Anthropological concepts in clinical /certified fixed orthodontic courses by Indian dental academy

Anthropological Concepts In
Clinical Orthodontics
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


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Introduction
What Is Anthropology?
Classification of Anthropology
Evolution
The Various Eras of Evolution.
Theories of Evolution
Hominid Evolution Process
Evolution of Human Face
Evolution of the jaw and joints
Evolution of teeth and its attachment apparatus
Orthodontic aspects of dental anthropology
Indices in anthropology
Crown shape, winged and shovel shaped incisors
Theory of overbite and buccal segment reproximation.
Carabelli Trait
Conclusion


Introduction





Orthodontists are functioning anthropologists.
We measure the bones of the skull, face, and
teeth and study the relationships of these
structures.
We should also be interested, then, in
learning as much as possible about the
origins of human beings and evolutionary
development of our anatomy.


What is Anthropology ?




Anthropology is the study of
humans in all places and at
all times. The term itself
comes from the Greek
(anthropos=man, logos=the
study of).
Anthropologists study
modern humans and their
direct ancestors whom we will
refer to as hominids.

CLASSIFICATION OF
ANTHROPOLOGY
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Physical Anthropology
Cultural Anthropology
Archaeology
Linguistic Anthropology


Physical Anthropology
It involves
mechanisms of
biological evolution,
genetic inheritance,
human adaptability
and
variation,
primatology, and
the fossil record of
human evolution



Cultural Anthropology


Branch of Anthropology
that deals with Culture,
subsistence and other
economic patterns,
kinship, sex and
marriage, socialization,
social control, political
organization, class,
ethnicity, gender,
religion, and cultural
changes .


Linguistic Anthropology
It is the human
communication process
focusing on the
importance of sociocultural influences;
nonverbal
communication; and
the structure, function,
and history of
languages



Archaeology
Prehistory and early
history of cultures
around the world; major
trends in cultural
evolution; and
techniques for finding,
excavating, dating, and
analyzing material
remains of past
societies.




WHAT IS DENTAL
ANTHROPOLOGY?


Dental Anthropology is the study of teeth in a
perspective beyond clinical science. That
perspective includes the study of dental
growth, theories on dental origin, primate
dentition, and population variation


Evolution


Evolution is a continuous process of change
from one form to another.



Acc. to theory of evolution or origin of species
,all present forms of life have been derived
from earlier simple forms.


Various eras of evolution


Paleozoic era


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Fossil fish first appear in the rocks of silurian
period.
Fossil amphibians in the Devonian period.
And the reptiles in the pennsylvanion period


Mesozoic era


This era was dominated by reptiles.



In early triassic period fossils of first of primitive
mammals were found, and later those of first birds
were found.

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In cretaceous period, fossils of first modern
mammals appeared, but by the end of this period
primitive mammals got extinct.


Caenozoic era

The tertiary

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1.
2.
3.
4.
5.

The paleocene
The eocene
The oligocene
The miocene
The piliocene

The quaternary



1.
2.


The pleistocene
The halocene

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Fossil primates first appeared in the rocks of
paleocene epoch .
Fossil anthropoid apes appeared in the rocks
of oligocene epoch.
Australopithecus fossils from upper pliocene
and lower pleistocene epoch.
Earliest human fossils from pleistocene
epoch.


Theories of evolution
Four main theories to explain the method by
which species of life that exist today have
evolved from earlier simpler forms.

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1.
2.
3.
4.

The lamarckian theory.
The theory of orthogenesis.
The theory of natural selection.
The mendelian theory.


The lamarckian theory
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Characters acquired and changes taking
place during life of an organism are inherited
after the acquired character and changes
have persisted for a long time.
They are due to change in environment and
to the concerned effects of use and disuse.
Eg: girrafes with long necks.


Theory of orthogenesis [development
in straight line]
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Put forth by Haldane and Julian Huxley.

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They considered that evolution proceeds in any
particular direction ,not because of any advantage
gained by the race or because of direct moulding
effect by the surrounding, but because of some
inner urge ,some necessity for the hereditary
constitution to change in just that particular way.


Natural Selection
or Survival Of The Fittest


Charles Darwin
propounded this theory of
organic evolution.



This theory assumes that
every life on earth was
developed from previous
form.




