Comparitive anatomy of dentition /orthodontic courses by Indian dental academy

COMPARATIVE ANATOMYCOMPARATIVE ANATOMY
OF HUMAN DENTITIONOF HUMAN DENTITION
WITH APESWITH APES
www.indiandentalacademy.com

 CONTENTS
 Terminology
 Attachments of teeth
 Evolution of dental occlusion
 Evolution of teeth
 Comparisons with :
 - old world monkeys
 - new world monkeys
 - lesser apes
 - greater apes
 - gorilla
 Bibliography

TERMS ON THE BASIS OFTERMS ON THE BASIS OF
TEETHTEETH
Homodont: - Teeth all alike e.g. Dolphin ,
Crocodile.
Heterodont: - Teeth differ in form. E.g. Man
Monophyodont: - Having only set of teeth.
E.g. Rodents
Diphyodont: - Having two set of teeth. E.g.
Man

Polyphyodont: - Having endless succession of
teeth e.g. most of Fishes, Amphibians.
Acrodonts: - Anchylosed teeth, the base of
which are wholly Situated upon the bones of
attachment e.g. Sphenodon.
Plearodont: - Anchylosed teeth, outer side of
bone of Attachment e.g. Mackerel.
Lophodont: - Ridged teeth (transversely) e.g.
Tapir and Elephant.

Bilophodont: - Teeth having two ridge e.g.
Tapir .
Polylophodont: - Teeth having more than two
ridges e.g. Elephant.
Bunodont: - Tooth crown supporting
tubercles or cones e.g. pig
Selenodont: - Bicrescentic teeth elongated
before backward e.g. Ox.

Brachyodont: - Teeth having short crown and
long root e.g. Man
Hypsodont: - Teeth having long crown and
short root e.g. Horse and Camel
Haplodont: - Simple conical tooth having
simple crown and roots e.g. Dolphin .

Thecodont: - Contain a bony socket, which
persist for successional tooth .
 Carnassial Teeth: - Teeth special for tearing
flesh e.g. Carnivores and Rodents
Cynodontism: - The condition in which the
pulp cavity is confined to crown. The tooth
having large root or roots.
 Secodont: - Sectorial or cutting teeth e.g. cat
family.

Polyprotodont: - Numerous Incisors
- Having two lower Incisors
Ciliiform / Setiform: - Closely set and
very fine teeth e.g. some fishes .
Tusk: - Incisors or canines of persistent
growth, which protrude beyond Lip, when
mouth is closed.

ATTACHMENT OF TEETHATTACHMENT OF TEETH
The attachment of teeth with underlying
structures also shows the variation in
different species. There are four methods of
tooth attachment in animal kingdom -
1. Fibrous attachment
2. Hinged attachment
3. Anchylosis
4. Gomphosis

 FIBROUS ATTACHMENT :
 Well illustrated in Sharks and Rays.
 Skeleton is cartilaginous, teeth is not attached
directly to cartilaginous Jaw.
 Here the one end of fibers (unmineralized) is
embedded at one end into the dentine, and the
other end into the bone of attachment.
 In this group the fiber anchors the teeth to a sheet
of outer fiber, which run over the surface of jaw
cartilage underneath the tooth rows.

HINGED ATTACHMENT :
Mobile teeth are found in large number of
Telosts e.g. Eels and Cod.
The teeth are some time capable of a certain
amount of movement in all directions, but
usually movement is more or less restricted to
labiolingual plane.

Considerably more mobile teeth are found in
Hake, Pig and Angle fish.
Inward tilting of tooth around its hinge aids
the ingestion of prey easier into the oral
cavity. Where as outward movement erect
the teeth there by trapping the prey.
In HAKE the teeth can be depressed
lingually almost 90° angle by gentle pressure

ANCHYLOSIS :
Found in Python, Frog, Eel, etc.
In a rigidly attached tooth the region of
union with the bone is completely
mineralized. This condition is referred to
ANCHYLOSIS.
Where teeth anchylosed, the stress of biting
must be take a byte hard tissue and the
shape of tooth may be modified in such a
way as to absorb stress more efficiently.

