Fracture resistance of simulated immature maxillary anterior teeth restored with various canal filling materials, with micro-posts or with a fiber post.

The aim of this in vitro study was to compare the fracture resistance of immature anterior teeth restored with different biomaterials. After preparation of bovine incisors to simulate immature permanent teeth, 98 specimens were assigned into seven groups as follows: G1 -negative control group; G2 -apexification with hydraulic calcium silicate cement in the whole root; G3 -apexification and gutta percha; G4 -apexification and fiber post; G5 -apexification with micro-posts; G6 -apexification with composite; and G7 -revascularization. Both the fracture resistance and the location where the fracture occurred were recorded. Group 4 with a fiber post increased fracture resistance value compared to control (p<0.05). The different tested biomaterials did not influence the location where the fractures occurred among the seven groups (χ21=1.760, p=0.1846).

In vitro phenotypic effects of Lipoxin A4 on M1 and M2 polarized macrophages derived from THP-1.

BACKGROUND: Lipoxin A4 (LXA4) is a specialized pro-resolving mediator involved in the resolution phase of inflammation that is crucial for the return of tissues to homeostasis, healing, and regenerative processes. LXA4 can modify the microenvironment via its receptor, formyl peptide receptor 2 (FPR2) and thus modulate the inflammatory response. However, the effect of exogeneous LXA4 application on polarized macrophages remains unstudied. The objective of this study was to assess the effect of LXA4 on macrophage activity and on the phenotype modulation of polarized M1 and M2 macrophages derived from THP-1 monocytes. METHODS AND RESULTS: Once differentiated, human macrophages were incubated with interleukin 4 (IL-4) and IL-13 to obtain M2-polarized macrophages or with interferon gamma and lipopolysaccharide for classical macrophage activation. The mRNA and protein expression of M1 and M2 markers confirmed the polarization of THP-1-derived macrophages. LXA4 (0-100 nM) did not affect the viability of M1 and M2 macrophages or the phagocytic activity of these cells. Gene expression of FPR2, referred as a receptor for the LXA4, was higher in M1 compared with M2, and was not modified by the LXA4 at the doses used. Moreover, LXA4 exhibited anti-inflammatory properties illustrated by the decreasing in the gene expression of pro-inflammatory cytokines (IL-6, tumor necrosis factor alpha, IL-1ß) in M1 and by the increase in the expression of anti-inflammatory cytokines (IL-10) in M2 macrophages. CONCLUSIONS: These results provide new insights regarding the potential of LXA4 to regulate the polarization state of macrophages.

Specialized pro-resolving lipid mediators in endodontics: a narrative review.

Endodontics is the branch of dentistry concerned with the morphology, physiology, and pathology of the human dental pulp and periradicular tissues. Human dental pulp is a highly dynamic tissue equipped with a network of resident immunocompetent cells that play major roles in the defense against pathogens and during tissue injury. However, the efficiency of these mechanisms during dental pulp inflammation (pulpitis) varies due to anatomical and physiological restrictions. Uncontrolled, excessive, or unresolved inflammation can lead to pulp tissue necrosis and subsequent bone infections called apical periodontitis. In most cases, pulpitis treatment consists of total pulp removal. Although this strategy has a good success rate, this treatment has some drawbacks (lack of defense mechanisms, loss of healing capacities, incomplete formation of the root in young patients). In a sizeable number of clinical situations, the decision to perform pulp extirpation and endodontic treatment is justifiable by the lack of therapeutic tools that could otherwise limit the immune/inflammatory process. In the past few decades, many studies have demonstrated that the resolution of acute inflammation is necessary to avoid the development of chronic inflammation and to promote repair or regeneration. This active process is orchestrated by Specialized Pro-resolving lipid Mediators (SPMs), including lipoxins, resolvins, protectins and maresins. Interestingly, SPMs do not have direct anti-inflammatory effects by inhibiting or directly blocking this process but can actively reduce neutrophil infiltration into inflamed tissues, enhance efferocytosis and bacterial phagocytosis by monocytes and macrophages and simultaneously inhibit inflammatory cytokine production. Experimental clinical application of SPMs has shown promising result in a wide range of inflammatory diseases, such as renal fibrosis, cerebral ischemia, marginal periodontitis, and cancer; the potential of SPMs in endodontic therapy has recently been explored. In this review, our objective was to analyze the involvement and potential use of SPMs in endodontic therapies with an emphasis on SPM delivery systems to effectively administer SPMs into the dental pulp space.

Transforaminal and systemic diffusion of an active agent from a zinc oxide eugenol-based endodontic sealer containing hydrocortisone-in an in vivo model.

