Graphene-based nanomaterials for tissue engineering in the dental field

The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedure

Strontium Substituted Tricalcium Phosphate Bone Cement: Short and Long‐Term Time‐Resolved Studies and In Vitro Properties

Due to a significant influence of strontium (Sr) on bone regeneration, Sr substituted beta-tricalcium phosphate (Sr-TCP) cement is prepared and investigated by short- and long-term time-resolved techniques. For short-term investigations, energy-dispersive X-ray diffraction, infrared spectroscopy, and, for the first time, terahertz time-domain spectroscopy techniques are applied. For long-term time-resolved studies, angular dispersive X-ray diffraction, scanning electron microscopy, mechanical tests, and behavior in Ringer solution are carried out. After 45 min of the cement setting, the Sr-TCP phase is no longer detectable. During this time period, an appearance and constant increase of the final brushite phase are registered. The compressive strength of the Sr-TCP cement increases from 4.5 MPa after 2 h of setting and reaches maximum at 13.3 MPa after 21 d. After cement soaking for 21 d in Ringer solution, apatite final product, with an admixture of brushite and TCP phases is detected. The cytotoxicity aspects of the prepared cement are investigated using NCTC 3T3 fibroblast cell line, and the cytocompatibility-by human dental pulp mesenchymal stem cells. The obtained results allow to conclude that the developed Sr-TCP cement is promising for biomedical applications for bone tissue

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behaviour of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg-0.63Ca and Mg-0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer’s solution at 37 ºC by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behaviour showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer’s solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion processes. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in sit

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Rezumat Sindromul de compartiment abdominal -complicaåie în chirurgia defectelor parieto-abdominale voluminoase Incidenåa hipertensiunii intraabdominale (HTIA) şi a sindromului de compartiment abdominal (SCA) este subapreciatã în chirurgia defectelor parieto-abdominale de mari dimensiuni, cu diametrul transversal maxim de peste 10 cm, acesta fiind considerat principalul factor de risc pentru dezvoltarea hipertensiunii intraabdominale, alãturi de restricåia ventilatorie sub 60% şi obezitate. Hipertensiunea intraabdominalã înregistreazã o prevalenåã de cel puåin 50% în rândul bolnavilor critici şi a fost identificatã ca factor de risc independent, ameninåãtor de viaåã. Încã, medicii nu evalueazã corespunzãtor şi nu sunt conştienåi de consecinåele potenåial letale ale hipertensiunii intraabdominale netratate. Aceste consecinåe pot fi sindromul de compartiment abdominal, urmat de insuficienåã organicã multiplã şi chiar moartea pacientului. Lucrarea doreşte sã evidenåieze imperiozitatea recunoaşterii în timp util a acestei patologii, ca factor cheie în managementul corect al acestor complicaåii. Cuvinte cheie: sindrom de compartiment abdominal, hipertensiune intraabdominalã, hernie incizionalã. Abstract The incidence of Intraabdominal Hypertension (IAH) and Abdominal Compartment Syndrome (ACS) is underestimated within the surgery of large size parietal-abdominal defects, with the maximum transverse diameter above 10 cm, being considered the main risk factor for the development of intraabdominal hypertension, together with ventilatory restraint under 60% and obesity. Intraabdominal hypertension has a prevalence of at least 50% among critical patients and was identified as an independent life-threatening risk factor. However, doctors do not evaluate it properly and do not realize the potential lethal consequences of untreated intraabdominal hypertension. These consequences may be abdominal compartment syndrome, followed by multiple organ dysfunction and even patient death. The paper intends to highlight the importance of the early recognition of this pathology, as a key factor in the correct management of these complications

COMPARATIVE STUDIES REGARDING HEAVY ELEMENTS CONCENTRATION IN HUMAN CORTICAL BONE

The heavy metal metabolism in the human hard tissues biostructures can be assessed by individual studies made on targeted groups from the same living area. During lifetime the exposure to the heavy metals due to environment and professional sources leads to their concentration increment at calcified tissues level, their study reflecting thaw the integrated or cumulative exposure. This study is conducted on 16 samples from human hard tissue in order to assess the metallic elemental concentration in bone and to find the influence of the human subject age on the results. Due to the fact that previous studies showed high differences in bones metals concentrations relative to the sex, living area and bone type we used in this study only male human bones, from the same area (Bucharest) and the same bone type (cortical). We supposed that this selection would allow us to assess the average value of the bone metal concentration function of age factor and similar with the natural concentration. Scanning electron microscopy coupled with energy dispersion spectrometry method was chosen to assess the morphology of the studied bones and Ca/P ratio. X-ray fluorescence spectrometric method is proposed for the heavy elements analysis and its accuracy is proved using atomic absorption spectrometry, a well known precise method

