middle mesial
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Mandibular first molarmiddle mesial canal
Carmen Cohn
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With the advent of magnification, the astute
clinician must be aware of literature reports that
state that the mandibular first molar has a 1-15 %
chance of a fifth canal.
Middle mesial canal of the mandibular first molar: a case report and
Literature review. Baugh. JOE 2004
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Investigator Year N teeth Method Three
canals (%)
Skidmore &
Bjorndol
1971 45 Vitro 0
Pineda & Kuttler 1972 300 Vitro 0
Vertucci 1984 100 Vitro 1
Pomeranz 1981 100 Vivo 12
MartinezBerna
& Badanelli
1983 1418 Vivo 1,5
Fabra - Campos 1985 145 Vivo 2,1
Fabra - Campos 1989 760 Vivo 2,6
Goel 1991 60 Vivo 15
Middle mesial canal of the mandibular first molar: a case report and
Literature review. Baugh. JOE 2004
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Fabra Campos (1989):
760 first mandibular molars
-20 (2.6 %) had three canals in the mesial root.
-13 (65 %) intermediate canal joined the
mesiobuccal canal in the apical third.
-6 (30 %) it joined the mesiolingual canal in the
same area.
-1 case - the intermediate or third canal retained
its individual nature and ended in anindependent foramen.
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Dr. Castellucci
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Dr. Castellucci
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Dr. J Avillon
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Dr. M. Dreyer
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Dr. M. Dreyer
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Dr. D. Rakich
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Many reports deal with three orifices in the mesial
root, but very few describe three independent
canals, indicating a rare anatomical configuration.
Three independent canals in the mesial root of a mandibular first
molar. Ricucci. Endod Dent Traumatol. 1997
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Apical foramina: in mesial root two apical
foramina were observed in 60 percent of
specimens, three in 6.7 percent and four in 3.3
percent (n=60 teeth). (Goel 1991 Study of root canalsconfiguration in mandibular first permanent molar).
The morphological pattern of separate apical
terminations of the three mesial root canals, is a
very rare one (Holtzmann 1997 Root canal treatment of a mandibularfirst molar with three mesial root canals).
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Dr. Dan Shalkey
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Dr. D. Rakich
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Dr C. Barrington
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This is not an extra canal but rather the sequelae ofinstrumenting the isthmus between the mesiobuccal
and mesiolingual canals.
Mandibular first molars with three mesial canals.
Mortman. Gen Dent. 2003
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Isthmus?
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Isthmus - a narrow, ribbon-shaped
communication between two root canals, thatcontains pulp tissue (Weller 1995)
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The incidence of canal isthmuses in mesial roots of
mandibular first molars ranges from 54 to 89%(Hsu & Kim 1997).
In studies evaluating serial sections at differentlevels from the apex, the highest incidence of canal
isthmuses in mesial roots of mandibular first
molars was found at 3-5 mmfrom the apex (Weller
1995, Hsu & Kim 1997, Teixeira 2003)
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Type I Type II Type III Type IV Type V
Frequency and type of canal isthmuses in first molars detected by
endoscopic inspection during periradicular surgery.
Von Arx Int Endod J. 2005
Mandibular first molar
Mesial root (n=52)
-One canal (no isthmus) 3 (6%)
-Two canals (no isthmus) 6 (11%)
-Two canals (with isthmus) 43 (83%)
Mesial roots of mandibular firstmolars most often presented
with type IV and V canal
isthmuses.
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Courtesy Dr. B. Schein
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Von Arx Int Endod J. 2005
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So, what do we treat,
canal or isthmus
or BOTH?
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Clinical case
Courtesy Dr. D. Shalkey
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Failure 11 months p.o.
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There was no indication of a third mesial
canal or an isthmus between the MB and
ML canals in the chamber.
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???
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Huge lateral canal coming off
the ML canal.
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Coronal
Apical
Isthmus
Middle mesial (no isthmus!)
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With the high isthmus incidence in mind, weshould search for any permeable space in the
mesial root anatomy and clean, shape and
obturate it as thorough as possible.
Never forget that even a rare occurrence, the
presence of additional POE in the mesial root of
mandibular teeth is possible and when not sealed,
could lead to failures of the RCT.
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It is very difficult to completely clean an isthmus, especially
at 3-5 mm from the apex.
If a canal performed in an isthmus is helping its cleaning
and shaping , we can do as many canals as possible(without damaging the root structure) in order to divide the
isthmus and facilitate the access of disinfectants to spaces
that files cant reach.
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Conclusions:
The difficulties in cleaning and shaping the
canal system of the mesial root during
conventional root canal treatment may lead to
eventual failure necessitating retreatment.
The relatively high incidence of canal isthmuses
in mesial roots of mandibular molars indicates
the necessity to carefully explore the rootanatomy searching for every additional way
through this intricate system, and its possible
portal of exit (POE).
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Thank you