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instrumentation and obturation CE article | Radiographic appearance of filled root canal systems Summary and conclusions Prepared and filled canals should demonstrate a homogenous radiopaque appearance, free of voids and filled to working length. The fill should approximate canal walls and extend as much as possible into canal irregularities such as an isthmus or a c-shaped canal system. This is difficult to achieve clinically and frequently requires the clini- cian to use a thermoplastic obturation technique. This complicated procedure may benefit from the use of the dental operating microscope. Other anatomical spaces that may be filled in- clude accessory canals that are most common in the apical root third (Fig. 3, mesial and distal root) but may be found in other locations such as the fur- cation. It has been well established that accessory anatomy may contribute to periapical periodon- titis34 but clinical experience suggests the role of accessory anatomy in causing bone resorption is comparatively small. Indeed, it appears that filling accessory canals is not predictable and not per se a prerequisite for success.35 In order to avoid overextension of root filling material into the periapical tissue, specifically in the mandibular canal, it is recommended to accu- rately determine working length to prevent de- struction of the apical constriction. For infected root canal systems, it seems that the best healing results are achieved when the working length is slightly short of the tip of the root, as visible on a radiograph.25, 36 Determination of apical canal anatomy is often dif- ficult. It may be appropriate for second mandibular molars that are in close proximity to the mandibular canal to be referred to a specialist. Overfills are not only an impediment to healing but in the worst case can be associated with permanent nerve damage. In general, undesirable and uncorrectable outcomes of root canal treatment, identifiable on the final radio- graph, include: · Excessive dentine removal during access and in- strumentation. · Preparation errors such as perforation, ledge for- mation and apical zipping. · Presence of an instrument fragment in not fully disinfected canals. · Obturation material overfill and overextension. Each of these outcomes must be documented and the patient notified as they may reduce the likeli- hood of a successful outcome. In cases such as par- esthesia or dysesthesia after an overfill, immediate referral to a surgeon is indicated. Root canal preparation with contemporary instru- ments is a predictable procedure in most cases for a well-trained clinician following established guide- lines. Cases with a recognised high degree of difficulty are best referred to an endodontist. While many cases can be treated successfully in routine practice, the additional training, expertise and technology of en- dodontists is necessary in cases that are beyond the typical spectrum. The best long-term outcomes are obtained when a correctly planned final restoration is placed as soon as possible after root canal treatment is completed (Fig. 4). Root canals may be filled through various methods, typically using a combination of a cement and a solid filling material such as gutta-percha. The specific ob- turation material used appears to have a smaller role on outcomes. Overfills, particularly into the area of the in- ferior alveolar nerve, have the potential to permanently harm a patient. The absence of gross errors that are as- sociated with persistent presence of bacterial infection and excessive dentine removal during access and canal preparation have the greatest impact on outcomes._ This article originally appeared in ENDODONTICS: Colleagues for Excellence, Fall 2016. Reprinted with permission from the American Association of Endodontists, ©2016. The AAE clinical newsletter is available at www.aae.org/colleagues. Editorial note: A complete list of references is available from the publisher and also at www.aae.org/colleagues. Photos/Provided by American Association of Endodontists. contact Dr Ove A. Peters was awarded a degree in dentistry (Dr med dent) from the University of Kiel, Germany, in 1990. After two years in the Department of Neurophysiology at the University of Kiel, he served as an assistant professor of prosthodontics at the University of Heidelberg, Germany, from 1993 to 1996. Peters received post-graduate endodontic training at Zurich University Dental School (1997–2001) and at the University of California, San Francisco (2004–2006). He was an associate professor and head of the faculty practice in restorative dentistry at the University of Zurich from 1996 to 2001. Dr Peters also earned a certificate in endodontics and MS certificate in oral biology from UCSF and was board certified in endodontics in 2010. He received the Louis I. Grossman Award in 2012. Peters is currently a tenured professor and co-chair of the Department of Endodontics at the Arthur A. Dugoni School of Dentistry at the University of the Pacific, San Francisco, and the director of the Advanced Education Program in Endodontology. His main scientific interests are the performance of root canal instruments assessed by mechanical testing methods, three-dimensional imaging and the efficacy of antimicrobial regimes in root canal treatment. More recently, he became involved in endodontic biology and now runs a dental stem cell biology laboratory. Dr Peters has published more than 100 papers in peer-reviewed journals and has lectured extensively both nationally and internationally. He has written multiple chapters in leading textbooks and serves on the review panels and editorial boards of high-impact endodontic journals. He may be contacted at opeters@pacific.edu. roots 3 2017 21