Human dentition Dr. Hazem Al Ajrami First Year in Dentistry First Semester Al-Azhar University - Gaza Lama El Banna

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College of DentistryCollege of Dentistry
Human DentitionHuman Dentition
Maxillary First MolarMaxillary First Molar
Dr. Hazem Al AjramiDr. Hazem Al Ajrami

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MolarsMolars

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General featuresGeneral features
The twelve permanent molars are the largestThe twelve permanent molars are the largest
and strongest teeth in the mouth by their crownand strongest teeth in the mouth by their crown
bulk size and their root anchorage in the bone.bulk size and their root anchorage in the bone.
The molars have no deciduous predecessors.The molars have no deciduous predecessors.
The most developed of the molar is the firstThe most developed of the molar is the first
molar. The third molar exhibits the mostmolar. The third molar exhibits the most
variable morphology in the mouth.variable morphology in the mouth.

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Molars are multi-rooted teeth, they have atMolars are multi-rooted teeth, they have at
least two roots (mandibular) or three rootsleast two roots (mandibular) or three roots
(maxillary).(maxillary).
They function in grinding of food duringThey function in grinding of food during
mastication, this is because they have widemastication, this is because they have wide
occlusal surface with prominent cusps.occlusal surface with prominent cusps.
Molars are used in grinding food, but mostMolars are used in grinding food, but most
important they support and maintain theimportant they support and maintain the
vertical dimension of the face.vertical dimension of the face.

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The characteristics common to all posteriorThe characteristics common to all posterior
teeth (differentiated from the anterior teeth)teeth (differentiated from the anterior teeth)
are as follows:are as follows:
 Greater relative bucco-palatal measurement asGreater relative bucco-palatal measurement as
compared with the mesiodistal measurement.compared with the mesiodistal measurement.
 Broader contact areas.Broader contact areas.
 Contact areas more nearly at the same level.Contact areas more nearly at the same level.
 Less curvature of the cervical line mesiallyLess curvature of the cervical line mesially
and distally.and distally.
 Shorter crown cervico-occlusally whenShorter crown cervico-occlusally when
compared with the anterior teeth.compared with the anterior teeth.

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The Permanent Maxillary MolarsThe Permanent Maxillary Molars
They are six in number, three in each side, theThey are six in number, three in each side, the
first, second, and third molars.first, second, and third molars.

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Maxillary First MolarMaxillary First Molar

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Universal Numbering System:Universal Numbering System:
3 and 143 and 14
Palmer Notation System:Palmer Notation System:
FDI Numbering System:FDI Numbering System:
16 and 2616 and 26
66 andand 66

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Chronology:Chronology:
A.A. First evidence of calcification:First evidence of calcification: at birthat birth ..
B.B. Enamel completed:Enamel completed: 33 -- 44 years .years .
C.C. Eruption:Eruption: 66 -- 77 years .years .
D.D. Root completed:Root completed: 99 -- 1010 years .years .

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Cervico-Cervico-
OcclusalOcclusal
LengthLength
ofof
CrownCrown
LengthLength
ofof
RootRoot
MesiodistalMesiodistal
DiameterDiameter
of Crownof Crown
MesiodistalMesiodistal
DiameterDiameter
of Crownof Crown
at Cervixat Cervix
MaxillaryMaxillary
First MolarFirst Molar
7.57.5
B = 12B = 12
P = 13P = 13
1010 88

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Bucco-Bucco-
PalatalPalatal
DiameteDiamete
r ofr of
CrownCrown
Bucco-Bucco-
PalatalPalatal
DiameterDiameter
of Crownof Crown
at Cervixat Cervix
CurvatureCurvature
ofof
CervicalCervical
LineLine
(Mesial)(Mesial)
CurvatureCurvature
ofof
CervicalCervical
LineLine
(Distal)(Distal)
MaxillaryMaxillary
First MolarFirst Molar
1111 1010 11 00

