Mand Premolars.pdf occlusion table slide

About teeth

1. PREMOLARS

2. •Mand.PMare4innumber.
•2aresituatedinthert.Side&2intheleftside
•Theyareimmediatelypost.tothemand.canine&ant.tothe
molars.
•Mand.1stpremolarsaredevelopedfrom4lobesaswerethe
max.premolars,butinmostinstances2ndpremolarsare
developedfrom5lobes.
MANDIBULAR FIRSTPREMOLAR

3. •Fourthtoothfrommedianline
•Location-betweenmandibularcanine,2
ndpremolar
Function
•Masticationoffood.
•Maintainverticaldimensionofface.
•Assistcanineinshearingorcutting
•Supportthecornerofthemouth&cheektokeepthemfrom
sagging

4. CharacteristicsResembleMand.Canine
•Viewedbuccally,thebuccalcuspislongandsharp.Itistheonly
functionalcusp
•Fromtheproximalview,thebuccolingualmeasurementis
similartothatofthecanine
•Theocclusalsurfaceslopesdramaticallylinguallyinacervical
direction.Thisisbecause,thelingualcuspisverysmall
•Viewedocclusally,theocclusaloutlineofthecrownresembles
theincisaloutlineformofthemandibularcanine.

5. CharacteristicsResembleMand. SecondPremolar:
•Thetoothhastwocuspslikethe2ndpremolar
•Viewedbuccally,thecrownandrootformresemblesthatofthe
2ndpremolar
•Boththecontactareasonmesialanddistalsurfacesareatthe
samelevel….Thisfeatureiscommontoallposteriors
•Thecurvatureofcervicallinemesiallyanddistallyissimilar.

7. BUCCALASPECT
•Crownisnearlybilaterallysymmetrical.
•Middlebuccallobeiswelldeveloped,resultinginlarge
pointedbuccalcusp.
•Shape(outline)-Appearsshortsymmetrical
•Contactareas-Becauseofthegreaterlengthofthe
buccalcuspcontactareasofthe1stpmarelocatedmore
cervically
•M-Junctionoftheocclusal&middlethird.
•D-Slightlymoreocculsalinpositionthanthemesial
contactarea.

8. •Buccalsurface–moreconvexthanmax.
premolar.
•DevelopmentaldepressionseenB/Wthree
lobes
•Ridgerunsfromcervicalmargintocusptip–
BuccalRidge
•Tipofthebuccalcuspispointed&islocateda
littlemesialtothecenterofcrownbuccally.
•Rootis3-4mmshorterthanthatofmand.
Canine,apexdistallytilted.

10. LINGUAL ASPECT
•Lingualcuspsize&shape-alwayssmall.
•Majorportionofthecrownismadeupofmiddle
buccallobe…resemblecanine
•Lingualcusp-short,underdevelopedhaspointedtip
•Alignmentofcusptip-Cusptipisinalignment
withthebuccaltriangularridgeoftheocclusal
surface.
•Contactareas&marginalridgesarepronounced

11. •Occlusalsurface–slopestowardslingualincervical
directiontotheshortlingualcusp
•M&Docclusalfossaeareoneachsideofthetriangular
ridge.
•Charactersticfeaturesoflingualsurfaceofmandibular
1stpmismesio-lingualdevelopmentalgroove.
•Thisgrooveactsasalineofdemarcationb/wthem-b
lobe&thelinguallobe&extendsintothemesialfossaof
theocclusalsurface

14. MESIAL ASPECT
•Crownoutline-roughlyrhomboidal&tipofbuccal
cuspisnearlycenteredovertherootortipisonline
withlingualborderoftheroot.
•Buccaloutline-prominentlycurvedfromthecervical
linetothetipofthebuccalcusp.
•COC-jnofcervical&Middlethird.
•Lingualoutline-lingualcuspisacurvedoutlineofless
convexitythanthatofbuccalsurface.
•COC-Middlethird

15. •MMR—inclinescervically
•MLGroove-ThelingualborderofMMRmergeswiththe
developmentaldepressionthisharbourstheMLdevelopmental
groove.
•Cervicalline-Cervicallinecurvatureismoreonmesialthanondistal
side
•Root:tapersapically
•Deelopmentaldepressionpresent

17. DISTAL ASPECT
•DistalMMRislongerandismoreocclusal
•DistalMMRishorizontal,perpendicularto
longaxisoftooth:incontrasttoMMRwhich
showsingualinclination
•Noevidenceofdev.groove
•Rootismoreconvex
•Dev.depressionisalsoseen

19. OCCLUSAL ASPECT
•Crown-Outline-Roughlydiamondshape
•Middlebuccallobemakesupthemajorbulk
oftoothcrown.
•Buccalridgeisprominentbutnotasthatof
permanentmax.1stPM.
•MB&DBlineangleareprominenteven
thoughrounded

