بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL.
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Transcript of 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
Outline and Surface Anatomy 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 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
• Eruption: 10 – 12y
• Root completed: 13 – 15y
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
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.
Maxillary First Premolar Maxillary Second Premolar
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
Maxillary First Premolar Maxillary Second Premolar
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
Maxillary First Premolar Maxillary Second Premolar
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.
Maxillary First Premolar Maxillary Second Premolar
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.
Maxillary First Premolar Maxillary Second Premolar
Occlusal 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 Premolar
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
• Eruption: 10 – 12y
• Root completed: 12 – 13y
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
Outline and Surface Anatomy 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 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
• Eruption: 11 – 12y
• Root completed: 13 – 15y
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
Mandibular First PremolarMandibular Second Premolar
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
Mandibular First PremolarMandibular 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 PremolarMandibular Second Premolar
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
Mandibular First PremolarMandibular 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 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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