3 premolars

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THE THE PREMOLARSPREMOLARS

Dr: 3mmar

Premolars Premolars There are four maxillary and four mandibular premolars.

4 & 4 contact: 3 & 3 mesially and 5 & 5 distally

5 & 5 contact:

4 & 4 mesially and

6 & 6 distally.

Relations:Relations:

General Features of PremolarsGeneral Features of Premolars

They are They are transitionaltransitional teeth teeth located between the canine located between the canine and molar teeth. and molar teeth.

By definition: By definition: Premolars Premolars are permanent teeth distal are permanent teeth distal to the canines, and to the canines, and successors to deciduous successors to deciduous molars. molars.

There are two premolars There are two premolars per quadrant and are per quadrant and are identified as first and identified as first and second premolars. second premolars.

They have usually two They have usually two cusps(bicuspid) : cusps(bicuspid) : One large buccal cusp,One large buccal cusp, Smaller lingual cuspSmaller lingual cusp

The lower second The lower second premolar may- premolar may- sometimes- have two sometimes- have two lingual cusps. lingual cusps.

General Features of PremolarsGeneral Features of Premolars

MAXILLARY FIRST PREMOLARMAXILLARY FIRST PREMOLAR

ChronologyChronology: : •Enamel organ appearance: 7 mIU.

•Beginning of calcification: 1½-1¾y•Crown completed: 5 – 6y•Eruption: 10 – 11y

•Root completed: 12 – 13y

Number of lobes: four lobesNumber of lobes: four lobes : :

• Three buccally Three buccally • One linguallyOne lingually

DistalDistalMesialMesialPalatalPalatal

OcclusalOcclusal

BuccalBuccal

No. of rootsNo. of roots

Two roots(60%Two roots(60%(.(. One root(40%One root(40%(.(.

Geometric Outline of the CrownGeometric Outline of the Crown

The smallest of the uneven sides

cervically.

Facial and lingual aspects have Facial and lingual aspects have trapezoid out line.trapezoid out line.

Buccal AspectBuccal Aspect Outlines:

•Mesial and distal outlines: are nearly concave and both become convex at cont. areas. •Mesial and distal cusp slopes: are also slightly concave Contact areas:

Mesially: at the middle third(broad) Distally: Little more cervically than the mesial one(broader)

M. slope > D. slope(sometimes convex) Bucc. cusp pointed, long and the tip is slightly distal to the vertical axis

Cervical line:

convex rootwise.

MD

Surface Anatomy of the CrownSurface Anatomy of the Crown

•The surface is convex with maximum convexity at cerv. 1/3 representing cervical ridge

Elevations:

Depressions: Shallow depressions are present mesial and distal to the buccal ridge.

The middle lobe is prominent buccally forming bUCCAL ridge.

Buccal AspectBuccal Aspect

.

Outline and Surface AnatomyOutline and Surface Anatomyof the Rootof the Root

The surface of the root is convex and smooth

The M and D outlines of the root taper to a pointed apex curved distally. If two roots:

The buccal root hides the lingual root as it is shorter and narrower than the buccal root.


MD

• The surface is convex with maximum convexity at the middle 1/3.

• The root is convex.

Outlines:• M and D outlines are convex• The L. cusp is shorter by 1 mm but sharper than the B cusp• The D slope of L cusp is longer than M slope

M D

Cervical line: is convex rootwise. Surface Anatomy :Surface Anatomy :

Lingual AspectLingual Aspect•Lingual convergence: Ling.s. is narrower than buccal s.

The M and D outlines of the root taper to a pointed apex that curves distally.

If two roots:

The lingual root appears shorter and narrower than the buccal root.

Lingual AspectLingual Aspect Outline and Surface AnatomyOutline and Surface Anatomy of the Root of the Root

M D

If one root:

The ling. Surface is convex and narrower MD than the buccal portion.

Proximal AspectsProximal AspectsMesial aspect Distal aspectProximal Proximal

aspects have aspects have trapezoid out trapezoid out line.line.The smallest of

the uneven sides

occlusally.

