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Oral Morphology

It include the external morphology and internal composition of the

individual teeth, the relationship of the teeth to each other and to the

skull.

The teeth are arranged in upper and lower arches. Those teeth in the

upper arch are termed maxillary teeth; while the teeth in the lower

arch are termed mandibular teeth. The mandible is the movable

member of the two jaws, while the maxilla is stationary.

The imaginary vertical line which divides each arch, as well as the

body, into two approximately equal halves, is the midline. The two

approximately equal portions of each arch divided by the midline are

termed quadrants, since there are four in the entire mouth. They are

termed: Maxillary (upper) right and left, Mandibular (lower) right and

left.

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Types of teeth: 1. Incisors (2)

2. Canine (1)

3. Premolars (2)

The incisors are the two teeth of each

quadrant, which are closest to the midline.

They are named central and lateral incisors.

Their normal functions in mastication are

biting, cutting, incising and shearing.

There are four incisors per arch, and a total of

eight in the mouth.

The canine is the third tooth from the midline in each

quadrant.

Its function in mastication is cutting, tearing, piercing,

and holding. It also is called a cuspid.

There are two canines per arch, and a total of four in

the mouth.

The premolars are the fourth and fifth teeth from

the midline. They are termed first and second

premolars.

Their masticatory role is tearing, holding, and

grinding. They are called bicuspids.

There are four per arch, and eight total premolars.

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4. Molars (3)

Classification of Dentitions: In man, the two dentitions are termed deciduous and permanent, while

the transitional phase when both deciduous and permanent teeth are present

is called the mixed dentition period.

1. Deciduous dentition:

The molars are the sixth, seventh, and eighth

teeth from the midline. They are termed first,

second, and third molars.

Their masticatory function is grinding.

There are six permanent molars per arch, and

twelve total permanent molars.

The teeth of the first or primary dentition.

They erupt into the mouth from about 6 months to 2 years of age.

Normally, there are 20 total deciduous teeth.

Other non-scientific names for the deciduous teeth include "milk"

teeth. '-baby" teeth, and "temporary" teeth.

Each quadrant of man's deciduous dentition contains the following

types of teeth

i. Incisors (2), which are named central and lateral

incisors.

ii. Canine (1), or cuspid.

iii. Molars (2), which are named first and second molars.

Therefore, there are five deciduous teeth per quadrant. Ten per arch

and a total of twenty in the primary dentition.

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2. Permanent dentition

iv. Molars (3): The molars are the sixth, seventh, and eighth teeth from

the midline. They are termed first, second, and third molars. They

are also called six year molar, twelve year &, and wisdom tooth, in

that order. There are six permanent molars per arch, and twelve

total permanent molars.

3. Mixed dentition period

That period during which both deciduous and permanent teeth are

present.

From approximately 6 years to 12 years of age.

Mixed dentition period ends with the exfoliation of the last deciduous

tooth, normally the maxillary second molar.

Permanent teeth (incisors, canines and premolars) that replace

exfoliated deciduous teeth are called succedaneous teeth, which

simply means "succeeding" deciduous teeth. Since there are twenty

deciduous teeth to be replaced, there must be twenty succedaneous

teeth.

Therefore, the only permanent teeth which are not succedaneous are

the molars. It may be said, then, that all succedaneous teeth are

permanent teeth, but not all permanent teeth are succedaneous teeth

The teeth of the second or adult dentition.

They erupt from 6-21 years of age.

Normally, there are 32 permanent teeth (16 per arch, 8 per

quadrant)

i. Incisors (2): They are named central and lateral

incisors.

ii. Canine (1): There are two permanent canines per arch,

and a total of four in the mouth.

iii. Premolars (2): The premolars are the fourth and fifth

teeth from the midline. They are termed first and

second premolars. There are four per arch, and eight

total premolars.

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Dental Formula A number and letter designation of the various types of teeth found in

a dentition. It indicates the dentition of only one side of the mouth, but includes

both the upper and lower quadrants, and so must be multiplied by a

factor of two to provide the number of teeth in the entire dentition.

Permanent dentition is as follow:

I C P M (X2 = 32 total teeth)

Deciduous dentition is as follow:

I C M (X2 = 20 total teeth)

Numbering Systems

Numbering systems in dentistry serve as abbreviations. Instead of writing

out the entire name of a tooth.

These symbols indicate whether the tooth is:

Deciduous or permanent

Upper or lower

Right or left

The tooth type

There are 3 numbering systems:

A. Palmer notation system.

B. International (Two Digit) system.

C. Universal numbering system.

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A. Palmer Notation Method: The system used simple bracket to represent the four quadrants of the

dentition

The permanent teeth are numbered from 1-8 on each side from the midline,

so 1 is a central incisor, 3 is a canine and 8 is a third molar

The deciduous teeth are lettered of alphabet from A to E.

