46 is "four six", where 4 is the quadrant and 6 is the tooth position.

How the FDI system works

The FDI system encodes position in two digits, which is why it transfers cleanly across languages and is the international standard. The first digit is the quadrant, numbered clockwise from the patient upper right as seen by the clinician facing them. The second digit is the tooth position counting outward from the midline, from 1 at the central incisor to 8 at the third molar.

• Position digits: 1 central incisor, 2 lateral incisor, 3 canine, 4 first premolar, 5 second premolar, 6 first molar, 7 second molar, 8 third molar.
• Primary teeth use positions 1 to 5 only, because there are no premolars and only two molars in the primary dentition.

Converting between systems

The most common conversions in practice are between Universal and FDI, and the mapping below covers the teeth people most often ask about. Wisdom teeth and first molars account for most queries, because they are the teeth most often extracted or restored.

Limitaciones

• Left and right are always the patient left and right, not the viewer. A chart viewed as an image is mirrored relative to the patient, which is the single most common source of confusion.
• Supernumerary and congenitally missing teeth are handled differently by each system, and conventions vary between practices.
• Mixed dentition in children, where primary and permanent teeth are both present, requires care because the two sets use different notation within the same system.
• This chart identifies teeth. It says nothing about their condition, and cannot be used to interpret a treatment plan clinically.
• Some practices use local variants or shorthand that do not match any of the three standard systems exactly.
• If a treatment plan is unclear, ask the practice which system they use rather than inferring it from the numbers.

Preguntas frecuentes

What tooth is number 30?

In the Universal system used in the United States, tooth 30 is the lower right first molar. The same tooth is 46 in the FDI system used internationally.

Which numbering system does my dentist use?

In the United States, almost certainly Universal, with numbers 1 to 32 for adult teeth. Outside the US, most likely FDI two-digit numbers such as 11, 26 or 46. UK practices and orthodontists often use Palmer notation. If a plan is ambiguous, ask.

What are the wisdom tooth numbers?

In the Universal system they are 1, 16, 17 and 32. In FDI they are 18, 28, 38 and 48. Both sets refer to the four third molars, one in each quadrant.

How do I read an FDI number like 46?

As two separate digits. The first digit, 4, is the quadrant, in this case lower right. The second digit, 6, is the position counting from the midline, in this case the first molar. So 46 is the lower right first molar.

How are baby teeth numbered?

Universal uses letters A to T. FDI uses two-digit numbers from 51 to 85, with quadrant digits 5 to 8. Palmer uses letters A to E per quadrant. Primary teeth use only positions 1 to 5 because there are no premolars.

Referencias

1. American Dental Association, MouthHealthy. Eruption charts.
2. Nanci A et al. Anatomy, Head and Neck, Tooth Eruption. StatPearls, NCBI Bookshelf.
3. MedlinePlus. Dental health.
4. National Institute of Dental and Craniofacial Research. Tooth Decay.