Lingual outline: convex with maximum convexity at middle 1/3Cervical line: curves occlusally and less curved distally

Outlines of Proximal AspectsOutlines of Proximal Aspects

Buccal outline : Convex with maximum convexity at cervical 1/3 representing cervical ridge.

Mesial Mesial aspectaspect

Distal Distal aspectaspect

Occlusal outline:Bucc. cusp is longer than Ling. cusp by 1mm.

Bucc. cusp tip is below the center of Bucc root.

Ling. cusp tip is on line with Ling. border of the ling. root.

MMR concave, at the junction of occ. & middle thirds.

DMR more cervical.

Mesial Mesial aspectaspect

Distal Distal aspectaspect

Surface Anatomy Surface Anatomy of of

Proximal Proximal AspectsAspects

Contact areas:

Mesial Mesial AspectAspect

Distal Distal AspectAspect

At the middle 1/3, bucc. to midline

More cervically positioned & more buccally.•Mesial marginal

developmental groove crossing MMR and located lingual to the contact area.

Smooth and convex surface except for a small flat area cervical to contact area(no canine fossa or develop. groove crossing the DMR) .•Mesial Developmental

depression in the crown & continues on the root (canine fossa).

Cervical line curvature:

Curves occlusally Less curved

In case of two roots (more common).



Root trunk about half the root length.

Root trunk is longer as bifurcation is near apical 1/3

Surface is smooth and convex except deep developmental depression below bifurcation that continue with the mesial dep. on the crown.

Surface is smooth and convex except shallow devlop. depr. on the root trunk

Outline and Surface AnatomyOutline and Surface Anatomy of the Root of the Root

In case of one root

(less common)

The B and L outlines tapere to a blunt apex in line with the center of the crown.

The surface is smooth and convex except for a shallow depression in the center that is deeper mesially than distally.

Occlusal Occlusal AspectAspect

Hexagonal2 equal buccal sides (MB, DB)

M side shorter than D side.

ML side shorter than DL side.

Thickness(BL) is greater than width(MD).

The crown is wider buccally than lingually, due to lingual convergence of the crown

MD

Geometric outlineGeometric outline

Surface anatomySurface anatomyElevations:Bucc. triangular ridge.

Ling. triangular ridge.M & D marginal ridgesDepressions:Central developmental grooveM and D triangular fossae.

M marginal developmental groove

Occlusal Occlusal AspectAspect

MD

Mesial marginalMesial marginal developmental groovedevelopmental groove

The most charecteristic identifying feature of the max. first premolar

MAXILLARY FIRST PREMOLAR

MD section BL section

Pulp chamber:Narrow Wide

Root canals:2 root canals (B&L) but rarely 3 canals

lingual canal is larger & more accessible

PULP CAVITYPULP CAVITY

oval or kidney shaped Cervical cross sec.

MAXILLARY SECOND PREMOLARMAXILLARY SECOND PREMOLAR

MAXILLARY SECOND PREMOLARMAXILLARY SECOND PREMOLAR

ChronologyChronology: : •Enamel organ appearance: 8 mIU.

•Beginning of calcification: 2-2¾y•Crown completed: 6 – 7y•Eruption: 10 – 12y•Root completed: 13 – 15y

Maxillary Second PremolarMaxillary Second Premolar

BuccalBuccal LingualLingual MesialMesial DistalDistal

OcclusalOcclusal

Geometric Shape of Geometric Shape of the Crownthe Crown

Facial & Lingual Facial & Lingual Aspects Aspects


cervically.

Trapezoid shapeTrapezoid shape..

Comparison betweenComparison between Maxillary First and Second PremolarsMaxillary First and Second Premolars

Buccal AspectsBuccal Aspects

MD D M

• B cusp is short and not pointed• Shorter M slope than D

•Mesial contact : in the occ.1/3 while distally more cervically.

•Cervical line less curved.

• B cusp is long and pointed• Longer M slope than D

•Mesial contact: in the middle1/3 while distally more cervical.

• Cervical line curved rootwise.

Maxillary First Premolar Maxillary Second Premolar


Buccal AspectsBuccal Aspects

Prominent B ridge Less prominent B ridge

Narrow cervical portion. Wider cervical portion.

