Access opening of permanent Posterior teeth.

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ACCESS
OPENING
ANANTHESH H S

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MAXILLARY FIRST PREMOLAR
Average Tooth Length: The average length of this tooth is 21.5
mm.
Pulp Chamber: The pulp chamber of the maxillary first premolar
is narrow mesiodistally
 It is wide buccopalatally, and the buccal pulp horn is more
prominent than the palatal in young teeth
 two canal orifices, one buccal and the other palatal, and it lies
deep in the coronal third of the root below the cervical line.
Roots and Root Canals: The maxillary first premolar has two
roots in 54.6% of cases.
 21.9% of the double-rooted cases, the roots are separated,
whereas in 32.7%, the roots are partially fused

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MAXILLARY FIRST PREMOLAR
Access Opening
 Using a No. 2 round carbide bur in a high-speed contra-angle, one
penetrates the enamel in the center of the occlusal surface
between the buccal and lingual cusps, and the bur is directed into
the long axis of the tooth
 The operator frequently feels the bur “drop” into the pulp chamber
 remove the roof of the pulp chamber without cutting into the
chamber floor; one should avoid an access opening that is too
shallow and exposes only the pulp horn tips
 To remove the roof of the pulp chamber, one should place the bur
alongside the walls of the chamber and cut occlusally
 A tapered cylinder, self-limiting diamond bur is used to remove the
remaining roof of the pulp chamber

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MAXILLARY SECOND PREMOLAR
Average Tooth Length: The average length of this tooth is 21.6 mm.
Pulp Chamber: The maxillary second premolar, like the maxillary first
premolar, has a narrow chamber mesiodistally
 The roof of the pulp chamber is similar to that of the maxillary first
premolar
Root and Root Canals: Maxillary second premolars have only a single
root in 90.3% of patients. Only 2% have two well-developed roots,
whereas 7.7% have two roots that are partially fused
 The majority of canals are curved
 If one root canal is present, the root canal Orifices will be indistinct,
but if two canals are present, two distinct orifices will be visible.
 The root(s) of the maxillary second premolar are situated below and
therefore closer to the maxillary sinus than the maxillary canine

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MAXILLARY SECOND PREMOLAR
Access Opening: The access opening for the maxillary
second premolar is basically the same as that for the
maxillary first premolar. It is varied only as dictated by
the anatomic structure of the pulp chamber
Anomalies: The maxillary second premolar in rare
cases has three root canals

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MAXILLARY FIRST MOLAR
Average Tooth Length: The average length of this tooth is 21.3 mm.
Pulp Chamber
 The pulp chamber of the maxillary first molar is the largest in the dental
arch, with four pulp horns: mesiobuccal, distobuccal, mesiopalatal, and
distopalatal.
 pulpal roof a rhomboidal shape in cross-section.
 The four walls forming the roof converge toward the floor where the
lingual wall almost disappears; the floor of the pulp chamber thus has a
triangular form in cross-section
 The orifices of the root canals are located in the three angles of the
floor
 The palatal orifice is the largest, round or oval in shape, and easily
accessible for exploration.

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MAXILLARY FIRST MOLAR
 The mesiobuccal orifice is under the mesiobuccal cusp
 It is long buccopalatally, and may have a depression at the palatal end in which the
orifice of a fourth canal may be present.
 The distobuccal orifice is located slightly distal and palatal to the mesiobuccal orifice
 Roots and Root Canals: The maxillary first molar has three roots with, usually,
three canals situated mesiobuccally, distobuccally, and palatally.
 The mesiobuccal (MB) canal is not always patent along its entire length and is
divided to form a second root canal known as the Mb-2 canal
 The distobuccal root is small and is more or less round in shape. The distobuccal
root usually has a single root canal, which is a narrow and tapering canal.
 The palatal root has the largest diameter and is the longest root of the maxillary first
molar. It is straight in only 40% of cases and may curve buccally (55%).

