Removal efficacy and cytotoxicity of a calcium hydroxide paste using N-2-methyl-pyrrolidone as a vehicle

Synergistic effects of reduced graphene oxide on the antibacterial activity of calcium hydroxide-based intracanal medicaments containing different vehicles

PURPOSE

This study investigated the synergistic effects of reduced graphene oxide (RGO) on the antibacterial activity of three calcium hydroxide-based intracanal medicaments with different vehicles.

METHODS

Multispecies biofilms were cultured in a bovine root canal model. Intracanal medicaments containing nonaqueous vehicles, including N-methyl-2-pyrrolidone (NMP; CleaniCal), propylene glycol (PG; UltraCal XS), and polyethylene glycol (PEG; Calcipex II), were placed in the model. The synergistic effects of RGO were evaluated by analyzing colony-forming units, extracellular deoxyribonucleic acid (eDNA) levels, and findings from confocal laser-scanning microscopy (CLSM) and scanning electron microscopy. To evaluate the cytotoxicity of each vehicle, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed. To determine whether RGO altered the physicochemical properties of the medicaments, flowability and pH were measured. A P-value of <0.05 was considered to indicate statistical significance.

RESULTS

In the CleaniCal group, bacterial viability, eDNA levels, and extracellular polymeric substrate (EPS) were significantly lower in the presence of RGO. However, only bacterial viability significantly differed in the other groups. PEG resulted in the highest cell viability among the vehicles. Furthermore, there was no significant difference in flowability or pH in relation to the inclusion of RGO.

CONCLUSION

The results suggest that RGO enhances the antibacterial effect of intracanal medicaments containing NMP.

Rheological properties and handling characteristics of four injectable calcium hydroxide pastes

The aim of this study was to investigate the rheological properties and handling characteristics of four brands of injectable calcium hydroxide pastes (Calcipex II, CleaniCal, DiaPaste, Well-Paste). Shear viscosity was measured with a rotational rheometer. A universal mechanics analyzer assembled in the laboratory was used to quantify the force for extrusion and extruded weight of the materials. The apical pressure during injection into an artificial root canal was measured using a pressure sensor. All materials exhibited pseudoplastic behavior. The force for extrusion was highest for DiaPaste, and lowest for CleaniCal, while the extruded weight was lowest for DiaPaste and highest for CleaniCal (p<0.05), indicating a need for caution when using CleaniCal. However, the pressure generated at the apex may vary depending on the shape, and taper of the needle tip, as well as the viscosity of the materials.

Lipoteichoic Acid from Lacticaseibacillus rhamnosus GG as a Novel Intracanal Medicament Targeting Enterococcus faecalis Biofilm Formation

The demand for safe and effective endodontic medicaments to control Enterococcus faecalis biofilms, a contributor to apical periodontitis, is increasing. Recently, lipoteichoic acid (LTA) of family Lactobacillaceae has been shown to have anti-biofilm effects against various oral pathogens. Preliminary experiments showed that LTA purified from Lacticaseibacillus rhamnosus GG (Lgg.LTA) was the most effective against E. faecalis biofilms among LTAs from three Lactobacillaceae including L. rhamnosus GG, Lacticaseibacillus casei, and Lactobacillus acidophilus. Therefore, in this study, we investigated the potential of Lgg.LTA as an intracanal medicament in human root canals infected with E. faecalis. Twenty eight dentinal cylinders were prepared from extracted human teeth, where two-week-old E. faecalis biofilms were formed followed by intracanal treatment with sterile distilled water (SDW), N-2 methyl pyrrolidone (NMP), calcium hydroxide (CH), or Lgg.LTA. Bacteria and biofilms that formed in the root canals were analyzed by scanning electron microscopy and confocal laser scanning microscopy. The remaining E. faecalis cells in the root canals after intracanal medicament treatment were enumerated by culturing and counting. When applied to intracanal biofilms, Lgg.LTA effectively inhibited E. faecalis biofilm formation as much as CH, while SDW and NMP had little effect. Furthermore, Lgg.LTA reduced both live and dead bacteria within the dentinal tubules, indicating the possibility of minimal re-infection in the root canals. Collectively, intracanal application of Lgg.LTA effectively inhibited E. faecalis biofilm formation, implying that Lgg.LTA can be used as a novel endodontic medicament.

