The Premolars 2016 ppt[1] · Occlusal Aspect of Mandibular 2nd Premolar: o Three-cusp form(...
Transcript of The Premolars 2016 ppt[1] · Occlusal Aspect of Mandibular 2nd Premolar: o Three-cusp form(...
General Information
Function:u Hold and grind
foodu Work with molars
in mastication.u Even without
molars one may be able to chew well with the premolars.
u There are two in each quadrant
Fig17-1
General Features – All premolars
uDevelop from four lobes except the mandibular 2nd premolar which develops from five
uLingual lobe forms cusp rather than cingulum as in anterior teeth
uPremolars have occlusal surface, bordered by marginal ridges.
uOcclusal surfaces have cusps, grooves, ridges, and fossae.
uCrownsareshorterthantheanteriorteeth.
uTheyhaveaverticalbuccalridgeonthebuccalsurface(similartothelabialridgeoncanines)
uTheproximalcontactareasaremorecervicallylocatedthanincisors.
uTherearenopremolarsintheprimarydentition.
General Information
uPermanent premolars are succedaneous teeth -they replace the deciduous molars.
CEJ
uTheCEJislesspronouncedontheposteriorsthanontheanteriors.
uTheCEJisoftenquitestraightforposteriors.
Figure17-6
Development
PermanentMaxillary1stPremolaro Evidenceofcalcification- 1.5yrs.
o Eruption- 10- 11yrs.o Rootcomplete13yrs.
Permanent Maxillary 2nd Premolaro Evidence of calcification - 2
yrs.o Eruption -10 - 12 yrs.o Root complete 13 yrs.
Development
PermanentMandibular1stPremolaro Evidenceofcalcification- 2yrs.o Eruption- 10- 12yrs.o Rootcomplete13yrs.
Permanent Mandibular 2nd Premolaro Evidence of calcification - 2.5
yrs.o Eruption -11 - 12 yrs.o Root complete 14 yrs.
General Characteristics
Maxillary Premolars• Wider F-L than M-D
dimensions
• Two major cusps on each
• Resemble each other
• Trapezoidal shaped proximal.
Mandibular Premolars• F-L and M-D dimensions
almost equal
• Facial cusps much larger
• Do not resemble each other.
• Rhomboidal shaped proximal.
Maxillary First PM• Two roots (usually)
• Lingual cusp shorter and narrower than facial cusp
• Mesial marginal groove and depression
Maxillary Second• One root (usually)
• Cusps of nearly equal length and width.
• No mesial marginal groove or depression
Maxillary premolars
MaxillaryFirstPremolarOcclusalAspect:
• Longcentraldevelopmentalgroove.
• Fewsupplementalgrooves• Hexagonalshapetoocclusaloutline.
MaxillarySecondPremolarOcclusalAspect:
• Shortercentraldevelopmentalgroove.
• Manysupplementalgrooves• Ovoidshapetoocclusaloutline,rounder.
Mandibular First• There is one root with
two pulp horns
• Small lingual cusp(nonfunctional cusp); facial cusp is twice as large.
• Occlusal anatomy can be seen from the lingual view.
Mandibular Second• There is one root with
three pulp horns
• Well developed lingual cusp, with the possibility of two lingual cusp.
• Can see little of occlusal anatomy from lingual view.
Mandibular Premolars
Mandibular First Premolar Occlusal Aspect:
u Occlusal outline is diamond shape
u M-L groove is present. u No central pit.
Mandibular Second PremolarOcclusal Aspect:
uOcclusal outline is square.
uNo M-L groove.
uHas “Y” groove pattern or an “H” groove pattern
Maxillary First Premolars #5, #12
uHavebuccalandlingualcusp;buccalslightlylonger
uUsuallyhavetworoots***(onlypremolarwiththisfeature)
uTwopulpcanalsmostcommon,evenifonerootispresent
uBroadermesialanddistalcontactareas
Fig 17-11
*** check your tooth ID sheets from lab
LabialAspect:uLookssimilartomaxillarycaninethoughnarrower&shorter
uContactareasatsameheightmesiallyanddistally
uWell-developedmiddlefaciallobe
Maxillary First Premolars #5, #12
Fig17-13
• Hasmesialmarginalgrooveandconcavity(depression).
• Thisrequiresspecialconsiderationwhenscaling.
Maxillary First Premolars #5, #12
Fig17-14
uBifurcatedrootmostcommonalthoughsinglerootpossible
uBuccalrootlargerandlongerthanlingual:
uTworootcanalspresent,eveninsinglerootedtooth
uTwopulphornsuRarely,singlerooted,singlecanal1stpremolarfound
Maxillary First Premolar Root and Pulp cavity.
Fig17-12
Maxillary Second Premolars #4, #13
uSimilarinformandfunctionto1stpremolar,thoughmorerounded
uOnerootpresentmostcommonly
uAppearancevariesmorethan1stpremolars
uRootlongerthan1stpremolar
Fig17-17
LingualAspect:o Buccal&lingualcuspsareaboutthesamelength
MesialAspect:o Nodeepdevelopmentalgroovesandnodepressionsarepresentonthemesialsurface
o Grooveonsingle-rootedtoothgivesfusedrootappearance
LingualDistal
Maxillary Second Premolars #4, #13
Fig17-17
OcclusalAspectofMaxillarySecondPremolar:
uMoreroundedoutlinethan1stpremolar,appearsovoid.
uManysupplementalgrooves.
uMorewrinkledinappearance.
