September 1, 2014
by Trisha Charland, DMD; Randolph Todd, DMD
Root canal therapy starts with the diagnosis and identification of the disease etiology. As originally determined in the classic study by Kakehashi et al.,1 bacteria must be present in order to develop apical periodontitis. Root canal therapy involves diagnosis, cleaning, shaping, irrigation, and obturation. The bacterial load must be eliminated or decreased sufficiently for the periradicular host tissue to heal.2 Gaining access to all primary and lateral canals is essential for debridement.3 An accurate knowledge and understanding of the root and canal anatomy is imperative to properly perform these steps.
Two-dimensional radiologic imaging is traditionally used to identify primary and secondary canals. Unfortunately, these images minimally satisfy diagnostic and treatment requirements. Conventional periapical and bitewing radiographs are impaired by the following factors.
• Geometric distortion — a change in the proportions of the radiographic image due to variations in angulation.4
• Anatomic noise — The visual obstruction of structures due to the superimposition of normal anatomy.
These limitations are not a concern when implementing cone beam technology (CBCT). Three-dimensional imaging offers a pretreatment awareness of existing anatomic anomalies and pathology. Many times, these complex anatomies even elude observation with the dental operating microscope (DOM). Use of both technologies has the ability to enhance patient care as described below.
A 39-year-old Caucasian female was referred for endodontic evaluation and treatment of her maxillary right first bicuspid. The referring dentist forwarded a pretreatment periapical radiograph (Fig. 1). Her past medical history was not a contributing factor in her care. The patient had a temporary crown inserted two weeks prior subsequent to a fractured buccal cusp. She complained of a chronic radiating pain and thermal sensitivity. Comprehensive endodontic testing revealed an irreversible pulpitis and symptomatic apical periodontitis. Limited anatomic information was obtainable from the periapical radiograph due to anatomic noise. To improve the radiologic diagnostic value, Brynholf5 recommends taking three images. This would result in a cumulative exposure of approximately 32 microsieverts. A narrow filed of view CBCT of the same area would only expose the patient to 9.8 microsieverts.6-11 The decision was made to take a narrow field of view CBCT to enhance pretreatment anatomical identification of the roots and canals (Fig. 2).
FIGURE 2. Axial and Coronal CBCT views of tooth #14 exhibiting anatomy with three canals. (A) Two canals observed at cervical level. (B) Furcation of buccal canals observed midroot. (C) Three separate canals observed at the apical level.
According to the literature, the presence of three canals in the first maxillary premolar is reported to be present with a frequency of .66-5 percent.12-14 Figure 2A demonstrates what a clinician would observe through the access; note that only two centered canals are evident. Bifurcation of the buccal root occurs about 8mm from the reference point. This is observed in the axial view as it moves apically (buccal bifurcates) (Fig. 2B) and eventually splits into two separate and distinct buccal roots (Fig. 2C). With prior knowledge, the operator is able to plan and execute the instrumentation and obturation (Figs. 3 & 4). In this case, it was determined from the axial view that there was sufficient root structure to safely enlarge the coronal portion of the buccal canal to facilitate treatment of the MB and DB root canals. Most recent endodontic outcome studies have reported a success rate of 94 percent in initial treatment and 85.9 percent in retreatment cases.15 Using three-dimensional imaging to gain knowledge of the root structure and canal anatomy ensures treatment that can be planned and performed with more accuracy, and therefore a more predictable outcome. OH
Dr. Trisha Charland practices endodontics in New York City. She completed both her doctoral training and endodontic residency at The University of Medicine and Dentistry of New Jersey. She is an active member of the ADA, NYSDA and AAE. Dr. Charland is board eligible, most recently lectured at the New York Greater Dental meeting, and published research in the Journal of Endodontics.
Dr. Randolph Todd is a technology inspired Diplomate of the American Board of Endodontics who began his academic dental career at Tuft’s University School of Dental Medicine. Upon completion of a General Practice Residency at the then Cornell University Affiliate Hospital (North Shore University Hospital / LIJ) in New York he pursued his Endodontic specialty training at New York University College of Dentistry (NYUCD). Over the past thirty-three years Dr. Todd has maintained an exclusive private practice Limited to Conventional and Microsurgical Endodontics in NYC. He has educated countless students at various institutions including Stony Brook University College of Dentistry, NYUCD and NSUH/LIJ. He was elected to the Board of Directors for the College of Diplomates of the American Board of Endodontics (COD) and is the current Director of their Board Review Course. Dr. Todd has been a National Lecturer for Carestream Dental (Kodak) on CBCT and was selected to be a Scientific Reviewer for the esteemed Journal of Endodontics.
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