METHODS: An electronic search in PubMed and major endodontic journals was conducted using appropriate key words to identify investigations that examined the effectiveness of obturation material removal assessed by micro-computed tomography.

RESULTS: Among 345 studies, 22 satisfied the inclusion criteria. Seven studies compared hand instrumentation with Nickel-Titanium rotary or reciprocating systems. Three studies investigated rotary systems, and another three studies explored reciprocation. Eight studies compared rotary systems and reciprocation in removing filling materials from the root canal system. Other factors, such as the role of solvents and irrigant agitation, were discussed.

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.

DATA SOURCES: Literature searches of PubMed, Scopus, Cochrane Library, Trip Database, Web of Science and Open Grey databases were conducted from their inception until November 2018 with no language restriction. Hand searching of most likely relevant journals was performed. The review followed the PRISMA guidelines.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS AND INTERVENTIONS: Studies that compared pre-clinical endodontic training using extracted teeth and artificial teeth were included.

STUDY APPRAISAL AND SYNTHESIS METHODS: The quality of included studies was appraised by Joanna Briggs Institute Critical Appraisal tools. The findings were tabulated and summarized according to their outcomes with distinct narrative syntheses.

RESULTS: Five studies were included. The component studies included 359 operators in total, mainly consisting of undergraduate students (97%, n = 349) and 10 endodontists (3%). Forty-seven per cent (n = 170) operated on artificial teeth only, whilst 19% (n = 67) worked primarily on extracted teeth, with the final treatment outcome being evaluated by independent observers using objective criteria. Operators in two studies (34%, n = 122) used both artificial teeth and ET and compared their experiences in surveys. Regarding technical outcomes, no significant differences between training with artificial teeth and extracted teeth were found, but the performance tended to be better in artificial teeth than extracted teeth. Operators trained solely on artificial teeth appeared to be adequately educated for subsequent root canal treatment (RCT) in the clinical setting.

LIMITATIONS: Due to the scarcity of research on the topic overall, and the methodological variation between the studies, it was not possible to perform a quantitative analysis (meta-analysis).

METHODS: Enterococcus faecalis, Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia were suspended as follows: Iso-osmotic group 0.9% NaCl; Hypo-osmotic group "ultrapure water"; Hyper-osmotic group 9% NaCl solution for 120 hours before exposure to 0.0001% NaOCl for 10 minutes. Quantitative analyses of viable cells were performed at 0 and 120 hours and after exposure to NaOCl to obtain colony forming units (CFU/mL). A linear mixed-effects model was used to find the association between mean CFU/mL (logarithmic transformation) and the interaction of solution Group and Time (P<0.001).

RESULTS: F. nucleatum, P. gingivalis and P. intermedia did not survive after 24 hours in any of the solutions and were excluded from further testing. For S. sanguinis there were significant differences at each time interval, when holding solution group constant. After 120 hours, the Hyper-osmotic group presented with the highest CFU/mL and was significantly different to the Iso-osmotic group (P<0.001). For E. Faecalis, there was a significant difference for each pairwise comparison of time (P<0.001) in mean CFU/mL between 0 hours and 120 hours for the Iso-osmotic and Hyper-osmotic groups. At 120 hours, no significant differences were found between the three groups. Significant differences were also found between 0 hours and Post-NaOCl administration, and between 120 hours and Post-NaOCl administration for all three groups (P<0.001). Exposure to NaOCl after hypo-osmotic stress was associated with significantly less CFU/mL for S. sanguinis compared to hyperosmosis and iso-osmosis (P<0.001) and for E. Faecalis only compared to hyperosmosis (P<0.001).

METHODS: A literature search was performed in 3 electronic databases for articles published before August 2018. Randomized clinical trials published in English that compared PP between machine-assisted agitation and syringe irrigation with needles as part of nonsurgical root canal treatment were included. Two authors were independently involved in the article selection process, data extraction, and assessment of the quality of included studies using the revised Cochrane risk of bias tool. The pooled effect estimates of the standardized mean difference (SMD) between machine-assisted agitation and syringe irrigation with needle was calculated by a random effects-modeled meta-analysis. A subgroup meta-analysis was performed. The quality of evidence was evaluated by the Grading of Recommendations, Assessment, Development and Evaluations approach.

RESULTS: Six studies were included for systematic review. Meta-analysis was performed using 3 studies and showed that machine-assisted agitation resulted in less PP compared with syringe irrigation with needle at 24 hours (SMD = -0.73; 95% confidence interval, -1.04 to -0.42; I2 = 30.6%) and 48 hours (SMD = -0.60; 95% CI, -0.85 to -0.35; I2 = 0%). The quality of evidence by Grading of Recommendations, Assessment, Development and Evaluations for the PP outcomes (24 hours and 48 hours) was graded as "moderate" quality.