Endodontic retreatment in a first maxillary molar with two palatal root canals and a single orifice

Drs. Konstantinos Kalogeropoulos, Vasiliki Diamantopoulou, and Marouan Khabbaz present a case report of a successful nonsurgical endodontic retreatment in a first maxillary molar with two palatal root canals and a single orifice

Educational aims and objectives
The clinical article aims to illustrate the endodontic retreatment of a maxillary first molar with bifurcation of the palatal root canal at the middle third, aided by the use of magnification provided by the dental operating microscope.

Expected outcomes
Correctly answering the questions on page 29, worth 2 hours of CE, will demonstrate you can explain the occurrence of a rare aberration in the palatal root of a maxillary first molar, and discuss the importance of the anatomy of the root canal system combined with a careful clinical and radiographic examination.

One of the reasons that endodontic treatment fails is the fact that additional root canals remain undetected and do not undergo cleansing, shaping, and obturation (Siqueira, 2001). Thorough knowledge of the root canal system anatomy coupled with the use of microscope magnification is required by the clinician to avoid such incidents (Schwarze et al, 2002).

Maxillary first molars exhibit variations in the canal morphology. In the mesiobuccal root, two root canals are usually present at a frequency of 56.8% according to clinical and laboratory studies (Cleghorn et al, 2006). Furthermore, in the distobuccal root, the presence of two root canals systems is rare, with an incidence of 1.7% (Cleghorn et al, 2006). Anatomic variations involving the number of roots or root canals in the palatal root of permanent maxillary molars are rare (Stone and Stroner, 1981), less than 1%, and also infrequently reported (Christie et al 1991; Cleghorn et al, 2006). The anatomy of the first maxillary molar’s palatal root features one orifice and one foramen at a prevalence of 99% (Cleghorn et al, 2006).

However, Thews et al (1979) and Johal (2001) reported cases with two orifices joining into one foramen within a single palatal root. Moreover, Holderrieth and Gernhardt (2009) reported a case with one palatal root with one orifice bifurcating into two foramina at the apex. As for the incidence of two separate root canals, it may be rare, 1% (Cleghorn et al, 2006); nevertheless it has been reported by Thews et al (1979), Jacobsen and Nii (1994), Aggarwal et al (2009), and Holderrieth and Gernhardt (2009). Regarding the existence of two palatal roots, it appears to be less common in the maxillary first molar than in the maxillary second molar (Christie et al, 1991; Gopikrishna et al, 2008; Tomazinho et al, 2010). Finally, a case of a single palatal root canal orifice, which trifurcated into three separate foramina has also been published (Wong, 1991).

The purpose of this article is to illustrate the endodontic retreatment of a maxillary first molar with bifurcation of the palatal root canal at the middle third, aided by the use of magnification provided by the dental operating microscope.

Case report

A 37-year-old woman, with a noncontributory medical history, was referred by a prosthodontist for retreatment of a maxillary first molar. The patient was asymptomatic, but periapical radiolucency was present, and the previous root canal treatment was performed with silver points more than 10 years ago (Figure 1). The treatment plan was to restore the tooth with a cast dowel and porcelain-fused-to-metal crown.

After administration of local anesthesia, the old crown was removed. A rubber dam was placed, and the old restoration was removed by means of ultrasonic tips under magnification by the dental operating microscope. Care was taken not to harm the underlying silver points in order to facilitate their removal; these were removed with the aid of specialized forceps (Hu-Friedy). The root filling material in the palatal root canal was paste-like and was also removed with ultrasonic tips.

Copious irrigation with 2.5% sodium hypochlorite solution was used throughout the treatment. Flaring of mesiobuccal, distobuccal, and palatal root canals was done with a combination of Gates Glidden burs and rotary nickel-titanium instruments. Observation of the pulp chamber floor under high magnification revealed no sign of additional canals in the mesiobuccal root. Instead, in the palatal root, two separate orifices could be distinguished in the middle third (Figure 2). Initial scouting with a number 10 K-file revealed that both were patent, but had completely different angles while leaving the main canal. Working length (WL) was calculated with the use of an apex locator and confirmed with radiographs (Figure 3). The root canals were all instrumented to size 40, taper .04 with the BioRace rotary instruments (FKG Dentaire, La Chaux-de-Fonds, Switzerland). Smear layer was removed by irrigation for 1 minute with ethylenediamine tetra-acetic acid (EDTA) 17% (Ultradent). Passive ultrasonic irrigation was performed with 2.5% sodium hypochlorite solution and EMS ESI needles (EMS, Nyon, Switzerland) for three times of 1 minute each in every canal. The canals were dried, and calcium hydroxide was placed with a lentulo spiral as an intracanal medicament. Cavit-G (3M ESPE) was used as temporary filling material. The patient was given oral and written postoperative instructions and was told to return after 10 days.

