Modified Triadan System

Introduction

The modified Triadan system provides a consistent method of numbering teeth across different animal species.

The system is based on the permanent dentition of the pig, which has 11 teeth in each quadrant - three incisors, one canine, four premolars and three molars. The grand total is 44 teeth.

Quadrant

The first digit of the Triadan numbering system refers to the quadrant: right maxilla, left maxilla, left mandible, right mandible.

The quadrants are numbered 1-4 starting with the right maxilla and ending with the right mandible in a clockwise direction as viewed from the front of the animal.

For deciduous dentition, numbers 5-8 are used in the same way.

Tooth Position

The second and third digits refer to the tooth position within the quadrant, with the sequence always starting at the midline.

Certain rules should be followed in species that have fewer teeth, such as cats, rabbits and horses.

The central incisor is always 01 and the following incisors are 02 and 03.

The canines are always 04.

The premolars are 05 to 08 and the last premolar is always 08.

The first molar is always 09 and the following molars are 10 and 11.

The carnassials of carnivores can be used as landmarks to help number the teeth, as the upper carnassials are always the last premolars (108 and 208) and the lower carnassials are always the first molars (309 and 409).

The numbers of the other teeth can then be determined.

Examples

In the dog: the mandibular left canine is 304 for the permanent tooth and 704 for the deciduous tooth.

The mandibular right first molar is 409.

In the cat: the "second" mandibular left premolar is 308. (1 tooth forward from the lower left carnassial which is always 09).

The "first" maxillary right premolar is 106. (the largest cheek tooth in the cat maxilla is the fourth premolar 108, 2 teeth rostrally from this is the first premolar 106. There is no 105 in the cat)

In the rabbit: the second incisor in the left maxilla (the peg tooth) is 202. There is no third incisor or canine in the rabbit maxilla, so these numbers are missing.

Modified Triadan System Learning Resources
Flashcards Test your knowledge using flashcard type questions	Veterinary Dentistry Q&A 03

References

Tutt, C. (2006) Small animal dentistry: a manual of techniques Wiley-Blackwell

Johnston, N. Veterinary Dentistry interactive programme

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