He attributed changes
in living organisms to
the action of natural
selection and in many
instances to the effect
of use and disuse.


This theory can be summarized briefly as:



1.
2.
3.
4.

Struggle for existence
Natural selection
Heredity
Survival of the fittest.




As the world has a limited surface, and more
animals are born into it than it is capable of
holding, this produces struggle for existence,
the outcome of which is natural selection or
survival of the fittest and new species
originates.

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Natural selection exterminates the unfit.


Mendel's law of inheritance
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Mendel discovered the fact of segregation or
dissociation of characters from each other in
the course of formation of germ cell.

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His research work was on edible pea.


Hominid evolution
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Hominids and apes have common ancestors.
They parted their way about 6 million years ago.
The study of the evolution of hominid provides
important clues about locomotion, behavior,
adaptation and lifestyle.
Homosapiens, maturing more slowly than other
primates, retained many primitive features, which
may be why the genus has been successful. Hands
and teeth, for eg, are quite primitive.
Genera that become specialized tend to become
extinct when their environment changes.

Hominid evolution process


The following order can be followed:
1) The Great apes : Chimpanzee, gorilla
and
orangutan.
2) The 'gracile' Australopithecines.
3) The 'robust' paranthropus group.
4) Homohabilis 'handy man' - early Homo.
5) Homo erectus 'upright man'
6) Neanderthals 'Archaic homosapiens'
7) Homo Sapiens 'wiseman'.

The Great Apes
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Orangutan
limited to borneo and
Indonesia
arboreal and frugiverous
(fruit eaters).
Legs are shortened with
arms lengthened.
skull and face are elongated
and surrounded by fur.
Dental formula
I-2,C-1,PM-2,M-3.
narrower jaws than Gorilla
and molars are of equal
size.
enamel on molar shows
marked wrinkling


The Great Apes
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Gorilla
Largest of living primates
Restricted to Africa.
Have clavicles which help in
brachiating.
Dental formula
I-2,C-1,PM-2,M-3.
Strong incisors with chisel
like edges.
Diastema between the
laterals and canines in both
arches.
Well defined maxillary
premolars
Canines exhibit sexual
dimorphism.


The Great Apes
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Chimpanzees
Closest match to Homo
Sapiens genetically.
Have a complex social
behaviour.
Dental formula
I-2,C-1,PM-2,M-3.
Have little wider arches than
organgutan's
Canines exhibit sexual
dimorphism - male have
heavier, longer and more
curved canines.


The 'gracile' Australopithecines
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Walked upright
Small brains, cranial capacity
of about 450 cc.
Large protruding faces.
Were highly dimorphic; male
about twice the size of
females.
Dental features are
intermediate between those of
apes and modern humans.
Arcade is omega shaped,
intermediate between the box
row and the parabolic curve in
humans
Lower first premolar has two
cusps.
Design of dentition being
more effective for grinding.


The 'Robust' Paranthropus group
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First identified by Robert
Broom
More sturdier
Molars are enormous
Lower jaws is very large
The entire skull has been
reorganized to
accommodate the massives
chewing apparatus.


Homohabilis 'handy man' - 'Early
Home'
The evolutionary trend towards:

relatively greater cranial
capacity, i.e. about 600-650 cc.

orthognathy,
 dental reduction,
 greater body size,
which had begun in H.Habilis,
continued in its descendants.
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Associated with stone tools.


Homo Erectus 'upright man'
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thick cranial vault
Cranial capacity of
about 850 cc.
prominent browridges
and the sagittal keel
sizes of the posterior
teeth are decreased
while anteriors are
larger than modern
humans
upper central incisors
are distinctively shovel
shaped.


Neandertals, often called 'Archaic
Ruggedly built, and short
Homosapiens'
stocky bodies
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Developed skilled stone tool
technology
Had larger brains
Skull had characteristic
presence of an occipital 'bun'
at the rear end.
Have large canines and
incisors relative to their molars
and premolars
Dentition as a whole is placed
forward relative to the skull
vault, because of this
anatomical change - the
retromolar space is seen.
Frequent feature was
taurodontism.


Homosapiens 'Wiseman'
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Anatomically modern
Homosapiens first appeared
100,000 years ago
Skull is high and well
rounded
Orthognathic face
Modern humans have small
faces tucked under
enlarged brain cases
Cranial capacity increased
to about 1300 cc.
Teeth progressively
reduced in size, concurrent
with the reduction of
masticatory apparatus.


