Middle Mesial

8/11/2019 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

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