Maxillary Second Premolars #4, #13
Fig17-19
Root&PulpCavity:uSinglerootmostcommonwithgrooveonmesialanddistalsurfaces
uOnecanalmostcommonthoughdividedcanaloccursfrequently
uTwopulphorns
Maxillary Second Premolars #4, #13
Fig17-18
Mandibular First Premolars #21, #28
uSharecharacteristicswithmandibularcanine
uGenerallysmallerthanmandibular2ndpremolar(oppositepatternformaxillarypremolars)
uFourlobescontributetothistoothwithlingualcuspsmall,non-occludingand,therefore,afunctional
Fig17-20
LabialAspect:uLookssimilartocanineuSinglesharpbuccalcuspuBuccolingualdimensionsimilartoadjacentcanine
uWelldevelopedbuccalridgeuMesialcuspridgeshorterthandistal
uMesialanddistalcontactareasatsameheight
uShorterrootthancanine
OcclusalAspectofMandibularpremolars:
uMorevariationinocclusalanatomyispresentonmandibularpremolarsthanmaxillarypremolars
uSharpconvergencefrombuccaltolingualcusp
uLargebuccaltriangularridgew/mesialanddistalfossae
uFossaemaycontainpits
Fig17-23
LingualAspect:o Severelytaperstowardthelingual
o Verysmalllingualcuspo Occlusalpitsinfossaeoneithersideoftriangularridges
o Prominentmesiolingualdevelopmentalgrooveseparatesmesialmarginalridgefromlingualcusp
Mandibular First Premolars
Figure 17-22
Root&PulpCavityuSingle-rootedformmostcommon,althoughbuccal-lingualtwo-rooted1stpremolarpossible
uIfbifurcated,alongitudinalgroovefoundproximally
uTwopulphorns,onecanalmostcommon
Mandibular First Premolars
Fig17-21
Mandibular Second Premolars #20, #29
uLargerthan1stpremolaruContactareasatsameheightmesiallyanddistally
uShorterbuccalcuspandlongerrootthan1stpremolar
uMoredevelopedlingualcusp(s)functionasmolar
uMarginalridgeshigherthan1stpremolar
uTwoforms:two-cusptypethree-cusptype
LabialAspect:o Shorterbuccalcuspthan1stpremolar
o Mesialanddistalcuspridgesmorerounded
o Wider,longerroot
Mandibular Second Premolars
Fig17-26
LingualAspectuVariesduetocuspvarietyuAtleastonelingualcusp(in3-cuspvariety)islongerthan1stpremolar
uMesiolingualcuspusuallylargerin3-cuspform
uLargesinglecuspin2-cuspformcomparedto1stpremolar
uWiderlingualsurfacethan1stpremolar
Mandibular Second Premolars
Fig17-26
Occlusal Aspect of Mandibular 2nd Premolar:o Two-cusp form (U or H-shaped)
u Occlusal outline more rounded than 3-cusp form
u No lingual developmental grooveu U shape groove pattern and a H
shape groove patternu No central pitu Mesial and distal pit may be
present
Mandibular Second Premolars
Fig17-32
OcclusalAspectofMandibular2ndPremolar:
o Three-cuspform(Y-shaped)uBuccallargest,thenmesiolingual,thendistolingual
uEachcusphastriangularridgeuMesial,distalandlingualdevelopmentalgroovesseparatecusps
uMesial,distalandcentralpitmaybepresentaswellasmesialanddistaltriangularfossae
uDevelopmentalgroovesmorecommonandlessdeep
Mandibular Second Premolars
Fig17-27
Root&PulpCavityuSingle-rooteduDistalrootdepressioninmiddlethirdofroot
uSinglepulpcanalmostlikely
Mandibular Second Premolars
Fig17-28
ClinicalConsiderationsforPremolars
• Single,permanentpremolarscanbeextractedineachquadrantduringorthodontictherapytoimprovedentalarchspacing.• Ifapremolarhasbeenextracted,thedistinctivepitandgroovepatternsontheocclusalsurfacewillhelpinidentifyingtheremainingpremolarswhenthearchspacefromtheextractionislostiftheremainingmolarsarenotrestored.However,orthodontictherapytendsinsteadtoincludeexpansionofthejaw,ifneeded,insteadofremovingpremolarstoretainamorenaturalroundedcurvedshapetothearches.Ifstillneeded,firstpremolarsareusuallyextractedmoreoftenthansecondpremolars.
Fehrenbach, MJ. Slide Collection.
SpecificOverallFeatures• Adistinctmesialrootconcavityispresentontheroottrunkofmaxillaryfirstpremolar,extendingfromthecontactareatothebifurcation.
Surgicalaccessfacilitatesdebridementoftherootsurface.
Fehrenbach, MJ. Slide Collection.
ClinicalConsiderationsforMaxillarySecondPremolars
�Withprematurelossoftheprimarysecondmolars,thedevelopingpermanentmaxillaryfirstmolarinclinesanddriftsmesially.
�Thedevelopingpermanenttoothispreventedfromnormaleruptionbecauseitsarchleeway space isnearlyclosed.
Figure20-3