Fig. 1

We can divided Maxillary molars in two big families multirooted and monoradicular or fused.

Fig. 2

We can observe in the rx clear differences between multirooted and fused tooth, this will lead us to modify our cavity access ,more mesial in the fused tooth.

Fig. 3

Shape of the pulp chamber, and location of the root canal orifices.

Multirooted tooth morphology:the pulp chamber is widest  in the buccolingual dimension

Fused configuration with two canals: narrow pulp chamber  canals in a straight line.

Fused configuration with 3 canals: Mb-Db canals are close

Fig. 4

Multi-rooted upper second molars with mb2 According to literature mb2 is present in 60-70% of the cases. (6-7-9)

Fig. 5

The mb2 is on a line between mb1 ad palatal canal, it is usually located 2–3 mm from the mesio-buccal canal.  (suggested article)

Fig. 6

Color test  one of the three laws of pulp chamber anatomy that were published in Journal of endodontic by Krasner et al. 2004 is the law of color change. The developmental root fusion lines or root map are narrow lines on the pulpal floor of furcated teeth and provide a visual trail that has a darker color than the chamber floor. This will lead us to other canal orifices.

Fig. 7

According to the literature,(7) Weine’s method was used to classify mesiobuccal root canal morphology in upper second molars. 

Here is a short video showing canal confluence

Fig. 8

monoradicular configuration; one tooth out of ten has 1 or 2 canals, while 24% of multirooted and fused has 3 canals.(7-8)

In this clinical case we can see how knowing the correct bases of anatomy and knowing how to correctly interpret the pre-op x-ray can solve many problems and guide us in finding the canals.


The second upper molar is certainly a complex tooth from the anatomical point of view and for the position it has inside the mouth.

Knowledge of anatomy and its variables remains a fundamental step during endodontic treatment.

Everything starts from the correct interpretation of the pre-op RX so as to modulate the treatment according to the anatomy and trying to be as conservative as possible.


  1. Soares JA, Leonardo RT. Root canal treatment of three-rooted maxillary first and second premolars-a case report. International Endodontic Journal 2003; 36: 705-710
  2. Eskoz N1, Weine FS.Canal configuration of the mesiobuccal root of the maxillary second molarJ Endod. 1995 Jan;21(1):38-42.
  3. Ingle JJ, Backland LK Endodontics 5th Edition. Hamilton Ontario Canada 2002
  4. al Shalabi RM1 Root canal anatomy of maxillary first and second permanent molars.Int Endod J. 2000 Sep;33(5):405-14
  5. Lautrou A. Anatomia dentaria. Milano . Masson; 1982
  6. Stropko JJ1Canal morphology of maxillary molars: clinical observations of canal configurations.J Endod. 1999 Jun;25(6):446-50.1
  7. Naji Kharouf, 2Davide Mancino An In Vivo Study: Location and Instrumentation of the Second Mesiobuccal Canal of the Maxillary Second Molar JCDP 2019
  8. R. Ordinola-Zapata  Morphological evaluation of maxillary second molars with fused roots: a micro-CT study IEJ 2017
  9. J. Parker, A. Mol, EM. Rivera & P. Tawil  CBCT uses in clinical endodontics: The effect of CBCT on the ability to locate MB2 canals in maxillary molars  IEJ 2017