Evolution of human face

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In a typical non
primates :dog ,sheep or
hedgehog ,the facial
skeleton projects in
front of cranial region of
skull.


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During primate
evolution facial
skeleton bent gradually
more downwards until
in man it lies below the
overhanging frontal
region of cranium.


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Erect posture in humans.

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The arms and hands have become freed.
The manipulation of food and other objects
and defense, offense, and so forth, utilize
primarily the hands, rather than the shortened
jaws.


The large size of the human
brain also relates to a
rotation of the orbits toward
the midline.
This results in a binocular
arrangement of the orbits, a
feature that complements
finger-controlled
manipulation of food, tools,
weapons, and so forth.
The absence of a long,
protrusive muzzle does not
block the close-up vision of
hand-held objects


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Complete orbital rotation into a forward-pointing direction,
however, has also caused a marked reduction in the
interorbital part of the face.

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This is significant, because the area involved is the root of
the nasal region, and the result of man's close-set eyes is a
narrow nose

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Reduction in nasal
protrusion is accompanied by
a more or less equivalent
reduction of the jaw .


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The downward rotation of the olfactory bulbs and the whole
anterior cranial floor by the enlarged frontal lobes of the
cerebrum has caused a corresponding downward rotation of
the nasomaxillary complex.


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Facial rotation has led to the development of the human
maxillary sinus beneath the orbital floor and above the
shortened maxillary arch .
Because of its adaptation to facial rotation, the human maxilla
is uniquely rectangular, rather than triangular like that of most
other mammals. It is a distinctively shaped upper jaw.
An orbital floor has also been added to the human maxilla
because the middle and lower parts of the face have been
rotated to a position beneath the eyes.

Evolution of jaws and joints

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The first vertebrates did not have jaws.
These are collectively referred to as the "Agnatha"
(a=without, gnath=jaws), or jawless fish.


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Placoderms, an extinct group of early fishes, had 7
arches. The first arch was lost. Their new ‘first’ arch
became the mandibular arch that formed jaws.

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The upper half of the mandibular arch became the
palatoquadrate cartilage, the lower half became the
mandibular or Meckel’s cartilage.

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At about the same time in the fossil record there
appears several major groups of fishes,
Elasmobrancs, in these groups, the jaws were
formed by components of arch #1 and #2. Arch #2 is
called the hyoid arch (upper half = hyomandibular
cartilage, lower half = hyoid cartilage).

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Amphibians
In amphibians, the hyomandibular cartilage became the
stapes in the middle ear.
The hyoid apparatus supports the tongue and larynx.
With the loss of remaining gill arches, associated dermal
bones that connected the head to pectoral girdle were also
lost creating an independent neck region.

Reptiles and the evolution of the
secondary palate and middle ear ossicles
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Reptiles invented the secondary palate that allows
us to eat and breathe at the same time.
The reptile line that led to mammals substantially
increased bite force by ultimately redesigning the
articulation of the jaw joint.
This in turn led to the development of the malleus
(hammer) and incus (anvil) ossicles in the middle
ear.

The secondary palate
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Fish have good noses.
They smell by passing water through a loop located on
their snout and extract dissolved oxygen.
The loop does not connect to the mouth cavity.
The lobe finned fishes (Sarcopterygii) breathed
atmospheric oxygen. One of the consequences of air
breathing is that the olfactory loop became redirected.
Instead of exiting back to the outside environment, the
loop turned and entered the anterior margin of the mouth
cavity, forming the internal nares. Thus, these fish could
breathe by bringing the tip of their snout to the surface.

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Amphibians inherited this
anatomy. Because the
internal nares are at the
anterior margin of the
mouth, amphibians have to
hold their breath while they
eat.
Amphibians can use
cutaneous gas exchange
until the prey is swallowed.


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Reptiles, with their hardened, dry skin do not have
that luxury. Any reptile that did a better job of eating
while breathing would be favored by natural
selection.
Over evolutionary time, the fossil record shows a
second shelf of bone forming across the roof of the
mouth.
First the premaxilla bone, then later, the maxilla
bone, then finally the palatine bone all extended a
shelf from each side of the jaw and met in the
middle.
This shelf formed a separate passage for air from
the external nares.
Over time, the internal nares entered the mouth
further and further toward the throat.
This shelf is the secondary palate. We know it in
humans as the hard palate.

