Mechanical Properties of Fused Deposition Modeling of Polyetheretherketone (PEEK) and Interest for Dental Restorations: A Systematic Review

The aim of this systematic review was to determine the optimal printing parameters for the producing of fused deposition modeling (FDM) 3D-printed polyetheretherketone (PEEK) elements with mechanical properties suitable for dental restorations. Indeed, the mechanical properties are a critical prerequisite for the study of other parameters, such as physical, aesthetic and biological properties. An exhaustive electronic search was carried out in the PubMed, Embase and Web of knowledge databases to gather all the studies evaluating the influence of the printing parameters on the obtained mechanical properties of FDM 3D-printed PEEK elements were selected. Initially, the search resulted in 614 eligible papers. Independent screenings of the abstracts were performed by two authors to identify the articles related to the question. Twenty-nine studies were selected, of which eleven were further excluded after reading of the full text, and finally, eighteen articles were included in this review. The studies were difficult to compare due to the variability of the printing parameters and the types of PEEK. However, it seems interesting to use a high infill rate, a high chamber temperature close to that of the printing temperature and a heat post-treatment to obtain 3D PEEK elements presenting properties adapted to use as dental restorations. The analysis of the available literature suggested that the properties of PEEK could make it an interesting material in dental restorations to be performed with FDM additive manufacturing.

Behaviour of human dental pulp stem cell in high glucose condition: impact on proliferation and osteogenic differentiation

OBJECTIVE

The aim of this study is to investigate the changes of human dental pulp stem cell (hDPSC) viability, proliferation and osteogenic differentiation in high glucose condition.

DESIGN

After 21 days of culture in low (5.5 mM) and high (20 mM) glucose medium, hDPSC viability and proliferation were assessed with respectively the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Hoechst assays. To investigate the influence of glucose on osteogenic differentiation hDPSCs were cultured for 28 days in low or high glucose medium with osteoinductive cocktail. Mineralization was examined by alizarin red staining/quantification and the expression of osteogenic-related genes [Runt-related transcription factor 2 (RUNX2), Osteocalcin (OCN), Collagen 1A1 (COL1A1)] analyzed by RT-qPCR.

RESULTS

We observed no significant difference (p >  0.05) on hDPSC proliferation or cell viability between low or high glucose groups. We did not highlight a significant difference after alizarin red staining and quantification between hDPSCs cultured with high or low glucose concentration in the culture medium. In the same manner, high glucose concentration did not appear to modify osteogenic gene expression: there was no significant difference in osteogenic-related gene expression between high or low glucose groups.

CONCLUSION

Proliferation, viability, and osteogenic differentiation of hDPSCs were not changed by high glucose environment.

The effect of nacre extract on cord blood-derived endothelial progenitor cells: A natural stimulus to promote angiogenesis?

Angiogenesis is a critical parameter to consider for the development of tissue-engineered bone substitutes. The challenge is to promote sufficient vascularization in the bone substitute to prevent cell death and to allow its efficient integration. The capacity of nacre extract to restore the osteogenic activity of osteoarthritis osteoblasts has already been demonstrated. However, their angiogenic potential on endothelial progenitor cells (EPCs) was not yet explored. Therefore, the current study aimed at investigating if nacreous molecules affect EPC behavior. The gene and protein expression levels of endothelial cell (EC)-specific markers were determined in EPCs cultivated in presence of a nacre extract (ethanol soluble matrix [ESM] at two concentrations: 100 μg/mL and 200 μg/mL (respectively abbreviated ESM100 and ESM200)). Cell functionality was explored by proangiogenic factors production and in vitro tube formation assay. ESM200 increased the expression of some EC-specific genes. The in vitro tube formation assay demonstrated that ESM200 stimulated tubulogenesis affecting angiogenic parameters. We demonstrated that a stimulation with 200 μg/mL of ESM increased angiogenesis key elements. This in vitro study strongly highlights the proangiogenic effect of ESM. Due to its osteogenic properties, previously demonstrated, ESM could constitute the key element to develop an ideal prevascularized bone substitute. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Dental Pulp Stem Cell-Derived Conditioned Medium: An Attractive Alternative for Regenerative Therapy

Mesenchymal stem cells (MSC) have a lot of potential in regenerative medicine, and MSC-based therapies are currently explored in numerous research fields. Among these cells, deciduous or permanent dental pulp-MSC represent a promising option in tissue engineering. This expectation is based on their capacity to self-renew, to repair various damaged tissues and organs due to their multipotency, as well as their ability to modulate immune system. They present other advantages such as the harvesting by a simple, painless, and noninvasive procedure and the absence of ethical considerations. The role played by these cells in the reparative process is mainly attributed to paracrine mechanisms mediated by their secreted factors, namely the secretome. The secreted factors can be found in the cell culture medium, called conditioned medium (CM). Moreover, CM presents many advantages compared with cells such as possible use in allogeneic therapies. This minireview aims at investigating the therapeutic use of dental pulp MSC-derived CM to develop cell-free therapies. The analysis of the available literature illustrates its massive panel of potential applications: mainly reduction of inflammation, promotion of angiogenesis and neurogenesis, reduction of stroke or ischemia, and organ regeneration. Furthermore, studies often highlight its superiority over the other sources of CM derived from other stem cells for the same applications. Dental pulp MSC-derived CM is an attractive, noninvasive, and acellular tool for therapeutic approaches in regenerative medicine. This promising novel approach should be further explored for clinical applications.