20. •Buccaltip-entered
•Lingualcus--small
•MR-welldeveloped
•Heavybuccaltriangularridge&smalllingualtriangularridge
•2fossa:MTFandDTF
•Pit:DTF
•

21. •3grooves:
•Mesialdevelopmentalgroove:Itislocatedinthemesialfossa;
isshortandextendsbuccolingually
•Distaldevelopmentalgroove:Itisinthedistalfossaislonger
•Mesiolingualdevelopmentalgroove:Itiscontinuousfrom
mesialgrooveanditextendsbetweenmesialmarginalridge
andmesiolingualcuspridgeontothelingualsurfacemesially.
Thisgrooveisthecharacteristicfeatureofmandibular1st
premolar

23. •MarginalRidges•Mesialmarginalridgeisshorterandisconstricted
becauseofmesiolingualdevelopmentalgroove.Itslopessharply
linguallyinacervicaldirection.
•Thedistalmarginalridgeisconfluentwiththedistolingualcusp
ridge.

24. ROOT
•Singleroot
•Slightlyshorterthanthemandibular2ndpremolar
rootand3to4mmshorterthanthatof
mandibularcanine
•Developmentaldepressiononthemesialsurface
oftherootisdeeperthanonthedistalsurface.
•Adeepdevelopmentalgrooveisoftenpresenton
themesialsurfaceofrootrunninglongitudinally.
•Theapicalthirdofrootisoftencurveddistally

25. DEVELOPMENTAL ANOMALIES
••Supernumerarypremolarintheregion
••Densevaginatus/Leong’spremolar

28. MANDIBULAR SECOND PREMOLAR
Itresemblesmandibular1
stPMfromthebuccalaspectonly.
Althoughthebuccalcuspisnotaspronounced,themesiodistal
measurementofthecrownanditsgeneraloutlinearesimilar.
Thetoothislargerandhasbetterdevelopmentinotherrespects.
Thetwotypesdiffermainlyintheocclusalaspect.
Thesinglerootofthe2
nd
PMislargerandlongerthanthatof
the1
st
PM.

29. Thistoothassumestwocommonforms.
Thefirstform,whichprobablyoccursmostoften,isthethree
cusptype,whichappearsmoreangularfromtheocclusal
aspect.
Thesecondformisthetwocusptype,whichappearsmore
•roundedfromtheocclusalaspect.

30. CHRONOLOGY
Firstevidenceof calcification
Enamelcompleted
Eruption
Rootcompleted
2¼ to2 ½ yrs
6to7 yrs
11to12yrs
13 to14yrs

31. BUCCALASPECT
Buccalcusp-shorterthanthe1
stPM,with
mesiobuccalanddistobuccalcuspridgespresenting
angualtionoflessdegree.
Contactareas-bothmesialanddistal,arebroad.
Contactareasappeartobehigherbecauseoftheshort
buccalcusp.

32. •Therootisbroadermesiodistallythanthatofthe1
st
PM,theextrabreadthappearingformostofitslength,and
therootendsinanapexthatismoreblunt.
•Inotherrespects,thetwoteetharequitesimilarfromthis
aspect.

34. LINGUALASPECT
Thelinguallobesaredevelopedtoagreaterdegree,
making
thecusporcuspslonger.
Lessoftheocclusalsurfacemaybeseenfromthisaspect.
Inthethreecusptype:Thereareamesiolingualanda
distolingualcusp,theformerbeingthelargerandthe
longeroneismostcases.
Thereisagrooveb/nthem,extendingaveryshortdistance
onthelingualsurfaceandusuallycenteredovertheroot.

35. Inthetwocusptype,thesinglelingualcusp
nogroove,butitshowsadevelopmentaldepression
distolinguallywherethelingualcuspridgejoinsthe
distalmarginalridge.
Thelingualsurfaceofthecrownofallmandibular2
nd
PMissmoothandspheroidal,havingabulbousform
abovetheconstrictedcervicalportion.

36. Therootiswidelingually,althoughnot
quitesowideasthebuccalportion.
Thelingualportionoftherootis
smoothlyconvexformostofitslength.
Consideredoverall,the2
nd
PMislarger
thanthe1
st
PM.

38. MESIALASPECT
Itdiffersfrom1
st
PMasfollows:
1.Thecrownandrootarewiderbuccolingually.
2.Thebuccalcuspisnotsonearlycenteredover
theroottrunk,anditisshorter.
3.Thelinguallobedevelopmentisgreater.
4.Themarginalridgeisatrightanglestothe
longaxisofthetooth.
5.Lessoftheocclusalsurfacemaybeseen.