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MAXILLARY FIRST MOLAR
Access Opening
 The enamel is penetrated with a high-speed bur by positioning the
instrument in the central fossa and angling it towards the palatal
root
 After penetration into the enamel, one uses the bur to penetrate
the dentin; the bur is angled toward the palatal root until the pulp
chamber is reached.
 A “drop” of the bur into the pulp chamber may be felt if the
chamber is large
 Cutting occlusally from within the pulp chamber, one removes the
bulk of the roof of the pulp chamber
 A tapered-cylinder, self-limiting diamond bur is used to remove the
remaining roof of the pulp chamber
 The walls of the access cavity are refined with this diamond to be
divergent towards the occlusal surface

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MAXILLARY FIRST MOLAR
 The access opening is usually triangular, with round corners extending toward,
but not including, the mesiobuccal cusp tip, marginal ridge, and oblique ridge.
 The anatomic dark lines in the pulpal floor (dentinal map) should be examined
and followed with an endodontic explorer to identify the orifices, as described
previously
 ŠThe triangular access preparation in a maxillary molar is modified into a
rhomboidal shape whenever the MB-2 canal is suspected or traced
ŠAccording to Nallapati, the following are the possible locations of the MB-2 canal in
the maxillary first molar:
 Present on the developmental line that connects MB-1 and palatal canal
 Present mesial to the developmental line that connects MB-1 and palatal canal
 Appears as a groove on the palatal wall of the MB-1 canal
 Splits off the MB-1 canal in the middle third of the canal
 Splits off the MB-1 canal in apical third of theCanal
 Comes off the buccal wall of the palatal canal

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MAXILLARY SECOND MOLAR
Average Tooth Length: The average length of this tooth is 21.7 mm.
Pulp Chamber: The pulp chamber of the maxillary second molar is similar to that of the maxillary
first molar, except it is narrower mesiodistally
 the roof of the pulp chamber is more rhomboidal in cross-section
 floor of the pulp chamber is an obtuse triangle in cross-section, and the mesiobuccal and
distobuccal canals are closer together and may appear to have a common opening
 Sometimes, all three canal orifices may be almost in a straight line
Roots and Root Canals: The maxillary second molar usually has three roots, which are closely
grouped
 Because of this close grouping, the buccal roots may fuse, and occasionally all three roots fuse
to form a single conical root
Access Opening: The maxillary second molar access opening is basically the same as that for the
maxillary first molar

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MANDIBULAR FIRST PREMOLAR
Average Tooth Length: This tooth averages 21.9 mm.
Pulp Chamber: The mandibular first premolar is the transitional tooth between anterior and posterior
teeth
 The mesiodistal width of the pulp chamber is narrow. Buccolingually, the pulp chamber is wide,
with a prominent buccal pulp horn that extends under a well-developed buccal cusp
 The prominent buccal cusp and the smaller lingual cusp give the crown of the mandibular first
premolar about a 30° lingual tilt
 the chamber is ovoid, with the greater diameter present in a buccolingual direction
Roots and Root Canals: The mandibular first premolar usually has a short, conical root

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MANDIBULAR FIRST PREMOLAR
 The root is usually straight (48%), but some roots curve
distally (35%).
 divide in the apical third into two or three roots.
 One canal and one foramen are present in 70% of cases.
 One canal bifurcates into two canals and exits in two foramina in 24% of cases.
 Two canals exit in two foramina in 1.5% of cases.
 One canal bifurcates into two canals, uniting into one canal in the apical third and
then exiting in one foramen in 4% of cases.
 Three canals exit in three foramina in 0.5% ofcases

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MANDIBULAR FIRST PREMOLAR
Access Opening
 To compensate for the tilt and prevent perforations, the enamel
is penetrated at the upper third of the lingual incline
 The procedure is the same as for the maxillary premolars
 The resulting access cavity is ovoid
 This ovoid access preparation permits exploration for
bifurcations or trifurcations in the middle and apical thirds