At the second appointment, the antimicrobial irrigation regimen was repeated, and the canals were dried with sterile paper points. Gutta percha points of adequate size and taper were placed in the canals, and a master cone radiograph was taken (Figure 4). The sealer used was AH-plus (Densply Maillefer, Baillaigues, Switzerland). The obturation technique used was the vertical compaction with the System-B (SybronEndo) device at 3 mm from the apical terminus of the canal (Figures 5 and 6) and backfilling with injection of thermoplasticized gutta percha with the Obtura III device (Obtura Spartan) (Figure 7). Post space was left in the palatal root canal above the bifurcation, as requested by the referring dentist, in order to place an intraradicular post. Cavit-G (3M ESPE) was used as temporary filling material. The patient was referred back to the prosthodontist for the final restoration and was told to return to the practice after a 6-month period for a recall examination.

At the recall appointment, seven months later, radiographic examination revealed partial dissolution of the extruded sealer in the mesiobuccal root canal and no evident radiolucency in the periradicular tissues of the tooth (Figure 8).

Discussion

It is highly important to note that aberrations in the root canal system are frequent, and clinicians should therefore be cautious during endodontic treatment.

In this case report, a maxillary first molar appeared to have one canal in the palatal root, which bifurcated into two canals towards the apex. According to Weine’s (1982) classification of root canal morphology, this case belongs to type IV.

The diagnosis of the second orifice was made with the combination of clinical and radiographic examinations. The contribution of magnification in the detection of the untreated root canal was crucial, as the dental operating microscope enhances visibility (Machtou, 2009).

The initial preoperative radiograph revealed radiopaque material diverging into the apical third in two separate directions. In addition, after the removal of the previous root filling materials, it was observed that the file was not centrally located into the palatal canal, which was confirmed afterward by an additional off-angle radiograph. Off-angle radiographs are of utmost importance if there is a suspicion of extra root canals (Naoum et al, 2003).

Regarding the instrumentation of the root canals, nickel titanium (NiTi) rotary instruments were preferred because they can achieve a larger final root canal preparation corresponding to the general shape and direction of the original canal (Tan and Messer, 2002). Larger apical diameters were desirable in this case, due to the existence of apical periodontitis. Finally, the presence of periradicular lesions led to the decision to carry out the procedure in two sessions, instead of one-visit therapy (Sjögren et al, 1997).

In cases with difficult anatomy and when in doubt of existence of extra canals, CBCT imaging can be used to facilitate detection of aberrations in the root canal system (Gopikrishna et al, 2008; Faramarzi et al, 2010). In this specific case, this was not necessary.

Holderrieth and Gernhardt (2009) reported a similar case of a maxillary first molar with a large ovoid palatal canal, which bifurcated in the middle third of the root.

The present article is the second report of this morphological aberration in a maxillary first molar’s palatal root.

Conclusion

Practitioners should keep in mind that all teeth, including maxillary first molars, are likely to present variations in their root canal systems. Knowledge of the complexity of the root canal system anatomy, combined with a thorough clinical and radiographic examination is the key to treating individual cases successfully.

Bios:

Dr. Konstantinos Kalogeropoulos is a postgraduate endodontics resident at the Dental School of the University of Athens. He has published endodontic articles in national and international scientific journals and has presented a large number of oral presentations and posters in endodontic congresses.   

Dr. Vasiliki Diamantopoulou graduated from the Dental School of the University of Athens in 2009. She is affiliated with the endodontics department undergraduate program.

Dr. Marouan Khabbaz gained his DDS and his PhD from the University of Athens. He has attended his postgraduate program in Karolinska Institute, Sweden. He is an associate professor at the University of Athens Dental School, department of endodontics. His research is focused on chemomechanical preparation of the root canals.

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