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C.E. article_ microscopes I mission on Dental Accreditation to add a micro- scope proficiency standard to the CODA educational standards for postgraduate endodontic programs in 1998. The latest standard requires the teaching of magnification devices “beyond that of magnifying eyewear” at an in-depth level, which is the highest of the levels of knowledge prescribed by CODA.5 Based on two surveys, in 1999 and 2008, the acces- sibility and use of the microscope by endodontists increased from 52 percent to 90 percent.6,7 It is now also increasingly being used by other specialties8 and in dental education.9 _Microscope use for nonsurgical procedures For the endodontic practitioner, the dental mi- croscope is useful for diagnosis and clinical pro- cedures. The microscope may aid diagnostically in identifying caries, insufficient crown or restorative filling margins (Fig. 1), or assessing craze or fracture lines. During root canal therapy, magnification and illumination provided by the operating microscope aids with caries removal, access preparation, re- moval of pulp chamber calcifications, identification of root canal orifices, identification of cracks and fracture lines (Fig. 2), and the treatment of internal resorptions. Under the microscope, subtle changes in dentin color and texture become apparent, such as developmental lines on the pulp floor guiding the practitioner toward root canal orifices, or the darker color of the pulp floor itself, allowing the practitioner safer dentin removal. High magnification can help in the localization and instrumentation of obstructed and calcified canals, the identification of canal bifurcations (Fig. 3), the removal of canal obstructions such as denticles and calcifications, and obturation (Figs. 4a,b). Ad- ditional primary endodontic procedures benefiting from microscope use include vital pulp therapy and regenerative endodontics by allowing careful and gentle manipulation of the pulpal tissues or a blood clot, respectively. Enhanced vision also aids in the treatment of dental anomalies, such as dens invagi- natus, or fused teeth. In endodontic retreatments, the microscope is helpful in identifying and removing leftover filling materials, such as sealer remnants, pastes or gutta- percha,10 silver points and carrier-based materials, posts or fractured instruments11 (Figs. 5a-d). It also aids in nonsurgical perforation repair, allowing the practitioner to clean the perforation site and place the perforation repair material more precisely.12,13 _Microscope use for surgical procedures Surgical endodontics has been completely trans- formed by microscopic procedures. For many years Fig. 2 Fig. 3 Fig. 4a Fig. 4b Fig. 2_Evaluation of extent of mesial fracture line (arrows) in left second maxillary molar. Microscopic inspection confirmed restorability. Fig. 3_Deep canal bifurcation. Microscope-controlled filling of first canal just below split (arrow). Fig. 4a_Situation after irreversible pulpitis of left maxillary first molar two weeks after delivery of fixed partial denture. High magnification allowed for identification and treatment of three mesio-buccal canals through existing restoration. Fig. 4b_Post-operative radiograph. surgical burs and amalgam for root-end fillings were the standard of care. The incorporation of the microscope, and also to a certain degree the endoscope, together with the use of ultrasonic tips and biocompatible filling materials, has evolved the classical apicoectomy into modern endodontic microsurgery.14 All steps of endodontic microsur- gery are carried out under varying degrees of mag- nification, including flap preparation, osteotomy, identification of root apices, root-end resection, inflammatory tissue removal, observation of the resected root surface (Fig. 6), root-end preparation, root-end filling, and suturing.15 The microscope is also helpful for cervical or external resorption or perforation repairs. _Treatment effects There has been great debate over whether the use of magnification would actually increase the success rate of endodontic procedures. It is an accepted fact in endodontics that microbes and their endotoxins are responsible for the majority of inflammatory periapical lesions. Healing of these lesions in cases of a diagnosis of pulp necrosis has been associated with disinfection of the root canal system, reduction of the microbial content, filling of the root canal system and the permanent restora- tion of the tooth. It is thus assumed that the identification and treatment of all parts of the root canal system in- crease the chances of a successful treatment and good long-term prognosis. Ample literature has been published with regard to the identification of addi- tional canals with the help of higher magnification roots 1_ 2018 I 07