METHODS: A systematic review was undertaken following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive literature search was performed by 2 independent reviewers using a customized search strategy in major Endodontic journals through Scopus until November 2019. Studies investigating root and canal anatomy were included. The selected publications were divided into 7 categories according to the study design: micro-computed tomography (microCT) and cone-beam computed tomography (CBCT) experimental studies (extracted teeth), CBCT and 2D clinical studies, CBCT and 2D case reports in addition to others (i.e. staining and clearing method and root sectioning). The selected studies were evaluated according to three domains: 1) Criteria for study sample selection; 2) Criteria for methodological procedures and 3) Criteria for detection and evaluation.

RESULTS: After the removal of duplicated and irrelevant papers, 137 articles were included. Results showed that microCT studies reported accurately the tooth type, number of teeth, classifications used, qualitative and/or quantitative analysis (if required) and the evaluation process. However, sample size calculation, calibration, and reproducibility were not reported in the majority of microCT studies. CBCT clinical studies presented information for the type of study, inclusion/exclusion criteria, number of patients, tooth type, and number of teeth. However, the majority did not report sample size calculation and calibration of examiners. Radiographic exposure descriptions and classifications used were not reported adequately in CBCT and 2D case reports. Sample size calculation, calibration and reproducibility were not reported in staining and clearing method.

METHODS: A comprehensive analysis was undertaken on the most common, existing classification for root canal morphology. The advantages and potential applications of a new system for classifying roots and canal systems in research and clinical practice are discussed.

RESULTS: The analysis demonstrates deficiencies of the existing classification including lack of information on the number of roots, pulp chamber outline, lack of clarity in multi-rooted teeth, inability to define complex root canal configurations. The new coding system addresses the root and canal morphology in an accurate and systematic manner to provide detailed information of the tooth, root and canal anatomical features.

METHODOLOGY: A total of 700 maxillary premolars were examined using CBCT in an Egyptian subpopulation. The number of roots was identified, and root canal configurations were classified according to Vertucci's classification and a new system for classifying root and canal morphology. In addition, the position where roots bifurcated and the levels where canals merged or diverged were identified. Fisher's exact test and independent t-test were used for statistical analysis, and the level of significance was set at 0.05 (P = 0.05).

METHODS: This study enrolled patients (N = 36) who required root canal retreatment (RCR) on mandibular molar teeth, presented with periapical lesions with periapical index scores of 2 or 3, and had a pain visual analog scale (VAS) <50 and a percussion pain VAS <50. The participants were divided into 2 groups: (1) patients scheduled for RCR followed by LLLT (n = 18) and (2) patients scheduled for RCR followed by a mock LLLT (placebo) (n = 18). Postoperative pain was assessed using the VAS. Data were collected and statistically analyzed with the chi-square test, the independent sample t test, and the Mann-Whitney U test (P = .05).