access cavity preparation 1
TRANSCRIPT
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Mandibular first premolar
Overall tooth length- 22.5mm Average crown length- 8.5mm
Average root length- 14mm
External root morphology:-
Single rooted
Buccolingually Wider
Mesiodistally Narrower
Developmental depressions or grooves- mesial anddistal surface of root
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Root number and canal systems:-
Single rooted with single canal
High failure rate of RCT 11.4% because of the numerous
variations in root canal morphology
Buccal canal has straight line access
Lingual canalbranches are at sharp angle
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Variations and Anaomalies
Number of roots
Number of canal and apices
No. ofstudies
No. ofteeth
One root Two root Threeroot
Four root
8 4462 97.9% 1.8% 0.2%
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3 rooted mandibular 1st premolar
mandibular 1st premolarI root and 3 canals
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Mandibular left premolar with 3 canal and 2 roots
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Anatomy and morphology
Sharp buccal cusp
Small lingual cusp- resembles cingulum
Occlusal view
Outline: diamond shaped
Crown is lingually placed
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Mandibular second premolar
Overall length 22.5mm
Average crown length - 8mm
Average root length - 14.5mm
External root morphology:-
Single rooted
Mesial surfaceflat or convex
Distal surface- longitudinal developmental depression
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Number of roots and canal systems:- Single rooted with single canal
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Variations and anomalies
Number of roots
Number of canal and apices
Number ofstudies
Number ofteeth
One root Two roots Three roots
8 4019 99.6% 0.3% 0.1%
Number
of studies
Number
of teeth
One canal Two or
morecanal
One canal
at apex
Two or
morecanal atapex
10 2983 91.1% 8.9%
7 1970 91.6% 8.4%
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Premolar exhibiting dens evaginatus
One root two root canals
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Mandibular right 2nd premolar with 2canals and one apical foramen
2nd premolar with hypertaurodontmesial and distal root
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Mandibular left 2nd premolar with 2 roots and 3 canals
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Anatomy and morphology:-
Has two forms from occlusal aspect:
3 cusp type (most common)
2 cusp type
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Access preparation of mandibular
premolar teeth1) Entrance through occlusal surface
Initial preparation
center of center groove and the bur is directed parallelto the long axis of the tooth
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2) No. 4 round bur is used to open into the pulp
chamber
In removing the bur, the occlusal opening is widened
buccolingually to twice the width of the bur
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3) Endodontic explorer is used to locate the central
canal
Tension of the explorer against the walls of
preparation will indicate the amount and direction of
extension
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4) Working from inside the pulp chamber to outside,
no.2 or 4 round bur is used to extend the cavity buccolingually by removing the roof
of the pulp chamber
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5) 702 U fissure bur is used for buccolingual extension
and finish of cavity walls
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6) Final ovoid preparation is a tapered funnel from the
occlusal to the canal, providing unobstructed access
to the canal
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7) Occlusal view of final access opening
Anatomy of pulp chamber ---ovoid buccolingually
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Mandibular 1st molar
Overall length -21.5mm Average crown length -7.5mm
Average root length -14mm
External root morphology
Two rooted teeth
Mesial and distal
Broader buccolingually than mesiodistally
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Number of roots and canal systems
Two roots with three or four canals
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Variations and anomalies
Number of roots
Number of canals and apices
No. ofstudies
No. ofteeth
One root Two roots Threeroots
Fourroots
10 3263 - 96.9% 2.97% -
No. ofcanals
andapices
No. ofstudies
Numberteeth
Onecanal
2 ormore
Onecanal at
apex
Two ormore
canals atapex
Mesial 16 3375 4.2% 95.85
13 1731 46.3% 53.7%
distal 15 3304 68.3% 31.7%
13 1805 82.4% 17.6%
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Anomalies
Mandibular 1st molar with 3 roots (M, D, DL) and four canal systems
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Mandibular right 1st molar exhibiting mesotaurodontism
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Anatomy and morphology:-
Buccal cusp tips are located more to the midline on
occlusal table compared to lingual cusp tips
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Mandibular 2nd molar Overall length-20mm
Average crown length-7mm
Average root length-13mm
External root morphology:- Two rooted
Mesial and distal ( most frequently fused)
Broader buccolingually than mesiodistally
Root convcavities Mesial surfaces of both roots
Distal surface of mesial root
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Variations and anomalies
Number of roots
Number of canals and apices
No. ofstudies
No. ofteeth
Incidence offusedroot
One root(conical)
One root( c-shaped)
Tworoots
Threeroots
9 997 21.8% - - 96.9% 2.97%
6 674 8.3% 8.5%
No. ofcanals
andapices
No. ofstudies
Numberteeth
Onecanal
2 ormore
Onecanal at
apex
Two ormore
canals atapex
Mesial 8 1194 14% 86%
7 778 60.3% 39.7%
distal 8 1194 85.1% 14.9%
7 778 95% 5%
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Number of roots and canal systems
Two roots with three canals
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Fused roots
One root one root canal
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Mandibular left 2nd molar 2 mesial rootand 1 distal root(3 canal systems)
Mandibular right 2nd molar with 2roots and
2 root canals
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Anatomy and morphology:-
Occlusal tablemore symmetrical and rectangular
with four cusps
roots are inclined more distally in relation to occlusal
table
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Access preparation of mandibular
molars1) INITIAL EXTERNAL OUTLINE FORM Staring location is on the central groove way between
mesial and distal boundaries
Bur is directed prependicular to the occlusal table
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2) PENETRATION OF THE PULP CHAMBER
ROOF
No. 4 or 6 round bur is used to open into pulp chamber
Bur should be directed towards the orifices
of the mesiobuccal or distal canal ,where the
greatest space in the chamber exists
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3) An endodontic explorer is used to locate the
orifices of the distal, mesiobuccal and mesiolingual
canals.
Orifices of the canal forms theperimeterof the preparation
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4)Complete roof removal
Goal funnel the corners of the access cavity directly
into the orifices
Round bur hooks under the lip of the pulp horn
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The safety tip diamond or carbide bur is passed
between the orifices along the axial wall to taper the
internal wall
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5) Removal of cervical dentin bulges and coronal
and orifice flaring
Cervial bulges are removed with gates glidden drill
Constricted coronal portion flared with GG drill used insweeping upward motion with lateral pressure away from
furcation
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6) Finally the canals should have a straight line of
access
Leaning the entire preperation towards the mesial
improve ease of access
Walls should be perfectly smooth and
orifices located at exact pulpal-axial angle
of cavity floor
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7) Anatomy of the pulp chamber
trapezoidal
Both mesial and distal walls slope mesially