Evaluation of the pro-angiogenic effect of nanoscale extracellular vesicles derived from human umbilical cord mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a common tool in regenerative medicine. The nanoscale extracellular vesicles (nEVs) secreted by these cells were recently brought up to light thanks to their therapeutic potential. In this study, we assessed the in vitro behaviour of human umbilical vein endothelial cells (HUVECs) exposed to nEVs derived from human umbilical cord mesenchymal stem cells (hUC-MSCs). Nanoscale extracellular vesicles were isolated and characterized by NanoSight® and flow cytometry. HUVECs were stimulated with various concentrations of nEVs. To assess nEV interactions with HUVECs, confocal microscopy and angiogenesis assay were performed. The use of nEVs derived from hUC-MSCs was able to produce positive outcomes on HUVECs by acting on their angiogenic potential.

Oral Streptococcal Endocarditis, Oral Hygiene Habits, and Recent Dental Procedures: A Case-Control Study

BACKGROUND.

We aimed to compare oral hygiene habits, orodental status, and dental procedures in patients with infective endocarditis (IE) according to whether the IE-causing microorganism originated in the oral cavity.

METHODS.

We conducted an assessor-blinded case-control study in 6 French tertiary-care hospitals. Oral hygiene habits were recorded using a self-administered questionnaire. Orodental status was analyzed by trained dental practitioners blinded to the microorganism, using standardized clinical examination and dental panoramic tomography. History of dental procedures was obtained through patient and dentist interviews. Microorganisms were categorized as oral streptococci or nonoral pathogens using an expert-validated list kept confidential during the course of the study. Cases and controls had definite IE caused either by oral streptococci or nonoral pathogens, respectively. Participants were enrolled between May 2008 and January 2013.

RESULTS.

Cases (n = 73) were more likely than controls (n = 192) to be aged <65 years (odds ratio [OR], 2.85; 95% CI, 1.41-5.76), to be female (OR, 2.62; 95% CI, 1.20-5.74), to have native valve disease (OR, 2.44; 95% CI, 1.16-5.13), to use toothpicks, dental water jet, interdental brush, and/or dental floss (OR, 3.48; 95% CI, 1.30-9.32), and to have had dental procedures during the prior 3 months (OR, 3.31; 95% CI, 1.18-9.29), whereas they were less likely to brush teeth after meals. The presence of gingival inflammation, calculus, and infectious dental diseases did not significantly differ between groups.

CONCLUSIONS.

Patients with IE caused by oral streptococci differ from patients with IE caused by nonoral pathogens regarding background characteristics, oral hygiene habits, and recent dental procedures, but not current orodental status.

Nacre, a natural, multi-use, and timely biomaterial for bone graft substitution

During the past two decades, with a huge and rapidly increasing clinical need for bone regeneration and repair, bone substitutes are more and more seen as a potential solution. Major innovation efforts are being made to develop such substitutes, some having advanced even to clinical practice. It is now time to turn to natural biomaterials. Nacre, or mother-of-pearl, is an organic matrix-calcium carbonate coupled shell structure produced by molluscs. In vivo and in vitro studies have revealed that nacre is osteoinductive, osteoconductive, biocompatible, and biodegradable. With many other outstanding qualities, nacre represents a natural and multi-use biomaterial as a bone graft substitute. This review aims at summarising the current needs in orthopaedic clinics and the challenges for the development of bone substitutes; most of all, we systematically review the physiological characteristics and biological evidence of nacre's effects centred on osteogenesis, and finally we put forward the potential use of nacre as a bone graft substitute. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 662-671, 2017.

The Nebivolol action on vascular tone is dependent on actin cytoskeleton polymerization and Rho-A activity into ECs and SMCs

Nitric oxide is implicated in the target action of Nebivolol, a selective β1 adrenoceptor blocker used in hypertension treatment. As the Nitric Oxide (NO) production and the actin cytoskeleton are linked, the aim of this work was to study the involvement of actin cytoskeleton on mechanism of action of Nebivolol in cultured endothelial cells. We studied the effect of Nebivolol (200 μM) on actin filaments remodeling and its impact on NO production and eNOS activation. Results showed that Nebivolol perturbs actin filaments polymerization, increases NO production and eNOS activity between 30 minutes and 1 h. Stabilization of actin filaments with phalloïdine (50 μM) abolishes Nebivolol effects on eNOS activation and NO production. Furthermore, Rho-kinase activity decreased during the first hour of Nebivolol treatment, then increased after 3 h, while actin filaments repolymerized, eNOS activation and NO production decreased. In SMCs, Nebivolol induced a decrease in the Rho-kinase activity from 1 h until 24 h of incubation. In conclusion, we suggest that Nebivolol induced NO production in Endothelial Cells (ECs) via complementary actions between actin cytoskeleton remodeling inducing eNOS activation and Rho-kinase implication. The effect of Nebivolol on ECs occurs during the first hour, this effect on SMCs seems to be maintained until 24 h, explaining persisted action of Nebivolol observed in vivo.