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It is the first permanent tooth to erupt into theIt is the first permanent tooth to erupt into the
maxillary arch.maxillary arch.
The normal location of the first permanentThe normal location of the first permanent
molar is at the center of the fully developedmolar is at the center of the fully developed
adult jaw antero-posteriorly.adult jaw antero-posteriorly.
It is the largest tooth in maxillary arch. It hasIt is the largest tooth in maxillary arch. It has
four well developed cusps (two buccal and twofour well developed cusps (two buccal and two
palatal) and a fifth supplementalpalatal) and a fifth supplemental
nonfunctioning elevation which is callednonfunctioning elevation which is called
Tubercle of Carabelli.Tubercle of Carabelli.

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This fifth cusp serves to identify the maxillaryThis fifth cusp serves to identify the maxillary
first molar.first molar.
The crown of this tooth is widerThe crown of this tooth is wider
buccopalatally than mesiodistally.buccopalatally than mesiodistally.
There are three well developed and separatedThere are three well developed and separated
roots, two buccal and one palatal. They giveroots, two buccal and one palatal. They give
this tooth the maximum anchorage againstthis tooth the maximum anchorage against
forces.forces.

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Buccal AspectBuccal Aspect
The crown is roughly trapezoid. The cervicalThe crown is roughly trapezoid. The cervical
line is the shortest of the uneven sides. Theline is the shortest of the uneven sides. The
tips of all cusps are usually visible from thistips of all cusps are usually visible from this
aspect.aspect.
The buccal surface is much wider from that ofThe buccal surface is much wider from that of
the premolars but it is slightly shorter.the premolars but it is slightly shorter.

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MesialDistal

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The mesial outline of the crown follows aThe mesial outline of the crown follows a
nearly straight path downward and mesially,nearly straight path downward and mesially,
curving occlusally as it reaches the crest ofcurving occlusally as it reaches the crest of
contour of the mesial surface which is thecontour of the mesial surface which is the
contact area.contact area.
The contact area is just cervical to the junctionThe contact area is just cervical to the junction
of the occlusal and middle thirds. Then, theof the occlusal and middle thirds. Then, the
mesial outline continues downward andmesial outline continues downward and
distally and becomes corresponding with thedistally and becomes corresponding with the
outline of the mesial slope of the mesiobuccaloutline of the mesial slope of the mesiobuccal
cusp.cusp.

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The distal outline is convex, and the contactThe distal outline is convex, and the contact
area is in the center of the middle third.area is in the center of the middle third.
The cervical line is slightly curved with theThe cervical line is slightly curved with the
curvature root wise.curvature root wise.
This line is not so smooth and regular as foundThis line is not so smooth and regular as found
in some other teeth.in some other teeth.
Although the mesiobuccal cusp is broader thanAlthough the mesiobuccal cusp is broader than
the distobuccal cusp, the distobuccal cusp isthe distobuccal cusp, the distobuccal cusp is
usually sharper and longer. The mesial slopeusually sharper and longer. The mesial slope
of the mesiobuccal cusp meets its distal slopeof the mesiobuccal cusp meets its distal slope
at an obtuse angle.at an obtuse angle.

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The mesial slope of the distobuccal cusp meetsThe mesial slope of the distobuccal cusp meets
its disal slope at approximately right angle.its disal slope at approximately right angle.
Separating the two buccal cusps is the buccalSeparating the two buccal cusps is the buccal
developmental groove. This shallow groovedevelopmental groove. This shallow groove
runs in occluso-apical direction parallel to theruns in occluso-apical direction parallel to the
long axis of the distobuccal root. It terminateslong axis of the distobuccal root. It terminates
at a point half the distance from its origin as aat a point half the distance from its origin as a
horizontal groove.horizontal groove.

