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 Mandibular First Molar Middle Mesial Canal

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PostSubject: Mandibular First Molar Middle Mesial Canal   Sat Aug 09, 2008 1:47 pm

Mandibular First Molar Middle Mesial Canal

With the advent of magnification, the astute clinician must be aware of
chance of a fifth canal. literature reports that state that the mandibular first molar has a 1-15 % (Middle mesial canal of the mandibular first molar: a case report and Literature review. Baugh. JOE 2004)

Fabra – Campos (1989) in his study
on 760 first mandibular molars found:

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 an independent foramen.

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)

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 canals configuration in mandibular first permanent molar).[/SIZE]

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 mandibular first molar with three mesial root canals).

“This is not an extra canal but rather the sequelae of instrumenting the isthmus between the mesiobuccal and mesiolingual canals.” (Mandibular first molars with three mesial canals.Mortman. Gen Dent. 2003)

!! ?? Isthmus

Isthmus - a narrow, ribbon-shaped communication between two root canals, that contains pulp tissue (Weller 1995)

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 different levels from the apex, the highest incidence of canal isthmuses in mesial roots of mandibular first molars was found at 3-5 mm from the apex (Weller 1995, Hsu & Kim 1997, Teixeira 2003)

??? So, what do we treat, canal or isthmus… or BOTH

Clinical case: Courtesy Dr. D. Shalkey

Failure 11 months p.o.

Huge lateral canal coming off the ML canal.

With the high isthmus incidence in mind, we should 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.

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 can’t reach.


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 root anatomy searching for every additional ‘way’ through this intricate system, and its possible portal of exit (POE).e

[SIZE=14]The Source :
Mandibular First Molar Middle Mesial Canal, Presentation by Carmen Cohn

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