بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

بسم الله الرحمن الرحيم

IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

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:

General Features of Premolars

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

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

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

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

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

General Features of Premolars

MAXILLARY FIRST PREMOLAR

Chronology :• 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 lobes:

• Three buccally • One lingually

DistalMesialPalatal

Occlusal

Buccal

No. of roots

Two roots(60%).

One root(40%).

Geometric Outline of the Crown

The smallest of the uneven sides

cervically.

Facial and lingual aspects have trapezoid out line.

Buccal 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 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 Aspect

.

Outline and Surface Anatomyof 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.

Buccal Aspect

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 :

Lingual 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 Aspect

Outline and Surface Anatomy of the Root

M D

If one root:

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

Proximal Aspects

Mesial aspectDistal aspectProximal aspects have trapezoid out 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 Aspects

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

Mesial aspect

Distal aspec

t

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

aspect

Distal

aspect

Surface Anatomy of Proximal Aspects

Contact areas:

Mesial Aspect

Distal Aspec

t

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).

Mesial

Aspect

Distal Aspect

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


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 Aspect

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 outline

Surface anatomy

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

Occlusal Aspect

MD

Mesial marginal developmental 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 canalslingual canal is

larger & more accessible

PULP CAVITY

oval or kidney shaped Cervical cross

sec.

MAXILLARY SECOND PREMOLAR

MAXILLARY SECOND PREMOLAR

Chronology :• Enamel organ appearance: 8 mIU.• Beginning of calcification: 2-2¾y

• Crown completed: 6 – 7y



Maxillary Second Premolar

Buccal

Lingual

Mesial

Distal

Occlusal

Geometric Shape of the Crown

Facial & Lingual Aspects

The smallest of the uneven

sides cervically.

Trapezoid shape.

Comparison between

Maxillary First and Second Premolars

Buccal 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 Aspects

Prominent B ridge

Less prominent B ridge

Narrow cervical portion.

Wider cervical portion.

Short root. Longer root.


Lingual 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 Aspects

Trapezoid in shape

Smallest of the uneven sides:

occlusaly

4 5 Geometric Shape of the Crown

BL


Mesial 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 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.


Distal Aspects

Distal AspectsMaxillary First Premolar Maxillary Second Premolar

Root trunk is long as the bifurcation is near apical 1/3

Surface 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 Aspect

hexagonal oval(less angular) B & L triangular

ridges.Thin M & D marginal ridges

B & L triangular ridges.Thicker M & D marginal ridges


Occlusal 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 CAVITYof maxillary second premolarMD 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

THANKS

بسم الله الرحمن الرحيم

IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

MANDIBULAR FIRST PREMOLAR

Chronology :

• Enamel organ appearance: 7 miu.• Beginning of calcification: 1 ¾ - 2y• Crown completed: 5 – 6y



Mandibular First Premolar

Buccal

Lingual

Mesial

Occlusal

Distal

No. of rootsOne root

Geometric Outline of the Crown

Facial and lingual aspects have trapezoid out line.

The smallest of the uneven sides

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 Aspect Outlines:

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

D

Surface anatomy of the crown

Elevations:

Depressions:

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

Buccal 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).

Buccal Aspect


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

Surface Anatomy :

MD

Lingual 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 have rhomboid shape Mesial Distal

With narrow

occlusal table

Prominent lingual inclination (much more than any other premolar)

Proximal 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 aspects

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

Mesial

Aspect

Distal Aspect

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.

Mesial

Aspect

Distal Aspect

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

Mesial

Aspect

Distal Aspect

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. Passes over the MM ridge(extension of M groove on the occl. surf.

Contact areas:

Proximal surface anatomy

nearly at same level

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

Mesial

Aspect

Distal Aspect

Outline 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

Mesial

Aspect

Distal Aspect

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.

Occlusal Aspect

The B cusp is much larger than the L cusp.

M D

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 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

MANDIBULAR FIRST PREMOLAR

Mandibular Second Premolar

MANDIBULAR SECOND PREMOLAR

Chronology :

• Enamel organ appearance: 8 miu.• Beginning of calcification: 2 ¼ - 2 ½ y• Crown completed: 6 – 7y



Mandibular Second Premolar :Two Cusp Type

Buccal

Lingual

Mesial

occlusal

Distal

No. of rootsOne root

Buccal

Lingual

Mesial

occlusal

Distal

Mandibular Second Premolar :Three Cusp Type

Occurs most often

THE 2 TYPES DIFFER MAINLY FROM THE OCCLUSAL ASPECT. THE OUTLINES AND GENERAL APPEARANCE FROM ALL OTHER ASPECTS ARE SIMILAR.

Geometric outline of the crown

Facial and lingual aspects have

trapezoid shape But wider cervicallythan 4.

Comparison Between Mandibular First and Second

Premolars

Facial 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 PremolarMandibular Second Premolar

Lingual 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:

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 Type

of Mandibular Second 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

Mesial

Aspect

Distal Aspect

Develop.depression

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

Occlusal Aspect

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 type

Lower 4

. .

M DM D

Elevations & DepressionsEach 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

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

MANDIBULARSECOND PREMOLAR

3 cusp type

2 cusp type

PULP CAVITYMD BL

Cross sec. at the cerv. lineround or oval

www.oralbiology.azhar.edu.eg

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بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

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