GOMPHOSIS :
Attachment occurs in teeth of man,
mammalians, in some reptiles and in some
fishes (e.g. sow - fish)
The presence of Periodontal ligament is
characteristic feature of this type of
attachment.
Most advance type of attachment.

Evolution of Dental OcclusionEvolution of Dental Occlusion
Study of the evolution of dental occlusion
involves the study of the complex of
general skeleton, which includes jaws and
hence teeth.
It is believed truly, from the study of Patten,
that, vertebrates were closely related to
Palaeozoic Eurypterids.
The jaws of vertebrates were derived by the
appendages of Trilobites.

The earlier trilobites were well equipped
with numerous appendages, which combined
the function of oars and gills.
In the eurypterids and their modern relative,
Limulus, the appendages around the mouth
had become specialized in connection with
the finding and prehension of food.

Chordates, shows direct evidence that in the
ostracoderms the cavity of the mouth was in
series with those of the primitive gill
pouches and that the floor of the mouth
could be moved up and down, somewhat
like that of a frog.
In certain ostracoderms the slit-like mouth
was bordered by exoskeletal plates.

 The beginning of jaws:
 An Ostracoderm , showing
the position of the slit like
mouth.
 Head shield, seen from
below, showing the jaw –
like rims of the mouth and
mosaic of bony plates on
the floor of the mouth.
 The black spots represent
the opening of the gill
cavities.

The ostraco-derms, together with their
highly specialized descendants, are classed
as Agnathi ( jawless) because they did not
possess internal jaws of the shark type.
 In the sharks the underlying oralo-
branchial arches became enlarged into a
great fish-trap, while the surface layers of
the dermal plates disintegrated into shark
teeth which rest on "cartilage jaws"; these
are serially homologous with the gills
arches.

 Sharks have probably lost the
primitive bony dermal jaw
plates and have greatly
enlarged and specialized the
inner or gill arch jaws.
 The upper bony plate
(corresponding to the maxilla)
was fixed and toothless.
 The lower or mandibular plate
bore a series of vertical rows
of small teeth arranged along
the upper margin.

 In the lobe-finned, air-
breathing fishes, both
the upper and lower
jaws were of complex
type, consisting of an
inner core
corresponding
respectively with the
Meckel's cartilage in
the lower and the
palatoquadrate in the
upper, covered by a
number of bony plates.

 The jaw muscles arose as
specialized gill-arch
muscles.
 In the higher mammal-
like reptiles, however,
there was begun a
movement to emancipate
the jaw muscles proper
from their hyoid and
branchial companions.

 This was carried to an extreme in
the mammals, and meanwhile the
old fulcrum at the back of the
compound jaws began to
diminish, while a totally new
joint was established between the
ascending ramus of the dentary
plate and the squamosal plate.
 This mandibulo-temporal joint,
together with the increasing
functional differentiation of the
jaw musculature from that of the
hyobranchial complex,
determines all types of dental
occlusion found in the
mammals.

Evolution of the teethEvolution of the teeth
 The earliest known acanthodians, the denticles
around the mouth were loosely attached on or near
the surface of the lower jaw.
 In the air-breathing, lobe-finned fishes of late
Mesozoic time there were, two classes of teeth,
comprising a row of numerous smaller teeth on the
margins and a few much larger sabre-like tusks,
forming a widely spaced inner row on the roof of
the mouth, and inner sides of the lower jaw.

 This labyrinthodont type of attachment was
transmitted to the early amphibians.
 By the time of the earlier reptiles the pits in which
the labyrinthodont teeth were sunk at the base and
gradually changed into sockets and the
labyrinthodont folds were gradually lost.
 These simple laniariform socketed teeth, which are
seen in the earliest mammal-like reptiles, were set
in jaws of a simple scissors-like type, in which the
upper teeth overhung the lower teeth and sheared
past them in simple vertical arcs.

