Commercial Sealants Research Articles

A tough bioadhesive hydrogel supports sutureless sealing of the dural membrane in porcine and ex vivo human tissue.

Complete sequestration of central nervous system tissue and cerebrospinal fluid by the dural membrane is fundamental to maintaining homeostasis and proper organ function, making reconstruction of this layer an essential step during neurosurgery. Primary closure of the dura by suture repair is the current standard, despite facing technical, microenvironmental, and anatomic challenges. Here, we apply a mechanically tough hydrogel paired with a bioadhesive for intraoperative sealing of the dural membrane in rodent, porcine, and human central nervous system tissue. Tensile testing demonstrated that this dural tough adhesive (DTA) exhibited greater toughness with higher maximum stress and stretch compared with commercial sealants in aqueous environments. To evaluate the performance of DTA in the range of intracranial pressure typical of healthy and disease states, ex vivo burst pressure testing was conducted until failure after DTA or commercial sealant application on ex vivo porcine dura with a punch biopsy injury. In contrast to commercial sealants, DTA remained adhered to the porcine dura through increasing pressure up to 300 millimeters of mercury and achieved a greater maximum burst pressure. Feasibility of DTA to repair cerebrospinal fluid leak in a simulated surgical context was evaluated in postmortem human dural tissue. DTA supported effective sutureless repair of the porcine thecal sac in vivo. Biocompatibility and adhesion of DTA was maintained for up to 4 weeks in rodents after implantation. The findings suggest the potential of DTA to augment or perhaps even supplant suture repair and warrant further exploration.

Physicomechanical Properties of Resin-Based Pit and Fissure Sealants Reinforced with Rice Husk Derived Nano Silica and Nanohydroxyapatite

Resin-based pit fissure sealants (RBS) are used to prevent occlusal caries in children. The success of RBS in preventing dental caries is largely influenced by its retention on the tooth surface, which is also affected by its physicomechanical properties. The physicomechanical properties of RBS can be enhanced through the addition of fillers. With the advent of nanofillers, the physicomechanical properties were improved without altering RBS flowability. The present study developed an RBS with a 70 wt% resin matrix and 30 wt% nanofillers. The resin matrix consisted of urethane dimethacrylate (55 wt%), triethylene glycol dimethacrylate (45 wt%), camphoroquinone (0.3 wt%), and 2-(dimethylamino) ethyl methacrylate (0.7 wt%). Silane-treated rice husk-derived nanosilica (20 wt%) and nanohydroxyapatite (10 wt%) were added as fillers. Clinpro, Fissurit FX, and an unfilled sealant were controls. All RBS were tested for surface roughness, Vickers hardness, flexural strength, and flowability. Statistical analysis with oneway ANOVA revealed significant differences between groups in surface roughness, hardness, flowability (p < 0.001), flexural strength, and flexural modulus (p < 0.05). Experimental sealants had higher flexural strength (78 MPa) and flow distance (29.05+1.16 mm) than commercial controls. However, the surface roughness of experimental sealants (0.25+0.08 µm) was higher than Clinpro (0.087+0.027 µm) but lesser than Fissurit FX (0.35+0.19 µm). The Vickers hardness of experimental sealants (23+1.63 VHN) was less than Fissurit FX (28.80+1.69 VHN) but higher than Clinpro (21.74+1.68 VHN). This novel RBS had physicomechanical properties comparable to commercial sealants. The use of nanosilica from rice husk makes this pit and fissure sealer sustainable and environmentally friendly in dentistry.

Preparation and Characterization of Dental Pit and Fissure Sealant Based on Calcium Sodium Silicate Bioactive Glasses

