Endodontic management of a maxillary first and second premolar with three canals.

Unusual anatomical configurations must be considered in the radiographic and clinical evaluation during the endodontic treatment. The canal anatomy maxillary first and second premolar has been studied extensively and the presence of three canals is relatively rare especially in the maxillary second premolar. The occurrence of three canals with separate foramina in both the first and second premolar is shown to be in extremely low percentages and has been documented as practically non-existent in Asian populations. This article describes a case of a maxillary first and second premolar with three canals each.

INTRODUCTION

One of the keys to a successful endodontic therapy is a sound knowledge of the root canal anatomy and morphology. Identification and access to pulp canals is particularly challenging in the endodontic treatment of teeth with atypical canal configurations. The lack of knowledge of the internal anatomy will often lead to errors in all the stages of endodontic therapy including, access, localization, cleaning and shaping and obturation of the root canal.[12] However, anatomic variations if recognized early in the diagnostic phase of therapy can lead to critical changes in the treatment strategies thereby ensuring better predictability of the outcome of treatment.[3]

The incidence of three canals in the maxillary premolars is quite low. In the case of the first premolar, three root canals were found at a frequency between 0.5% and 6%,[456] whereas in the second premolar the incidence was from 0.3% to 2%.[78] It has been studied and analyzed that the presence or absence of a third root canal is influenced by genetic factors and that three rooted premolars are more frequent in Caucasian populations and virtually non-existent in Asian populations.[39]

Accurate pre-operative radiographs both straight and angled are a pre requisite and provide vital insights into the internal anatomy and the number of roots. Sometimes additional radiographs are necessary whenever a variation seems suspect.

The possibility of the presence of a third root canal is suspected during the access cavity preparation or most often when post-operative pain was encountered and had to be evaluated.[10]

The objective of this article is to report a clinical case and discuss the treatment approach for a rare occurrence of three canals in the maxillary first and second premolars.

CASE REPORT

This was a case report of a of 45-year-old female patient with non-contributory medical history reported to the dental office complaining of intermittent pain in the maxillary left quadrant since 1 week. Clinical examination revealed a large amalgam restoration with secondary caries on both first and second maxillary left premolars [Figure 1a]. The teeth were sensitive to percussion. Vitality test on both the premolars elicited no response to both cold and Electric Pulp Tester (EPT). Radiographs showed loss of lamina dura and peri apical widening in both the teeth (24 and 25).

Figure 1

(a) Pre-operative radiograph. (b) Working length determination. (c) Master cone radiograph

A diagnosis of Irreversible pulpitis with Apical Periodontitis was made and non-surgical endodontic treatment was planned for both tooth 24 and 25 followed by fixed partial denture prosthesis. Local anesthetic was administered with buccal infiltration of 1.8 ml of 2% Lignocaine with 1:200,000 epinephrine. The teeth were isolated with a rubber dam and coronal access prepared. On careful examination of the pulp chamber floor of both 24 and 25 three separate root canal orifices were identified (mesiolingual, mesiobuccal and distal). The root canals were negotiated with DG 16 explorer (Hu Freidy, USA) and ISO Size 10 files. The working length was registered with Root ZX Mini apex locater (J. Morita, Japan) which was confirmed later with radiographs [Figure 1b] The cleaning and shaping was done with crown down technique with Protaper Rotary instruments (Dentsply Maillefer) as per the manufacturer's instructions using 17% of ethylenediaminetetraacetic acid (Glyde, Dentsply) as lubricant and 5.2% of sodium hypochlorite as irrigant. Considering the time taken to complete the therapy, the teeth were completed in two visits. After the biomechanical preparation of both the premolars, the root canals were dried with paper points and a paste of calcium hydroxide (Ultracal, Ultradent USA) was used as intracanal medication. A provisional restoration of Cavit (3M ESPE) was placed between visits. At the second appointment, the patient was completely asymptomatic. The root canals of both the teeth were once again flushed with 5.2% sodium hypochlorite and the canals were dried. The master cone radiograph was taken [Figure 1c] and the root canals were then obturated using F2 Protaper Gutta-percha (Dentsply Maillefer) using AH plus resin sealer (Dentsply, Detrey) and post obturation radiograph was taken [Figure 2a].