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MANDIBULAR SECOND PREMOLAR
Average Tooth Length: The length of this tooth averages 22.3 mm.
Pulp Chamber: The pulp chamber of the mandibular second premolar is similar to
that of the mandibular first premolar, except that the lingual horn is more prominent
under a well-developed lingual cusp.
Roots and Root Canals: The mandibular second premolar usually has a single root,
but on rare occasions two to three roots are present
 Usually, one canal exits in one apical foramen (97.5%), but in some roots (2.5%), a
single canal may bifurcate exiting in two foramina
Access Opening: The access opening for the mandibular second premolar is
basically the same as for the mandibular first premolar, except that the enamel
penetration is initiated in the central fossa

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MANDIBULAR FIRST MOLAR
Average Tooth Length: The average length of this tooth is 21.9 mm.
Pulp Chamber: The roof of the pulp chamber of the mandibular first molar is often rectangular in
shape
 The mesial wall is straight, the distal wall round, and the buccal and lingual walls converge to
meet the mesial and distal walls and form a rhomboidal floor
 The roof of the pulp chamber is located in the cervical third of the crown just above the cervix of
the tooth, and the floor is located in the cervical third of the root.
 The mesiobuccal orifice is under the mesiobuccal cusp
 To penetrate this orifice, insert a long-shank explorer in a mesiobucco-apical inclination into the
point angle created at the juncture of the mesial wall, buccal wall and subpulpal floor of the pulp
chamber
 The mesiolingual orifice is located in a depression formed by the mesial and lingual walls
 This orifice can be explored from a distobuccal direction
 The distal orifice, which is oval in shape, with the widest diameter present in a buccolingual
direction, can be explored by starting from a mesial direction

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MANDIBULAR FIRST MOLAR
Roots and Root Canals: Usually, two well-differentiated roots
are present in the mandibular first molar, one mesial and one
distal
 A third root is found in some cases, either distally or
mesially (5.3%), and is often referred to as the radix
entomolaris
 The mesial root has
 Two canals that exit in two foramina in 41% of cases
 Two canals that coalesce to exit in one foramen in 28%
 Two canals that coalesce to form one canal and bifurcate and
exit in two foramina in 13%
 One canal that exits in one foramen in 12%
 One canal that bifurcates and exits in two foramina in 8%

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MANDIBULAR FIRST MOLAR
 The distal root has:
 One canal exiting in one foramen in 70% of cases
 Two canals coalescing and exiting in one foramen in 15%
 One canal bifurcating and exiting in two foramina in 8%
 Two canals exiting in two foramina in 5%
 Two canals coalescing to form one canal and later bifurcating to exit in two
foramina in 2% of cases
Access Opening
 The enamel and dentin are penetrated in the central fossa with the bur
angled towards the distal root, where the pulp chamber is largest
 The preparation follows the procedures outlined for the maxillary molar. The
access opening is usually trapezoidal with round corners
 The access opening extends toward the mesiobuccal cusp to uncover the
mesiobuccal canal, lingually slightly beyond the central groove and distally
slightly beyond the buccal groove.

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MANDIBULAR SECOND MOLAR
 Average Tooth Length: This tooth averages 21.4 mm in length.
 Pulp Chamber: The pulp chamber of the mandibular second molar is smaller
than that of the mandibular first molar, and the root canal orifices are smaller
and closer together.
 Roots and Root Canals: The majority of the mandibular second molars have
two roots (71%), but teeth with one root (27%) and teeth with three roots (2%)
are also seen.
 Access Opening: The access opening for the mandibular second molar is
created as for the mandibular first molar, with the variations that a smaller tooth
demands

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REFERENCES
 Grossman’s ENDODONTIC PRACTICE 13TH EDITION
 Ingle’s ENDODONTICS 7

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