This study aimed to prepare a resin based dental sealant loaded with novel bioactive glass formulated from (50 wt% calcium silicate and 50 wt% sodium silicate) with different percentages of fluorapatite. Four glass batches were formulated then characterized using Fourier Transform Infrared Spectroscopy analysis, X-ray powder diffraction analysis and Transmission electron microscopy. Density, microhardness and bioactivity testing after insertion in artificial saliva were done. Four bisphenol A-glycidyl methacrylate (Bis-GMA) based sealants loaded with the glass batch that showed the preeminent properties and silica fillers were prepared. The prepared sealants were compared to commercial sealants regarding flow, curing depth, compressive strength and microhardness. Sealant composition that showed comparable properties to that of the commercial sealant was selected for pH changes and ion release testing after immersion in artificial saliva for different time intervals. Results indicated amorphous nature, bioactive behavior and apatite forming ability of the tested glass batches. Experimental sealant revealed comparable tested properties with lower compressive strength compared to the commercial sealants at P < 0.001. The mean pH values of the tested sealants ranged from 6.75 to 6.35 with extended calcium and phosphorus ion release up to 90 days. It was concluded that the 85 wt% calcium silicate and sodium silicate with 15 wt% fluorapatite had the best trend regarding ion release and apatite forming ability. Sealant loaded with 65 wt% bioactive glass, 10 wt% sintered nanosilica and 10 wt% nanosilica had the best acceptable mechanical properties. The novel pit and fissure sealant is a promising bioactive and ion releasing material.

Poly-Catecholic Functionalization of Biomolecules for Rapid Gelation, Robust Injectable Bioadhesion, and Near-Infrared Responsiveness.

Mussel-inspired catechol-functionalization of degradable natural biomaterials has garnered significant interest as an approach to achieve bioadhesion for sutureless wound closure. However, conjugation capacity in standard coupling reactions, such as carbodiimide chemistry, is limited by low yield and lack of abundant conjugation sites. Here, a simple oxidative polymerization step before conjugation of catechol-carrying molecules (i.e., 3,4-dihydroxy-l-phenylalanine, l-DOPA) as a potential approach to amplify catechol function in bioadhesion of natural gelatin biomaterials is proposed. Solutions of gelatin modified with poly(l-DOPA) moieties (GelDOPA) are characterized by faster physical gelation and increased viscosity, providing better wound control on double-curved tissue surfaces compared to those of l-DOPA-conjugated gelatin. Physical hydrogels treated topically with low concentrations of NaIO4 solutions are crosslinked on-demand via through-thickness diffusion. Poly(l-DOPA) conjugates enhance crosslinking density compared to l-DOPA conjugated gelatin, resulting in lower swelling and enhanced cohesion in physiological conditions. Together with cohesion, more robust bioadhesion at body temperature is achieved by poly(l-DOPA) conjugates, exceeding those of commercial sealants. Further, poly(l-DOPA) motifs introduced photothermal responsiveness via near-infrared (NIR) irradiation for controlled drug release and potential applications in photothermal therapy. The above functionalities, along with antibacterial activity, render the proposed approach an effective biomaterial design strategy for wound closure applications.

Bioceramic Sealants: A Review

Bioceramic sealants are considered an advantageous technology in modern endodontics. The aim of this article is to highlight the characteristics of bioceramic sealants and to compare them with other root system sealing materials. An extensive search of the endodontic literature was conducted to identify publications related to bioceramic sealants. The results of laboratory and clinical studies on the biological and physical properties of bioceramic-based sealants, as well as comparative studies with other sealants, were evaluated. Several studies evaluated different properties of bioceramic-based sealants, including physical properties, biocompatibility, sealability, adhesion, solubility and antibacterial efficacy. Bioceramic-based sealants were found to be biocompatible and comparable to other commercial sealants. Clinical outcomes associated with the use of bioceramic-based root canal sealants are not established in the literature.

Evaluations of Asphalt-Based Sealant Used in Concrete Caulking: Rheology, Adhesion Properties, and Microstructures

A concrete expansion joint can be damaged due to certain conditions. The performances in terms of temperature sensitivity and adhesion of used sealant materials in concrete caulking have strong relations to the joint service life. In this work, a composite-modified asphalt-based sealant (AS-M) with added styrene-butadiene-styrene (SBS), crumb rubber (CR), and tackifier resin (TR) modifiers was prepared, and its microstructure, high-temperature viscoelasticity, low-temperature crack resistance, and adhesion properties were evaluated, with two commercial finished sealants (AS-A and AS-B) as a reference. Specifically, Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical compositions of asphalt sealants, and the results showed that the physical blending and chemical reactions coexisted in the self-prepared sealant. A good compatibility and continuous structure for each sealant could be observed by fluorescence microscopy (FM). A dynamic shear rheometer (DSR) experiment was conducted to characterize the viscoelastic properties at high temperatures. The self-prepared sealant obtained the highest complex modulus, phase angle, and deformation resistance ability; the composite modifiers showed an outstanding modified effect. The glass transition temperature (Tg) was measured by dynamic mechanical analysis (DMA) testing. The Tg value of the self-prepared sealant was similar to that of the commercial sealant with SBS modifiers, whereas the stress relaxation modulus at a low temperature of the self-prepared sealant was the lowest, indicating that the combination of the modifiers made it obtain a better stress relaxation ability at low temperatures. The self-prepared sealant possessed the best interface adhesive capacity between sealant and aggregate based on surface free energy theory. The experimental results showed that the asphalt sealant modified by SBS/CR/TR has excellent performances in various properties and can be used for concrete caulking.