Examples:

6 Permanent upper left 1st molar

D Deciduous lower right 1st molar

4 Permanent lower left 1st premolar

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B. The international numbering system (two

digit system) The first number identifies the quadrant, and whether the tooth is

permanent or deciduous.

The second number identifies the particular tooth in the quadrant,

exactly like the Palmer notation method for permanent teeth (1-8).

The deciduous teeth in each quadrant are numbered (1-5).

Permanent teeth

Deciduous teeth

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C. Universal Numbering System It employs a different number (1-32) in a consecutive arrangement for

all permanent teeth, and a number-letter (ld-20d) for each of the

deciduous teeth.

The number is always preceded by the sign # to designate that the

system is used for universal system.

Permanent Teeth

The universal numbering system assigns a specific number to each

permanent tooth starting from the upper right third molar is #1, and so

forth around the entire maxillary arch to the upper left third molar,

which is #16.

Since there are no more permanent teeth in the maxillary arch, the

succession drops to the lower left third molar which is #17, and

continues around the entire mandibular arch where the lower right

third molar is #32.

Deciduous Teeth

The twenty teeth of the deciduous dentition are numbered in the same

manner, as are the permanent teeth (1-20), except that a small (d) is

added as a suffix to each number to designate deciduous.

The deciduous upper right second molar is thus #1d, while the upper

left second molar is #10d.

The lower right canine, for example, is #18d.

The other most common system in use today for designating

deciduous teeth uses the capital letters A through T. The maxillary

right deciduous second molar is tooth A, so that the mandibular right

deciduous second molar is tooth T.

6 7 8 9 10 1 2 3 4 5

15 14 13 12 11 20 19 18 17 16

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Macro-anatomy of the teeth

1. Anatomical crown –

That portion of the tooth that is

covered by enamel.

2. Clinical crown –

That portion of the tooth that is

visible in the mouth.

3. Anatomical root -That portion of the tooth that is covered with

cementum.

4. Clinical root -That portion of the tooth that is not visible in the mouth.

5. Cervical line - separates anatomical crown from anatomical root.

Micro-anatomy of the teeth

The dentin constitutes the bulk, or majority, of the total tooth tissues.

1. Enamel –

The hard mineralized tissue, which

covers the dentin of the anatomical

crown of a tooth. It is the hardest

living body tissue.

2. Dentin –

The hard tissue, which forms the

main body of the tooth.

It surrounds the pulp cavity.

It is covered by the enamel in the

anatomical crown and by the

cementum in the anatomical root.

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3. Cementum –

The layer of hard, bonelike tissue, which covers the dentin of the

anatomical root of a tooth.

4. Pulp –

The living soft tissue, which occupies the pulp cavity of a vital tooth. It

contains the tooth's nutrient supply in the form of blood vessels as well

as the nerve supply.

Tooth surfaces

1. Anteriors

All anterior teeth exhibit four surfaces and one edge on their Crowns.

They are named as follows:

Mesial - The surface toward the midline.

Distal - The surface away from the midline.

Facial (labial) - the term facial surface describes the "outside" surface

of either the anterior teeth or the posterior teeth. Labial: The

"outside" surface of anterior teeth which is toward the lips.

Lingual / palatal - The "inside" surface which is toward the tongue /

palate.

Incisal edge (or ridge) - The biting edge.

2. Posteriors

All posterior teeth exhibit five surfaces on their crowns:

Mesial, Distal, and Lingual - These surfaces may be defined like the

corresponding of anterior teeth.

Facial (buccal) - The "outside" surface which is toward cheek.

Occlusal - The chewing surface.

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Line angle Formed by the junction of two crown surfaces, and its name is derived

by combining the names of those two surfaces.

Line angles of anterior teeth:

1. Mesiolabial 4. Labioincisal

2. Mesiolingual 5. Linguoincisal

3. Distolabial 6. Distolingual

Line angles of posterior teeth:

1. Mesiobuccal 5. Bucco-occlusal

2. Mesiolingual 6. Linguo-occlusal

3. Distobuccal 7. Disto-occlusal

4. Distolingual 8. Mesio-occlusal

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Point angle Formed by the junction of three crown surfaces, and its name is

derived by those three surfaces.

Point angles of anterior teeth:

1. Mesio-labio-incisal

2. Mesio-linguo-incisal

3. Disto-labio-incisal

4. Disto-linguo-incisal

Point angles of posterior teeth:

1) Mesio-bucco-occlusal

2) Mesio-linguo-occlusal

3) Disto-bucco-occlusal

4) Disto-linguo-occlusal