Comparison of DentitionComparison of Dentition
 Marmosets and Tamarins
(Callithricidae) :
 The most primitive of the latin
American monkeys.
 The V-shaped mandible has a
slender body and somewhat
square ramus, the coronoid
process and angle vary in size
but the latter is usually well
developed.
 The marmosets can be
distinguish from other New
World monkeys by the shape of
the skull and the number or
molar).

 All the group have two molars
except Callimico (Goeldi's
marmoset) which retains a very
much reduced third molar.
 Marmosets are described as
'shorttusked' (where the incisors
are as large as the canines) or
'longtusked' (the canines project
above the occlusal plane).
 The upper molars have only the
smallest suggestion of a
hypocone, the lower molars are
fourcusped. The last molar is
always the smallest and the first
is the largest of the series.

NEW WORLD MONKEYSNEW WORLD MONKEYS
(CEBIDAE)(CEBIDAE)
 All the cebids have
forward facing orbits
which are complete
posteriorly, a tympanic
bulla with an external
tympanic ring fused to the
bulla and three premolars
in each jaw quadrant.
 They show Massive
laryngeal expansion and
modification of the shape
of both the skull and
lower jaw.

Aotus (night monkey), CebusAotus (night monkey), Cebus
(capuchin), Saimiri (squirrel(capuchin), Saimiri (squirrel
monkey)monkey),,CallicebusCallicebus
 The first three are short-faced and have an
anthropoid mandible; the lower dental arcade is
V-shaped and the ramus rectangular with a
moderately developed coronoid process and a
slightly expanded angle.
 In contrast, the laryngeal enlargement found in
Callicebus and Aloriarta.
 The coronoid process is small, the condyle is high
above the tooth row and the angle is greatly
expanded.

Atele, Brachyteles andAtele, Brachyteles and
LagothrixLagothrix
 The members of this group have fairly long faces
with well-developed jaws. The mandible has a
large angle (biggest in Brachyteles).
 The dentition is similar to that of the first group,
but a hypoconulid is often developed on molar and
although upper third molar is the smallest of the
molars, all these teeth are of similar size.

CCacajao (uakari), Pitheciaacajao (uakari), Pithecia (( saki) alltisaki) allti
Chirpotes (bearded saki)Chirpotes (bearded saki)
 These monkeys have a highly specialized anterior
dentition.
 The upper incisors are spatulate and project
forwards so sharply as to be almost horizontal.
 Both upper and lower incisors are separated from
the tusk-like laterally flaring canines by a large
diastema.
 The post-canine teeth conform to the general cebid
pattern of bicuspid premolars and four-cusped
molars but appear small in comparison to the
anterior dentition.

Terrestrial groupTerrestrial group :: Erythrocebus (patasErythrocebus (patas
monkeys):monkeys): MandrillusMandrillus (( mandrills),mandrills),
Papio(baboons), TheropithecusPapio(baboons), Theropithecus
 This are the ground-
living monkeys, and
all shows marked
sexual dimorphism of
body size: the adult
female weighs
approximately half as
much as the male. This
difference extends to
the skull and dentition.

 The canines, large in both
sexes, become long and
dagger-like in the males.
 The molars are
bilophodont and the third
molars are large in size.
 In Mandrills, the anterior
teeth are very large and
the cheek teeth are
unusually small.

Colobus (guerezas), Presbytis ( langurs),
Pygathrix ( Douc langurs ), Rhinopithecus
(snub nosed langurs)
 This are 'leaf-eating
monkeys’.
 The distinctive
features of these
monkeys, including a
sacculated stomach,
have been associated
with a herbivorous
diet.

