3 premolars
TRANSCRIPT
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.
Buccal AspectBuccal 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 :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).
Mesial Mesial AspectAspect
Distal Distal AspectAspect
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
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
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
The smallest of the uneven sides
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
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.
Maxillary First Premolar Maxillary Second Premolar
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
Maxillary First Premolar Maxillary Second Premolar
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
Maxillary First Premolar Maxillary Second Premolar
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.
Maxillary First Premolar Maxillary Second Premolar
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
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
MANDIBULAR FIRST PREMOLARMANDIBULAR FIRST PREMOLAR
ChronologyChronology: :
•Enamel organ appearance: 7 miu.
•Beginning of calcification: 1 ¾ - 2y•Crown completed: 5 – 6y•Eruption: 10 – 12y
•Root completed: 12 – 13y
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.
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 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).
Buccal AspectBuccal Aspect
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(.
Mesial Mesial AspectAspect
Distal Distal AspectAspect
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 Mesial AspectAspect
Distal Distal AspectAspect
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 Mesial AspectAspect
Distal Distal AspectAspect
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.
Mesial Mesial AspectAspect
Distal Distal AspectAspect
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
Mesial Mesial AspectAspect
Distal Distal AspectAspect
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 AspectOcclusal Aspect
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
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
•Root completed: 13 – 15y
Mandibular Second PremolarMandibular Second Premolar: : Two Cusp TypeTwo Cusp Type
BuccalBuccal LingualLingual MesialMesial
occlusalocclusal
DistalDistal
No. of rootsNo. of rootsOne rootOne root
BuccalBuccal LingualLingual MesialMesial
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
Mandibular First Premolar Mandibular Second Premolar
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
Mandibular First Premolar Mandibular Second Premolar
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
Mandibular First Premolar Mandibular Second Premolar
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
Mesial Mesial AspectAspect
Distal Distal AspectAspect
Develop.depression
Cerv. line: slightly curved. Cerv. line: nearly straight.
Occlusal AspectOcclusal Aspect
Two cusp type
Diamond-shaped.
Lingual convergence is
sharp.
The outline is round
Slight lingual convergence Three cusp type
The outline is square
Mandibular First Premolar Mandibular Second Premolar
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