Figure 2

(a) Post-obturation radiograph. (b) at 1-year follow-up radiograph. (c) 1-year follow-up radiograph (mesial angulation)

The orifice was then sealed with Flowable composite (Ivoclar Vivadent) and the access cavity was then restored using SureFil composite resin (Dentsply).

The 1 year follow-up radiographs with two angulations was taken to clearly identify the canals [Figure 2b and c].

DISCUSSION

The presence of a third canal in the maxillary premolars cannot be disregarded and should not be overlooked just because it is reported to be less than 6% in the maxillary first premolar[47] [Table 1] and less than 1% in the Maxillary second premolar[456] [Table 2] in the literature. The second maxillary premolars have fewer cases reported and both first and second maxillary premolars having three canals have rarely been reported.[4567811]

Table 1

Percentage of number of root canals of maxillary first premolar as reported in various studies

Table 2

Percentage of number of root canals of maxillary second premolar as reported in various studies

Identification and accessing of pulp canals is challenging and requires a thorough understanding of the basic root canal anatomy coupled with a high level of proficiency and clinical acumen of the treating dentist. Most often good quality radiographs especially digital radiographs are essential for the detection of additional roots and root canals especially when analyzing the anatomic details when the radicular anatomy is not clearly visible or distinct.[13] Guidelines like “fast break” (Sudden narrowing or a disappearing pulp space) should be taken into consideration while assessing the pre-operative radiographs. If the root canal abruptly seems to straighten or broaden or if the course cannot be traced the presence of a second canal in the same root or of a canal in another root superimposed on the first one because of the radiographic projection should be suspected and anticipated.[16] Therefore a radiograph of good quality with the parallel technique and “mesial shift" (and if required a “distal shift”) will provide useful insight into the internal anatomy of the root canal. The use of cone beam computed tomography is also recommended to identify unusual anatomy.[17] In this particular case, the authors decided against its use due to the patient's unwillingness to undergo the procedure due to radiation concerns and time.

Though the maxillary first premolar has two canals, a third canal should be suspected clinically if the pulp chamber appears too large in the mesio distal plane. The outline of the access cavity is determined by the size and shape of the pulp chamber and the position of the root canal orifices. Balleri et al. suggested a T shaped access outline in since this can allow for straight line access to the canals.[18] If a third canal is suspected the outline should be extended by making a cut at the bucco proximal angles from the entrance of the buccal canals to the cavo surface angle. In the treatment of maxillary first and second premolars with three canals the buccal orifices may be close to each other and hard to locate. During the initial placement of K-files in the canal one may encounter an obstruction and a deflection of the file to the buccal or the lingual before it can be explored further. The shape of the canal entrance will probably be ovoid or flattened in the bucco–palatal direction if the bifurcation is found in the middle-third of the root.[19] A great deal of tactile feel and precurving of the K-file tip will thus be crucial in the diagnosis of a third canal.

The presence of a third root canal should also be suspected if at the working length radiograph the instrument is totally displaced in either the mesial or distal direction.

Once established, allowing straight line access to the three canals is of vital importance. This can be achieved with a Gates-Glidden drill set on a slow hand piece at 750-1000 rpm in the crown down fashion. This helps to reduce the stress on the root canal instruments, decreases the fracture risk and extent of canal transportation.[20]

The use of magnification and fiber optic illumination offers a remarkable advantage while locating and treating extra canals.

Obturation with vertical compaction with apical back filling has been shown to allow the creation of an effective apical plug and excellent adaptation.

Successful endodontic treatment is dependent on adequate removal and prevention of recolonization of microorganisms from the canal system by placement of root fillings that obturates the entire space and then a restoration that produces a satisfactory coronal seal. The success in multi rooted teeth presents more of a challenge and their failure rates are more often due to factors other than filling technique alone e.g., Lack of access, accessory anatomy etc.[21] According to Slowey[22] extra root canals, which are left untreated accounts for many of the endodontic failures. With regard to the maxillary premolars a variations in canal anatomy though relatively less reported would pose a significant threat to the success of endodontic therapy and have to evaluated and studied further.

CONCLUSION

It thus becomes imperative to encourage the possibility of the presence of an extra root canal and be skillful in the interpretation of clinical and radiographic data especially while treating maxillary premolars. The challenges faced in endodontic treatment and predictable root canal treatment would therefore be dependent of not only a thorough knowledge of the anatomic variants but also skillfully mastering newer diagnostic techniques and clinical intelligence.