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Root Canal Treatment of Maxillary Premolars With Three Roots: A Case Series

May 1, 2018
by Rodrigo Sanches Cunha DDS MSc PhD FRCD(C); Howard M. Fogel, DDS, MSc FRCD(C)


Abstract
The successful outcome of endodontic treatment depends on an appreciation of the internal and external tooth morphology. Teeth with unusual root canal anatomy present a unique challenge even to experienced clinicians. This case series describes the endodontic treatment of maxillary premolars with three root canals. The identification and management of this uncommon anatomical variation of the root canal systems is discussed.

Keywords
Maxillary premolar; root canal anatomy; root canal morphology

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Introduction
Successful endodontic outcomes depend on correct diagnosis, meticulous shaping, thorough disinfection followed by three-dimensional obturation of the root canal system. The inability to locate, disinfect or fill one or more of the root canals is one the most common failures in endodontics (Karabucak, et al, 2016). Therefore, clinicians should have a thorough understanding of the most common root canal morphologies as well as the less common morphological variations in the different tooth groups before initiating endodontic treatment. In addition, incorporating technology such as the Dental Operating Microscope (DOM) and small field of view cone beam computed tomography scanners (CBCT) is also an important strategy to avoid missed-canals (Matherne et al, 2008; Wu et al, 2011; Mohammadi et al, 2016).

Maxillary First Premolar – Anatomic Considerations
The pulp chamber of the maxillary first premolar is significantly wider buccolingually than mesiodistally. Usually, these teeth have two roots with two canals. Nevertheless, a third root with a third canal has been reported in the literature. Pineda and Kutler (1972) used a radiographic method to evaluate the anatomy of first maxillary premolars and found a third root with a third canal in 0.5% of the cases. Numerous studies using the clearing method showed a higher incidence of this anatomic variation, ranging from 1.7% (Kartal et al, 1998) to 4% (Sert and Bayirli, 2004). Abella et al, 2015 used CBCT scans to analyze the morphology of the first maxillary premolars and found an incidence of 2.6% of three-rooted teeth. Ahmad and Alenezi (2016) reviewed the available literature with respect to the root and root canal morphology of the first maxillary premolars and found that 1.7% had three roots.


CASE 1
Fig. 1

Clinical aspect of tooth #14 showing a sinus tract on the buccal aspect in between the #13 and #14.

Fig. 2
Pre-operative periapical radiograph showing a deep distal filling on tooth #14 and a radiographic finding compatible with a lesion of endodontic origin.

Fig. 3A
Coronal plane of the small field CBCT scan image showing the MB and P roots.

Fig. 3B
Sagittal plane of the small field CBCT scan image showing the MB and DB roots. It is noteworthy to state that these roots split at the middle portion.

Fig. 3C
Axial plane of the small field CBCT scan image showing three separate roots with three canals.

Fig. 4
Post-operative radiograph showing three canals filled in a three-dimensional manner. A lateral canal was filled at the furcation level.


Maxillary Second Premolar – Anatomic Considerations
The pulp chamber of the maxillary second premolar is also considerably wider buccolingually than mesiodistally. Maxillary second premolars may also have one, two or three roots and canals. Its most common configuration is one canal followed by two canals (Pineda and Kutler 1972; Green et al, 1973, Vertucci, 1984). Although, once again, the incidence is low, ranging from 1% (Vertucci, 1984) to 5% (Sert and Bayirli, 2004), a third root with a third canal may also occur. Abella et al, 2015 used CBCT scans to analyze the morphology of the second maxillary premolars and found an incidence of 1.6% of three-rooted teeth.

Even though the external and internal morphologies of three-rooted maxillary premolars varies considerably (Beltes et al, 2017), in both first and second maxillary premolars the most common finding is two buccal canals (MB and DB) and one palatal canal (P). When three canals are present the access cavity outline should be slightly modified to a triangular shape, with the base on the buccal aspect of the crown and the apex of the triangle on the palatal. In a case of three root canals, the buccal orifices (MB and DB) may not be clearly visible and these canals may sometimes divide deeper inside the root.

The purpose of this case series was to present an uncommon anatomic variation in maxillary premolars, where the roots with three canals were treated endodontically.


CASE 2
Fig. 1 
Pre-operative periapical radiograph showing a deep distal filling on tooth #14 and a radiographic finding compatible with a lesion of endodontic origin.

Fig. 2A
Coronal plane of the small field CBCT scan image showing the MB and P roots.

Fig. 2B
Sagittal plane of the small field CBCT scan image showing the MB and DB roots. Once again it is noteworthy to state that these roots split at the middle portion.

Fig. 2C
Axial plane of the small field CBCT scan image showing three separate roots with three canals.

Fig. 3
Working length confirmation.

Fig. 4
Post-operative radiograph showing three canals filled in a three-dimensional manner. A lateral canal was filled at the apical portion of the palatal root.


CASE 3
Fig. 1
Pre-operative radiograph showing #14 which had previously been opened by the referring dentist. Three roots are visible.

Fig. 2
Post-operative radiograph showing three canals filled.


CASE 4
Fig. 1
Same patient as in case #3 nine years later. Tooth #15 has deep
caries on the mesial.