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The buccal surface is characterized by buccalThe buccal surface is characterized by buccal
ridges on each buccal cusp. They are convexridges on each buccal cusp. They are convex
areas which extend cervically about half itsareas which extend cervically about half its
length. It is also characterized by the buccallength. It is also characterized by the buccal
cervical ridge which extends horizontally fromcervical ridge which extends horizontally from
mesial to distal in the entire cervical third.mesial to distal in the entire cervical third.

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The molar roots originate as a single root onThe molar roots originate as a single root on
the base of the crown, and then they dividethe base of the crown, and then they divide
into three roots. The common root base isinto three roots. The common root base is
called root trunk. Usually the palatal root is thecalled root trunk. Usually the palatal root is the
longest and the two buccal roots arelongest and the two buccal roots are
approximately equal in length.approximately equal in length.
The roots are about twice as long as the crown.The roots are about twice as long as the crown.

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There is a deep developmental groove buccallyThere is a deep developmental groove buccally
on the root trunk which starts at the bifurcationon the root trunk which starts at the bifurcation
and progresses downward to end in a shallowand progresses downward to end in a shallow
depression at the cervical line.depression at the cervical line.
All three roots may be seen from the buccalAll three roots may be seen from the buccal
aspect. The point of bifurcation of the twoaspect. The point of bifurcation of the two
buccal roots is located approximately 4 mm.buccal roots is located approximately 4 mm.
above the cervical line.above the cervical line.

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The roots are not straight; the buccal roots areThe roots are not straight; the buccal roots are
curved halfway between the point ofcurved halfway between the point of
bifurcation and the apices.bifurcation and the apices.
The mesiobuccal root curves distally startingThe mesiobuccal root curves distally starting
at the middle third.at the middle third.
The distobuccal root is straighter with its longThe distobuccal root is straighter with its long
axis at an acute angle distally with the cervicalaxis at an acute angle distally with the cervical
line. It has a tendency toward curvatureline. It has a tendency toward curvature
mesially at the middle third.mesially at the middle third.

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Palatal AspectPalatal Aspect
It is trapezoid in shape and shows moreIt is trapezoid in shape and shows more
convexity occlusocervically than the buccalconvexity occlusocervically than the buccal
surface. The height of contour is located in thesurface. The height of contour is located in the
middle third of the surface.middle third of the surface.
The palatal cusps are the only ones to be seenThe palatal cusps are the only ones to be seen
from this aspect.from this aspect.

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Mesial Distal

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The mesiopalatal cusp is much larger. ItsThe mesiopalatal cusp is much larger. Its
mesiodistal width is about three fifths of themesiodistal width is about three fifths of the
mesiodistal diameter of the crown, themesiodistal diameter of the crown, the
distopalatal cusp making up the remaining twodistopalatal cusp making up the remaining two
fifthsfifths..
The angle formed by the mesial outline of theThe angle formed by the mesial outline of the
crown and the mesial slope of the mesiopalatalcrown and the mesial slope of the mesiopalatal
cusp is about 90 degrees. The mesial and distalcusp is about 90 degrees. The mesial and distal
slopes of this cusp meet at an obtuse angle.slopes of this cusp meet at an obtuse angle.

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The fifth cusp appears attached to theThe fifth cusp appears attached to the
mesiopalatal surface of the mesiopalatal cusp.mesiopalatal surface of the mesiopalatal cusp.
The fifth cusp is separated from theThe fifth cusp is separated from the
mesiopalatal cusp by an irregularmesiopalatal cusp by an irregular
developmental groove. This is called the fifthdevelopmental groove. This is called the fifth
cusp developmental groove.cusp developmental groove.
The distopalatal cusp is smooth and spheroidalThe distopalatal cusp is smooth and spheroidal
without angulations on the mesial and distalwithout angulations on the mesial and distal
slopes.slopes.