Removal of Calcium Hydroxide Paste Leaked Into the Maxillary Sinus

Calcium hydroxide is a widely used endodontic medicament with antibacterial activity. When excessive pressure is applied during injection of calcium hydroxide paste or apical perforation occurs, calcium hydroxide can leak into the maxillary sinus and is adsorbed onto the sinus membrane. Although a leakage of calcium hydroxide may not usually cause clinical symptoms, when a large amount of leakage occurs, it can cause degeneration of adjacent tissue and functional disorder, requiring immediate surgical removal. However, due to adsorption to the sinus membrane, calcium hydroxide leaked into the maxillary sinus is difficult to remove completely. Here, we describe the case of a 47-year-old patient in whom a large amount of calcium hydroxide leaked into the maxillary sinus and was successfully removed using modified endoscopic-assisted sinus surgery, and favorable bone regeneration and sinus membrane regeneration were achieved. In addition, histological and ultrastructural changes of the membrane resulted from the calcium hydroxide were presented.

Sonic irrigation for removal of calcium hydroxide in the apical root canal: A micro-CT and light-coupled tracking analysis

Objective

This study aimed to evaluate the efficacy of three sonic irrigation systems for removal of calcium hydroxide dressing from the apical root canal.

Materials and methods

A total of 96 single-rooted teeth in three categories of root canal curvatures (straight: 0–5°, moderate: 6–20°, and severe: > 20°) were allocated to four groups: conventional needle irrigation, EndoActivator, EQ-S, and Vibringe. The root canals were instrumented using Protaper NEXT and filled with calcium hydroxide. After removal of calcium hydroxide, the remaining volume of calcium hydroxide was measured by micro-CT analysis. Data were compared among root canal curvatures and irrigation systems using the Kruskal-Wallis test and Mann-Whitney test (p < .05). The oscillating range of each irrigation system was measured using light-coupled motion tracking.

Results

The volumes of calcium hydroxide remaining in the canals with severe curvature were significantly higher than in those of straight curvature (p < .05). In the canals of moderate or severe curvature, EQ-S showed the highest removal percentage, followed by EndoActivator, Vibringe, and needle irrigation (p < .05). Light-coupled tracking showed the largest oscillating range in EQ-S (p < .05).

Conclusions

Sonically activated irrigation systems with a flexible tip can be beneficial for calcium hydroxide intracanal dressing removal in the curved apical canals.

Characterization, Antimicrobial Effects, and Cytocompatibility of a Root Canal Sealer Produced by Pozzolan Reaction between Calcium Hydroxide and Silica

This study aimed to evaluate a newly developed pozzolan-based bioceramic sealer (PZBS) regarding setting time, radiopacity, antibacterial effect, and cytocompatibility. The PZBS was manufactured by mixing calcium hydroxide and silica. The pozzolan reaction was verified by identification of calcium silicate hydrate (C-S-H) using X-ray diffraction analysis. The initial setting time and radiopacity were measured using the ISO 6876/2012 protocol in comparison with other commercially available calcium silicate (CS) sealers. The antibacterial effect of PZBS on biofilms cultured in the bovine root canal was evaluated by measurement of colony-forming units and volume of biofilms in comparison with other calcium hydroxide pastes. The morphological features of the biofilms were observed by scanning electron microscopy (SEM). The cytocompatibility of PZBS was assessed by the viability of bone marrow–derived mesenchymal stem cells and scratch wound healing rate in comparison with other CS sealers. The morphology of the cells cultured on the tested sealers was observed by SEM. The detection of the CS peak confirmed the formation of C-S-H. The initial setting time of PZBS was around 11 h, which was twice as long as the other tested sealers. The radiopacity of PZBS was 4.3 mm/Al, which satisfied the ISO criteria. The antibacterial effect and cytocompatibility of PZBS were comparable to those of the commercially available intracanal medicaments and CS endodontic sealers, respectively. The PZBS has the potential to be used for root canal obturation, and is expected to exert a favorable antibacterial effect.

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.

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

This study investigated the effect of a calcium hydroxide (CH) paste (CleaniCal^®) containing N-2-methyl pyrrolidone (NMP) as a vehicle on Enterococcus faecalis (E. faecalis) biofilms compared with other products containing saline (Calasept Plus™) or propylene glycol (PG) (Calcipex II^®).