Complicated canal morphology of mandibular first premolar.

The aim of this article was to report an unusual anatomic variation of mandibular first premolar, with one root and three distinct canals, which leave pulp chamber and merge short of apex to exit as two separate apical foramina. The incidence of three canals existing as two apical foramina has only been documented in the literature by a few case reports. To achieve successful endodontic treatment, the clinician has to identify the different canal configurations and treat them properly.

The prevention and healing of endodontic pathology depend on a thorough chemicomechanical cleaning and shaping of the root canals before a dense root canal filling with a hermetic seal. An awareness and understanding of the presence of unusual root canal morphology can thus contribute to the successful outcome of the root canal treatment.

In general, mandibular premolars are difficult to treat and show high flare-up and failure rate possibly due to extreme variations in the root canal morphology.[1] Slowey had suggested that mandibular premolars may present with the greatest difficulty of all teeth to treat endodontically.[2] A University of Washington study assessed the failure rate of nonsurgical root canal treatment in all teeth and found it to be the highest for mandibular first premolars at 11.45%.[3] Vertucci and Pecora et al. have studied the canal anatomy and configuration of mandibular premolars. Vertucci using a transparent method found 25.5% of 400 mandibular premolars had two apical openings, and 0.5% of the teeth had three apical openings.[4] Pecora et al. observed that 22.3% of the mandibular first premolars possessed two canals and two separate foramina while 5.12% had two canals and one foramen. Only 0.46% of the first and second premolars examined showed a three-canal and three-foramen configurations.[56] Zillich and Dawson reported that a second or third canal existed in at least 23% of first premolars.[7] There seems to be racial predisposition for the presence of two or more canals in maxillary and mandibular premolars.[8910]

The occurrence of three orifices with three separate canals and two apical foramina in single-rooted mandibular premolar is rare. The purpose of this article is to report the case of a South Indian patient who has this variation in canal morphology and its subsequent treatment.

Case Report

A 19-year-old female patient presented with a chief complaint of pain in left lower back tooth region since 10 days. On intraoral examination, mandibular left first premolar showed a large Class I caries involving pulp. The tooth was tender on percussion and showed no response to electrical and thermal pulp testing. Radiographic evaluation with intraoral periapical (IOPA) radiograph showed periapical radiolucency in relation to lower left first premolar [Figure 1]. More than one root canal was suspected in that tooth and extra medially and distally angulated periapical radiograph was taken to help in a better interpretation of the canal system. Based on the clinical and radiographic evidences, it was diagnosed as chronic apical periodontitis in relation to the mandibular left first premolar.

Figure 1

Preoperative intraoral periapical of mandibular first premolar

Anesthesia was achieved by means of inferior alveolar nerve block with 1.8 ml of 2% lignocaine with 1:80,000 adrenaline. Teeth were isolated using rubber dam and all caries were removed prior to access opening. After access opening, the trunk of the canal seemed to trifurcate at mid-root level giving rise to three separate canals. The orifices to the three root canals were found and enlarged with Gates Glidden Drill. The pulpal tissue was removed using barbed broach; the working length was determined using periapical radiograph. Working length radiograph revealed three canal orifices leading to three separate canals but exited as two apical foramina's [Figure 2]. The three root canals were thoroughly instrumented and shaped by step back technique to a size 30 (apical preparation), and the root canals were irrigated using 3% sodium hypochlorite and 3% hydrogen peroxide solutions during root canal cleaning. The teeth were then dried with sterilized paper points. Intracanal medication with calcium hydroxide powder mixed with saline, carried through lentulo spirals, was placed. At the second appointment, the root canals were obturated with zinc oxide sealer and laterally condensed Gutta-percha [Figure 3]. A final radiograph was then taken to confirm the quality of the obturation [Figure 4]. The access cavity was sealed with IRM and the patient was then given appointment for permanent restoration.

Figure 2

Working length intraoral periapical showing three canals with two apical foramina's

Figure 3

Master cone intraoral periapical

Figure 4

Intraoral periapical immediately after obturation

Discussion

The clinician must be aware of various pathways root canals take to the apex. Failure to recognize anatomical complexities will result in treatment failure. The clinician should view mandibular premolar tooth group as complex and use all available armamentarium to achieve a successful outcome.

Good quality radiographs and thorough radiographic examination are essential for detection of additional canals.[2] In the present case, the IOPA radiographic features suggested the possibility of three canals. However, because of the superimposition of roots, radiographic diagnosis of three canals is not always possible in all cases. Several other indications may be useful such as use of magnification and fiber optic illumination, dyes, advanced imaging techniques like computed tomography (CT),[11] spiral CT,[12] micro-CT.[13]

An optimum access cavity is equally important criterion to negotiate buccally or lingually deviated canals. A good tactile sense and precurved files will help the clinician to negotiate the canals better for a predictable outcome.

Conclusion

Careful interpretation of the radiograph, close clinical inspection of the pulpal floor and proper modification of access opening are essential for a successful treatment outcome along with accurate knowledge of anatomical variations.