Evolution of TMJ

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In reptiles generally, including the now extinct early synapsid
reptiles that gave rise to mammals, the jaw joint is formed by
the articular (lower) and quadrate (upper) bones.
The joint was a simple hinge at the posterior of the jaw.
The jaw closed putting even pressure along its margin
therefore, the force exerted on the joint was in proportion to
the bite pressure.

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In mid to late synapsid reptiles, the dentary bone (lower jaw)
increased in size as muscle and bite force increased, but force on the
joint decreased.
This was because muscle insertion points shifted to allow greater jaw
mobility.
The looser the joint became, the more control synapsids had over
specialized processing of food along regions of the jaw margin.
The articular and quadrate bones at the jaw joint became smaller and
more loosely associated with the dentary.
The coronoid process of the dentary bone formed to accommodate
these changing forces.

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Ultimately, the jaw joint shifted from a articularquadrate joint to a dentary-squamosal joint.

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The condyloid process formed to create a new
articulating surface.

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Freed from jaw mechanics, selection pressure favoring
perception of sound took the evolutionary opportunity of
the articular and quadrate bones adrift at the margin of
the jaw joint and incorporated them into the middle ear.
The articular became the malleus (hammer) and the
quadrate became the incus (anvil). Humans, and all
mammals, have these bones to this day.

Functional adaptation of TMJ in
various species.
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In carnivora :
They mainly shear the food.
The condyle is almost on a level with the
lower teeth.
The condyle is much more rounded and
shorter in A-P direction.
But the condyle is elongated and large in the
transverse plane and is locked in a closefitting glenoid cavity which allows only a
hinged movement of the lower jaw.

In Omnivora:
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There is a slight lateral movement in the
omnivorous species where the condyle is
less firmly held in glenoid cavity.
The temporal muscle is huge and the
masseter is highly developed


In herbivora:
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The condyle is broad, flattened and slightly
convex and the glenoid cavity is shallow to
permit much free movement in all directions.
They mainly grind the food.
So it has a strong pterygoid muscles, i.e. the
lateral pterygoid muscles and medial
pterygoid muscles.


EVOLUTION OF HUMAN MOLAR
OR TEETH
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Six main theories :
1) Concrescence theory
2) Cingulum theory
3) Kinetogenetic theory
4) Tritubercular theory
5) Multitubercular theory
6) Dimer's theory

Concrescence theory :
Ameghino, Rose and Kekentha

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Given by



Mammalian teeth were developed from simpler cones
(Haplodont teeth) and the modern multiple -cusped
teeth are formed by the fusion of 2 or more of these
simple haplodont teeth into a compound tooth.



This might be due to - shortening of jaws, uniting the
teeth of the same series or by a fusion bucco-lingually,
uniting the teeth of one series with those of their
successors.


Cingulum theory


Mammalian tooth is derived from haplodont
tooth.



"Marrett Tims" considers that basal ridge or
cingulum, with surrounds a tooth at its neck,
develops into a fresh cusp or cups- which
explains to a great extent the evolution of
complex tooth form.


Kinetogenetic theory


Ryder, who upholds this theory, again regards the
earliest mammalian teeth as haplodont in origin.



He mentioned that the movements of TMJ, govern
the form of the tooth.

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The simple cones become flattened by mutual
pressure, and the ridge and hollows are produced
by the movements of the lower jaw in mastication.


Tritubercular theory or Cope - Osborn
theory


He considered that multicuspid mammalian are
developed from a simple haplodont or reptilian form
of tooth by the addition of extra cusps.



In this theory - original haplodont cone is known as
the protocone



When this original cone has two small accessory
cones on its mesial and distal surface and it is
known as protodont tooth.



These small accessory cones develop in size until
the tooth consists of 3 cones in a straight line and
this is known as triconodont teeth.

