In Vitro Antimicrobial Efficacy of Irrigants With Ni-Ti Instruments on Mixed Biofilm in Premolar Root Canals With Conservative Access Cavity.

Conservative access cavity (ConsAC) has been increasingly advocated to preserve tooth structure, but its effect on disinfection efficacy against complex biofilms remains unclear. This study evaluated the effectiveness of different irrigants combined with Ni-Ti instruments on mixed biofilms of Enterococcus faecalis and Candida albicans in maxillary premolars with ConsAC or traditional access cavity (TradAC). A total of 208 extracted intact premolars were divided into ConsAC and TradAC groups. Root canals were infected with mixed biofilms and treated with 2.5% NaOCl, 2% CHX or 1% farnesol, followed by preparation using ProTaper Gold (PTG) or XP-endo Shaper (XPS). Efficacy was assessed using CFU counting, SEM, and CLSM. PTG was more effective than XPS under the same conditions. NaOCl showed superior antimicrobial activity compared with CHX and farnesol. TradAC achieved better microbial reduction than ConsAC. This study provides evidence-based insights into the disinfection performance of different irrigation-instrument combinations under varying access designs.