Outcomes reporting in systematic reviews on non‐surgical root canal treatment: A scoping review for the development of a core outcome set

BACKGROUND: Studies related to non‐surgical root canal treatment are amongst the most frequently performed clinical studies in endodontics. However, heterogeneity in reporting outcomes and lack of standardization is a significant challenge to evidence synthesis and guideline development. OBJECTIVES: The aims of the present scoping review were to (a) identify outcomes reported in systematic reviews evaluating non‐surgical root canal treatment; (b) identify how and when the reported outcomes were measured; (c) assess possible selective reporting bias in the included studies. The information obtained in this study should inform the development of a core outcome set (COS) for non‐surgical root canal treatment. METHODOLOGY: Structured literature searches were performed to identify systematic reviews on non‐surgical root canal treatments published in English between January 1990 and December 2020. Two reviewers undertook study selection and data extraction. Outcomes were categorized according to a healthcare taxonomy into five core areas (survival, clinical/physiological changes, life impact, resource use, and adverse events). The outcome measurement tools and length of follow‐up were recorded. RESULTS: Seventy‐five systematic reviews were included, of which 40 included meta‐analyses. Most reviews reported on physiological and clinical outcomes, primarily pain and/or radiographic assessment of periapical status, and a variety of measurement tools and scales were used. Few reviews focused on tooth survival, life impact, resources, and adverse events. The heterogeneity amongst the reviews was large on all parameters. Less than 40% of the reviews assessed the risk of selective reporting. DISCUSSION: Overall aims of the included reviews were highly heterogenic; thus, outcomes and how they were measured also varied considerably. Patient‐centred outcomes and the use of resources were rarely reported on. CONCLUSIONS: Most studies reported on physiological and clinical outcomes, in particular pain and/or radiographic healing. Measurement tools, scales, thresholds, and follow‐up periods varied greatly within each outcome, making comparison across studies complicated. Less than 40% of the reviews assessed risk of selective reporting; thus, selective bias could not be ruled out. The presented information on reported outcomes, measurement tools and scales, and length of follow‐up may guide the planning of future research and inform the development of a COS for non‐surgical root canal treatment.