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.

Knowledge and Opinions of French Dental Students in Operative Dentistry - Management of Deep Carious Lesions.

PURPOSE: A questionnaire survey was recently undertaken among French dental students (FDSs) to investigate their practices, knowledge and opinions in various domains of minimal intervention (MI) in cariology. The present work focuses on management of deep carious lesions (DCLs). MATERIALS AND METHODS: The questionnaire was administered (Spring 2018) to all the fifth-year students of the 16 French dental schools. Descriptive analyses were performed. RESULTS: Among 1370 FDSs (response rate: 84.5%), hardness was the most commonly reported criterion for assessing the endpoint of carious tissue removal (53.9%), followed by firm dentin (40.0%). Regarding FDSs' opinion of leaving carious dentine under a restoration, 41.9% of the respondents agreed that carious tissues should always be removed completely. For an asymptomatic tooth with DCLs and exposed pulp, direct pulp capping was mainly chosen (93.9%). In a clinical case correctly diagnosed as a reversible pulpitis by 79.7% of respondents, nearly half of FDSs chose a one-step complete excavation (48.3%) followed by selective excavation (25.1%), then two-step complete excavation (20.9%) and a minority (5.7%) opted for pulpal therapy (biopulpotomy or endodontic treatment). CONCLUSION: The present results suggest an inadequate dissemination of MI concepts among FDSs towards DCL management. The present results show the need for a harmonisation and a reinforcement of teaching evidence-based MI according to the latest European recommendations.

Knowledge and Opinions of French Dental Students Toward Occlusal and Proximal Restorative Thresholds.

PURPOSE: To investigate the practices, knowledge and opinions of French dental students (FDSs) in various domains of minimal intervention (MI) in cariology. MATERIALS AND METHODS: A cross-sectional, questionnaire-based study was conducted in spring 2018 among all fifth-year French dental students (FDSs) from the 16 French dental schools. The present article focuses on restorative management. Statistical analyses (descriptive, chi-squared) were performed. RESULTS: The response rate was 84.5%. Overall, 97.4% of respondents would have operatively intervened for proximal and 83% for occlusal carious lesions, respectively, while non-or micro-invasive intervention would have been possible. Interestingly, 15% would completely open the occlusal fissures. For both occlusal and proximal lesions requiring a restoration, composite resin was indicated by over 95% of the respondents. In a clinical case, 51.6% of FDSs who rightly diagnosed an enamel carious lesion would operatively intervene. When FDSs could not diagnose the type of carious lesions, a high proportion of invasive actions were also reported (40%). FDSs who read scientific articles were more likely to consider the high importance of not filling sound teeth unnecessarily (p = 0.033). CONCLUSION: FDSs do not have sufficient awareness of MI guidelines regarding occlusal and proximal restorative thresholds. Efforts are required in dental schools to teach FDSs to postpone invasive/restorative strategies to later stages of carious progression. There is a need to strengthen prevention techniques and non-invasive options in the teaching of MI in cariology.

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.

Knowledge and opinions of French dental students related to caries risk assessment and dental sealants (preventive and therapeutic).

OBJECTIVES: A national questionnaire study was performed to document knowledge and opinions of French dental students (FDSs) about minimal intervention (MI) in dentistry especially caries risk assessment (CRA) and dental sealants (DSs). MATERIALS AND METHODS: A questionnaire was administered to the fifth-year dental FDSs (n = 1370) from the 16 French dental schools. Descriptive and statistical analyses were performed. RESULTS: The response rate was 84.5%. A large majority of respondents (87.8%) linked MI with minimally invasive dentistry and 77.4% considered MI as a concept based on prevention. About 80% stated they use CRA in clinical practice, mostly without any specific form. If 80.4% of the respondents would base their treatment plans on CRA, only 55.1% would regularly plan preventive regimens according to individual risk level. However, while 96.6% declared they perform preventive DSs, only 44.3% considered therapeutic sealants as a routine treatment. Although 75.1% of FDSs stated that they had sufficient learning and training related to CRA, 55.9% thought that they need further education about preventive and therapeutic DSs. CONCLUSION: Although FDSs seem to be aware of the importance of CRA and preventive strategies, this study shows the need to harmonize the teaching in cariology according to the latest European recommendations. CLINICAL RELEVANCE: A national questionnaire study showed variability towards knowledge and opinions of FDSs related to MI in cariology. This may impact care provisions in their future professional life showing the urgent need to harmonize the teaching of MI in cariology in France.

