BACKGROUND AND OBJECTIVE

Orthodontic brackets predispose dental biofilm accumulation causing caries and gingivitis. Chlorhexidine is an adjunct to mechanical plaque removal, but has side-effects (tooth staining, bacterial resistance) due to long term use. This study tested the efficacy of Photodynamic Therapy, which produces reactive oxygen species, to reduce Streptococcus mutans in dental biofilm on orthodontic brackets.

A 5-day S. mutans biofilm was grown on forty enamel-bracket specimens. Thirty-nine specimens were randomized to three treatment groups: A. Distilled Water; B. 0.12% Chlorhexidine (CHX); C. Photodynamic Therapy (PDT) using Toluidine Blue O (TBO) as a photosensitizer, activated by red LED (630nm). After treatment, one random specimen from each group was viewed under Environmental Scanning Electron Microscopy (ESEM); the other 12 specimens, biofilms were collected, weighed, and cultured onto BHI agar plates to determine the number of CFU/mg. For baseline evaluation, one clean and one untreated specimens were preserved for ESEM.

Based on Tukey HSD test, group A had the most S. mutans (37.0573 CFU/mg) and was significantly different (pCONCLUSION

Both Photodynamic Therapy and 0.12% Chlorhexidine showed a significant reduction of S. mutans in dental biofilm on orthodontic brackets. However, there is no significant difference between them in reducing S. mutans CFU/mg. Photodynamic therapy could be an alternative adjunctive tool to mechanical removal of plaque adhered to orthodontic brackets.

OBJECTIVES: This study aimed to compare the effectiveness of ultrasound and acoustic and laser cleaning of curved root canals. METHODS: A total of 92 molars with independent root canals with a curvature of 20°-40° were prepared and standardized at 04 25# and stained with gentian violet solution for 72 h. Among them, 52 were randomly divi-ded into four groups for final rinsing (n=13): NI group, PUI group, EDDY group, and PIPS group. Ten samples in each group were cut horizontally along the long axis perpendicular to the root and divided into curved upper, curved, and apical segments. Images were taken with a stereomicroscope and Image J measurements were taken to calculate the depth of rinse penetration. The remaining three samples from each group were split along the long axis of the dentin, photographed by scanning electron microscope to record the dentin tubule exposure and staining layer, and scored for staining layer by double-blind method. SPSS 26.0 software was used to perform statistical analysis and select the best flushing method. An extra 40 samples were randomly divided into four groups for detection of flushing fluid penetration depth (n=10): 10, 20, 30, and 40 s. RESULTS: In the upper part, the mean depth of infiltration was not significantly different between the experimental and control groups (P>0.05). The PIPS group had a significantly lower smear layer score than the control group and the EDDY group (P<0.01). In the curved segment, the mean depth of infiltration was significantly greater in the PUI group than in the control group (P<0.05); the tarnish layer score was lower in each experimental group than in the control group. At the top, the mean depth of infiltration was greater in the PUI and PIPS groups than in the control group (P<0.05), and the smear layer score was lower in the PIPS group than in the other groups (P<0.05). After the time was changed, the depth of infiltration of PUI increased only in the apical segment as the flushing time increased. CONCLUSIONS The PUI and PIPS methods facilitate the penetration of irrigation solution into the dentin canal in curved root canals, especially in the apical segment. The PIPS technique is effective in removing the smear layer in curved root canals.
Humans ; Dental Pulp Cavity ; Microscopy, Electron, Scanning ; Root Canal Irrigants ; Root Canal Preparation/methods* ; Smear Layer ; Sodium Hypochlorite ; Therapeutic Irrigation/methods* ; Double-Blind Method