Tooth

anterior

middle

posterior

Maxillary

Paracone

Protocone

Metacone

Mandibular

Paraconid

Protoconid

Metaconid


mesial
lingual
distal

Paracone
Protocone
Metacone
Paracone
Protocone
Metacone
Paracone
Metacone

Protocone
Hypocone

M-B cusp
D-B cusp

Trigon
M-L cusp
D-L cusp


Lower molar
Mesial
Buccal
distal

paraconid
protoconid
metaconid
paraconid

protoconid
metaconid
protoconid

metaconid

protoconid
hypoconid

metaconid
entaconid
hypoconulid


Finally lower molar
M-B cusp

Trigon

D-B cusp

M-L cusp
D-L cusp

Talon
Distal cusp

Multitubercular (or polybuny) theory



Forsyth Major, refutes the statement that the 1st
mammalian tooth can be traced back to a simple
haplodont or a tritubercular tooth.



Forsyth Major considers that human molars and
modern mammalian molar (whether tritubercular or
not) are derived from multitubercular teeth by
reduction in the number of tubercles.


Dimer theory


It is the result of investigation by Prof. Bolk of
Amsterdam and advances the view that there is
one origin for all mammalian teeth, whether,
incisors, canine, premolars or molars.



Bolk's views are expressed under 4 headings :

i)

Hypothesis of triconodonty
Hypothesis of dimery
Hypothesis of concentration
Hypothesis of equivalence

ii)
iii)
iv)


i) Hypothesis of triconodonty -



mammalian teeth are evolved from a
triconodont teeth, not a haplodont with one
large and 2 small cusps in a straight line
anteroposteriorly.


ii) The hypothesis of dimery :










Every mammalian tooth = two reptilian teeth.
Labial and incisal portion of the incisors, canines
and buccal cusps of premolars and molars = one
series of reptilian teeth.
Cingulum of incisors, canine and lingual cusps of
premolars and molars = second or later series of
reptilian teeth.
Each longitudinal half of human tooth = monomere
buccal half = protomere
lingual half = deuteromere
together form a dimerous tooth.

iii) Hypothesis of concentration :


The polyphyodont in reptiles is reduced to
diphyodontism in modern mammals.



There is a concentration of the tooth germs of
two reptilian teeth to form one mammalian
tooth.


iv) Hypothesis of equivalence :






Elements of mammalian set of teeth are all
morphologically alike.
The terms monocuspidate and multicuspidate
possess only a descriptive anatomical value
and do not indicate any morphogenetic
differences.
The tooth germ of every tooth possesses the
potentiality of developing all the cusps found
in the most complicated tooth of set.


Butler's Field Theory


In 1939, Butler, an English paleontologist,
proposed that the mammalian dentition can be
divided into several developmental fields - incisors,
canines and check teeth.



Within each field there is one tooth that is
presumed to be the stable 'best copy' - i.e., "Key"
tooth, the remaining teeth within the field become
progressively less stable.




Considering each quadrant separately, the
molar/premolar field would consist of the first
molar as the key tooth, the second and third
molars on the distal end of the field, and the
first and second premolars on the mesial end.



The theory predicts that the third molar and
first premolar would be most variable in size
and shape


Evolution of socket or attachment of
teeth


Four methods of attachment of teeth in
animal world:

1.

Fibrous
Hinged
Ankylosis
Gomphosis

2.
3.
4.


Fibrous attachment


Seen in sharks and
rays.



The teeth are fixed by
the means of fibrous
bands to the
submucosa of the
fibrous membrane
which covers the jaws.


Hinged attachment


Three main fishes have to be discussed as
they have different types of hinge
attachments.

1.

Angler
Hake
Pike

2.
3.


Angler


This fish has 2 rows of teeth
an outer anchylosed and
inner hinged row.



A hinged tooth is supplied
posteriorly by fibrous elastic
ligament, while its anterior
free edge rests upon a
buttress of bone.



The teeth bent towards the
throat, the hinge
compresses and teeth
return to their original
positions upon the force
being removed.


The hake

i)

ii)







Calcified elastic part of hinge
which prolong downwards to the
bone of attachment
ii) Uncalcified fibrous part of hinge
which lies in front of the calcified,
elastic portion.
- Between two part of hinge is a
triangular area containing
interlacing fibres - elastic in nature.
- The labial edge of base of teeth thickened and rounded - adapted
for resisting shock.
- This edge is at higher level - than
the lingual edge and fits upon a
buttress of bone. So that tooth
cannot be bent outward without
injury to lingual hinge.


Pike


The hinged teeth of pike sit
anteriorly on a small pedestal of
bone - but posterior hinge does
not possess elasticity.