Short root. Longer root.


Lingual AspectsLingual Aspects

• The L and B cusps are nearly of same height.• Rarely has 2 roots•In case of two roots the L root is shorter & its apex more blunt.

•The L cusp is shorter by 1 mm than the B cusp.• 60% has 2 roots with • L root is shorter than B root and its apex is pointed.

Mesial and Distal Mesial and Distal AspectsAspects

Trapezoid in shape

Smallest of the uneven sides:

occlusaly

4 5 Geometric Shape of Geometric Shape of the Crownthe Crown

BL


Mesial AspectsMesial Aspects

• B cusp is longer than L cusp by 1mm

•The occlusal table is wide.•Mesial marginal dev. groove in crown & deep canine fossa extending on root surface.

•The cusps are shorter & nearly at the same level.

•The crown surface is smooth & convex. The root has shallow dev. dep.

•The occlusal table is narrow


Mesial AspectsMesial Aspects

At the occlusal third (OC dimension) and slightly buccal to midline (BL dimension)

MMR positioned more occlusal.

Contact area: At the middle third (OC dimension) and slightly buccal to midline (BL dimension)

MMR at the junction of M1/3 &Occ1/3

DMR more cervical than MMR

CA cervically positioned and more buccally than MCA.

Smooth and convex surface.

DMR more cervical than MMR

CA cervically positioned and more buccally than MCA.

Smooth and convex surface except for a small flat area cervical to contact area.

Maxillary First Premolar Maxillary Second PremolarDistal AspectsDistal Aspects

Distal AspectsDistal AspectsMaxillary First Premolar Maxillary Second Premolar

Root trunk is long as the bifurcation is near apical 1/3Surface is smooth and convex except shallower DD on the root trunk than mesially.

One root and if 2 the bifurcation will be more apically.Surface is smooth and convex except deeper DD in the middle of the root than mesially.


Occlusal AspectOcclusal Aspect

hexagonal oval(less angular(

B & L triangular ridges.

Thin M & D marginal ridges

B & L triangular ridges.

Thicker M & D marginal ridges

Maxillary First Premolar Maxillary Second PremolarOcclusal AspectOcclusal Aspect

Shorter Central dev gr.Not present. Multiple supplemental grooves

M and D fossae.

Long Central dev.gr.

M and D fossae.

M marginal dev. groove

Thin marginal ridges Thick marginal ridges

MAXILLARY SECOND PREMOLAR

PULP CAVITYPULP CAVITYof maxillary second premolarof maxillary second premolar

MD section BL section

Narrow(MD) Wide(BL)

Root canals:2 root canals one B & one L

Oval or kidney

Cervical cross sec.

Dentin island

Buccal horn)longer(

Lingualhorn

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MANDIBULAR FIRST PREMOLARMANDIBULAR FIRST PREMOLAR

ChronologyChronology: :

•Enamel organ appearance: 7 miu.

•Beginning of calcification: 1 ¾ - 2y•Crown completed: 5 – 6y•Eruption: 10 – 12y


Mandibular First PremolarMandibular First Premolar

BuccalBuccal LingualLingual MesialMesial

OcclusalOcclusal

DistalDistal

No. of rootsNo. of rootsOne rootOne root

Geometric Outline of the CrownGeometric Outline of the Crown

Facial and lingual aspects have Facial and lingual aspects have trapezoid out line.trapezoid out line.


cervically.

Contact areas:

•Mesially and Distally: are nearly at the same level, just occlusal to the middle of the crown. Cervical line:

•convex root wise.

M

Bucc. cusp pointed and long

Buccal AspectBuccal Aspect Outlines:

•Mesial and distal outlines: are nearly concave •Mesial(shorter) and distal cusp slopes: are also slightly concave

D

Surface anatomy of the crownSurface anatomy of the crownElevations:

Depressions:

•The middle lobe is convex buccally forming prominent BUCCAL ridge.

Buccal AspectBuccal Aspect•The surface is convex with maximum convexity at C 1/3 representing cervical ridge

Shallow depressions are present mesial and distal to the buccal ridge.

The surface of the root is convex and smooth.