Self-Healable, Strong, and Tough Polyurethane Elastomer Enabled by Carbamate-Containing Chain Extenders Derived from Ethyl Carbonate.

Commercial diol chain extenders generally could only form two urethane bonds, while abundant hydrogen bonds were required to construct self-healing thermoplastic polyurethane elastomers (TPU). Herein, two diol chain extenders bis(2-hydroxyethyl) (1,3-pheny-lene-bis-(methylene)) dicarbamate (BDM) and bis(2-hydroxyethyl) (methylenebis(cyclohexane-4,1-diy-l)) dicarbamate (BDH), containing two carbamate groups were successfully synthesized through the ring-opening reaction of ethylene carbonate (EC) with 1,3-benzenedimetha-namine (MX-DA) and 4, 4′-diaminodicyclohexylmethane (HMDA). The two chain extenders were applied to successfully achieve both high strength and high self-healing ability. The BDM-1.7 and BDH-1.7 elastomers had high comprehensive self-healing efficiency (100%, 95%) after heated treatment at 60 °C, and exhibited exceptional comprehensive mechanical performances in tensile strength (20.6 ± 1.3 MPa, 37.1 ± 1.7 MPa), toughness (83.5 ± 2.0 MJ/m3, 118.8 ± 5.1 MJ/m3), puncture resistance (196.0 mJ, 626.0 mJ), and adhesion (4.6 MPa, 4.8 MPa). The peculiar mechanical and self-healing properties of TPUs originated from the coexisting short and long hard segments, strain-induced crystallization (SIC). The two elastomers with excellent properties could be applied to engineering-grade fields such as commercial sealants, adhesives, and so on.

Effect of Cross-Linkers on Mussel- and Elastin-Inspired Adhesives on Physiological Substrates.

Surgical adhesives can be useful in wound closure because they reduce the risk of infection and pain associated with sutures and staples. However, there are no commercially available surgical adhesives for soft tissue wound closure. To be effective, soft tissue adhesives must be soft and flexible, strongly cohesive and adhesive, biocompatible, and effective in a moist environment. To address these criteria, we draw inspiration from the elasticity and resilience of elastin proteins and the adhesive of marine mussels. We used an elastin-like polypeptide (ELP) for the backbone of our adhesive material due to its elasticity and biocompatibility. A mussel-inspired adhesive molecule, l-3,4-dihydroxyphenylalanine (DOPA), was incorporated into the adhesive to confer wet-setting adhesion. In this study, an ELP named YKV was designed to include tyrosine residues and lysine residues, which contain amine groups. A modified version of YKV, named mYKV, was created through enzymatic conversion of tyrosine residues into DOPA. The ELPs were combined with iron(III) nitrate, sodium periodate, and/or tris(hydroxymethyl)phosphine (THP) cross-linkers to investigate the effect of DOPA- and amine-based cross-linking on adhesion strength and cure time on porcine skin in a warm, humid environment. Incorporation of DOPA into the ELP increased adhesive strength by 2.5 times and reduced failure rates. Iron cross-linkers improved adhesion in the presence of DOPA. THP increased adhesion for all proteins tested even in the absence of DOPA. Using multiple cross-linkers in a single formulation did not significantly improve adhesion. The adhesives with the highest performance (iron nitrate mixed with mYKV and THP mixed with YKV or mYKV) on porcine skin had 10-18 times higher adhesion than a commercial sealant and reached appreciable adhesive strength within 10 min.

Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity.

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag0 nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO3, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag0 nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag0. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver–silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity.