39. 6.Thereisnomesiolingualdevelopment
grooveonthecrownportion.
7.Therootislongerandinmostcases
slightlyconvexonthemesialsurface;
however,thisconvexityisnotalways
present.
8.Theapexoftherootisusuallymoreblunt
onthe2
nd
PM.

41. DISTALASPECT
Similartomesialaspect,exceptthatmoreoftheocclusalsurfacemay
beseen.
Crownistippeddistallytothelongaxesoftherootssothatwhenthe
specimentoothisheldvertically,moreoftheocclusalsurfacemaybe
seenfromthedistalaspectthanfromthemesialaspect.

42. OCCLUSALASPECT
Two common forms
The outline form of each type shows some variation from the occlusal
aspect.
The two types are similar in that portion which is buccal to the mesio-buccal
and disto-buccal cusp ridges.
1
st
PM 2ndPM

43. Three cusp type appears square lingual to the buccal cusp ridges when
highly developed.
The two cusp type appears round lingual to the buccal cusp ridges.
The square type has three cusps that are distinct, the buccal cusp is the
largest, the mesio-lingual is the next and the distolingual cusp is the smallest.

44. ThreeCuspsType(MoreCommon)
Therearethreecusps:
1.Buccalcuspisthelargestone,followedbymesiolingualcuspand
distolingualcuspinthatorder.
2.Thelinguallobesarewelldeveloped.
3.Eachcusphasmesialanddistalcuspridgesofitsown,anda
triangularridgeslopingfromcusptiptowardsthecenterofthe
occlusalsurface

45. Eachcusphaswellformedtriangularridgesseparatedbydeep
developmentalgrooves.
ThesegroovesconvergeinacentralpitandformaYontheocclusal
surface.
Nocentraldevelopmentalgroove

46. Startingatthecentralpit,themesialdevelopmentalgroovetravelsina
mesiobuccaldirectionandendsinthemesialtriangularfossajustdistaltothe
mesialmarginalridge.
Thedistaldevelopmentalgroovetravelsinadistobuccaldirectionandendsin
thedistaltriangularfossamesialtothedistalmarginalside.
Supplementalgroovesanddepressionsareoftenseen,radiatingfromthe
developmentalgrooves.

47. 3pits:
1.Centralpitislocatedinthecenterofocclusalsurface
buccolinguallyandslightlydistaltothecentermesiodistally.
2.Mesialpitisinthemesialtriangularfossa.
3.Distalpitisinthedistaltriangularfossa.
MarginalRidges–Mesial&Distal-well-developed
Sometimessupplementarygroovecancrossthem.
twosmalltriangularfossae—mesialanddistal
Triangularfossaeharbormesial/distaldevelopmentalgroove,
mesial/distalpitandsomesupplementalgrooves

49. Roundortwocusptypehasthefollowingocclusalcharacteristics:
Theoutlineofthecrownisroundedlingualtothebuccalcuspridges
Thereissomelingualconvergenceofmesialanddistalsides,althoughnomorethan
isfoundinsomevariationsofthesquaretype
Themesiolingualanddistolinguallineanglesarerounded.
Thereisonewelldevelopedlingualcuspdirectlyoppositethebuccalcuspinalingual
direction.

50. Cusps
•Thetwocuspsarebuccalandlingual
•Buccalcuspislargerandlingualcuspisalsowelldevelopedthough
itisslightlysmaller
•Thecrowntapersslightlytowardslingualaspect
•Thecuspshavemesialanddistalcuspridgesandocclusally
convergingtriangularridges
Grooves
•Thecentraldevelopmentalgrooveextendsmesiodistallyacrossthe
occlusalsurfaceandendsinmesialanddistalfossae
•Itmaybestraight/crescentshapedandseparatesthetriangularridges
ofbuccalandlingualcusps

51. Therearetwogroovepatterns:
1.‘U’pattern:Wherecentralgrooveiscrescentshaped.
2.‘H’pattern:Wherecentralgrooveisstraightconnectingmesialand
distalfossa.
Pits
•Theremaybemesialanddistalpitslocatedinthemesialanddistal
fossae
•Intwocuspstype,thereisnocentralpit.
MarginalRidgesandFossae
•Mesialanddistalmarginalridgesarestronglydeveloped
•Thefossaeareirregularratherthantriangularandarecalledas
mesialanddistalocclusalfossae

52. ROOT
•Singlerootalmostneverbifurcated
•broader,strongerandlongerthanthatofthe
mandibular1stpremolar
•conicaltaperingfromcervixtoapex
•Itiswidermesiodistallyanddoesnottapermuch
towardslingualaspect
•Apex:blunt,straightoritsapicalendmayhavea
distalcurvature.