permanent+mandibular+first+molar

7/30/2019 Permanent+Mandibular+First+Molar

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Manish Pandey


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Introduction The mandibular molars are larger than any other

mandibular teeth.

The mandibular first molar is the largest tooth inmandibular arch.

It has 5 well developed cusps-2 buccal,2 lingual and 1distal

It has 2 well developed roots ,1 mesial and 1 distal.


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Importance of permanent

mandibular first molar It maintains arch perimeter

It bears maximum masticatory load

It is a key factor in occlusion Has maximum root surface area

It provides best anchorage

Is a growth center

It is most commonly decayed


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Chronology 1st evidence of calcification-- at birth

Enamel completed -- 2 and a half to 6 yrs

Eruption -- 6 to 7 yrs Root completed -- 9 to 10 yrs


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Dimensions

(in mm) Cervico occlusal length of crown -- 7.5

Length of root -- 14

Mesiodistal diameter of crown -- 11 Mesiodistal diameter of crown at cervix -- 9

Buccolingual diameter of crown --10.5

Buccolingual diameter of crown at cervix -- 9

Curvature of cervical line mesially --1

Curvature of cervical line distally --0


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Dental formula Palmers notation -- 6 6

FDI notation -- 36,46

Set -- permanent Class -- molar

Arch -- mandibular

Type -- first


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BUCCAL

ASPECT Crown is roughly trapezoidal 5cusps are present-

mesiobuccal,distobuccal,dista

l,mesiolingual anddistolingual

Mesiobuccal distobuccalcusps andbuccal portion oflingual cusp with the tips oflingual cusp can be seen fromthis aspect.


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BUCCAL

ASPECT Mesial outline-is concave at

cervical third upto the convexoutline of broad contact area

Distal outline- is straightabove cervical line to its

junction with convex outlineof distal contact area


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BUCCAL

ASPECT Cervicval line-is

regular,dipping apicallytowardsroot bifurcation


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BUCCAL

ASPECT 2developmental groovesappear on crown-

Mesiobuccal developmental

groove-separates mesiobuccaland distobuccal lobe.it isshorter and terminatescentrally crvico-occlusally.


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BUCCAL

ASPECT Distobuccal developmentalgroove-separates distobuccaland distal lobes.it terminates

near the distobuccal ine angleat cervical third.


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BUCCAL

ASPECT

Mesiobuccal,distobuccalcusps are flat while distal cuspis pointed

Mesiobuccal cusp is widestmesiodistally.


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BUCCAL

ASPECT distobuccal cusp is almost aswide with cusp ridge ofsomewhat greater curvature.

the distal cusp ridge is veryround occlusally and issharper than other 2 buccalcusps


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BUCCAL

ASPECT Surface is smoothly convex atthe cusp portions withdevelopmental grooves

between the cusps. in the middle third a

developmental depression isnoticeable which runs in

mesiodistal direction abovecervical ridge.


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BUCCAL

ASPECT Cervical rigde may showsmooth depressionprogressing cervically.

Mesial Distal outline of mesialroot is concave frombifurcation to apex

root is curved mesially fromcervical line to middle thirdportion.


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BUCCAL

ASPECT From here it curves distally to

tapered apex.

Distal root is less curved than

mesial ,its axis is in distaldirection from cervix to apex.


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BUCCAL

ASPECT Point of bifurcation of of roots

is located 3mm below cervicalline.

Deep developmentaldepression is present bucallyon root trunk.


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LINGUAL

ASPECT

From this aspect Mesiolingual,distolingualcusps and lingualportion of distal cusp is

The lingual cusps arepointed.mesiolingual cusp is

widest mesiodistally and ismore pointed.


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LINGUAL

ASPECT The lingual develomental

groove is present between2cusps and extends for a short

distance


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LINGUAL

ASPECT Mesial outline-is convex from

cervical line To marginalridge.

Distal outline is straight fromcervical line to distal contactarea,this area is representedby convex curvature that

outlines distal surface of distalcusp.


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LINGUAL

ASPECT Cervical line is irregular and

tends to point sharply towardsroot bifurcation.


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LINGUAL

ASPECT The angle formed by

distolingual cusp ridge ofmesiolingual cusp and vice

versa is more obtuse thanangle formed cusp ridges attips of lingual cusps.i.e 100degrees.