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The palatal developmental groove separatingThe palatal developmental groove separating
the two large palatal cusps and runs cervicallythe two large palatal cusps and runs cervically
to end at the center of the palatal surface of theto end at the center of the palatal surface of the
crown. From this point a shallow depressioncrown. From this point a shallow depression
extends cervically and continues in an apicalextends cervically and continues in an apical
direction on the palatal root till the middledirection on the palatal root till the middle
third.third.
The mesial outline is as straight as it isThe mesial outline is as straight as it is
buccally.buccally.
The distal outline of the crown is smoothlyThe distal outline of the crown is smoothly
curved becoming confluent with the curvaturecurved becoming confluent with the curvature
of the distopalatal cusp forming a semicircleof the distopalatal cusp forming a semicircle
arc.arc.

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The cervical line is slightly convex toward theThe cervical line is slightly convex toward the
apex in an irregular manner.apex in an irregular manner.
All three roots are visible from the palatalAll three roots are visible from the palatal
aspect.aspect.
The palatal portion of the root trunk isThe palatal portion of the root trunk is
continuous with the entire cervical portion ofcontinuous with the entire cervical portion of
the crown palatally.the crown palatally.
The palatal root is conical with blunt roundedThe palatal root is conical with blunt rounded
apex.apex.

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Mesial AspectMesial Aspect
It is trapezoid in shape with the smallestIt is trapezoid in shape with the smallest
uneven side located occlusally, which is theuneven side located occlusally, which is the
reverse of the buccal and palatal surfaces.reverse of the buccal and palatal surfaces.
The buccal outline of the crown starting fromThe buccal outline of the crown starting from
the cervical line is curved with the crest ofthe cervical line is curved with the crest of
curvature within the cervical third. As itcurvature within the cervical third. As it
progresses downward, it becomes less convexprogresses downward, it becomes less convex
to circumscribe the mesiobuccal cusp.to circumscribe the mesiobuccal cusp.

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The palatal outline is curved with the crest ofThe palatal outline is curved with the crest of
curvature located near the middle third. If thecurvature located near the middle third. If the
tubercle is well developed, the palatal outlinetubercle is well developed, the palatal outline
dips inward to illustrate it. If it is undevelopeddips inward to illustrate it. If it is undeveloped
the palatal outline continues from the crest ofthe palatal outline continues from the crest of
curvature as a smooth curved arc to the tip ofcurvature as a smooth curved arc to the tip of
the mesiopalatal cusp.the mesiopalatal cusp.
The mesial marginal ridge, which is confluentThe mesial marginal ridge, which is confluent
with the mesiobuccal and mesiopalatal cuspwith the mesiobuccal and mesiopalatal cusp
ridges, is irregular and curved cervically aboutridges, is irregular and curved cervically about
one-fifth the crown length.one-fifth the crown length.

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The cervical line is irregular, curvingThe cervical line is irregular, curving
occlusally not more than 1 mm.occlusally not more than 1 mm.
The mesial contact area is above the marginalThe mesial contact area is above the marginal
ridge approximately at the junction of theridge approximately at the junction of the
middle and occlusal thirds of the crown andmiddle and occlusal thirds of the crown and
some what toward the buccal side.some what toward the buccal side.
The mesiobuccal root is broad and flattened onThe mesiobuccal root is broad and flattened on
its mesial surface. The width of this root at theits mesial surface. The width of this root at the
point of bifurcation is about 2/3 thirds of thepoint of bifurcation is about 2/3 thirds of the
crown width at the cervical linecrown width at the cervical line
buccopalatally.buccopalatally.
The buccal outline of this root is curved, butThe buccal outline of this root is curved, but
its palatal outline is straight to end at a bluntits palatal outline is straight to end at a blunt
apex.apex.

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The palatal root is longer than the mesiobuccalThe palatal root is longer than the mesiobuccal
root but it is narrower from this aspect. Itsroot but it is narrower from this aspect. Its
buccal outline is concave and its palatalbuccal outline is concave and its palatal
outline is convex. At its middle and apicaloutline is convex. At its middle and apical
thirds, it is outside of the confines of thethirds, it is outside of the confines of the
greatest crown projection.greatest crown projection.
The level of the bifurcation is a little closer toThe level of the bifurcation is a little closer to
the cervical line than is found between thethe cervical line than is found between the
roots buccally. There is smooth depressionroots buccally. There is smooth depression
extends from the bifurcation to the cervicalextends from the bifurcation to the cervical
line.line.