Polyelectrolyte multilayer films: effect of the initial anchoring layer on the cell growth

In tissue engineering, surface characteristics of a biomaterial are one of most important factors determining the compatibility with the environment. They influence attachment and growth of cells onto the material. In many cases, the surface should to be modified and engineered in the desired direction. The modification of non-adhesive surfaces with polyelectrolyte multilayer films (PMF) was recently depicted as a powerful technique to promote the growth of different cell lines. In this study, we evaluated the possible use of two different PMF as surface modification for the culture of mesenchymal stem cells (MSC). We used two types of PMF which differed by the nature of the initial anchoring layer which was poly(ethylenimine) (PEI) or poly(allylamine hydrochloride) (PAH). This initial polyelectrolytes adsorption was followed by the alternated deposition of poly(sodium 4-styrenesulfonate) (PSS) and (PAH) in order to obtain a PEI-(PSS-PAH)(3) film or a PAH-(PSS-PAH)(3) film. In order to control the behaviour of MSC, the cell viability was evaluated by Alamar Blue assay and the actin cytoskeleton was labelled and visualised in a confocal microscope. The behaviour of cells on the two PMF was compared to cells cultivated on surfaces treated with fibronectin. The results showed that PAH-(PSS-PAH)(3) PMF improve the growth of cells, inducing a higher cell viability compared to PEI-(PSS-PAH)(3) PMF and fibronectin at 2, 3 and 7 days of culture. Moreover, those cells showed a well-organized actin cytoskeleton. In conclusion, PAH-(PSS-PAH)(3) polyelectrolyte multilayer film seems to constitute an excellent material for MSC seeding.

Poly(styrenesulfonate)/poly(allylamine) multilayers: a route to favor endothelial cell growth on expanded poly(tetrafluoroethylene) vascular grafts

Small-diameter synthetic vascular grafts of expanded poly(tetrafluoroethylene) (ePTFE) polymer concern one of the most common alternatives for the replacement of diseased vessels. However, high failure rates arise especially due to the lack of endothelial cells (ECs). EC seeding was developed to build a monolayer on the luminal surface. Because ECs show little or no adhesion on synthetic prostheses, it is necessary to promote their retention. On ePTFE surfaces we successfully deposited polyelectrolyte multilayer films (PMFs) consisting of poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) to obtain PEI-(PSS-PAH)3 films. EC adhesion and spreading on modified ePTFE were assessed by scanning electron and confocal microscopies. Cell viability was evaluated by Alamar Blue assay. After 7 days of culture, the ePTFE modified with PMF exhibited improvements of EC viability as compared to that of the controls (nonmodified ePTFE) or even ePTFE coated by a PAH monolayer (p < 0.05). Moreover, the spreading of ECs was largely enhanced compared to that of the same controls, resulting in a healthy confluent cell monolayer formation. Positive staining for the von Willebrand factor confirmed the EC phenotype. Promoting EC attachment and function on ePTFE modified with PMFs could become in the future a promising treatment for synthetic small-diameter vascular grafts.

The ideal small arterial substitute: Role of cell seeding and tissue engineering

Although autogenous vessels are useful in surgery, often patients cannot furnish suitable vessels. If there are not available, two possible alternatives for vessel replacements are to use vascular synthetic prostheses such as Dacron((R)) and polytetrafluoroethylene (PTFE) or cryopreserved allografts. However, their success has been limited to replace small-diameter (<6 mm) arterial vessel because of their high thrombogenicity and compliance mismatch. On account of a clear clinical need for a functional arterial substitute, tissue engineering techniques have been developed. This review encompasses the use of mature endothelial, endothelial progenitor and bone marrow cells combined with natural or synthetic scaffolds whose surface has been modified with multiple origin matrices.

Initial adhesion of endothelial cells on polyelectrolyte multilayer films

Polyelectrolyte multilayer films were recently investigated to favour attachment of Human Vein Umbilical Endothelial Cells (HUVECs) on non-adhesive surfaces. In this study, we evaluated the initial adhesion of HUVECs after 3 h of seeding on two polyelectrolyte multilayer films ending by poly(D-lysine) (PDL) or poly(allylamine hydrochloride) (PAH). In order to obtain information about initial adhesion of HUVECs, cell morphology as well as the expression of beta1 integrins, specific receptors of adhesion, were evaluated after 3 h of seeding on polyelectrolyte multilayer films. The data were also compared to PDL or PAH monolayers (polyelectrolytes terminating the multilayer architecture). The expression of beta1 integrins was not different, whatever are the studied surfaces. However, HUVECs spreading on polyelectrolyte multilayer films, in particular on PAH ending film, was more important as compared to polyelectrolyte monolayers or glass. In conclusion, the best initial adhesion conditions of HUVECs on polyelectrolyte films could not be elucidated, moreover the results suggested also that beta1 integrins could only play a limited role.