Welcome to the home page of

Dr.Sheetal Jain

Age Determination by Teeth

Teeth are formed in alveolar cavities around the third or fourth month of intrauterine lie.

Development of the tooth begins in the shape of the crown.

At birth, the rudiments of all the temporary teeth and of the first permanent molars may be found in the jaws.

Root formation begins after completion of the crown and as the root becomes longer the crown erupts through the bone and finally emerges into the oral cavity.

The teeth calcify from crown to neck to roots.

During eruption of a permanent tooth The overlying root of its deciduous tooth simultaneously undergoes resorption, until only the crown remains. The unsupported crown is then shed.

The age of eruption of teeth is depending on heredity, environment, nutrition, and endocrine reactions.

Human age can be determined (a) by the study of state of, development and (b) by secondary changes. in the developing teeth.

Temporary, deciduous or milk teeth are 20 in number;

4 incisors,

2 canines and

4 molars in each jaw.

In week children, and especially in rickets, dentition may be delayed, while in syphilis teeth may be premature or even present at birth.

At about 4 years, there is .usually spacing between the deciduous teeth..

The temporary teeth commence to be shed about at the sixth or seventh year after the eruption of permanent first molar teeth.

At the age of nine, 12 Permanent teeth are in the mouth;

8 .incisors and 4 first molars.Deciduous molars and canines should still be present.

At the age 11, there are 20 permanent teeth : 8 incisors, 8 premolars and 4 molars. At the age 14, thereare 28 permanent tcefh, and no deciduous teeth.

Permanent teeth are 32 in number: 4 incisors, 2 canines, 4 premolars, and 6 molars in each jaw.

Developmentally teeth are divided into two sets:

Superadded permanent teeth are 6 in each jaw.

Successional teeth are ten in each jaw.

Morphology of permanent teeth :

Each tooth has crown,

a neck and

a root embedded in the jaw bone.

Teeth are composed of dentin, covered on the crown by enamel and on the root by cementum, which is attached to the alveolar bone by periodontal membrane

Incisors :

The crown is shaped like chisel and is convex on its labial surface and concave on its lingual surface, except near the neck, where the surface becomes convex. The neck is slightly constricted. The root is single.

Canines :

They are larger than the incisors.

The crown is large and conical, very concave on its labial surface and slightly concave on its lingual surface.

Its masticatory edge tapers to a blunt point, which projects slightly beyond the level of the other teeth. The root is single, larger and thicker than that of an incisor.

Premolars or bicuspids :

They are smaller and shorter than the canines.

The crown of each is nearly circular in cross-section and slightly compressed

The chewing surface is surmounted by two cusps.

The root is usually single, but may be double.

They are largest with broad crown.

The crown is cubical; convex on its labial and lingual surfaces, and flattened on its medial and distal surfaces.

It has three, four or five cusps. Each upper molar has three roots and lower two.

Deciduous teeth :

In both deciduous and permanent teeth dentition occurs earlier in lower jaw except for the lateral incisors which erupt earlier in upper jaw.

Wisdom tooth first erupts in the lower and on the left side and then on the right side.

The number and eruption of deciduous teeth is more regular than the permanent dentition.

Tooth eruption in females may be one year before that of males, and females tend to have smaller teeth (esp. lower canines) than males.

The dental and skeletal ages, correspond closely in the male, but in the female the skeletal age is generally one year ahead of the dental age.

Eruption tends to occur earlier in warmer climates and in urban areas.

From birth to 14 years of age the age can be determined By:

The .degree of formation of root and crown structures,

the stage of eruption and the_inter mixing of temporary and permanent teeth .

Dental X-rays reveal the developmental status of unerrupted teeth and the degree of root completion in erupted teeth.

From 14 to 20 years,

Dental age estimation is based upon the stage of development of the third molar.

There is much variation in these, and the accuracy of dental age estimation during this period varies by about plus/minus 3 years.

The body of the jaw grows posteriorly and the ramus is elongated after eruption of second molar teeth.

If third molars are absent, than space behind the 2nd molar is present.

In some persons due to inadequate jaw space, the third molars never erupt into oral cavity, particularly the mandibular third molar. Such trapped teeth are known as impacted teeth.

The age estimation of adult over 21 years depends on the physiologic age changes in each of the dental tissues

First involving the enamel, then dentin and at last pulp is exposed in advancing age.

It depends on the functional use of teeth and also upon the hardness of the enamel.

Poor oral hygiene increases paradentosis.

First it is deposited at the pulp chamber and gradually extends downwards to the apex, and may completely obliterate the pulp cavity.

This is partly due to ageing and partly due to pathological conditions like ,caries, and paradentosis.

[6]Transparancy o the root : It is not seen until about 30 years of age. The canals in the dentin are at first wide. With age they are filled by mineral so that they become invisible and the dentin becomes transparent . It is the most reliable of all criteria. Before the tooth is extracted from a body, the degree of paradentosis is estimated.