Objective To assess the effects of different application sequences of neodymium-doped yttrium aluminum garnet(Nd∶YAG)laser and the desensitizing toothpaste containing stannous fluoride on dentinal tubule occlusion.Methods Twelve intact third molars freshly extracted from human were selected and prepared into dentin slices with a thickness of 0.8 mm.Each dentin slice was subdivided into four small slices,three of which were etched with 6% citric acid and randomly assigned to the following three groups(n=12):(1)control group:no treatment;(2)Nd∶YAG+toothbrushing(TB)group:first irradiated with Nd∶YAG laser and then brushed with desensitizing toothpaste;(3)TB+Nd∶YAG group:first brushed with desensitizing toothpaste and then irradiated with Nd∶YAG laser.The Nd∶YAG laser irradiation were carried out at 1 W,15 pulses/s,and the pulse width of 150 μs for 10 s(for a total of 6 cycles).After the above treatment,the 12 dentin slices from the Nd∶YAG+TB and TB+Nd∶YAG groups were randomly assigned to four subgroups(n=3)and subjected to acid etching in the Coca-Cola solution for 0,5,10,and 15 min.A scanning electron microscope was used to observe and photograph the dentin slices in each group,and eight single-blinded examiners scored the slices according to uniform criteria.The analysis of variance was carried out to compared the scores between groups.Results Before acid etching,the dentin tubule occlusion scores of the Nd∶YAG+TB and TB+Nd∶YAG groups were(4.83±0.09) scores and(3.85±0.66) scores,respectively,which had no significant difference between each other(P=0.0590)and were higher than that[(0.10±0.07)scores]of the control group(both P<0.0001).The dentin tubule occlusion scores of the Nd∶YAG+TB group after acid etching for 5,10,and 15 min were(4.33±0.60)scores,(4.27±0.24)scores,and(3.63±0.07)scores,respectively,which were not significantly different from those[(4.04±0.10)scores,(3.76±0.59)scores,and(3.17±0.29)scores,respectively]of the TB+Nd∶YAG group(all P>0.05).In the Nd∶YAG+TB subgroup,the dentin tubule occlusion score after acid etching for 15 min was significantly lower than that before acid etching(P=0.0011).In the TB+Nd∶YAG group,there was no statistically significant difference in the score between before and after acid etching(P>0.05).Conclusions Nd∶YAG laser irradiation with appropriate parameters combined with the use of desensitizing toothpaste could produce an excellent occluding effect on dentinal tubules regardless of the sequence.However,brushing with desensitizing toothpaste followed by Nd∶YAG laser irradiation produced more consistent dentin sealing after acid etching.
Humans ; Dentin ; Dentin Sensitivity/therapy* ; Lasers, Solid-State/therapeutic use* ; Microscopy, Electron, Scanning ; Toothpastes/pharmacology*

This research aims to investigate the encapsulation and controlled release effect of the newly developed self-assembling peptide R-LIFE-1 on exosomes. The gelling ability and morphological structure of the chiral self-assembling peptide (CSAP) hydrogel were examined using advanced imaging techniques, including atomic force microscopy, transmission electron microscopy, and cryo-scanning electron microscopy. The biocompatibility of the CSAP hydrogel was assessed through optical microscopy and fluorescent staining. Exosomes were isolated via ultrafiltration, and their quality was evaluated using Western blot analysis, nanoparticle tracking analysis, and transmission electron microscopy. The controlled release effect of the CSAP hydrogel on exosomes was quantitatively analyzed using laser confocal microscopy and a BCA assay kit. The results revealed that the self-assembling peptide R-LIFE-1 exhibited spontaneous assembly in the presence of various ions, leading to the formation of nanofibers. These nanofibers were cross-linked, giving rise to a robust nanofiber network structure, which further underwent cross-linking to generate a laminated membrane structure. The nanofibers possessed a large surface area, allowing them to encapsulate a substantial number of water molecules, thereby forming a hydrogel material with high water content. This hydrogel served as a stable spatial scaffold and loading matrix for the three-dimensional culture of cells, as well as the encapsulation and controlled release of exosomes. Importantly, R-LIFE-1 demonstrated excellent biocompatibility, preserving the growth of cells and the biological activity of exosomes. It rapidly formed a three-dimensional network scaffold, enabling the stable loading of cells and exosomes, while exhibiting favorable biocompatibility and reduced cytotoxicity. In conclusion, the findings of this study support the notion that R-LIFE-1 holds significant promise as an ideal tissue engineering material for tissue repair applications.
Exosomes ; Delayed-Action Preparations ; Hydrogels ; Microscopy, Electron, Scanning ; Peptides

Objective To establish an efficient method for isolating migrasomes from RAW264.7 macrophages and identifying these isolated migrasomes. Methods Scanning electron microscopy was used to observe the morphological characteristics of migrasomes produced by RAW264.7 cells. A 0.45 μm filter was employed for reverse filtration and elution to isolate the migrasomes. The morphological characteristics of the migrasomes were then observed using transmission electron microscopy. Western blot analysis was performed to determine the expression of characteristic markers of the migrasomes. The RNA carried by the migrasomes was analysed by using LabChip bioanalyzer. Results Scanning electron microscopy revealed that the migrasomes, with membranous structures, were attached to the tip or bifurcation of the retraction fiber formed in the tail of RAW264.7 cells. Transmission electron microscopy showed that the isolated migrasomes had a typical oval vesicle-like structure with wrinkled membrane surfaces. Western blot analysis confirmed the expression of the characteristic markers phosphatidylinositol glycan anchor biosynthesis class K (PIGK), epidermal growth factor domain-specific O-linked N-acetylglucosamine transferase (EOGT) and tetraspanin 4 (TSPAN4) in the migrasomes, while the EV (extracellular vesicle) markers tumor susceptibility gene 101 (TSG101) and Arabidopsis homolog of apoptosis-linked gene 2-interacting protein X (ALIX) were not detected. Furthermore, the isolated migrasomes were found to be rich in small RNA, which were approximately 25-200 nt in length. Conclusion A method for the extraction of well-structured and high quality migrasomes from macrophages is established.
Extracellular Vesicles ; Microscopy, Electron, Transmission ; RNA ; Macrophages