 For example, the mandibular
ramus is high, with
corresponding distance
between the level of the
mandibular joint and that of
the occlusal plane.
 The lower incisors occlude in
front of the uppers. This
condition is called 'underbite'
and may be an adaptation for
the more efficient ingestion
of leaves.

GIBBON AND SIAMANGGIBBON AND SIAMANG
HYLOBATIDAE (LESSER APES)HYLOBATIDAE (LESSER APES)
 Found in the tropical rain and
forest of south east Asia.
 The palate in gibbons is
exceptionally long (reaching 50-
54% of total skull length) and
broad.
 No distinct condylar neck, , the
posterior border of the
mandibular notch merges into the
condyle proper.
 The fossa has no distinct articular
eminence although there is a post-
glenoid process. www.indiandentalacademy.com

 The incisors are heteromorphic:
the upper centrals are weak and
spatulate, the lateral small and
often pointed. The lower incisors
are fanshaped.
 The lower first premolar is
sectorial, the remainder are
bicuspid although the lower
second is expanded distally.
 The upper molars are simple
fourcusped teeth with an
oblique ridge, the lower, have
the 'Dryopithecus' pattern or Y5
pattern.

GREAT APES (PONGIDAE)GREAT APES (PONGIDAE)
There are three great apes:
– The Chimpanzee (Pan),
– The OrangUtan (Pongo) and
– The Gorilla (Gorilla).
 They have different distributions, habits,
locomotor patterns and skulls but very
similar dentitions.
The general form of the dentition is the
same in all three great apes. 2123
2123

The juvenile skuII and deciduousThe juvenile skuII and deciduous
dentitiondentition
 The juvenile pongid skull is much more 'human' in
appearance than that of the adult
 This is due to the early development of the brain
and neurocranium and the much later growth of
the face.
 The first molar is the first tooth in the permanent
dentition to erupt followed by the incisors, second
molars, premolars and then the canine.
 As in man the shape of the second deciduous
molar closely resembles that of the first permanent
molar. www.indiandentalacademy.com

Chimpanzee ( pan )Chimpanzee ( pan )
 There are two species of
chimpanzee, Pan trog
lodytes which is widely
distributed across equa
torial Africa and Pan
paniscus, the pygmy
chimpanzee, which is
restricted to the area
between the Congo and
Lualaba Rivers of central
West Africa. Both live in
rain forest

 The face is prognathic with
a long premaxilla.
 The mandibular body is
pressed near the canine
region.
 The ramus is rectangular,
with large areas for the
attachment of masseter and
temporalis, although the
coronoid process is short
and the mandibular notch
shallow.
 The gently rounded condyle
articulate with an almost flat
glenoid fossa.

Orang-Utan (Pongo)Orang-Utan (Pongo)
 The cranium of the orang
is comparatively short and
domed.
 The dentition has the same
general form as in the
chimpanzee. The upper
canine is much larger in
the male.
 In both jaws the second
molar is normally the
largest and the third the
smallest.
 Supernumerary molars are
common.

GorillaGorilla
 Gorillas are found in
western (lowland gorilla)
and eastern equatorial
Africa (highland gorilla).
 Both the neurocranium
and facial skeleton are
large.
 The very prognathic face
has a rectangular hard
palate extending
backwards behind the
third molars.

 The lower jaw is strong and
heavy with a sloping
symphysis braced by a
simian shelf. The
rectangular ramus often
shows strong muscle
markings.
 The upper molars have an
oblique ridge and the lowers
have the Dryopirheclis'
pattern but both have very
sharply pointed cusps when
newly erupted.

ReferencesReferences
1. J.W.OSBORN, Dental anatomy and embryology,
Blackwell publications, vol.1 pg no. 401455.
2. William K.Gregory, evolution of dental occlusion
from fish to man, Angle Orthod 1941:3.
3. Dental anatomy, histology and development;
comparative anatomy, ed 1st
.pg no 179215.

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