Apical Extrusion of Bacteria during Canal Preparation: A Systematic Review of Laboratory Studies.

INTRODUCTION: Apical extrusion of bacteria is an unintended event that occurs during the chemical-mechanical preparation of infected root canals. Flare-ups and the spread of infection to periradicular tissues are possible consequences. This systematic review aimed to determine which type of engine-driven nickel-titanium systems, reciprocating or rotary, promote greater bacterial extrusion. Studies that compared manual and engine-driven systems or different brands of rotary instruments were also analyzed as a secondary objective. METHODS: Searches were performed in PubMed, Embase, Web of Science, Scopus, and ProQuest up to April 2024. Ex vivo studies that quantified the apical extrusion of bacteria comparing different instrumentation systems were included. The studies were critically assessed using a customized checklist. RESULTS: Of the 4938 articles initially retrieved, 38 were selected for full-text reading and 35 were included in this review. Thirteen studies compared rotary and reciprocating instruments, 11 compared manual and engine-driven systems, and 11 compared different rotary instruments. Among the 13 studies comparing rotary and reciprocating systems, 5 reported greater bacterial extrusion with the rotary systems, 5 found no significant differences, and 3 reported mixed results. The available evidence indicates a similar or greater apical extrusion of bacteria with rotary systems compared to reciprocating instruments. Additionally, manual preparation is associated with significantly greater bacterial extrusion than the 2 engine-driven methods. The results varied across studies primarily due to methodological differences, particularly the instrumentation systems employed. CONCLUSION: Rotary systems extrude similar or greater quantities of bacteria than reciprocating systems. Conversely, manual instrumentation promotes greater bacterial extrusion than the 2 engine-driven methods.