effect of treatment variables on apical extrusion of debris during root canal retreatment: a systematic review and meta-analysis of laboratory studies

Background. this study aimed to systematically and comprehensively review the effect of various treatment variables on apically extruded debris (aed) during non-surgical root canal retreatment (nsrcrt). methods. the study protocol is shared in the open science framework database (https://osf. io/kjtdg/?view_only=17060180705745ec9dae9a01614f3880). an electronic search was conducted up to july 2022 to reveal related studies. two reviewers critically assessed the studies for eligibility against inclusion and exclusion criteria and data extraction. quantitative data synthesis was performed, and the risk of bias in the studies was also evaluated. results. forty-six studies were included in the systematic review and 14 in the meta-analysis. conflicting or limited evidence was found for the effect of sealer type, obturation technique, and solvent use. the manual instrumentation increased the amount of aed compared to rotary instrumentation during the removal of filling materials (p<0.001). there was no significant difference in the amount of aed between the use of rotary and reciprocating files during the removal of filling materials (p=0.181). conclusion. rotary instruments can be recommended instead of manual instruments during the removal of filling materials to control the amount of aed. further studies with a low risk of bias are needed to clarify the effect of other treatment variables on aed during nsrcrt.