Distal cusp is at a lower levelthan mesiolingual cusp.

Crest of contour meially ishigher than distally.


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LINGUAL

ASPECT Surface is smooth and

spheroidaland becomes flatwhile approaching cervical

line.Roots measure 1mmlongerlingually than buccally

Root bifurcation lingually

starts at a point approx.4mmbelow cervical line.


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LINGUAL

ASPECT Bifurcation groove is in line

with developmental groove ofcrown.dev.depression is

smooth throughout and fadesbelow cervical line.


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MESIAL

ASPECT Mesiobuccal,mesiolingual ,

cusps and mesial root is seen

Buccolingual measurement is

greater mesially thendistally.buccolingualmeasurement of mesial root isgreater than distal root.

Crown is roughly rhoimboidaland entire crown has lesslingual tilt in relation to rootaxis.


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MESIAL

ASPECT Buccal outline is convex

immediately above cervicalline outlining buccal cervicalridge.above cervical ridge it isslightly concave or flatocclusally.

Lingual outline is straightfrom cervical line to middlethird .the crest of contour islocated at center of middlethird


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MESIAL

ASPECT Lingual outline is straightfrom

cervical line to junctionofmiddle and apical thirdthen it

is sharply buccal to bluntlytapered apex.

Cervical line is irregular andcurves occlusally about 1mm

towards center of mesialsurface.


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MESIAL

ASPECT The mesial marginal ridge is

placed about 1mm below levelof cusp tips.it is confluent

with marginal ridges ofmesiobuccal and mesiolingualcusps.

Surface is smooth and convex.

a slightly concave area existsat cervical line and joins theconcavity of central portion ofroot


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MESIAL

ASPECT Buccal outline of mesial root

drops straight down to thejunction of cervical and

middle third of root.a gentlecurve starts lingually from thispoint to apex.

Lingual outline of root is

slanted in buccal direction.


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Surface is convex at the buccaland lingual borders withbroad concavity between

convexities for full length ofroot.


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DISTAL

ASPECT The outline of crown and root

is similar to mesial aspect.

The distal cusp is placed a

little buccal to center bucco-lingually with distal contactarea appearing on its distalcontour.

Distal contact area is placedjust below the distal cuspridge of distal cusp at slightlyhigher level than cervical line.


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DISTAL

ASPECT Distal marginal ridge is short

and dipps sharply in cervicaldirection meeting at obtuse

angle. Often developmental groove

or ridge is found crossingmarginal ridge.

Cervical line distallyisstraght,dipping rootwise justbelow distal contact area.


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DISTAL

ASPECT The end of distobuccal

developmental groove islocated on distal surface andforms concavity at cervicalportion ofdistobuccal lineangle

More of tooth is seen fromdistal aspect because thecrown is shorter distally thanmesially and bucal and lingualsurfaces converge distally.


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DISTAL

ASPECT Smooth flat surface below

contact area remainsfairlyconstant to apical third

sometimes showingdevelopmental depression.

The apical third of root ismore rounded as it tapers to a

shorter apex


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OCCLUSAL

ASPECT It is hexagonal in shape .

The crown measures 1mmmore mesiodistally than

buccolingually. Buccolingual measurement is

greater on mesial than ondistal.

Crown converges linguallyfrom contact ares.


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OCCLUSAL

ASPECT The occlusal surface shows-

1 major central fossa which iscircular and centrally placed

2minor fossae- 1)mesial triangular fossa

2)distal triangular fossa


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OCCLUSAL

ASPECT The developmental grooves

are-

Central

Mesiobucal Distobuccal

And lingual

They all converge in the centerof central fossa at the centralpit.


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Occlusal

aspect

DBCR-distobuccal cuspridge

DBDG-distalcusp ridge

DTF-distaltriangular fossa

DLCR-distolingual cusp

rid e


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OCCLUSAL ASPECT

MLCR-mesiolingualcusp ridge

MTF-mesialtriangular fossa

MBCR-mesiobuccalcusp ridge

MBDG-mesiobuccaldevelopmentalgroove


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OCCLUSAL

ASPECTLDG-lingualdevelopmentalgroove

SG-supplementalgroove


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OCCLUSAL

ASPECT It shows 4 major cusps-

Mesiobuccal

Distobuccal

Mesiolingual Distolingual

And a minor cusp-

Distal cusp

Mesiobuccal cusp is thelargest and distal cusp issmallest.


