Nomenclature, Formulae for Mammalian Teeth and Tooth Numbering Systems.

Aims and Objectives • An introduction to deciduous and permanent human dentitions.

• Understanding the terms and nomenclature of teeth.

• Knowledge of the formulae for the human teeth.

• Familiarity with the available numbering systems of both human dentitions.

Introduction

Humans have 2 sets of teeth:

Primary or deciduous dentition.

Permanent dentition.

Primary Dentition

• 20 in number., First evidence of formation about 6 Weeks in utero.

• First teeth to erupt at 6 months of age (mandibular central incisors).

• Primary dentition completed around 3 years of age.

• The deciduous dentition remain functioning alone till around the age of 6 years, when the period of mixed dentition starts.

Mixed Dentition

• Permanent teeth begin to erupt around the age of 6 years.

• Mixture of primary and permanent teeth begins the transition or mixed dentition period.

• The mixed dentition stage ends with the shedding of all the primary teeth.

Permanent Dentition• Shedding of the primary teeth marks the beginning of the permanent dentition period.

• The first permanent tooth erupts around the age of 6 years.

• With the exception of the third molar, the permanent dentition is completed around the age of 15 years.

• The third molar erupts around the age of 18.

• 32 teeth.

Terms and Nomenclature

Teeth that erupt in the lower jaw (mandible) are called mandibular teeth.

Terms and Nomenclature

Teeth that erupt in the upper jaw (maxilla) are called maxillary teeth.

Terms and Nomenclature

Primary teeth: belonging to the first stage.

Deciduous: not permanent, transitory.

Milk teeth.

Baby teeth.

Terms and Nomenclature

Permanent teeth: not always the case due to caries and periodontal disease.

Succedaneous: successor dentition.

Formulae for Mammalian Teeth• Formulae exist to differentiate the human dentitions from other species.

• The initial letter of a tooth’s name is used to denominate it: I, C, P and M.

• A horizontal line with the number of each type of tooth follows the denomination letter: I 2 C 1 M 2

2 1 2

• The number of teeth on one side

Formulae for Mammalian Teeth

• Formula for primary dentition

I 2 C 1 M 2 = 10 2 1 2• Formula for permanent dentition

I 2 C 1 P 2 M 3 = 16 2 1 2 3

Tooth Numbering Systems

•A shorthand system for naming teeth is needed in clinical practice.

•Many systems around the world, different schools adopted different systems.

Zsigmondy/ Palmer System

• Recommended by the ADA in 1947

• The primary dentition is divided into quadrants.

E D C B A | A B C D EE D C B A | A B C D E

Zsigmondy/ Palmer System

•The permanent dentition is divided into quadrants.

• numbering from 1 to 8 starting from the central incisor.

8 7 6 5 4 3 2 1 | 1 2 3 4 5 6 7 88 7 6 5 4 3 2 1 | 1 2 3 4 5 6 7 8

Universal Numbering System

• Recommended by the ADA in 1968

• Uses uppercase letters for each of the primary teeth.

• Beginning at the maxillary right second molar.

A B C D E | F G H I J T S R Q P | O N M L KRight Left

Midsagittal plane

Universal Numbering System

• For the permanent dentition, numbering from 1 to 32

• Beginning at the maxillary right third molar.

1 2 3 4 5 6 7 8 | 9 10 11 12 13 14 15 1632 31 30 29 28 27 26 25 | 24 23 22 21 20 19 18 17

Haderup system

• Introduced by Viktor Haderup of Denmark in 1891

• Plus (+) and minus (-) used to differentiate upper and lower quadrants and between left and right.

• +1 = upper left central incisor

• 1- = lower right central incisor.

• Primary teeth were numbered as 05 to 01…etc

FDI system• Introduced by the Federation Dentaire Internationale (FDI) and adopted by the World Health Organization (WHO).

• Two-digit system

18 17 16 15 14 13 12 11 | 21 22 23 24 25 26 27 2848 47 46 45 44 43 42 41 | 31 32 33 34 35 36 37 38

Upper right

Lower left

Upper left

Lower right

55 54 53 52 51 | 61 62 63 64 6585 84 83 82 81 | 71 72 73 74 75

Upper right

Lower left

Upper left

Lower right

Recommended Textbook

Ash M. and Nelson S.: Wheeler’s Dental Anatomy, Physiology and Occlusion, 8th edition, Philadelphia, 2003, Saunders.