The M and D outline of the root tapered to a pointed apex that curved distally(similar to canine but slightly shorter).


Outline and Surface AnatomyOutline and Surface Anatomy of the Root of the Root

Outlines:•M and D outlines are convex

Cervical line: is convex rootwise.

Elevations: The lingual surface is convex

with maximum convexity at middle 1/3

•The L cusp is short and small reaching 2/3 of the length of the B. cusp(has a pointed tip).

Depessions: ML developmental groove separating

the MM ridge from the M slope of the L cusp.

Lingual AspectLingual AspectLingual convergence: Ling. s. is narrower than buc. s.

Surface Anatomy :Surface Anatomy :

MD

Lingual AspectLingual Aspect

MD

•Much of the occlusal and proximal surfaces can be seen from this aspect.

•The root is much narrower than on the buccal surface. It tapers from the cervix to a pointed apex.

Proximal aspects haveProximal aspects have rhomboid shaperhomboid shape Mesial Distal

With narrow

occlusal table

Prominent lingual inclination (much more than any other premolar)

Proximal AspectsProximal Aspects

Lingual outline is less convex with maximum convexity at the center of the crown length.

Cervical line convex occl. and less curved distally

Outlines of proximal aspectsOutlines of proximal aspects

Buccal outline is convex with maximum convexity at the junction of mid. and cerv. 1/3 )cervical ridge(.



Occlusal margin:

The two cusps are not on the same level

The lingual cusp is shorter by 1/3 length of crown

The B cusp tip centered over the root. This is due to the prominent lingual inclination.

The L cusp tip in line with lingual border of the root.



DMR is longer, straight and at right angle to the axis of the tooth.

(The only post. tooth in which this is true).

MMR inclined sharply from B to L surface // to ridge of B cusp



DMR is occlusal than MMR

MMR is cervical than DMR

M & D surfaces are smooth & convex except for the ML groove.

Mesio-ling. dev.gr.Mesio-ling. dev.gr. Passes over the MM ridge(extension of M groove on the occl. surf.

Contact areas:

Proximal surface anatomyProximal surface anatomy

nearly at same level

Contact area is broader, more lingually situated than the mesial one.



Outline of the RootOutline of the Root

B & L outlines are nearly straight cervically then taper apically to a pointed apex.

The surface is more convex with a shallow dev. depres. centered on the root

The surface is smooth & flat with a deep dev. groove in the mid.& apical 1/3



Occasionally the apical 1/3may be divided into a B. & L.roots by a deep dev. groove

It is diamond-shaped.

Lingual convergence is sharp.

Mesial outline is slightly curved.

Distal outline is more convex.


The B cusp is much larger than the L cusp.

M D

Surface anatomy of occlusal aspect:Surface anatomy of occlusal aspect:

Elevations:

B triangular ridge(long).

L triangular ridge(short).

M & D marginal ridges(well marked).

Transverse ridge (formed by union of 2 triang. ridges).

Depressions:

Central dev. groove crossing the transv. ridge.

M(oval) and D(circular) fossae.

Mesio-lingual develop. groove – extension of M groove on the occ. surface.

Each fossa has a dev. pit (called snake eyes)

M D

..

PULP CAVITYPULP CAVITY

Buccal p. horn: morepronounced than thelingual.

Cross sec. at the cervix:rounded or oval

BLMD

Usually have a single RC

Resemble that ofThe lower canine

MANDIBULARMANDIBULAR FIRST PREMOLARFIRST PREMOLAR

Mandibular Second PremolarMandibular Second Premolar

MANDIBULAR SECOND PREMOLARMANDIBULAR SECOND PREMOLAR

ChronologyChronology: :

•Enamel organ appearance: 8 miu.

•Beginning of calcification: 2 ¼ - 2 ½ y•Crown completed: 6 – 7y•Eruption: 11 – 12y


Mandibular Second PremolarMandibular Second Premolar: : Two Cusp TypeTwo Cusp Type


occlusalocclusal

DistalDistal

No. of rootsNo. of rootsOne rootOne root


occlusalocclusal

DistalDistal

Mandibular Second PremolarMandibular Second Premolar: : Three Cusp TypeThree Cusp Type

Occurs most oftenOccurs most often

the 2 types (2&3) differ mainly the 2 types (2&3) differ mainly from the OCCLUSAL ASPECT. from the OCCLUSAL ASPECT. The outlines & general The outlines & general appearance from all othe aspects appearance from all othe aspects are SIMILAR.are SIMILAR.

