Histological evaluation of energy-intensive irrigation systems for debridement of uninstrumented oval root canals...

This study aimed to evaluate the effectiveness of energy-intensive irrigation activation systems for removing residual pulp tissue in completely uninstrumented oval root canals with different access cavity designs, using histological analysis. Seventy extracted human mandibular premolars with oval root canal morphology and organic tissue remnants were randomly assigned to five irrigation protocols: syringe-needle irrigation (control), Er: YAG laser (SWEEPS, Fotona), Er, Cr: YSGG laser (Waterlase iPlus, Biolase), multisonic high-speed irrigation (GentleWave G4 with ProControl, SonEndo, 5-min protocol), and an extended multisonic protocol (9-min). Each group was further divided according to access cavity design into ultra-conservative and traditional cavities (n = 7). Following irrigation with sodium hypochlorite and EDTA, serial histological sections from the apical third were prepared, and the percentage of residual pulp tissue was quantified using ImageJ software. Data were analyzed using two-way ANOVA with Bonferroni multiple comparisons (p < 0.05). The irrigation activation system significantly affected residual tissue percentages (p < 0.001; η²=0.736), whereas access cavity design showed no significant effect (p = 0.965). Syringe-needle irrigation demonstrated the highest residual tissue values (≈ 20%). Both laser activation systems significantly reduced residual tissue compared with needle irrigation but showed comparable performance (≈ 4-6%). Multisonic high-speed irrigation further improved canal cleanliness, with the 5-min protocol showing lower residual tissue values (≈ 2%), and the extended 9-min protocol achieving the lowest percentages (< 1%), approaching near-complete debridement. Within the limitations of this in vitro histological study, energy-intensive irrigation systems significantly improved the removal of residual pulp tissue in uninstrumented oval root canals. The extended multisonic irrigation protocol demonstrated the highest debridement efficiency under the tested conditions. These findings may inform future minimally invasive endodontic strategies; however, they should not be interpreted as supporting the clinical replacement of mechanical instrumentation.