Heme/metabolism* ; Cryoelectron Microscopy ; Membrane Transport Proteins ; Escherichia coli Proteins/metabolism*

Reoviridae ; Cryoelectron Microscopy

The adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, IrtAB, plays a vital role in the replication and viability of Mycobacterium tuberculosis (Mtb), where its function is to import iron-loaded siderophores. Unusually, it adopts the canonical type IV exporter fold. Herein, we report the structure of unliganded Mtb IrtAB and its structure in complex with ATP, ADP, or ATP analogue (AMP-PNP) at resolutions ranging from 2.8 to 3.5 Å. The structure of IrtAB bound ATP-Mg2+ shows a "head-to-tail" dimer of nucleotide-binding domains (NBDs), a closed amphipathic cavity within the transmembrane domains (TMDs), and a metal ion liganded to three histidine residues of IrtA in the cavity. Cryo-electron microscopy (Cryo-EM) structures and ATP hydrolysis assays show that the NBD of IrtA has a higher affinity for nucleotides and increased ATPase activity compared with IrtB. Moreover, the metal ion located in the TM region of IrtA is critical for the stabilization of the conformation of IrtAB during the transport cycle. This study provides a structural basis to explain the ATP-driven conformational changes that occur in IrtAB.
Siderophores/metabolism* ; Iron/metabolism* ; Mycobacterium tuberculosis/metabolism* ; Cryoelectron Microscopy ; Adenosine Triphosphate/metabolism* ; ATP-Binding Cassette Transporters

Humans ; Dynorphins/metabolism* ; Receptors, Opioid, kappa/metabolism* ; Cryoelectron Microscopy

OBJECTIVES: The current study aimed to investigate the bonding properties of a novel low-shrinkage resin adhesive containing expanding monomer and epoxy resin monomer after thermal cycling aging treatment. METHODS: Expanding monomer of 3,9-diethyl-3,9-dimethylol-1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU) as an anti-shrinkage additive and unsaturated epoxy monomer of diallyl bisphenol A diglycidyl ether (DBDE) as a coupling agent were synthesized. A blend of DDTU and DBDE at a mass ratio of 1∶1, referred to as "UE", was added into the resin matrix at the mass fraction of 20% to prepare a novel low-shrinkage resin adhesive.Then, the methacrylate resin adhesive without UE was used as the blank control group, and a commercial resin adhesive system was selected as the commercial control group. Moreover, the resin-dentin bonding and micro-leakage testing specimens were prepared for the thermal cycling aging treatment. The bonding strength was tested, the fracture modes were calculated, the bonding fracture surface was observed by scanning electron microscope (SEM), and the dye penetration was used to evaluate the tooth-restoration marginal interface micro-leakage. All the data were analyzed statistically. RESULTS: After aging, the dentin bonding strength of the experimental group was (19.20±1.03) MPa without a significant decrease (P>0.05), that of the blank control group was (11.22±1.48) MPa with a significant decrease (P<0.05) and that of the commercial control group was (19.16±1.68) MPa without a significant decrease (P>0.05). The interface fracture was observed as the main fracture mode in each group after thermal cycling by SEM. The fractured bonding surfaces of the experimental group often occurred on the top of the hybrid layer, whereas those of the blank and commercial control groups mostly occurred on the bottom of the hybrid layer. Micro-leakage rating counts of specimens before and after thermal cycling were as follows: the experimental group was primarily 0 grade, thereby indicating that a relatively ideal marginal sealing effect could be achieved (P>0.05); meanwhile, the blank control group was primarily 1 grade, and the penetration depth of dye significantly increased after thermal cycling (P<0.05); the commercial control group was primarily 0 grade without statistical difference before and after thermal cycling (P>0.05), while a significant difference was observed between the commercial control group and experimental group after thermal cycling (P<0.05). CONCLUSIONS The novel low-shrinkage resin adhesive containing 20%UE exhibited excellent bonding properties even after thermal cycling aging treatment, thereby showing a promising prospect for dental application.
Composite Resins ; Dental Bonding ; Dental Cements ; Surface Properties ; Resin Cements ; Dentin-Bonding Agents ; Dentin ; Materials Testing ; Microscopy, Electron, Scanning