Abstract
AIM: This study aimed to quantify the effect of chitosan-hydroxyapatite precursor nanocomplexes (C-HA) on void reduction in the root canal system and isthmus regions, characterise void distribution patterns and assess sealer-dentin interface adaptation post-conditioning. METHODOLOGY: Vertucci type II and Yin type IV mesial root canals from 24 extracted mandibular first molars were randomly divided into two groups (n = 12): (1) C-HA conditioned and (2) control (deionised water). All canals underwent standardised preparation using ProTaper Next files with 3% NaOCl irrigation (2 mL per file change) and final irrigation with 17% EDTA (5 mL, sonic activation) followed by 3% NaOCl (5 mL) and a final deionised water rinse (5 mL). Before obturation, the C-HA group received 5 min of C-HA solution (2 mg/mL) treatment with active agitation by ProTaper Next X2 gutta-percha cone, while the control group received equivalent water treatment. Canals were obturated using the single-cone technique with Ceraseal. High-resolution Micro-CT (8.6 μm voxel size) quantified void percentages in the entire canal system and isthmus regions, with analysis stratified by coronal, middle and apical thirds. Selected specimens underwent SEM evaluation of interfacial adaptation. Statistical analysis used the independent samples t-test, two-way ANOVA with Tukey's post hoc tests (α = 0.05), and Fisher's exact test. RESULTS: No significant differences related to the canal/isthmus pre-treatment volumes and isthmus characteristics were noted between the two groups. Micro-CT analysis revealed significantly lower void percentages in C-HA-treated canals compared to controls (9.21% vs. 19.01% in the entire canal system and 19.07% vs. 55.65% in the isthmus regions, p < 0.001). Analysis of the void distribution patterns further demonstrated statistically significant differences between the groups in the cervical and middle root thirds (p < 0.05). SEM evaluation showed continuous, gap-free interfaces with bioactive mineralization in C-HA-treated canals, contrasting with discontinuous adaptation and sparse precipitates in controls. CONCLUSION: C-HA dentine conditioning significantly improved obturation quality with Ceraseal bioceramic sealer by reducing voids in isthmus regions and enhancing sealer-dentin interfacial adaptation.