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8/11/2019 Root Canal Anatomy and Access Openings of Upper Molars
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Slide 1
Slide 2
Root canal anatomy
and access openings
of upper molars
8/11/2019 Root Canal Anatomy and Access Openings of Upper Molars
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Slide 3
Classical anatomy:
Upper molars usual ly have
three roots:
Palatal,
Mesio-buccal &
Disto-buccal
Slide 4
•The palatal root is the longest and
round in cross-section.
•The distobuccal root is a little
shorter, but also rounded in cross-
section.
•The mesiobuccal root is more or
less as long as the distobuccal one,
but flatter mesiodistally, meaning it isoval in cross section, wide bucco-
lingual and narrow mesio-distal.
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Slide 5
Maxil lary First Molar
EXTERNAL ROOT MORPHOLOGY:
•The maxillary first molar normally
has three roots.
Slide 6
•The mesiobuccal root is broad
buccolingually and has prominent
depressions or flutings on its
mesial and distal surfaces.
•The internal canal morphology is
highly variable, but the majority of
the mesiobuccal roots contain twocanals.
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Slide 7
•The distobuccal root is generally
rounded or ovoid in cross section
and usually contains a single canal.
•The palatal root is broader mesio-
distally than bucco-lingually and
ovoid in shape but normally contains
only a single canal.
•Although the palatal root generally
appears straight on radiographs,
there is usually a buccal curvature in
the apical third.
Slide 8
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Slide 9
•The overall average length of the
maxillary first molar is 20.5 mm
with an average crown length 0f
7.5 mm and an average root
length of 13 mm.
Slide 10
ROOT NUMBER AND FORM:
•The maxillary first molar root
anatomy is predominantly a three-
rooted form.
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Slide 11
•The two rooted form is rarely
reported and may be due to:
- the fusion of the disto-buccal
root to the palatal root,or
- the fusion of the disto-buccal
root to the mesio-buccal root.
Slide 12
•The single root or the conical
form of root anatomy in the first
maxillary molar is very rarely
reported.
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Slide 13
CANAL SYSTEM
The internal root canal system
morphology reflects the external
root anatomy.
Slide 14
•The mesiobuccal root of the
maxillary first molar might contain
2 canals (greatest percentage) .
one of them is the main mesio-
buccal canal ( situated buccaly ),
the 2nd is MB2 ( or mesio-lingual)
is positioned palatally to the mainmesio-buccal canal.
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Slide 15
•The incidence of two canals in
the mesiobuccal root is about
57.1% and recent reports are
much more percentage.
•The presence of only one MB
canal is 42.9% or less in all
reported studies.
Slide 16
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Slide 17
•Less variation was found in the
distobuccal and palatal roots.
They usually have only one canal.
•The distobuccal root had only
one canal in 98.3% of teeth
studied, while
•the palatal root had only onecanal in over 99% of the teeth
studied.
Slide 18
MB root canals:
•The two-canal system of the
mesiobuccal root of the maxillary
first molar has a single apical
foramen in (66.0%)
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Slide 19
•The 2 MB canals might beseparate till the apex (34%)
•Rare cases with three canals inthe mesiobuccal root have beendescribed.
Slide 20
•The mesiobuccal root is often
curved distally.
•The degree of curvature varies
from case to case.
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Slide 21
•MB2 is the problematic: Of all thecanals in the maxillary first molar,the MB2 can be the most difficult tofind and negotiate in a clinicalsituation.
•Clinicians must be convinced thatMB2 does exist in the mesiobuccalroot of upper molars in 100% of
cases and therefore these teethmust be considered having 4 root
canals.
Slide 22
•The orifice of the“MB2” – moreappropriately named“ mesiopalatal canal” – is located on thegroove that joins thepalatal andmesiobuccal canals ata variable distance fromthe latter.
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Slide 23
•Sometimes, however, the probe
cannot enter, because it
encounters the mesial wall of the
pulp chamber where it forms a
very acute angle with the floor
that hampers the visual and
tactile detection of the canalopening.
Slide 24
•The mesial wall of
the pulp chamber has
a dentinal shelf, which
frequently hides the
underlying MB2
orifice.
•Because of this
angle, MB2 can bevery difficult to
negotiate.
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Slide 25
•In the first 1-3 mm the root canal
is sharply angled in a mesial
direction, and
•this is the reason why sometimes
the tip of the file doesn’t progress
apically more than a few
millimeters and stops against themesial wall.
Slide 26
•This can be done easily, safelyand efficiently with ultrasonics andthe specific tips, like CPR andProUltra
• Use multiple obliquely angledradiographs (disto-mesialinclination in particular) bothpreoperatively andintraoperatively: the broader theroot, the greater the likelihood of a second canal system.
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Slide 27
•The two canals do not always
have separate foramina; more
often, they join together in a
single foramen.
•Failure to detect and treat the
second MB2 canal system willresult in a decreased long-term
prognosis.
Slide 28
A transverse section at the level
of the cervical zone of the upper
first molar reveals that the pulp
chamber floor takes the form of a
quadrilateral with four unequal
sides.