The antibacterial effect and physical performance of pit and fissure sealants based on an antibacterial core–shell nanocomposite

The application of pit and fissure sealants is a well-established method to prevent and treat early childhood caries. Resin-based sealants with antibacterial properties provide additional benefits for caries prevention in a cariogenic oral environment. The objective of this study was to evaluate the effect of an antibacterial core–shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) on the properties of a resin-based pit and fissure sealant. A commercialized pit and fissure sealant without fluoride, Concise (3M, ESPE, USA), was used as the parent material and negative control. Experimental antibacterial sealants were formulated by the addition of AgBr/BHPVP nanoparticles at mass fractions of 0.5, 1.0, and 1.5 wt% to the parent material. A fluoride-releasing sealant, Clinpro (3M, ESPE), was used as the positive control. Bacterial colony-forming unit (CFU) counts, metabolic activity tests, field emission–scanning electron microscopy (FE–SEM), and confocal laser scanning microscopy (CLSM) observations were used to evaluate the antibacterial properties of AgBr/BHPVP-modified sealants against Streptococcus mutans before and after five months of aging. The Vickers microhardness, degree of conversion, and microleakage level of the sealants were also investigated. According to the results of CFU counts and metabolic tests, sealants containing AgBr/BHPVP showed better contact-killing bactericidal activity against S. mutans than the two commercial sealants, irrespective of aging conditions (both P < 0.05). The AgBr/BHPVP-modified sealants also showed a significant inhibitory effect on the planktonic S. mutans around the cured sealant surfaces. In addition, the Vickers microhardness, degree of conversion, and microleakage level of the parent material were not damaged by modification with AgBr/BHPVP (P > 0.05). AgBr/BHPVP-modified pit and fissure sealant with a dual bactericidal mechanism is a promising option for the prevention of pit and fissure caries.

Chemically Stable, Strongly Adhesive Sealant Patch for Intestinal Anastomotic Leakage Prevention

AbstractIntestinal anastomotic leaking, which involves the discharge of chemically aggressive, non‐sterile fluids into the abdomen, remains one of the most dreaded postoperative complications of abdominal surgery. Depending on the site and the patient condition, incidence ranging between 4% and 21% and mortality rates up to 27% are reported. Currently available surgical sealants only poorly address the issue, especially since most commonly used fibrin glues fail due to insufficient adhesion and chemical instability. Here, a chemically highly resistive, leak‐tight, and mucoadhesive hydrogel sealant, which is grafted on the surface of the intestinal wall using a mutually interpenetrating network that traverses hydrogel and tissue is presented. In contrast to clinically used fibrin‐based sealants (including Tachosil), the developed adhesive poly(acrylamide‐methyl acrylate‐acrylic acid) patch does not degrade and exhibits strong tissue adhesion even when exposed to intestinal fluid. The biocompatible hydrogel patch effectively seals anastomotic leaks in ex vivo intestinal models, greatly surpassing commercial sealants (time to patch‐failure &gt;24 h compared to 5 min for commonly used Tachosil). Importantly, the developed adhesive patch paves the way for the application of both mechanically and chemically robust sealants suitable for the treatment and prevention of intestinal leaks.

Tooth sealing formulation with bacteria-killing surface and on-demand ion release/recharge inhibits early childhood caries key pathogens.

Herein, we investigated a biointeractive tooth sealing material consisted of dimethylaminohexadecyl methacrylate (DMAHDM) and amorphous calcium phosphate nanoparticles (NACPs) to address the above issues simultaneously. Of note, 5% DMAHDM was incorporated into the resin blend, and 20% NACP was added to inorganic filler content of dental formulations intended as dental sealants. The sealing materials were used to seal human extracted teeth. The sealed teeth were subjected to an early childhood caries (ECC) key pathogen (Candida albicans and Streptococcus mutans) biofilm model using a dynamic caries tooth model (CDC reactor). The biofilm growth over the sealed teeth was assessed via colony-forming unit counting metabolic activity assays. The enamel surface hardness loss, degree of conversion, shear bond strength (SBS), and cytotoxicity were also investigated. Formulations having DMAHDM displayed antibacterial efficiency of 2.8-3.5 and 1.4-4.0 log inhibition for Streptococcus mutans and Candida albicans, respectively. Furthermore, the metabolic activity was reduced on the top of the sealed tooth with the biointeractive sealing materials (p < .05). The degree of conversion values was acceptable. The enamel surface hardness loss decreases (36 ± 9.8%) when in contact with the biointeractive tooth sealing material. The SBS of the combined formulation (5% DMAHDM + 20% NACP) was lower than commercial sealant but similar to experimental control. The investigated sealing material holds valuable dual antibacterial and antifungal activities associated with a reduced mineral loss against the cariogenic challenge promoted by ECC key pathogens.

