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 (p < 0.05) from groups B (0.1712 CFU/mg) and C (1.1193 CFU/mg), where both showed less bacteria than group A. The statistical difference between groups B and C was insignificant. ESEM images showed specimen A covered with more abundant and denser S. mutans biofilm than specimens B and C, with almost similar morphology showing sparse, less dense, and disintegrated biofilm with unclear cellular walls and presence of amorphous masses.

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.

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: 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

Background: Medical education has changed as a result of the COVID-19 pandemic. There has been a shift from face to face learning to virtual classes using online learning platforms such as Canvas. These virtual and online alternative methods to medical education brought up concerns about the preparedness of medical students in studying Histology. This study addresses the student’s preference and attitude on the learning of histology using light microscopy vs virtual microscopy. Objectives: The specific objectives of the study are to determine students’ preference, attitudes, and overall satisfaction on the use of light microscopy vs virtual microscopy using a Likert scale. Methods: An enhancement program was conducted by the Department of Anatomy, UP College of Medicine from June 13 to June 17, 2022 among first year medical students. The students were exposed to prosected cadavers, models, specimens, histologic glass slides, and electronic images. During the activity, the second and third floor of Calderon Hall was divided into several stations, each with its own learning outcomes.This is a descriptive cross-sectional study. In all the learning stations, both virtual and light microscopy learning modalities were made available to the students. The student was at liberty to select virtual microscopy, light microscopy or both. In one of the stations, allocated to OS 205 (The study of the anatomy and histology of the thorax), students were randomized to one learning modality (light vs virtual microscopy) and made to identify one predetermined structure. Students answered a short questionnaire that allowed them to express their preference for the modality that was assigned. The questionnaire survey included questions on students’ preference for either light microscopy (LM) or virtual microscopy (VM), ease of use, and satisfaction. A total of five statements were included in the survey questionnaire. All questions in the survey were scored on a 5-point Likert scale (5: strongly disagree, 4: disagree, 3: neutral, 2: agree, and 1: strongly agree). A comments section was also included in the survey to explore students’ experiences of the two learning methods. Results: A total of 160 students participated in the study. Seventy-nine (79) students were randomized to the light microscopy group and 81 one students were randomized to the virtual microscopy group. There were no differences in the demographic characteristics between those randomized to virtual vs light microscopy.There were no differences in the net ratings between those randomised to virtual vs light microscopy in the following domains: 1) ease in looking for structures, 2) ability to identify the structure correctly, 3) method enhancing learning, and 4) overall satisfaction. There was a difference in the net rating between those randomized to virtual vs light microscopy in the domain on quality of the image being easily adjusted (58% vs 97.5%). Conclusion Medical students who used light microscopes demonstrated a more positive attitude towards its ability to enhance learning and showed greater satisfaction in using this method. Ease in manipulating image quality was better in the light microscopy group. However, the accuracy of identification of histological structures using either platform did not differ. Both virtual and light microscopy are effective learning methods.
Microscopy ; Education, Medical ; Histology ; Teaching

Objective: To investigate the efficacy of the first-day suspension method for improving the success rate of construction of nasopharyngeal carcinoma-patient derived organoids (NPC-PDO). Methods: The tumor samples of 14 nasopharyngeal carcinoma(NPC) patients, i.e.,13 males and 1 female, with a mean age of 43.0±12.0 years old, were collected from the Affiliated Tumor Hospital of Guangxi Medical University and the First Affiliated Hospital of Guangxi Medical University from January 2022 to July 2022. The tumor samples of 3 patients were digested into single cell suspension and divided into 2 groups, for comparing the efficacy of NPC-PDO construction by the direct inoculation method and the first-day suspension method. The remaining 11 patients were randomized to receive either the direct inoculation method or the first-day suspension method for NPC-PDO construction. The diameter and the number of spheres of NPC-PDO constructed by the two methods were compared by optical microscope; the 3D cell viability detection kit was used to compare the cell viability; the survival rates were compared by trypan blue staining; the success rates of the two construction methods were compared; the number of cases which could be successfully passaged for more than 5 generations and were consistent with the original tissue by pathological examination was counted; and the dynamic changes of cells in suspension overnight were observed by live cell workstation. The independent sample t-test was applied to compare the measurement data of the two groups, and the chi-square test was used to compare the classification data. Results: Compared with the direct inoculation, the diameter and the number of spheres of NPC-PDO constructed by the first-day suspension method were increased, with a higher cell activity, and the success rate of construction was obviously improved (80.0% vs 16.7%, χ²=4.41, P<0.05). In the suspension state, some of the cells aggregated and increased their ability to proliferate. Conclusion: The first-day suspension method can improve the success rate of NPC-PDO construction, especially for those whose original tumor sample size is small.
Male ; Humans ; Female ; Adult ; Middle Aged ; Nasopharyngeal Carcinoma ; China ; Microscopy ; Organoids ; Nasopharyngeal Neoplasms

Humans ; Microscopy ; Vocal Cords

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

This paper reviews the research progress on live-cell super-resolution fluorescence microscopy, discusses the current research status and hotspots in this field, and summarizes the technological application of super-resolution fluorescence microscopy for live-cell imaging. To date, this field has gained progress in numerous aspects. Specifically, the structured illumination microscopy, stimulated emission depletion microscopy, and the recently introduced minimal photon fluxes microscopy are the current research hotspots. According to the current progress in this field, future development trend is likely to be largely driven by artificial intelligence as well as advances in fluorescent probes and relevant labelling methods.
Artificial Intelligence ; Microscopy, Fluorescence ; Fluorescent Dyes ; Technology