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.

Autosomal recessive Treacher Collins syndrome due to POLR1C mutations: Report of a new family and review of the literature.

Treacher Collins syndrome (TCS) is a frequent cause of mandibulofacial dysostosis. To date, TCS-causing mutations in three genes, namely TCOF1, POLR1D, and POLR1C have been identified. TCS is usually inherited in an autosomal dominant manner, with a high clinical variability and no phenotype-genotype correlation. Up-to now, five families have been reported with an autosomal recessive mode of inheritance due to mutations in POLR1D or POLR1C. We report here a new family with two sisters affected by mild TCS carrying compound POLR1C heterozygous mutations, and review the literature on mild forms of TCS, autosomal recessive inheritance in this syndrome and POLR1C mutations.

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.

Enhancement of the biocompatibility by surface nitriding of a low-modulus titanium alloy for dental implant applications.

To enhance their longevity, dental implants must be highly biocompatible and must have a low elastic modulus close to that of the bone. They must also possess a high superficial hardness and a high corrosion resistance. For these reasons, a recently developed low-modulus Ti-27Nb alloy with nontoxic elements was treated by gas nitriding at high temperature in this study. A very thin nitrided layer of 0.5 µm in thickness followed by an enriched nitrogen zone was observed. Consequently, a very high hardness evaluated at about 1800 HV was obtained in surface, which represents an increase of 4-5 times the hardness of the non-nitrided alloy. This superficial hardness was experimentally observed to decrease up to 800 nm in depth from the surface to the core. The low modulus of Ti-27Nb (evaluated at 55 GPa, which is twice lower than the commercially pure titanium) was not affected by the surface nitriding treatment. A better corrosion resistance was observed and a significant decrease in ion release rates for the nitrided alloy (ion release of 1.41 ng/cm2 compared to the 163.58 ng/cm2 obtained for the commercially pure titanium at pH = 7.48 in artificial Carter-Brugirard saliva). The cytocompatibility was not compromised and the cell viability performed on human osteoblasts, fibroblastic cells, and epithelial cells was enhanced on the nitrided surface in comparison with the non-nitrided surface. These combined properties make the nitrided Ti-27Nb alloy a good candidate for dental implant applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1483-1490, 2019.

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.

Spheroid model study comparing the biocompatibility of Biodentine and MTA.

The primary objective of this study was to assess the biological effects of a new dentine substitute based on Ca3SiO5 (Biodentine™) for use in pulp-capping treatment, on pseudo-odontoblastic (MDPC-23) and pulp (Od-21) cells. The secondary objective was to evaluate the effects of Biodentine and mineral trioxide aggregate (MTA) on gene expression in cultured spheroids. We used the acid phosphatase assay to compare the biocompatibility of Biodentine and MTA. Cell differentiation was investigated by RT-qPCR. We investigated the expression of genes involved in odontogenic differentiation (Runx2), matrix secretion (Col1a1, Spp1) and mineralisation (Alp). ANOVA and PLSD tests were used for data analysis. MDPC-23 cells cultured in the presence of MTA had higher levels of viability than those cultured in the presence of Biodentine and control cells on day 7 (P = 0.0065 and P = 0.0126, respectively). For Od-21 cells, proliferation rates on day 7 were significantly lower in the presence of Biodentine or MTA than for control (P < 0.0001). Col1a1 expression levels were slightly lower in cells cultured in the presence of MTA than in those cultured in the presence of Biodentine and in control cells. Biodentine and MTA may modify the proliferation of pulp cell lines. Their effects may fluctuate over time, depending on the cell line considered. The observed similarity between Biodentine and MTA validates the indication for direct pulp-capping claimed by the manufacturers.

In vitro effects of Choukroun's platelet-rich fibrin conditioned medium on 3 different cell lines implicated in dental implantology.