Novel pit and fissure sealant containing nano-CaF2 and dimethylaminohexadecyl methacrylate with double benefits of fluoride release and antibacterial function

ObjectivePit and fissure sealants with antibacterial and remineralization properties have broad application prospects in caries prevention. The objectives of this study were to: (1) develop a novel pit and fissure sealant containing CaF2 nanoparticles (nCaF2) and dimethylaminohexadecyl methacrylate (DMAHDM); and (2) investigate the effects of nCaF2 and DMAHDM on biofilm response and fluoride (F) ion release for the first time. MethodsHelioseal F was used as a control. Bioactive sealants were formulated with DMAHDM and nCaF2. Flow properties, enamel shear bond strength, hardness and F ion releases were measured. Streptococcus mutans (S. mutans) biofilms were grown on sealants. Biofilm metabolic activity, lactic acid production, colony-forming units (CFU), and pH of biofilm culture medium were measured. ResultsAdding 5% DMAHDM and 20% nCaF2 did not reduce the paste flow and enamel bond strength, compared to control (p < 0.05). Hardness of sealants with 20% nCaF2 and DMAHDM was higher than control (p < 0.05). The F ion release from 20% nCaF2 was much higher than that of commercial control (p < 0.05). The sealant with DMAHDM reduced the S. mutans biofilm CFU by 4 logs. The pH in biofilm medium of the new bioactive sealant was much higher (pH 6.8) than that of commercial sealant (pH 4.66) (p < 0.05). SignificanceThe new bioactive pit and fissure sealant with nCaF2 and DMAHDM achieved high fluoride release and strong antibacterial performance. This novel fluoride-releasing and antibacterial sealant is promising to inhibit caries and promote the remineralizaton of enamel and dentin.

Evaluation of a biocompatible sealant for on-demand repair of vascular defects—a chronic study in a large animal model

Existing surgical sealants fail to combine design requirements, such as sealing performance, on-demand activation and biocompatibility. The aim of this study was to compare the effectiveness and safety of the SETALIUM™ Vascular Sealant (SVS), a novel, on-demand activatable sealant, with the commercial sealant, BioGlue®, for the repair of vascular defects. In an in vivo porcine model, the use of SVS was compared with BioGlue, for sealing 2-mm defects of the carotid artery and jugular vein. Animals were followed for 7 days and 5 weeks (each time point and per experimental group, n = 4), respectively. The degree of stenosis and flow velocity was determined, and the local tissue response was evaluated. In vivo incision closure succeeded in all cases, and SVS was superior in clinical usability, enabled by its on-demand activation. Unlike BioGlue, SVS use did not induce stenosis and was associated with physiological blood flow in all cases. Moreover, closure with SVS was associated with a low inflammatory reaction and no thrombus formation or intima proliferation, in contrast to BioGlue. SVS demonstrated effective and rapid sealing of 2-mm vascular defects, with favourable biocompatibility compared to BioGlue. Thus, SVS seems to be an effective and safe vascular sealant.

Incorporation of hydrophobic nanochitosan improves wear resistance of dental sealants

This study evaluated the effect of addition of nanochitosan on the wear resistance of pit and fissure sealants. Hydrophobic N-(2-ethylhexanoyl)chitosan nanoparticles were synthesized, characterized, and added to commercial sealants. The sealants were subjected to customized abrasion test, followed by wear resistance analysis using weight loss measurement and 3-D profilometric methods. Analytical techniques confirmed the substitution. The particles ranged in size from 320 to 670 nm. Results showed a marginal improvement in the wear behavior of modified sealants compared to unmodified sealants. It can be concluded that this modification could prolong the life of these preventive restorations.