Effect of the Antimicrobial Agents Peppermint Essential Oil and Silver Nanoparticles on Bone Cement Properties

The main problems directly linked with the use of PMMA bone cements in orthopedic surgery are the improper mechanical bond between cement and bone and the absence of antimicrobial properties. Recently, more research has been devoted to new bone cement with antimicrobial properties using mainly antibiotics or other innovative materials with antimicrobial properties. In this paper, we developed modified PMMA bone cement with antimicrobial properties proposing some experimental antimicrobial agents consisting of silver nanoparticles incorporated in ceramic glass and hydroxyapatite impregnated with peppermint oil. The impact of the addition of antimicrobial agents on the structure, mechanical properties, and biocompatibility of new PMMA bone cements was quantified. It has been shown that the addition of antimicrobial agents improves the flexural strength of the traditional PMMA bone cement, while the yield strength values show a decrease, most likely because this agent acts as a discontinuity inside the material rather than as a reinforcing agent. In the case of all samples, the addition of antimicrobial agents had no significant influence on the thermal stability. The new PMMA bone cement showed good biocompatibility and the possibility of osteoblast proliferation (MTT test) along with a low level of cytotoxicity (LDH test)

Sic Parvis Magna: Manganese-Substituted Tricalcium Phosphate and Its Biophysical Properties

© 2019 American Chemical Society. Succeeding in the substitution of pharmaceutical compounds with ions deliverable with the use of resorbable biomaterials could have far-reaching benefits for medicine and economy. Calcium phosphates are known as excellent accommodators of foreign ions. Manganese, the fifth most abundant metal on Earth was studied here as an ionic dopant in β-tricalcium phosphate (β-TCP) ceramics. β-TCP containing different amounts of Mn2+ ions per MnxCa3-x(PO4)2 formula (x = 0, 0.001, 0.01, and 0.1) was investigated for a range of physicochemical and biological properties. The results suggested the role of Mn2+ as a structure booster, not breaker. Mn2+ ions increased the size of coherent X-ray scattering regions averaged across all crystallographic directions and also lowered the temperature of transformation of the hydroxyapatite precursor to β-TCP. The particle size increased fivefold, from 20 to 100 nm, in the 650-750 °C region, indicating that the reaction of formation of β-TCP was accompanied by a considerable degree of grain growth. The splitting of the antisymmetric stretching mode of the phosphate tetrahedron occurred proportionally to the Mn2+ content in the material, while electron paramagnetic resonance spectra suggested that Mn2+ might substitute for three out of five possible calcium ion positions in the unit cell of β-TCP. The biological effects of Mn-free β-TCP and Mn-doped β-TCP were selective: Moderately proliferative to mammalian cells, moderately inhibitory to bacteria, and insignificant to fungi. Unlike pure β-TCP, β-TCP doped with the highest concentration of Mn2+ ions significantly inhibited the growth of all bacterial species tested: Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Enterococcus faecalis. The overall effect against the Gram-positive bacteria was more intense than against the Gram-negative microorganisms. Meanwhile, β-TCP alone had an augmentative effect of the viability of adipose-derived mesenchymal stem cells (ADMSCs) and the addition of Mn2+ tended to reduce the extent of this augmentative effect, but without imparting any toxicity. For all Mn-doped β-TCP concentrations except the highest, the cell viability after 72 h incubation was significantly higher than that of the negative control. Assays evaluating the effect of Mn2+-containing β-TCP formulations on the differentiation of ADMSCs into three different lineages-osteogenic, adipogenic, and chondrogenic-demonstrated no inhibitory or adverse effects compared to pure β-TCP and powder-free positive controls. Still, β-TCP delivering the lowest amount of Mn2+ seemed most effective in sustaining the differentiation process toward all three phenotypes, indicating that the dose of Mn2+ in β-TCP need not be excessive to be effective