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Distal AspectDistal Aspect
The gross outline of this aspect is similar toThe gross outline of this aspect is similar to
that of the mesial aspect, but the followingthat of the mesial aspect, but the following
variation is noted:variation is noted:
 The buccopalatal measurement of the crownThe buccopalatal measurement of the crown
on the distal aspect is less than that of theon the distal aspect is less than that of the
mesial aspect.mesial aspect.
 The distal marginal ridge dips sharply in aThe distal marginal ridge dips sharply in a
cervical direction exposing the distal triangularcervical direction exposing the distal triangular
ridges of the occlusal surface.ridges of the occlusal surface.
 The cervical line is almost straight.The cervical line is almost straight.

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40. 40
 The distal surface is generally convex exceptThe distal surface is generally convex except
for a small concave area near the distobuccalfor a small concave area near the distobuccal
root at the cervical third. This concavityroot at the cervical third. This concavity
continues over the distobuccal root and end atcontinues over the distobuccal root and end at
the bifurcation point.the bifurcation point.
 The distobuccal root is narrow at its base thanThe distobuccal root is narrow at its base than
either of the others. Its outline follows aeither of the others. Its outline follows a
concave path from the cervical line for a shortconcave path from the cervical line for a short
distance then makes a convex arc to thedistance then makes a convex arc to the
rounded apex. The palatal outline of this rootrounded apex. The palatal outline of this root
is slightly concave from the apex to theis slightly concave from the apex to the
bifurcation.bifurcation.

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 The bifurcation is more apical. The area fromThe bifurcation is more apical. The area from
the cervical line to bifurcation is 5 mm. orthe cervical line to bifurcation is 5 mm. or
more in extent.more in extent.
 The three roots appears from the distal view,The three roots appears from the distal view,
the distobuccal root is the smallest and shortestthe distobuccal root is the smallest and shortest
root.root.

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Occlusal AspectOcclusal Aspect
It is RhomboidalIt is Rhomboidal in outline, the crown is widerin outline, the crown is wider
mesially than distally, and wider palatally thanmesially than distally, and wider palatally than
buccally (this the only tooth that is widerbuccally (this the only tooth that is wider
palatally than buccally).palatally than buccally).
The mesiobuccal and distopalatal angles areThe mesiobuccal and distopalatal angles are
acute in comparison to the mesiopalatal andacute in comparison to the mesiopalatal and
distobuccal angles which are comparativelydistobuccal angles which are comparatively
obtuse.obtuse.

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The four major cusps are well developed.The four major cusps are well developed.
The tubercle of carabelli on the palatal surfaceThe tubercle of carabelli on the palatal surface
of the mesiopalatal cusp is small andof the mesiopalatal cusp is small and
nonfunctional. It may be indistinct, andnonfunctional. It may be indistinct, and
instead, a developmental line in the enamel isinstead, a developmental line in the enamel is
present.present.
The mesiopalatal cusp is the largest cusp; it isThe mesiopalatal cusp is the largest cusp; it is
followed in point of size by the mesiobuccal,followed in point of size by the mesiobuccal,
distobuccal, distopalatal, and nonfunctionaldistobuccal, distopalatal, and nonfunctional
fifth cuspfifth cusp ((tubercle of Carabellitubercle of Carabelli))..