Development of Bis-GMA-free biopolymer to avoid estrogenicity

ObjectiveAlthough bisphenol A-glycidyl methacrylate (Bis-GMA)-based dental materials are widely used in dentistry, Estrogenicity from released bisphenol A remains a concern due to possibility of adversely affecting the growth of children and homeostasis of adults. Here, a new family of isosorbide-derived biomonomers were synthesized and experimentally utilized as a matrix of dental sealants to provide physico-mechanical and biological properties comparable to those of a conventional Bis-GMA-based material but without the the potential estrogenicity. MethodsAfter synthesis of isosorbide-derived biomonomers (ISDB) by light polymerization, an experimental dental sealant with different silica filler concentrations (0–15wt%) was characterized and compared to a commercially available Bis-GMA-based sealant. Cytotoxicity and estrogenicity assays were conducted with human oral keratinocytes and estrogen-sensitive MCF-7 cells, respectively. ResultsISDB-based dental sealants exhibited typical initially smooth surfaces with depth of cure, Vickers hardness, compressive strength/modulus, water resorption/solubility, and flowability comparable to those of the commercial sealant and met the ISO standard for dental sealants and polymer-based restorative materials. Indirect cytotoxicity tests using an extract showed comparable viability among experimental ISDB-based materials and a commercial Bis-GMA-incorporated control. DNA synthesis in MCF-7 cells (a marker of estrogenicity) and the release of bisphenol A under enzymatic incubation were not detected in ISDB-based materials. SignificanceIn conclusion, the comparable physico-mechanical properties of ISDB-based materials with their cytocompatibility and lack of estrogenicity suggest the potential usefulness of ISDBs as a newly developed and safe biomaterial.

Microinfiltration of Mg(NO3)2·6H2O into g-C3N4 and macroencapsulation with commercial sealants: A two-step method to enhance the thermal stability of inorganic composite phase change materials

Mg(NO3)2·6H2O is a promising thermal energy storage material owing to its suitable melting point and high latent heat; however, it suffers from poor thermal stability owing to dehydration. This paper presents a two-step encapsulation method to prepare a shape-stabilized Mg(NO3)2·6H2O composite phase change material (CPCM). First, Mg(NO3)2·6H2O is infiltrated into a novel porous matrix – the graphitic carbon nitride (g-C3N4). The g-C3N4 provides a microhousing for Mg(NO3)2·6H2O to prevent liquid from leaking out during the solid–liquid phase change. The g-C3N4 also significantly reduces the sub-cooling degree of Mg(NO3)2·6H2O from 29.2 °C to 1.9 °C. The Mg(NO3)2·6H2O/g-C3N4 composite with 80 wt% Mg(NO3)2·6H2O has a phase change temperature of 87.0 °C and a specific phase change enthalpy of 112.30 kJ kg−1. Second, the Mg(NO3)2·6H2O/g-C3N4 composite is shaped into a cylinder and then macroencapsulated with commercial adhesive sealants (an epoxy resin structural adhesive and silicon sealant). The sealants provide a shell for the hydrated salt to prevent dehydration. After 100 thermal cycles, the composite phase change material only lost 0.84% and 6.25% in weight with coatings of epoxy resin and silicon sealant, respectively, which are much lower than the 22.92% for the uncoated composite phase change material. The specific phase change enthalpy of the composite phase change material barely changed after 100 cycles; however, the loss for the uncoated composite phase change material reached 22.47%. The joint effect of the g-C3N4 matrix and the sealants improve the thermal stability and reliability of the Mg(NO3)2·6H2O. This sequential multi-scale encapsulation method is promising for solving the typical problems of hydrated salts.

A PEG-Lysozyme hydrogel harvests multiple functions as a fit-to-shape tissue sealant for internal-use of body

In situ formation of surgical sealants to stop internal fluids leakage is more attractive compared to the traditional suture or staple. However, commercial sealants have weak points in tissue adhesive, cell affinity, antibacterial etc., which make them remain suboptimal for internal use of body. It is required to develop multifunctional sealants that can meet clinical needs.Herein, a PEG-lysozyme (LZM) injectable sealant composed of 4-arm-PEG and lysozyme was developed. Lysozyme offers free amine groups to rapidly cross link with PEG. The hydrogel can tightly adhere to tissues and provide good mechanics to withstand high pressure. Moreover, lysozyme innately confers antibacterial and cell affinity on the hydrogel that are usually lacking in marketed sealants. The hydrogel is easily operated to seal gas or blood leakage in a rabbit trachea and artery defect. Moreover, it can close the transmural left ventricular wall defect on a beating heart. The traumatic organ functions completely recovered postoperatively. Considering the good biocompatibility and the simple fabrication process, the PEG-LZM hydrogel is promising to clinical transformation. More broadly, our work indicates that nature-occurring molecules are versatile building blocks for construction of materials and confer functions, which represents a simple tragedy to develop advanced functional biomaterials.