Assessment of the sealant/tooth interface using optical coherence tomography

Sealant materials are typically employed in dentistry in order to prevent the development of cavities on the teeth. They prevent bacterial adhesion to enamel, thus arresting the development of demineralization and of caries. In this study, the critical zone of the interface between different sealant materials and the results of the dental work for the teeth processed were investigated ex vivo using swept source (SS) optical coherence tomography (OCT). Optical inspection and X-ray investigation revealed no defects, while SS-OCT proved capable to asses exactly the position, the nature, and the dimensions of each type of these defects. Specifically, different failures were targeted into the structure of pit and fissure sealants, including bubbles, internal cracks, structural defects of sealant material, and structural defects of enamel, with uncovered sealant material and enamel/sealant interface (marginal integrity and marginal adaptation of dental sealant). The investigation of the possible types of defects that may appear into this dental interface was thus accomplished-for the dental practitioner

New metallic nanoparticles modified adhesive used for time domain optical coherence tomography evaluation of class II direct composite restoration

Non invasive investigation in class II fillings, such as optical coherence tomography (OCT), is slowly entering in the usual dental arsenal of the direct restoration analysis. Working at more than 2 mm depth inside the samples could lead to problems related to the evaluation of the adhesive layer. At this level is difficult to point out the area with adhesive or adhesive with aerie inclusions. For this reason a new metallic Nanoparticles modified dental adhesive is used in order to increase the scattering of the normal adhesive and gain a good contrast on the OCT investigation. The validation of the results were done with SEM and EDAX procedures. In conclusion, noninvasive evaluations methods like OCT, especially OCT working in Time Domain mode, have a great capability to evaluate the interfaces between dental structure, resin fillings and dental adhesive when a metallic Nanoparticles modified adhesive is used

Sic Parvis Magna: Manganese-Substituted Tricalcium Phosphate and Its Biophysical Properties

© 2019 American Chemical Society. Succeeding in the substitution of pharmaceutical compounds with ions deliverable with the use of resorbable biomaterials could have far-reaching benefits for medicine and economy. Calcium phosphates are known as excellent accommodators of foreign ions. Manganese, the fifth most abundant metal on Earth was studied here as an ionic dopant in β-tricalcium phosphate (β-TCP) ceramics. β-TCP containing different amounts of Mn2+ ions per MnxCa3-x(PO4)2 formula (x = 0, 0.001, 0.01, and 0.1) was investigated for a range of physicochemical and biological properties. The results suggested the role of Mn2+ as a structure booster, not breaker. Mn2+ ions increased the size of coherent X-ray scattering regions averaged across all crystallographic directions and also lowered the temperature of transformation of the hydroxyapatite precursor to β-TCP. The particle size increased fivefold, from 20 to 100 nm, in the 650-750 °C region, indicating that the reaction of formation of β-TCP was accompanied by a considerable degree of grain growth. The splitting of the antisymmetric stretching mode of the phosphate tetrahedron occurred proportionally to the Mn2+ content in the material, while electron paramagnetic resonance spectra suggested that Mn2+ might substitute for three out of five possible calcium ion positions in the unit cell of β-TCP. The biological effects of Mn-free β-TCP and Mn-doped β-TCP were selective: Moderately proliferative to mammalian cells, moderately inhibitory to bacteria, and insignificant to fungi. Unlike pure β-TCP, β-TCP doped with the highest concentration of Mn2+ ions significantly inhibited the growth of all bacterial species tested: Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Enterococcus faecalis. The overall effect against the Gram-positive bacteria was more intense than against the Gram-negative microorganisms. Meanwhile, β-TCP alone had an augmentative effect of the viability of adipose-derived mesenchymal stem cells (ADMSCs) and the addition of Mn2+ tended to reduce the extent of this augmentative effect, but without imparting any toxicity. For all Mn-doped β-TCP concentrations except the highest, the cell viability after 72 h incubation was significantly higher than that of the negative control. Assays evaluating the effect of Mn2+-containing β-TCP formulations on the differentiation of ADMSCs into three different lineages-osteogenic, adipogenic, and chondrogenic-demonstrated no inhibitory or adverse effects compared to pure β-TCP and powder-free positive controls. Still, β-TCP delivering the lowest amount of Mn2+ seemed most effective in sustaining the differentiation process toward all three phenotypes, indicating that the dose of Mn2+ in β-TCP need not be excessive to be effective