OBJECTIVE: The aim of this work was to determine the relevance of Choukroun's platelet-rich fibrin (PRF) in dental implantology by determining the in vitro effects of soluble factors released by PRF clot. We used 3 different cell lines implicated in dental implantology: osteoblast, keratinocyte, and fibroblast. METHODS: Cellular viability, cell proliferation, and gene expression were analyzed using PRF conditioned medium. Three different cells lines were used: SaOS2 (osteoblast), MRC5 (fibroblast), and KB (epithelial cell). RESULTS: The sulforhodamine B assay showed a significant increase in cell number for the undiluted and 1:3 diluted conditioned medium after 24 and 48 hours. There was no effect for the 1:9 dilution. Cell cycle analysis by flow cytometry confirmed the viability test results. After 48 hours, PRF conditioned medium induced gene expression in osteoblasts. Expression of osteopontin and osteocalcin, late osteogenic markers, was observed using reverse transcriptase-polymerase chain reaction (RT-PCR). CONCLUSIONS: This study establishes a model to evaluate, in vitro, the effects of soluble growth factors released by PRF clot. Our work confirmed PRF is useful in stimulating tissue healing and bone regeneration. This work should recommend Choukroun's PRF in numerous implantology clinical applications.

Effect of hydroxyapatite and beta-tricalcium phosphate nanoparticles on promonocytic U937 cells.

OBJECTIVES: Nanoparticles from implanted materials are reported as the main cause of implant failure. Monocytes are among the first cells to colonize the inflammatory site. We evaluated the biological effects of bone substitutes presented to U937 cells in vitro as micron- or nanometer-sized particles. METHODS: The HA (550 nm) and beta-TCP (550 nm) nanoparticles were incubated with U937 cells. Cell cycle modification, specific antigens expression, and the extent of cell death were determined. RESULTS: Firstly, by using the sulforhodamine B (SRB) test and the annexin V-FITC analysis by flow cytometry, our results provide evidence of the absence of cytotoxicity, and show that nanoparticles do not induce more apoptosis than microparticles in U937 cells. Secondly, although morphologic evidence of stimulation of U937-cells was found by confocal microscopy, neither bone substitute altered the distribution of the cells into different phases of the cell cycle (Kit Cycle Test Plus DNA). These results suggest that nanoparticles do not cause promonocyte maturation in macrophages. Thirdly, the flow cytometry results showed no differences in the expression of the adherence and activation markers. SIGNIFICANCE: The results suggest that nanoparticles do not promote the differentiation of promonocytic U937 cells into macrophages and do not induce an enhanced inflammatory response.

Effect of three nickel-titanium rotary file techniques on infected root dentin reduction.

OBJECTIVE: This study compared the bacterial reduction of in vitro infected root canals after instrumentation by 3 nickel-titanium (NiTi) rotary files with different taper and diameter versus manual stainless steel files. STUDY DESIGN: Sixty-four single-rooted human teeth were infected with a suspension of Streptococcus sanguis measured by optical density. Teeth were divided randomly into 4 groups of 16 and prepared with Flexofiles, GT rotary files, HERO 642, and ProFile. Bacterial samplings were performed before (S1), during (S2-S3), and after (S4) instrumentation. RESULTS: All techniques significantly reduced the number of bacterial cells in the root canals (P < .05). There was no significant difference between NiTi and manual instrumentation at S2, S3, or S4. Concerning bacterial reduction, the results suggest that a manual stainless steel file preparation is as efficient as a NiTi rotary instrumentation. CONCLUSION: Regardless of the root canal preparation technique, its taper, and diameter, the root dentin remained infected and was not bacteria-free at the end of the experiment.

Effect of a low-concentration EDTA solution on root canal walls: a scanning electron microscopic study.

OBJECTIVES: The aim of this study was to evaluate, in vitro, the ability of an 8% EDTA solution to remove debris and smear produced during root canal preparation. STUDY DESIGN: Single-rooted human teeth were used for this experiment. All root canals were instrumented in a similar fashion and irrigated with a 3.5% NaOCl solution. The teeth were divided into 6 groups. According to the groups, various final flushes were performed with a 15% or 8% EDTA solution for 1 or 3 min and with or without saline rinsing. After preparation, roots were separated into 3 thirds and each third was observed by SEM. Debris (D) and root canal smear (S) was evaluated twice. RESULTS: The results were subjected to ANOVA. The D and S scores for all test groups were statistically different from the control group without EDTA flush (P = .0001). The lowest D and S scores were obtained by a 3 min rinse with 8% EDTA solution and a statistical difference was observed in the apical third (P < .05). CONCLUSION: Under these in vitro conditions, 3 min 8% EDTA irrigation is as effective as 1 min 15% EDTA irrigation.