OBJECTIVES: This study aimed to quantify in vivo the release of hydrocortisone acetate (HCA) contained in a zinc oxide eugenol-based endodontic sealer, in various tissues. MATERIALS AND METHODS: Roots of human teeth, shaped with One Shape single file and sealed with Endomethasone N, previously radiolabelled with tritium (3H-HCA), were implanted in the back of 24 mice. Mice were sacrificed at 2, 8, 24, and 48 h to evaluate and quantify the amount of radioactivity in subcutaneous tissues surrounding the apex (periapical-like) of the implanted teeth, blood, spleen, kidneys, liver, and urine. RESULTS: Radioactivity was released from the apex of the tooth into the periapical-like tissues with a peak measured at 2 h post-implantation (2.25% of the initial radioactivity/g). This quantity decreased significantly over time between 2 h and each time points. Radioactivity was still measured up to 48 h in the periapical-like tissues (0.42% of the initial radioactivity). The same pattern of kinetic was observed for all organs. The total quantity of radioactivity significantly decreased over time from 4.36% measured 2 h post-implantation to 0.74% at 48 h. Finally, about 10% of the initial radioactivity from Endomethasone N used to fill the root canal was retrieved after 48 h in the urine. CONCLUSIONS: This study demonstrated that radioactive-HCA from Endomethasone N can diffuse through the apex of the root canal and follow a classical pharmacokinetics. CLINICAL RELEVANCE: This mouse model shows that radioactive-HCA can diffuse through the apex and do not accumulate in periapical-like tissues and organs.

Educational gaming for dental students: Design and assessment of a pilot endodontic-themed escape game.

INTRODUCTION: The concept of escape games dedicated to dental students is a new learning experience that has not yet been extensively explored. The aim of this pilot study was to assess the impact and perceived value of an endodontic-themed escape game as assessed by fourth-year dental students. METHODS: This study was conducted at the University of Nantes, Faculty of Dental Surgery using a cross-sectional pre- and post-test research design to assess students' changes in performance. Students in the fourth year of dental surgery study (n = 18) were divided in four groups for this study. The answers to the pre-test/post-test were 50 true/false questions. Moreover, a 20-question perception survey was given to all the participants after completion of the escape game. The study data were collected in May 2019. An unpaired t test analysed the mean differences between the groups. RESULTS: The results showed a statistically significant increase in post-test results (75.33% ± 10.17% of correct answers) compared to the pre-test results (67.33% ± 5.94% of correct answers) P < .05. Analysis of variance revealed that this change in score was not significantly different between the four groups. The students perceived the endodontic-themed escape game to be relevant. A one-sample t test indicated that students' mean (SD) perception 4.4 (0.7) was statistically significantly higher than the mean value of the evaluation scale P < .001. The students found this educational game to be a useful experience that helped them recall/apply knowledge whilst promoting teamwork. CONCLUSION: Therefore, this type of game can enhance students' learning and motivation.

The Effect of Magnification Loupes on Spontaneous Posture Change of Dental Students During Preclinical Restorative Training.

Scientific evidence validating the beneficial effect of loupes in preventing musculoskeletal disorders is very scarce. The aim of this study was to assess the impact of dental loupes on dental students' posture during a preclinical restorative dentistry course. Using a randomized crossover design, this study was conducted at the School of Dentistry, University of Nantes, France, in 2017. Forty students in their second year of dental study were randomly divided into two groups of 20 each: group A used loupes, whereas group B did not. The week after, students reversed configurations (each subject served as his or her own treatment and control group). Students were video-recorded during cavity preparation. Trunk, head and neck, and upper arm positions were analyzed using continuous scores based on the modified Posture Assessment Instrument. Additionally, cavities were rated, and students completed a questionnaire on their perceptions of the loupes. On a scale on which lower scores indicated better posture, the results showed significantly higher posture ergonomic scores per minute for students without loupes (146.3±6.64 points/min) than with loupes (123.2±6.77 points/min; p<0.05). The majority of the students (32/39, 82%) showed improvements in ergonomic postures with the use of loupes. Trunk, head, and neck were positively impacted by the use of loupes, but not the upper arms. Cavity preparations were not improved by the use of loupes. The questionnaire revealed negative aspects (pain and difficulty adapting) but underlined the perceived positive impact on posture. This study documented the ergonomic advantages and challenges of introducing magnification near the beginning of the dental training program.

Assessment and Quantification of Noncollagenic Matrix Proteins Released from Human Dentin Powder Incorporated into a Silated Hydroxypropylmethylcellulose Biomedical Hydrogel.

INTRODUCTION: The dentin extracellular matrix is a reservoir of bioactive molecules sequestered into dentin during dental initial development. They can be released under pathological conditions but also by controlled demineralization with bioactive materials. The purpose of this study was to investigate the ability of a biomedical hydrogel to extract and release these proteins from smashed dentin. METHODS: Smashed dentin was obtained with 2 different kinds of grinders: a blade mill and a zirconia mortar grinder. The particle size was measured by scanning electron microscopy. Dentin powder was incorporated into a silated hydroxypropylmethylcellulose hydrogel. Several types of mixtures with variable parameters were tested. The mixtures were immersed into phosphate-buffered saline. The supernatants were collected, and the total released proteins were quantified by gel shift migration and Coomassie staining. The presence of transforming growth factor beta 1 was investigated by Western blot analysis and the ELISA. RESULTS: The mixture dentin powder/hydrogel released proteins (from 49.1 µg/mL-137.9 µg/mL according to the mixtures). The release kinetics was growing and started from the first day until stabilization at 14 days. The quantity of released proteins was directly related to the size of the particles and the weight of the powder incorporated into the hydrogel. Gel shift with direct revelation by ultraviolet and Western blot analyses confirmed the presence of transforming growth factor beta 1 using ELISA. CONCLUSIONS: We showed that silated hydroxypropylmethylcellulose hydrogel was able to extract dentin matrix proteins from smashed dentin powder. This mixture could be considered a new way of dental treatment for the dentin-pulp complex and bone regeneration.