Geometric outline of the crownGeometric outline of the crownFacial and lingual aspects have Facial and lingual aspects have trapezoid shapetrapezoid shape But wider But wider cervicallycervicallythan 4.than 4.

Comparison BetweenComparison Between Mandibular First and Second PremolarsMandibular First and Second Premolars

Facial Outlines and surface anatomyFacial Outlines and surface anatomy

Crown is smaller & B cusp is longer & pointedProminent B ridge Less prominent B ridge

Crown is larger & B cusp is shorter and less pointed

Root: Shorter, narrower with pointed apex

Root: longer, broader, with blunt apex

Mandibular First Premolar Mandibular Second Premolar

Lingual outline and surface anatomyLingual outline and surface anatomy

The lingual surface is convex with maximum convexity in middle 1/3(center of crown)

The L cusp is short and small reaching 2/3 the crown length and has a pointed tip.

ML developmental groove at the ML line angle.

Two cusp type

L cusp is shorter and smaller than B cusp but larger than of 4

The surface is convex with maximum convexity in Occ.1/3.No MLDG


Ling. s. not sonarrow as in 1st

premolar

MD D M

Three cusp type:Three cusp type:

ML cusp is longer and larger than DL cusp. They both shorter than B cusp and less pointed.

DM

The surface convex with maximum convexity at occ.1/3.

The L developmental groove between the 2 ling. cusps

No ling. convergency.

Proximal outlines

Rhomboid in shape with narrow occlusal table.

Prominent lingual inclination

Rhomboid in shape with narrow occlusal table.

Lingual inclination less prominent


The crown is wider BLThe crown is narrower BL

Maximum convexity at M1/3 Maximum convexity at O 1/3

B cusp tip on line buccal to the root axis.

The mesial and distal marginal ridges are straight

L cusp is shorter and smaller than B cusp but larger than that of 4

The B cusp centered over the root.

The L cusp is short and small reaching 2/3 the crown length

The mesial MR is oblique while distally is straight


The root is wider BL

Three Cusp Three Cusp Type of Type of

Mandibular Mandibular Second Second Premolar Premolar

ML cusp is shorter than the B cusp & longer and larger than DL cusp.

DL cusp is shorter and smaller than ML cusp. Both are seen from this aspect.

Both lingual cusps are shorter than the buccal cusp and less pointed



Develop.depression

Cerv. line: slightly curved. Cerv. line: nearly straight.


Two cusp type

Diamond-shaped.

Lingual convergence is

sharp.

The outline is round

Slight lingual convergence Three cusp type

The outline is square


U- shaped H - shaped

M D

The 3 cusps are well developed

M D

Surface Anatomy of Occlusal Aspect:

Elevations:

B & L triang. ridges form a transv. ridge.

M & D marginal ridges

Lower 5

Two cusp type

Lower 4

Depressions:

Shallow central devel. groove

M(oval) and D(round) fossae.

Mesiolingual devel. gr.

Central devel. groove extending MD across the occ. surface, over the transv. ridge.

M and D fossae: Circular.

The D fossa is larger than

the M one

Lower 5

Two cusp typeLower 4

. .

M D M D

Elevations & Depressions

Each cusp has triang. ridge that converge toward a central fossa, which has cent. pit. M & D marginal ridges are well marked.

No central devel. gr. or transv. ridge No central devel. gr. or transv. ridge

Three cusp type Lower 5

Three devel. gr.(M,D, & L) radiatefrom the cent. Pit : Y-shaped.

The D triang. fossa is smaller than the M one.

M D

MANDIBULARMANDIBULARSECOND PREMOLARSECOND PREMOLAR

3 cusp type

2 cusp type

PULP CAVITYPULP CAVITYMD BL

Cross sec. at the cerv. lineround or oval

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3 premolars