Diagnostic and clinical treatment challenges

Endodontic treatment of two-rooted mandibular second premolars: Diagnostic and clinical challenges by Junaid Nayyar and Henry F Duncan.

Root canal treatment of mandibular second premolar teeth is often considered relatively straightforward as the vast majority of these teeth possess one root (99.6 per cent). Rarely, however, these teeth can have two (0.3 per cent) or even three roots (0.1 per cent).

However, within the common presentation of a single root there can be significant variation in the canal morphology. Historically, there have been several attempts to classify root canal anatomy of which the Vertucci2 classification of eight root canal morphology types is the most widely accepted (Figure 1).

Extrapolating Vertucci’s classification to mandibular second premolar teeth it is evident that the most common type of canal system is the classic type I, with a single canal being present in 91 per cent of cases. Two or more canals can be seen in 9 per cent of cases while two or more apical foramina seen in 8.2 per cent of cases1.

Therefore, while type I canals are found in the vast majority of cases, type IV and type V are the most common deviations (Fig 1).

Gender differences

It has been reported that there is a greater number of roots and increased complexity of canals in males than in females3. In a study of 547 patients attending for routine treatment in a dental school in New York, USA, 11.5 per cent of males had multiple roots or canals, compared to 5.1 per cent of females3. However, greater variations have been reported in a Turkish population, with 43 per cent of males with multiple canals compared to 15 per cent of females4.

Ethnic differences

The reported variation of root morphology in different ethnic groups is less clear. One Turkish study found 29 per cent of mandibular second premolars to have multiple canals4. However, another Turkish study found the incidence to be 6.4 per cent5, which is closer to the global average.

Trope6 and co-workers reported slight differences in his comparison of the incidences of multiple canals in Afro-Caribbean (7.8 per cent) and Caucasian (2.8 per cent) populations. A study of the Jordanian7 population found 28 per cent with multiple canals. They classified their findings into Vertucci canal types. The most common types were type I (72 per cent), type V (15.3 per cent) and type IV (7.5 per cent). This highlights a trend for mandibular second premolars to exhibit a wider range of canal morpholgies in Afro-Caribbean and Middle Eastern populations.

A working knowledge of root canal morphology is essential in identification and subsequent chemo-mechanical debridement of all root canal anatomy; this is critical to the success of root canal treatment. Below we describe the endodontic treatment of a two-rooted mandibular 2nd premolar that highlights the importance of careful assessment and specialist assistance in the treatment of these cases.

Case report

A 62-year-old male patient was treated on the undergraduate restorative dentistry clinic for irreversible pulpitis of the heavily restored mandibular left second premolar (LL5) (Fig 2a). The symptoms had been present for about two weeks, had worsened during the last week and were now disturbing sleep.

The patient was examined and an intraoral periapical radiograph was taken (Fig 2b). The options for treatment were discussed and the patient expressed a desire to keep the tooth if possible. After administration of local anaesthetic an access cavity was made and one root canal orifice identified.

A size 8 stainless steel K-file (Dentsply Maillefer, Baillegues, Switzerland) was negotiated to an estimated working length of 23 mm after coronal flare with gates glidden files. Thereafter, the canal was instrumented using a combination of K-files and ProTaper rotary nickel titanium files (NiTi) (Dentsply Maillefer) and a definitive working length established at 22 mm using an apex locater. The root canal system was irrigated throughout the procedure with copious volumes of a 2 per cent sodium hypochlorite solution.

A working length radiograph was taken, however the file appeared to be eccentrically placed (Fig 3a). The canal was dried with paper points and no bleeding was noticed. The electronic apex locater once again confirmed that the working length was correct. The tooth was dressed with calcium hydroxide and a second appointment made one week later. Uncertain to the reason for the mesially placed file, a gutta-percha point was placed in the canal at the second visit. Notably, this point was significantly short of the root apex (Fig 3b).

When the gutta-percha point was removed from the canal it was noticed that it had ‘folded over’ in the last few millimeters. A second master cone radiograph was taken, and the cone reached the full length, again confirming its mesial direction (Fig 3c). A specialist endodontist was consulted and a second root was identified from the radiographs.

Using the operating microscope, a second canal was located disto-lingually to the first (Fig 3d). The second canal separated from the main root canal trunk confirming a Vertucci type V pattern. Long tapered Ultrasonics (CPR, SybronEndo, CA, USA), hand K-files files (Dentsply Maillefer) and rotary ProTaper NiTi were used to negotiate the second sclerosed canal.

The canal was successfully instrumented to its full length and subsequently obturated using a calcium hydroxide sealer (Sealapex; Kerr corporation, CA, USA) combined with a single greater taper master cone (Dentsply Maillefer) in the apical portion and backfilled with thermo-plasticised gutta percha using a warm vertical condensation technique (Calamus Unit, Dentsply Maillefer) (Figs 3e and 3f). A post space preparation was carried out immediately in the mesial canal, and the tooth was later successfully restored with a cast metal post and core followed by a metal-ceramic crown (Figs 4 and 5).


What appeared to be a straightforward case proved not to be and required the help of a specialist endodontist and the operating microscope. This case highlights that root canal treatment in single rooted teeth can still be challenging and may require specialist treatment. Therefore general practitioners should be aware of the incidence and the common variations of root canal anatomy in mandibular premolar teeth as well as how to identify them.


A periapical radiograph is a two-dimensional image of a three-dimensional object, and this can limit the practitioner’s ability to identify the presence of complex anatomy. Two periapical radiographs at different angles to each other can be taken, as the chances of a root being hidden because of superimposition are reduced.

To identify the spatial relationship of the roots there is a time-tested method known as the “SLOB” rule, as originally described by Clark8 in 1910. The two radiographs should preferably be at different angles to each other in a mesio-distal direction. The root that is further away from the x-ray tube will always move in the direction that the tube was moved, while the root that is closer to the x-ray tube will seem to move in the opposite direction. This gives rise to the mnemonic SLOB – Same Lingual Opposite Buccal.


New technologies such as Cone Beam Computed Tomography (CBCT) have recently found novel applications in the field of endodontics. The great advantage of CBCT over conventional radiography is in its ability to describe teeth in 3D, without geometric distortion or superimposition9.

There are countless uses of CBCT with much literature supporting its superiority in the detection of roots10, periapical pathology11,12, dental fractures13 and in identifying the likely cause of endodontic failures14. With this in mind, CBCT should always be considered in cases that might be atypical, challenging or in which the dentist suspects an anomaly.


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About the author

Junaid Nayyar has recently graduated from Dublin Dental University Hospital.

Henry F Duncan is a lecturer/consultant in endodontics in the division of restorative dentistry and periodontology at Dublin Dental University Hospital.