In pike teeth (osteodentine) , the
central trabeculae do not calcify
but remain soft and elasticresponsible for returning the
teeth to their erect posture when
backward pressure is released.


Anchylosis attachment








When a tooth is fixed to the
jaw by calcified tissue it is said
to be anchylosed.
There is no intervention of
fibrous or uncalcified tissue.
Eel fish : The teeth of the Eel
rest upon little cylinder or cups
of bone of attachment and is
described as " Acrodont
anchylosis".
Here dentinal tubules do not
fuse with bone of attachment,
but little fibrous "annular
ligament" surrounds the base
of tooth and allows a slight
movement.


In Mackerel


Teeth are slung up between
the plates of the jaws by
means of osseous trabeculae
which pass between the inner
sides of the alveolus and outer
sides of teeth, the bases of
latter resting upon nothing
hard, the attachment is
pleurodont.


Gomphosis (attachment in sockets)


Seen in man, mammalia, reptiles and in
some fish eg :saw fish, pristis.



In man, mammals and crocodile, a
membrane (alveolar dental membrane) exists
between the tooth and the socket of bone in
which the tooth is situated.


Our field exists
today due to
excellent
remodeling capacity
of the PDL and
alveolar bone in
gomphosis type of
attachment

Orthodontic aspects of dental
anthropology


What is anthropometry ?


Anthropometry is a division of anthropology,it
has been described by Hrlicka as the
systemized art of measuring and taking
observations on man ,his skeleton , his brain
or other organs, by the most reliable means
and methods and for scientific purposes.


Method of holding sliding caliper

method of holding spreading caliper


Head height measurement


Face height measurement


Head length measurements


Head breath measurement


Face width measurement


What is craniometry ?


Craniometry, a subdivision of anthropometry, has
been an important study in orthodontic research
,because orthodontics is concerned primarily with
the correction of morphologic deviations from the
accepted norms in dentofacial area.



Measurements of the extent of these deviations
entails some knowledge of physical anthropology
and the ability to recognize and use the
anthropologic landmarks.


Indices in anthropology
Cephalic index


Index of skull height [profile]
basion – bregma height
max. cranial length




Chamecephalic
Orthocephalic
Hypsicephalic

< 69.9
70 – 74.9
> 75


X 100

Skull height [frontal]
basion – bregma
max. cranial breadth
Tapeinocephalic
 Matricephalic
 Acrocephalic


X 100

< 91.9
92 - 97.9
> 98


Facial index


Palatal height index
Given by Korkhaus.
 Palatal height X 100
posterior arch width
 Normal value is 42 in mixed
dentition




39.3

51.3

Rivet’s angle


Nasion – prosthion –
basion angle.



Prognathous < 69.9
Mesognathous 70 –
72.9
Orthognathous > 73.






What is Orthodontic odontometry?


The anthropologic science of measuring the size
and proportion of teeth is called odontometry.



Orthodontists practice some form of odontometry as
a part of routine case diagnosis.



Traditionally, orthodontic odontometry has been
limited to the determination of the amount of dental
arch space deficiency.


Crown Shape




In some odontometric studies, crown shape
has been found to be a determining factor in
the presence and absence of mandibular
incisor crowding.
MD
Crown shape = ------- ratio
FL



The maximum limit of desirable index values
for lower incisors are
88-92 for the mandibular central incisors
90-95 for the mandibular lateral incisors.



Lower incisors within or below the ranges is
considered favorably shaped.



Any lower incisor with MD/FL index above
these ranges, possesses a crown shape
deviation, which contribute to crowding
phenomenon.

Clinical implication:


The relationship between tooth shape and
lower incisor alignment is important in
mesiodistal enamel's stripping or
reproximation.


Overall and anterior intermaxillary ratio
[Bolton]


Winged incisors









A peculiar arrangement often
seen between central
incisors, both maxillary and
mandibular, was first reported
by Leigh in 1926.
Called incisor winging by
Dahlberg.
Characterised by mesiolinguo
version of the central incisors
creating a v-shaped notch in
the arch at the midline.
Noted in Mongoloid
dentitions.
Show unfavourable prognosis
for permanent orthodontic
correction.


Shovel shaped incisors


Present another variation of
incisor morphology.



Prominence of the mesial
and distal marginal ridges
enclosing the central fossa
in the lingual surface of
incisor teeth.



