Retreatment of a maxillary first molar with 5 canals using RetreatAll

Knowing the internal anatomy of the teeth accurately is vital to achieving a successful root canal treatment. Proof of this is this retreatment by Dr. Roberto Estevez of a first molar with 5 canals, a clinical case that is rarely seen since it only happens in 1% of the population.

One of the leading causes of root canal treatment failure is the omission of at least one root canal during the primary treatment. It is necessary to accurately know the internal anatomy of the teeth that make up the arch. The first alternative to endodontic treatment failure should be non-surgical retreatment, since it has a high success rate, according to De Chevigny et al.

Success at 4-6 years can be up to 92% (J Endod 2008). One of the most frequent anatomical variations is the presence of a second canal in the mesiobuccal root of the maxillary first molar. One of the most important articles that describes the peculiar anatomy present in this first molar is the work of Cleghorn et al. (J Endod 2006).

This author reviewed the most important articles published to date, concluding that the most frequent external anatomy is three roots (> 96% of cases) and four canals (> 57% of cases). The presence of four canals is mainly distributed between two in the mesiobuccal root, known as mesiobuccal 1 and 2, a canal in the distobuccal root and another in the palatal root.

However, according to this author, around 1% of the population have at least two canals in the palatal root, making it difficult to clean and fill the canal system.

Case Report: Retreatment of a maxillary first molar with 5 canals

The case presented below is a retreatment of a maxillary first molar with five independent canals: two in the mesiobuccal root, one in the distobuccal root and two in the palatal root.

The patient visited the exclusively endodontic consultation due to pain in the first quadrant. Upon examination, the maxillary first molar was observed to have a porcelain crown that was placed less than two years before. After the complementary tests, the diagnosis of a tooth previously treated with symptomatic apical periodontitis was reached, and the treatment proposed to the patient was an orthograde retreatment of tooth 16.

Diagnosis

In the ortho-radial X-ray (Fig. 1) an apical transport in the obturated canal is observed in the mesiobuccal root (mesiobuccal 1), an infraobturation in the distobuccal canal, and a palatal canal obturation that raises suspicion, due to the lack of centrality in the root, that there may be a bifurcation in the apical area.

Fig. 1: Ortho-radial projection where the causes of failure of the previous endodontic treatment can be seen.

When taking another deprojected (distal-radial) X-ray (Fig. 2) the existence of an apical lesion in the palatal root was verified, along with the suspicion of two missed canals: one in the mesiobuccal root and the other in the palatal root.

Fig. 2: Distal-radial projection that provides us with more diagnostic information.

Treatment

After anesthesia and absolute isolation, a round diamond bur was used to remove the porcelain that prevented access to the pulp chamber. The impediments were removed with the help of ultrasound, the entrance of the gutta-percha was softened so that its subsequent removal would be easier (Fig. 3, 4 and 5). With the help of magnification, the entry of a second mesiobuccal canal was detected soon after, which had not been detected during the first root canal treatment and had some pus discharge coming from it.

Fig. 3, 4 and 5: Removal of gutta-percha with ultrasound and localization of the omitted canal in the mesiobuccal root.

Treatment

The gutta-percha was removed from the coronal and middle third with the help of RetreatAll® rotary files, Zr1 (30.04 of 21mm) and Zr2 (25.04 of 25mm), activated in a rotary manner, manufactured by Zarc4endo (Gijon-Spain) (Fig. 6). The rotational speed used was 500 rpm and the movement was continuous rotation.

The omitted canal in the mesiobuccal root (MB2) was worked on using the BlueShaper® system (Zarc4Endo, Gijon-Spain) up to Z4 (25.06) using the sequence recommended by the manufacturer (500 rpm and 4.0 torque), with the Eighteeth endodontic motor, also using the files in continuous rotation.

Fig. 6: Zarc4Endo Retreat-All retreatment files

Fig. 7: Working length X-ray of the mesiobuccal 2, palatal 2 and distobuccal canals.

During the treatment, an X-ray (Fig. 7) was taken that showed the second untreated canal in the palatal root, and the second untreated canal in the mesiobuccal root (mesiobuccal 2), totally independent like the palatal canal 2. After removing all the gutta-percha (no solvent was necessary), we proceeded to the final irrigation protocol: sodium hypochlorite, 17% liquid EDTA, sodium hypochlorite, all sonically activated with the Endoactivator (Dentsply Sirona).

Final results

In the final X-rays (Fig. 8 and 9), both in ortho-radial and distal-radial views, the presence of 5 independent canals can be observed: two in the mesiobuccal root, one in the distobuccal root and two in the palatal root, to which the presence of a lateral canal can be added, highlighting the importance of irrigation to achieve a three-dimensional sealing of the canal system.

A provisional cement was placed while the patient waited for the referring dentist to permanently restore the treated tooth.

Fig. 8 and 9: ortho- and distal-radial projection where the five independent canals can be seen

Fig. 8 and 9: ortho- and distal-radial projection where the five independent canals can be seen

Dr. Roberto Estévez

Doctor in Dentistry and Master in Endodontics (Universidad Europea of Madrid). Coordinator of the Master of Endodontics Program at the Universidad Europea of Madrid. Lecturer for endodontic courses and conferences at a national and international level. Author of various articles in national and international scientific journals. Exclusively practicing endodontics since 2004.

More information

Have you ever encountered a first molar with five canals? Do you want to try our instrumentation systems? Get in touch with us, we are happy to help you.

Write us an email at hola@zarc4endo.com.