Tuning Nano-Amorphous Calcium Phosphate Content in Novel Rechargeable Antibacterial Dental Sealant

Dental sealants with antibacterial and remineralizing properties are promising for caries prevention among children and adolescents. The application of nanotechnology and polymer development have enabled nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) to emerge as anti-caries strategies via resin-based dental materials. Our objectives in this study were to (1) incorporate different mass fractions of NACP into a parental rechargeable and antibacterial sealant; (2) investigate the effects on mechanical performance, and (3) assess how the variations in NACP concentration would affect the calcium (Ca) and phosphate (PO4) ion release and re-chargeability over time. NACP were synthesized using a spray-drying technique and incorporated at mass fractions of 0, 10, 20 and 30%. Flexural strength, flexural modulus, and flowability were assessed for mechanical and physical performance. Ca and PO4 ion release were measured over 70 days, and three ion recharging cycles were performed for re-chargeability. The impact of the loading percentage of NACP upon the sealant’s performance was evaluated, and the optimized formulation was eventually selected. The experimental sealant at 20% NACP had flexural strength and flexural modulus of 79.5 ± 8.4 MPa and 4.2 ± 0.4 GPa, respectively, while the flexural strength and flexural modulus of a commercial sealant control were 70.7 ± 5.5 MPa (p > 0.05) and 3.3 ± 0.5 GPa (p < 0.05), respectively. A significant reduction in flow was observed in the experimental sealant at 30% NACP (p < 0.05). Increasing the NACP mass fraction increased the ion release. The sealant formulation with NACP at 20% displayed desirable mechanical performance and ideal flow and handling properties, and also showed high levels of long-term Ca and PO4 ion release and excellent recharge capabilities. The findings provide fundamental data for the development of a new generation of antibacterial and rechargeable Ca and PO4 dental sealants to promote remineralization and inhibit caries.

Evaluation of remineralization potential and mechanical properties of pit and fissure sealants fortified with nano-hydroxyapatite and nano-amorphous calcium phosphate fillers: An in vitro study.

Objectives:The aim of this study was: (i) to formulate pit and fissure sealants (PFS) containing nano-hydroxyapatite (nHAP) filler; nHAP filler and silica co-filler; nHAP and nano-Amorphous Calcium Phosphate (nACP) co-filler, (ii) to evaluate physical properties; degree of conversion (DOC), curing depth (CD) and mechanical properties; microshear bond strength (MBS) of fortified PFS, and (iii) to assess remineralization potential and release of Ca2= and PO4 ions from newly synthesized sealants.Materials and Methods:Four PFS were prepared using monomers with mixture of 35.5 wt % BisGMA, 35.5 wt % triethylene glycol dimethacrylate and 28 wt % hydroxyethyl methacrylate. Bioactive nanofillers (nHAP and n-ACP) were added in various concentrations (0%–30%). Three commercial sealants were used as follows: unfilled (Clinpro; 3M ESPE), Fluoride releasing (Delton FS plus, Dentsply), ACP filled (Aegis, Bosworth). The samples (n = 35.5/gp) were tested for MBS, DOC, and CD. Remineralization potential was assessed by scanning electron microscopy (SEM). The concentrations of Ca2= and PO4 released from the sealant specimens were analyzed with Ultraviolet-visible Spectrophotometer. Data obtained was statistically analyzed (one-way analysis of variance, Tukey's test, P < 0.05).Results:10% hydroxyapatite (HAP) =20% ACP sealant showed significantly higher DOC. A remineralized region on the surface between fissure sealant and tooth enamel was observed by SEM in all three HAP filled bioactive sealants. Decreasing the solution pH significantly increased ion release from sealant filled with 10% nHAP = 20% nACP (P ≤ 0.001).Conclusion:Results suggested that admixture of nHAP and nACP to PFS showed remineralizing capability, without declining their mechanical and physical properties.