Fig. 2
Post-operative radiograph showing three canals treated in #15 as well.


CASE 5
Fig. 1
Pre-operative radiograph showing a periapical radiolucency associated with #15. Note that #14 also has three roots.

Fig. 2
Post-operative radiograph showing three canals filled.


Case Descriptions
The authors (R.S.C and H.M.F) treated the cases described in this article. Prior to a brief description of how the cases were managed, it is important to state that diagnosis and interdisciplinary treatment planning are extremely important. Additionally, determining the restorability and analyzing the amount of remaining tooth structure should be the starting point as these play a major role in the longevity of the tooth.

After rubber dam placement, access was performed using a Dental Operating Microscope in order to have magnification and increased illumination. The canal orifices were located using a sharp probe (DG-16) and pre-flared using Gates-Glidden drills or NiTi rotary orifice shapers. Canals were negotiated and preliminary glide paths were established and developed with #10 hand files and rotary glide path instruments. Working lengths were established with an electronic apex locator (EAL) and confirmed radiographically. Canals were shaped using NiTi rotary and/or reciprocating instruments. In order to maintain apical patency a pre-curved #10 stainless steel hand-file was passively introduced 1 mm beyond the working length repeatedly throughout the shaping procedure. Disinfection was achieved using 5% sodium hypochlorite as the irrigating solution. Smear layer was removed using copious irrigation with EDTA 17%. Both solutions were agitated using a sonic device in order to promote deep cleaning and disinfection into lateral canals, fins, webs, and anastomoses. Obturation was completed using gutta-percha and sealer with the warm vertical compaction technique followed by injectable gutta-percha. A temporary filling was placed and the patient was advised to see their general dentist for the permanent restoration.

Discussion
Missed canals are one of the main causes of endodontic treatment failure. Failing to identify and treat this extra canal often leads to persistent periapical disease and symptoms. Therefore, thorough knowledge of usual anatomy and less common variations is extremely important. Endodontic treatment of teeth with unusual root canal anatomy presents a particular challenge. Even though the literature shows that the incidence of a three-rooted premolar is quite low, it is important to not overlook this anatomic variation. If a patient has a three-rooted maxillary premolar on one side, they will most likely have the same root morphology on the contralateral side. It is also worth noting that, in some patients, both the first and second premolars have three roots (cases #4 and #5). Careful radiographic examination is critical. Having more than one periapical image taken at various horizontal angles is advisable. Use of Cone Beam Computed Tomography will facilitate pre-operative assessment.

Three-rooted maxillary premolars are sometimes referred to as “mini molars” with two buccal canals (MB and DB) and one palatal canal (P). Clinically, careful exploration of cervical contours with an explorer or periodontal probe may reveal indications of a furcation on the buccal aspect of maxillary premolars with two buccal roots. An access preparation that optimizes visualization of the pulp chamber is required. A thorough examination of the pulp chamber floor can reveal hints to the location of canal orifices and to the type of canal system present. When treating a three-rooted maxillary premolar, the best access preparation usually is triangular in shape with the base towards buccal and the tip towards palatal (Mohammadi et al, 2016). The clinical search for canals may be assisted by magnification and enhanced illumination. Incorporating the use of technology such as the dental operating microscope is extremely helpful.

Conclusion
In conclusion, this paper focuses on an uncommon anatomical variation where there are three roots and three canals in maxillary premolars. The incidence of a third root in maxillary premolars is low. Nevertheless, clinicians should be alert to the possibility of extra roots to avoid missed canals and improve the success rate of endodontic treatment. OH

Oral Health welcomes this original article.

Disclaimer: The authors deny any conflicts of interest related to this study.

References

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About the Authors
Dr. Cunha 1,2 is an Associate Professor and Part-time Instructor at the College of Dentistry, Faculty of Health Sciences at the University of Manitoba. Dr. Cunha has been a guest speaker at more than 200 events worldwide and became Fellow of the Royal College of Dentists of Canada (Endodontics) in 2013. Dr. Cunha has an extensive clinical experience obtained working in Private Practice limited to Endodontics since 1995.

Dr. Howard Fogel 1 received his degree in dental medicine from the University of Manitoba College of Dentistry in 1980. He practiced general dentistry in Winnipeg for five years. In 1988, Dr. Fogel completed an endodontic residency and masters degree program at the Endodontic Advanced Education program at the Oregon Health Sciences University. Dr. Fogel is a Fellow of the Royal College of Dentists of Canada, a Diplomate of the American Board of Endodontics and a member of the College of Diplomates. He is a Specialist Member of the Canadian Academy of Endodontics and the American Association of Endodontists. He is also a member of the Canadian Dental Association, the Manitoba Dental Association and the Winnipeg Dental Society. He has served on the executive and is a past President of the Canadian Academy of Endodontics. Dr. Fogel taught in the Section of Endodontics, Department of Restorative Dentistry at the University of Manitoba College of Dentistry for over 35 years.

1-Private Practice limited to Endodontics, Winnipeg – MB, Canada.
2-College of Dentistry, University of Manitoba – MB, Canada.