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OCCLUSAL

ASPECT Mesial triangular fossa-is

small and concave.

The mesial portion of central

groove terminates in thispath.

A buccal and a lingualsupplemental groove join it atthe mesial pit.


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OCCLUSAL

ASPECT Distal triangular fossa-is less

distinct.

The central groove terminats

hereAn extension of central groove

often crosses the disalmarginal ridge.


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OCCLUSAL ASPECT

CP-central pit

MP-mesial pit

DP-distal pit


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OCLUSAL ASPECT

MMR-mesialmarginal ridge

DMR-distalmarginal ridge

CDG-centraldevelopmentalgroove


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OCCLUSAL

ASPECT The central fossa is a concave

area bounded by

distal slope of mesiobuccalcusp,

mesial and distal slopes ofdistobuccal cusps,

distal slope of mesiolingual

cusp, and mesial slope of

distolingual cusp.


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OCCLUSAL

ASPECT Central developmental

groove-starts at central pitand travels an irregular course

mesially.


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OCCLUSAL

ASPECTA short distance mesially from

central pit, it joinsmesiobuccal developmental

groove which courses in amesiobuccal direction at thebotom of sulcate grooveseparating mesio and

distobuccal cusps.


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OCCLUSAL

ASPECT The lingual developmental

groove of occlusal surface isan iregular groove coursing in

a lingual direction at thebotom of lingual sulcategroove to the junction oflingual cusp ridges.

Here it is confluent withlingual extension of samegroove


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OCCLUSAL

ASPECT Starting at central pit the

central developmental groovemay be followed in adistobuccal direction to a

point where it is joined bydisto buccal developmentalgroove of occlusal surface.

From this point it courses in

distolingual directionterminating at distaltriangular fossa


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OCCLUSAL

ASPECT The distobuccal

developmental developmentalgroove -passes from its

junction with central groovein a distobuccal direction ,

It joins its buccal extention onbuccal surface at the junction

of cusp ridges of distobuccaland distal cusps.


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OCCLUSAL

ASPECT The central developmental

groove is centally located inrelation to buccolingual

crown dimension This arrangement makes the

triangular ridges of lingualcusps longer tha buccal cusps.


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OCCLUSAL

ASPECT The mandibular first molar

mostly has a functioningdistal cusp

Occasionally, 4 cusp molarsare found

Sometimes distal anddistobuccal cusps may show

fusion.


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Class traits

(molar) Molars have largest occlusal surface than any other

teeth in the arch.

They have 3-5 major cusps.

They are the only teeth having 2 or more buccal cusps.

They have 2-3 large roots.

They are shorter cervico-occlusally but overall

dimensions are greater.


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Arch traits

(mandibular) Mandibular molars have generally 2 roots-mesial and

distal.

They genrally heve 4 major cusps and 5th of lesser size.

Crowns are always broader mesiodistally thanbuccolingually.


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Arch traits

(mandibular) They are the only units in dentition in which 2 major

lingual cusps are of equal size.

2 lingual cusps are at higher level and more or less

pointed.

Mesiobuccal and distobuccal cusps are appriximatelyequal in size.


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Type traits

(first) Presence of 3 buccal cusps and 2 lingual cusps.

Crown shows maximum mesiodistal diameter

It is widest of all molars.

Mesial and distal profile converge lingually.

Crown is narrower at cervix.

Almost half of distal surface is made up of distal cusp.


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Type traits

(first) Occlusal table is hexagonal.

Mesial and distal roots are highly separated and arerelatively vertical

Buccal crown profile and portion of lingual profile isvisible from lingual aspect

Distobuccal line angle is very much prominent while

mesiobuccal line angle is sharp and acute.


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Side determination 3 buccal and 2 lingual cusps are present.

Distal cusp is at distal most aspect and is smallest.

Mesiobuccal groove is shorter than distobuccal groove.

Mesial root is wider buccolingually than distal.


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WHEELERS-textbook of dental anatomy and occlusion

DAMLE-textbook of pediatric dentistry

permanent+mandibular+first+molar

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