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MesiopalatalMesiopalatal
cuspcusp
MesiobuccalMesiobuccal
cuspcuspDistobuccalDistobuccal
cuspcusp
DistopalatalDistopalatal
cuspcusp
Tubercle of CarabelliTubercle of Carabelli

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The occlusal surface is within the confines ofThe occlusal surface is within the confines of
the cusp ridges and the marginal ridges.the cusp ridges and the marginal ridges.
There are two major fossae, a central fossaThere are two major fossae, a central fossa
which is triangular concave area mesial to thewhich is triangular concave area mesial to the
oblique ridge, and a distal fossa which is linearoblique ridge, and a distal fossa which is linear
and distal to the oblique ridge.and distal to the oblique ridge.
The minor fossae are, the mesial triangularThe minor fossae are, the mesial triangular
fossa just distal to the mesial marginal ridge,fossa just distal to the mesial marginal ridge,
and the distal triangular fossa just mesial to theand the distal triangular fossa just mesial to the
distal marginal ridge.distal marginal ridge.

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Central fossaCentral fossa
Distal fossaDistal fossa
Major fossaeMajor fossae

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Mesial triangular fossaMesial triangular fossaDistal triangular fossaDistal triangular fossa
Minor fossaeMinor fossae

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The central developmental pit lies in theThe central developmental pit lies in the
central fossa. The buccal developmentalcentral fossa. The buccal developmental
groove radiates from this pit buccally betweengroove radiates from this pit buccally between
the two buccal cusps. The centralthe two buccal cusps. The central
developmental groove proceeds in a mesialdevelopmental groove proceeds in a mesial
direction originating in the central pit anddirection originating in the central pit and
terminating at the mesial triangular fossa,terminating at the mesial triangular fossa,
where it joins the mesiobuccal andwhere it joins the mesiobuccal and
mesiopalatal triangular grooves.mesiopalatal triangular grooves.

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Central pitCentral pit
Buccal grooveBuccal groove
Central grooveCentral groove MesiobuccalMesiobuccal
triangular groovestriangular grooves
MesiopalatalMesiopalatal
triangular groovestriangular grooves

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The mesial pit is found in the mesial triangularThe mesial pit is found in the mesial triangular
fossa.fossa.
Another developmental groove may be seenAnother developmental groove may be seen
radiating from the central pit distally andradiating from the central pit distally and
crosses the oblique ridge to end at the distalcrosses the oblique ridge to end at the distal
fossa. This is called the Transverse groove offossa. This is called the Transverse groove of
the oblique ridge.the oblique ridge.

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Mesial pitMesial pit
Central pitCentral pit
Transverse grooveTransverse groove

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From the distal pit the followingFrom the distal pit the following
developmental grooves radiate:developmental grooves radiate:
 The distopalatal groove which extendsThe distopalatal groove which extends
obliquely onto the palatal surface parallelingobliquely onto the palatal surface paralleling
the oblique ridge.the oblique ridge.
 The distopalatal triangular groove whichThe distopalatal triangular groove which
extends from the distal pit towards theextends from the distal pit towards the
distopalatal angle.distopalatal angle.
 The distobuccal triangular groove whichThe distobuccal triangular groove which
extends from the distal pit toward theextends from the distal pit toward the
distobuccal angle.distobuccal angle.

54. 54
Distopalatal grooveDistopalatal groove
Distopalatal triangular grooveDistopalatal triangular groove Distal pitDistal pit

55. 55
Distobuccal triangular grooveDistobuccal triangular groove Distal pitDistal pit

56. 56
The oblique ridge traverses the occlusalThe oblique ridge traverses the occlusal
surface from the top of the mesiopalatal cuspsurface from the top of the mesiopalatal cusp
to the top of the distobuccal cusp. It is reducedto the top of the distobuccal cusp. It is reduced
in hight in the center of the occlusal surfacein hight in the center of the occlusal surface
and is some times crossed by the transverseand is some times crossed by the transverse
groove of the oblique ridge.groove of the oblique ridge.
The mesial and distal marginal ridges areThe mesial and distal marginal ridges are
irregular elevations of enamel which areirregular elevations of enamel which are
confluent with the adjacent cusp ridges.confluent with the adjacent cusp ridges.

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58. 58
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