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Slide 29
Slide 30
•The MB canal is under the MBcusp tip
•The palatal canal is always under the MP cusp tip
•The DB canal has no relation toits cusp, as seen in the next
picture.
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Slide 31
Slide 32
Access preparation
•Preparation of the access cavity
begins with a round, diamond bur
mounted on a high speed
handpiece and applied at the
level of the central fossa.
•It is inclined toward the pulp horn
that radiographically seems
widest, generally the palatal one.
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Slide 33
Slide 34
•With the low-speed,
long-shafted round
bur, the dentin
undercuts are
removed, proceeding
internally to
externally.
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Slide 35
•Finally, the self-
guiding diamond bur
on high speed is
used for the finishing
and flaring.
Slide 36
Maxillary Second Molar
EXTERNAL ROOT MORPHOLOGY
•The maxillary second molar normally
has three roots.
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Slide 37
•The relative shape of each of theroots is similar to the maxillary firstmolar, but:
-the roots tend to be closer together and
- there is a higher tendency towardfusion of two or three roots.
- There is also usually more of adistal inclination to the root or roots
of this tooth compared to themaxillary first molar.
- the crown is smaller in size
Slide 38
•The overall average length of the
maxillary second molar is 19 mm
with an average crown length of 7
mm and an average root length of
12 mm.
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Slide 39
ROOT NUMBER AND FORM
•The majority of maxillary second
molars (88,6%) in the anatomical
studies were found to be three
rooted. Lower incidence than first
molar.
•The closer proximity of the roots
results in a higher incidence of root
fusion (25.8%), and C-shaped
canals (4.9%) when compared to the
maxillary first molar.
Slide 40
CANAL SYSTEM
•There was a single apical
foramen found in the mesiobuccal
root over 68% of the time.
•The distobuccal and palatal roots
exhibited a single canal over 99%
•Sometimes the three roots fuse
in one root.
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Slide 41
•It may have only two canals, one
buccal and one palatal in a single
root, or
•two canals in two separate
roots;
Slide 42
•it may have a single, wide canal
that extends almost directly from
the floor to the apex.
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Slide 43
•In comparison with the upper first
molar, the pulp chamber floor of
the upper second molar is flatter
mesiodistally, and the
distobuccal canal is found
quite palatally displaced.
Slide 44
UPPER THIRD MOLAR
•Loss of the first and second
molars is often the reason for
considering the third molar a
strategic abutment.
•In some cases, the third molar
has only one canal.
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Slide 45
•In other cases, it has two, but in
most there are three and,
sometimes, four.
•The access cavity should be
made according to the same rules
prescribed for the other molars.
Slide 46
Maxillary Molar Teeth
ERRORS in Cavity
Preparation
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Slide 47
A. UNDEREXTENDED
preparation.
•Pulp horns are exposed
but the entire roof of the
pulp chamber was not
removed.“White” color
dentin of the roof is a
clue to underextension.Instrument control is lost.
Slide 48
B. OVEREXTENDED
preparation
undermining enamel
walls.
•The crown is badly
gouged owing to
failure to observe pulp
recession in the
radiograph.
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Slide 49
C. PERFORATION intofurca using a surgical-length bur and failing torealize that the narrowpulp chamber had beenpassed.
•Operator error in failureto compare the length of the bur to the depth of
the pulp canal floor.•Length should bemarked on the bur shankwith Dycal.
Slide 50
D. LEDGE FORMATION
caused by using a large
straight instrument in a
curved canal.
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Slide 51
E. PERFORATION of
a palatal root which
is curved buccally at
its apex commonly
caused by assuming
the canal to be
straight and failing to
explore and enlargethe canal with a fine
curved instrument.
Slide 52
Strategies to search for MB2
a) First of all, strongly believe
that MB2 is always present!
b) Use of magnification, starting
from loops and magnification
glasses (2,5x – 4x) up to the
operating microscope.
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Slide 53
c) Start looking for MB2 only after
MB1 is completely cleaned and
shaped and, in theory, is ready for
obturation.
d) Use a piezo-electric ultrasonic
unit along with specially designed
tips (CPR, ProUltra) to remove
the dentinal shelf hiding the
underlying orifice.
Slide 54
e) Use of 1% solution of MethyleneBlue dye, to road map the anatomyby penetrating into orifices.
f)Flood the pulp chamber with awarm 5% solution of sodiumhyplochlorite to conduct the“champagne” or “bubble” test.
The clinician can frequently visualize
bubbles emanating from organictissue, which is being digested in theextra canal, and rising towards theocclusal table.
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Slide 55
g) Irrigate with 17% EDTA to
remove the smear layer, then
•with pure alcohol and then
•air-dry with a Stropko irrigator
fitted with a 27-gauge notched
endodontic irrigating needle.
Slide 56
h) Use multiple obliquely angled
radiographs (disto-mesial
inclination in particular) both
preoperatively and
intraoperatively: the broader the
root, the greater the likelihood of
a second canal system.i)Know the endodontic anatomy.
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