Often present a problem in
overjet correction.



In such cases, reducing the
prominence of the marginal
ridges is helpful.


Theory of Overbite







Overbite is present in greatly varying degrees among
modern populations.
Primitive people, past and present, tend to display
edge - to edge anterior bite (labidonty) or at most,
slight scissor bites (psalidonty) of less than two
millimeters.
Overbites in excess of two millimeters are largely
limited to those living in relatively civilized
environments.
It is generally reasoned that overbite has accrued
among the civilized because substantial tooth wear is
no longer present to compensate for natural incisor
eruption.






Another insight into the origins of overbite in man
has been suggested by Brace and Mahler in 1971.
They observed that overbite was widely expressed
among Europeans only after the Middle Age.
At that time, also the table fork was introduced in
Italy and aimed popularity in Europe.
The personal fork and knife took the functions of
holding and shearing food away from the incisors.
Protrusive function, essential to the holding and
shearing process, swiftly became obsolete, and
deep overbite and its related occlusal deviations
have since proliferated unchecked.


Buccal segment reproximation








The orthodontic community has known about natural
tooth wear, largely through the work of Raymond
Begg on the Australian aboriginal population.
All teeth become smaller mesiodistally as they wear
down with age.
The contact areas between become flatter and
broader.
The mesiodistal enamel reduction of all permanent
teeth in the developing adolescent dentition would
be a method to produce artificial tooth wear
mimicking the natural wear pattern of primitive
population.

The Carabelli Trait


In 1842, Carabelli gave
his name to a
frequently occurring
tubercle on the lingual
aspect of mesio lingual
cusp (protocone) of the
maxillary first
permanent molar.











Many theories have been advanced explaining the
occurrence of the Carabelli trait.
One holds that the Carabelli cusp has its origin in
the cingulum, and numbers among its proponents
Gregory (1922), Cope (1888), Osborn (1907), Adioff
(1908), and Korenhoff (1960).
A second school, led by Rose (1892) and Baufjeiff
(1896),.claims that the Carabelli cusp arose as a
separate tooth germ.
The third group bases its rea-soning upon the
"Dimer" theory of Bolk (1914) in calling upon a "tritomere" for the origin of the cusp.
Other explanations are brought forth by individual
authors such as Weidenreich (1937), who
considered the Carabelli cusp an accidental
variation" of the procone.



It is indeed a most remarkable phenomenon
in the history of biological research that so
little is known about a structure of which so
much has been written.



As Jorgensen rightfully points out that “our
actual knowledge of the evolutionary and
racial significance of Carabelli's cusp is quite
disproportionate to the number of pages
published about this structure


Conclusion






Variation in size, shape, number,
arrangement, and wear pattern of the teeth of
man has long been an area of great interest
to physical anthropologists.
It is important that orthodontist cultivates an
anthropologists eye for tooth variation.
Since the orthodontist ponders many of these
same variables in his daily battle with
malocclusion, many aspects of dental
anthropology can prove helpful in
understanding orthodontic problems and in
formulating their successful treatment.

References













Dimensions of anthropology – vol.2; V.Rami Reddy.
Dental anthropology – vol.1; V.Rami Reddy.
Anthropology and modern human teeth – Scott and
Turner.
Human adult odontometrics – Julius A. Kieser.
Anthropology and orthodontics – AO vol.67(1);1997,73
– 77.
Harmonious anthropometric relationships – AO
vol.31(1);1961,18 – 34.
Dental variation among population – an anthropologic
view – DCNA vol.19(1);1975,125 – 139.
Orthodontic aspects of dental anthropology – AO
vol.45(2);1975,95 – 102.











Crown dimensions and mandibular incisor alignment
– AO vol.42;1972,148 – 53.
Stone age man’s dentition – AJO vol.40;1954,298 –
312.
Begg orthodontic theory and technique – Begg and
Kesling – third edition.
An index to assessing tooth shape deviations
applied to mandibular incisors – AJO
vol.61;1972,384 – 402.
Textbook of orthodontics – Salzmann.
Color atlas of orthodontic diagnosis – Rakosi.
Evolution Atlas, Chapter 6: The Skeletal System:
Axial Division.(internet)
Functional adaptation of jaw joint,Evolution atlas,the
skeletal system;axial division(internet)

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