Apical Third Cleaning Efficiency of Hand, Rotary, and Reciprocating Root Canal Instrumentation: A Quantitative In Vitro Scanning Electron Microscopic Study

OBJECTIVE: This in vitro study quantitatively evaluated the cleaning efficiency of hand, rotary, and reciprocating instrumentation systems in the apical third of root canals using scanning electron microscopy (SEM). MATERIALS AND METHODS: Sixty extracted single-rooted human premolars with single canals were randomly assigned to three groups (n = 20 each): Group I: hand instrumentation using stainless steel K‑files; Group II: rotary preparation with ProTaper Next (Dentsply Maillefer, USA); and Group III: reciprocating shaping using WaveOne Gold (Dentsply Sirona, USA). Instrumentation protocols were standardized in working length, irrigation sequence (3% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA)), and drying. Following preparation, roots were grooved, split longitudinally, gold sputter-coated, and examined under SEM (×1500) for quantitative assessment of the apical third using ImageJ software (National Institutes of Health, Bethesda, MD, USA). Smear layer, pulpal debris, and inorganic debris were scored on a four-point scale. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). RESULTS: Hand instrumentation showed significantly lower mean scores for smear layer (3.00 ± 0.92), pulpal debris (2.40 ± 0.50), and inorganic debris (2.60 ± 0.50) compared to rotary and reciprocating systems (p < 0.001). No statistical difference was observed between the rotary and reciprocating groups across evaluated parameters (p > 0.05). CONCLUSION: Within the limitations of this study, hand instrumentation with stainless steel K‑files achieved superior apical cleanliness compared to ProTaper Next and WaveOne Gold systems. The effective scraping and debris dislodgment capability of hand files contributed to enhanced smear layer and debris removal in the apical third, underscoring their clinical relevance in achieving improved disinfection in complex canal anatomies.