The Premolars 2016 ppt[1] · Occlusal Aspect of Mandibular 2nd Premolar: o Three-cusp form( Y-shaped) uBuccal largest, then mesiolingual, then distolingual uEach cusp has triangular

ThePremolars

Chapter17PermanentPosteriorTeeth

(p.230-244)

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.

Development

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.

Trapezoid Shape Rhomboid Shape

Comparing Proximal View of Crown

MandMax

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 SecondMaxillary First

Mandibular First Mandibular Second

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

MaxillaryFirstPremolar

Fig17-16

• 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

ExampleofPossibleRootCanalConfigurations

• Tworootstwocanals • Oneroottwocanals

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

Figure 17-24

Mandibular First Premolars

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

39

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

ImpactedMandibularSecondPremolar

Darby ML, Walsh M. Dental Hygiene: Theory and Practice, ed 2. Mosby, St. Louis, 2003