intoduction oral morphology
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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