Effect of a calcium hydroxide-based intracanal medicament containing N-2-methyl pyrrolidone as a vehicle against Enterococcus faecalis biofilm

Synthesis, structure, and theoretical studies of a calcium complex of a unique dianion derived from 1-methyl-pyrrolidin-2-one

The title compound, catena-poly[[tetra-kis-(1-methyl-pyrrolidin-2-one-κO)calcium(II)]-μ-(E)-1,1'-dimethyl-2,2'-dioxo-1,1',2,2'-tetra-hydro-[3,3'-bipyrrolyl-idene]-5,5'-bis-(thiol-ato)-κ2 O:O'], [Ca(C10H8N2O2S2)(C5H9NO)4] n , 1, crystallizes in the triclinic space group P . The crystal studied was twinned by non-merohedry via two different twofold operations, about the normals to (001) and (10), giving four twin domains with refined occupancies of 0.412 (4), 0.366 (4), 0.055 (1), 0.167 (4). The Ca atoms are located on centers of inversion. Each Ca is surrounded by four 1-methyl-pyrrolidin-2-one (NMP) ligands and coordinated through one of the two O atoms to two (E)-1,1'-dimethyl-2,2'-dioxo-1,1',2,2'-tetra-hydro-[3,3'-bipyrrolyl-idene]-5,5'-bis-(thiol-ate), [C10H8N2O2S2]2-, dianions (abbreviation: DMTBT). This dianion thus facilitates the formation of a 1-D polymer, which propagates in the [011] direction. These ribbons are linked by inter-molecular C-H⋯S inter-actions. Each Ca atom is in an octa-hedral CaO6 six-coordinate environment with Ca-O bond lengths ranging from 2.308 (6) to 2.341 (6) Å, cis bond angles ranging from 88.2 (2) to 91.8 (2)° and the trans angles all 180° due to the Ca atoms being located on centers of inversion. Theoretical calculations were carried out using density functional theory (DFT) and the results showed that although the central DMTBT dianion is planar there is likely some resonance across the central bond between both aza-pentyl rings, but this is not sufficient to establish a ring current. The calculated UV-vis spectrum shows a peak at 625 nm, which accounts for the deep blue-purple color of solutions of the complex.

Combined Effect of Melittin and DNase on Enterococcus faecalis Biofilms and Its Susceptibility to Sodium Hypochlorite

Biofilm communities are tolerant to antimicrobials and difficult to eradicate. This study aimed to investigate the effect of melittin, an antimicrobial peptide, either alone or in combination with deoxyribonuclease (DNase), an inhibitor of extracellular deoxyribonucleic acid (eDNA), against Enterococcus faecalis (E. faecalis) biofilms, and biofilm susceptibility to sodium hypochlorite (NaOCl). Biofilms of E. faecalis were developed in root canals of bovine teeth. The biofilms were treated with distilled water (control), melittin, DNase, or DNase+melittin. The antibiofilm effects of the treatments were analyzed using colony forming unit (CFU) assay, crystal violet staining, confocal laser scanning microscopy (CLSM), and field emission scanning electron microscope (FE-SEM). The susceptibility of DNase+melittin-treated biofilms to NaOCl (0%, 2.5% and 5%) was investigated by the CFU assay. The data were statistically analyzed using one-way analysis of variance, followed by Tukey's test. A p-value of <0.05 was considered significant. Specimens treated with DNase+melittin showed a more significant decrease in the CFUs, eDNA level, and biofilm formation rate than those treated only with melittin or DNase (p < 0.05). CLSM analysis showed DNase+melittin treatment significantly reduced the volume of biofilms and extracellular polymeric substance compared to either treatment alone (p < 0.05). FE-SEM images showed a high degree of biofilm disruption in specimens that received DNase+melittin. 2.5% NaOCl in specimens pretreated with DNase+melittin showed higher antibacterial activity than those treated only with 5% NaOCl (p < 0.05). This study highlighted that DNase improved the antibiofilm effects of melittin. Moreover, DNase+melittin treatment increased the susceptibility of biofilms to NaOCl. Thus, the complex could be a clinical strategy for safer use of NaOCl by reducing the concentration.