Impact of Dentin Conditioning and Sealer Modification With Chitosan-Hydroxyapatite Nanocomplexes on the Antibacterial and Mechanical Characteristics of Root Dentin

Abstract

IntroductionThis study aimed to characterize the effectiveness of dentin conditioning with bio-mineralizable chitosan-hydroxyapatite precursor (CS-HA) nanocomplexes alone or associated with tricalcium silicate sealer (TCS/CS-HA) on the mechanical property and antibiofilm efficacy in root dentin. MethodsFlow tests were performed following ISO6876:2012 specifications. Solubility was measured. Micromorphology was assessed using scanning electron microscopy (SEM). Nanohardness/elastic modulus were also determined. Fracture resistance was determined on lower premolars that were prepared, and randomly distributed among 7 groups (n = 8/group), including the control, CS-HA dentin-conditioning, and root canal–filled groups. Similar canal preparation/distribution procedure was followed to test the antibacterial effect on Enterococcus faecalis–infected roots. Descriptive statistics was used to report SEM findings. Flowability results were analyzed using paired t test. Multiple comparisons from solubility, fracture, and antibacterial assays were assessed by one-way analysis of variance–Tukey's tests. ResultsTCS/CS-HA showed optimal flow and no effect on solubility after immersion for 4 weeks (P > .05). TCS/CS-HA significantly increased nanohardness and elastic modulus (210 ± 11.3 MPa, 7.9 ± 0.9 GPa) compared with TCS (44.5 ± 7.8 MPa, 2.1 ± 0.3 GPa, P < .05). SEM revealed needle-shaped mineralized structures resulting in fewer voids and a well-adapted sealer-dentin interface in the TCS/CS-HA groups. NaOCl-EDTA irrigation resulted in reduced fracture resistance (444.34 N), whereas CS-HA dentin conditioning alone (928.28 N, P < .05) and CS-HA dentin-conditioning plus CS-HA/TCS resulted in higher fracture resistance (1134.06 N, P < .05). CS-HA dentin conditioning also reduced bacteria by 2.04 log (4.50 ± 0.43) from the initial bacterial load (6.54 ± 0.07, P < .05). There was further bacterial reduction when CS-HA–conditioned root canals were filled with TCS or TCS/CS-HA (0.00 to 0.98 ± 0.57, P > .05). ConclusionDentin modification with CS-HA increased the fracture resistance of root dentin, and decreased the residual bacterial burden. TCS/CS-HA potentiated the nanomechanical and physical properties of TCS.