Introduction
Locating calcified orifices is a challenging task, requiring the dentist to search for orifice openings, often only fraction of a millimeter in size, across the broad surface of the pulpal floor. This task is further complicated when the tooth has been previously crowned, obscuring the size and angulation of the original crown, as well as the thickness of the tooth structure underneath. Additionally, artificial crowns may be designed to realign the teeth or to correct a defective contact by enlarging the occlusal table. Indiscriminate removal of tooth structure at the pulpal floor can lead to complications such as pulpal floor violations and perforations, potentially resulting in future fractures. Conversely, missing canals can cause persistent infections (1,2). It is crucial, therefore, to accurately locate the canals without harming the tooth structure.
How to Locate Canal Orifices
- Understand the occlusal anatomy.
- Understand the pulpal floor anatomy.
- Recognize the spatial relationships between the orifices.
- Apply the laws of centrality, symmetry, and color change (3).
- Utilize CBCT data to identify orifices on the pulpal floor (4).
Case Report
A male patient in his seventies was referred for evaluation and treatment planning for tooth 1.6 and missing teeth 1.5 and 1.7. He reported spontaneous pain along with pain upon chewing which had started a week prior. The patient had finished a course of antibiotic prescribed by his dentist for tooth infection and was also currently on Irbesartan. The patient also reported that he grinded his teeth. There were no symptoms associated with the tooth when he presented to the office. The porcelain crown was notably tall, featuring an enlarged occlusal table. The clinical examination showed gingival attachment and bone loss. Mobility was M1. There were no deep pockets. Cold test was negative. The canals were barely visible on the periapical and bitewing radiographs (Figs. 1 and 2). The general periodontal ligament (PDL) widening around the roots was likely due to traumatic occlusion, as the patient was chewing on a lone standing tooth. Tooth 1.6 was diagnosed with pulpal necrosis and normal periapical area, and a crack was suspected as well. Upon further consultation, the patient requested to save the tooth. The prognosis was guarded. During the treatment, no crack was noted. An intraoperative CT was taken (Fig. 3). The axial CBCT data helped accurately locate the canals on the pulpal floor (Figs. 4-7). The canals were cleaned conservatively and subsequently disinfected by Er:YAG laser (SkyPulse Endo Plus, SWEEPS Mode, Fotona) and sealed with warm vertical compaction of gutta-percha and a resin sealer (Fig. 9).
Discussion
Traditional two-dimensional radiography has several limitations, including geometric distortion and failure to detect periapical lesions, which are critical for endodontics. This modality struggles to explore the internal anatomy of the tooth three-dimensionally and to pinpoint the spatial location of calcified canals. This is also true for locating MB2 and either disto-buccal or disto-lingual canal of lower molars which are frequently missed. From an endodontic perspective, it also fails to measure distances between canals, especially in a buccal-lingual dimension. Fortunately, CBCT largely overcomes these challenges, allowing clinicians to acquire a more thorough understanding of the internal anatomy of teeth (4-8). In this discussion, it should be noted that the ALARA (As Low As Reasonably Achievable) principle should always be adhered to when utilizing this technology (5-7). In the present case, the axial CBCT view suggested the possibility of a MB2 canal, which was not clinically present, appearing instead as a wide MB orifice (Fig.4). The axial view confirmed that the MB canal was centrally located in the apical third (Fig. 8).
Conclusion
CBCT is invaluable in locating calcified orifices, MB2, and extra canals. It is advisable to request either a preoperative or intraoperative CBCT scan when calcified canals are suspected, to accurately understand the spatial relationships among canals at the pulpal floor. Additionally, it is prudent to have an oral radiologist report these findings (Figs.4 and 6).
References
- Association between missed canals and apical periodontitis
F Costa, et al IEJ 2019 - A 5-year Clinical investigation of second mesiobuccal canals in endodontically treated and retreated maxillary molars. Wolcott J, et al JOE 2005
- Anatomy of the pulp-chamber floor Paul Krasner , Henry J Rankow JOE 2004
- Intraoperative Endodontic Applications of Cone-Beam Computed Tomography
Randy L. Ball, et al JOE 2013 - The Impact of Cone Beam Computed Tomography in Endodontics: A New Era in Diagnosis and Treatment Planning
- AAE/AAOMR Revised Joint Position Statement on Cone Beam Computed Tomography in Endodontics (2016 update)
- European Society of Endodontology position statement: Use of cone beam computed tomography in Endodontics IEJ 2019
- Endodontic Applications of Cone-Beam Volumetric Tomography
Taylor P. Cotton, et al JOE 2007