## 7 Discussion  
The integration of clinical examination and diagnostic imaging forms the basis for endodontic diagnosis, decision making, treatment planning, and outcome assessments [3,38]. In recent years, CBCT imaging has become a common diagnostic tool in endodontics. If radiographic imaging is required, it should be carried out with a radiation dose as low as reasonably achievable (ALARA). The effective dose of CBCT scans is higher compared to that used for periapical radiography. The effective dose varies between CBCT scanners, and depending on the region of the jaw being scanned, exposure settings of the scanner, the size of the field of view (FOV), exposure time (s), tube current (mA), and the energy potential (kV) [39,40].Thus, due to its inherent risks of radiation, this use should be justified on an individual basis to ensure that the benefits to the patient exceed the risks [3,41, 42, 43]. An estimation of the predicted benefits to the patient should be based mainly on the efficacy of CBCT as a diagnostic imaging tool for the precisely needed endodontic indication [2,3,18,41,44]. The diagnostic efficacy of a technique is determined by the likelihood of a beneficial outcome when the procedure is conducted under optimal conditions [19]. Efficacy studies offer a means of understanding and comparing the usefulness of diagnostic imaging examinations and procedures [18]. In order to evaluate the influence of diagnostic imaging, it is important to determine the eventual profit of the procedure to the patient in a hierarchical manner. However, this benefit may be subjective and influenced by different perspectives. For example, the ability of diagnostic imaging to provide the finest and most accurate images does not necessarily mean that it will also improve our diagnosis ability or the treatment outcomes [2,18]. The decision to recommend the use of CBCT in endodontics should be supported by studies evaluating its efficacy in the specific clinical situation. [PERSON] and [PERSON] [18] presented a broad, organized method for appraisal of the literature that employs a diagnostic efficacy hierarchical model with a number of levels of evidence assigned to a diagnostic test [18]. This model was used in previous studies to evaluate the diagnostic efficacy of CBCT in endodontic treatment [3,11]. The levels of imaging efficacy relate not only to an evaluation of the technical characteristics of the imaging modality (defined as low levels of efficacy), but also to the efficacy of the technique to help a practitioner make decisions and plan treatment, and the eventual treatment outcome (defined as high levels of efficacy) [3,18]. Traditionally, CBCT has been used mainly for pre-operative evaluations [1,26,27,29,30,31,32,45,46], although the technique can also be used intra-operatively to support the course of treatment [5,47,48] and post-operatively to assess the treatment outcomes [29,35,36]. In six of the studies reviewed, CBCT was performed both pre- and post-operatively [4,12,14,15,28,36]. Intra-operative use of CBCT was found to be beneficial in the treatment of calcified canals in posterior teeth [24] and in its capacity to locate the MB2 canal in maxillary molars [30]. In two studies, CBCT was reported to be more effective than periapical radiography in detecting and following-up periapical lesions [22,35]. However, other results suggest a more questionable contribution of CBCT to the results. Resorption related to root canal infection and apical periodontitis was identified in 61.4% of the cases studied by SEM, whereas only 23.9% were detected by CBCT images [26]. Similarly, there was a significant variation in the PDL space of a healthy tooth as examined by CBCT, and about 19% of cases were wrongly diagnosed as having apical lesions when they were healthy, resulting in an overestimation of disease and overdiagnosis [34]. CBCT is specifically indicated for surgical endodontic treatments, for pre-surgical diagnosis, and treatment planning, and is suggested as a diagnostic method to assess the treatment outcome.