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DESCRIPTIVEANATOMY
OFMANDIBULAR
THIRDRMOLA.Prof.
A.
Els1ahnInitial
calcification8
–
10
yearsCompletion
of
crown12
–
16
yearsEruption17
–
21
yearsCompletion
of
roots18
–
25
yearsProf.
A.
2ElsahnCHRONOLOGY.The
lower
third
molar is
the
lasttooth
in
the
dental
arch
and
theeighth
from
the
middle
line.GENERAL
CHARACTERISTICSIt
is
the
shortest
ofthe
mandibular
teeth.431
28765.Prof.
A.
3ElsahnGENERAL
CHARACTERISTICSThis
tooth
is
a
very
variable
tooth,but
less
so
than
upper
third
molar.It
shows
variationsin
size,
form,
numberof
cusps
and
numberand
form
of
roots..Prof.
A.
4ElsahnThe
crown
of
this
tooth
in
most
casesresembles
that
of
the
lower
secondmolars
in
the
number
of
cusps
(fourcusps)
and
sometimes
resembles
thecrown
of
the
lower
first
molar
(fivecusps)
or
it
may
bear
little
resemblancetoeither.GENERAL
CHARACTERISTICS.Prof.
A.
Elsah5nIn
many
cases,
it
is
largerthan
the
lower
second
molar.GENERAL
CHARACTERISTICSThe
third
molar
maybesmall
or
large..Prof.
A.
Elsahn6Prof.
A.
ElsahnBUCCAL
ASPECTTHE
CROWNM
DThe
mesial
and
distal
outlinesof
the
crown
are
generallyasthose
of
all
lower
molars.The
distal
outline
is
markedlyconvex..7The
crest
of
contour
mesially
and
distallyis
located
a
little
more
than
half
thedistance
from
cervical
line
to
cusp
tips.BUCCAL
ASPECTTHE
CROWNThe
crown
is
wider
at
thecontact
area
mesio-distallythan
at
the
cervix.M
DProf.
A.
Elsahn.8In
the
four-cusp
type;
the
molar
issmall
and
shows
two
buccal
cuspsonly.
Prof.
A.
ElsahnBUCCAL
ASPECTTHE
CROWNThe
buccal
cusps
areshort
and
rounded..9The
mesio-buccal
cusp
is
thewidest
and
usuallyhighest
ofthe
two
or
three
buccal
cusps.BUCCAL
ASPECTTHE
CROWNThe
buccal
surface
is
very
convex..Prof.
A.
Elsah1n0This
molar
usually
showtworoots,
one
mesial
and
one
distal.BUCCAL
ASPECTTHE
ROOTSM
D.Prof.
A.
Elsahn11Prof.
A.
ElsahnBUCCAL
ASPECTTHE
ROOTSThese
roots
are
usuallyshorter
than
thoseoffirst
or
second
molars.111.81.6::.The
root
to
crown
ratio
is
smallerthan
that
of
first
and
second
molar(1.6
to
1
compared
to
1.8
to
1).12The
roots
are
more
inclineddistally
than
those
of
the
firstand
second
molars.Prof.
A.
ElsahnBUCCAL
ASPECTTHE
ROOTSM
D13M
D.The
roots
may
be
separated
orfused
for
all
or
part
of
their
length.BUCCAL
ASPECTTHE
ROOTS.Prof.
A.
Elsahn14If
the
roots
are
separated,
theroottrunk
is
long
and
the
roots
areusually
more
pointed
at
theapexthan
on
other
molars.BUCCAL
ASPECTTHE
ROOTS.Prof.
A.
Elsahn15The
proximal
sides
of
the
crownconverge
slightly
lingually.LINGUAL
ASPECTTHE
CROWN.Prof.
A.16ElsahnThe
lingual
surface
is
also
very
convex,
butmore
than
the
buccal
surface.LINGUAL
ASPECTTHE
CROWNThe
lingual
cuspsare
longerthan
the
buccal
cusps.Themesio-lingual
is
largerthan
thedisto-lingual.D
M.Prof.
A.17ElsahnFrom
the
mesial
aspect,thetooth
resembles
the
secondmolar
except
in
dimensionsand
the
more
bulbous
crown.Prof.
A.18ElsahnMESIAL
ASPECT.The
mesial
rootis
taperingmorefrom
cervix
to
apex
and
its
apexis
usually
more
pointed
thanthatof
the
second
molar.Prof.
A.
ElsahnMESIAL
ASPECTThe
buccal
cusp
tips
are
closerto
the
lingual
cusp
tips
than
onfirst
and
second
molars,
givinga
small
occlusal
table.LB.19From
the
aspect,
the
tooth
isalsosimilar
to
that
of
second
molarexcept
for
size,
absence
of
the
distalcontact
areaand
the
more
pointedapex
of
the
distal
root.Prof.
A.
ElsahnDISTAL
ASPECTsecond
molar.20The
occlusal
aspect
is
similar
tothatof
the
second
or
first
mandibularmolar
according
to
the
type
of
thethird
molar
(four-cusp
type
orfive-cusp
type).Prof.
A.
ElsahnOCCLUSAL
ASPECT.21The
occlusal
outline
is
rectangularor
oval
mesio-distally
but
morerounded
than
that
of
lower
first
orsecond
molars
and
the
distal
side
ismuch
smallerbucco-lingually.OCCLUSAL
ASPECTM
DLB.Prof.
A.
E2l2sahnThe
occlusal
surface
has
irregulargroove
pattern
with
numeroussupplemental
grooves
and
pits
thatproduce
a
wrinkled
appearance,which
is
a
constant
finding.Prof.
A.
ElsahnOCCLUSAL
ASPECT.23VARIATIONSIt
is
very
variabletooth
but
less
so
thanupper
third
molar.Crown
may
show
three,
four,
five
or
multi-cusped
variations.Most
of
the
anomalies
have
largecrownportio
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