There is an ever‐evolving need of customized, anatomic‐specific grafting materials for bone regeneration. More specifically, biocompatible and osteoconductive materials, that may be configured ...dynamically to fit and fill defects, through the application of an external stimulus. The objective of this study was to establish a basis for the development of direct inkjet writing (DIW)‐based shape memory polymer‐ceramic composites for bone tissue regeneration applications and to establish material behavior under thermomechanical loading. Polymer‐ceramic (polylactic acid PLA/β‐tricalcium phosphate β‐TCP) colloidal gels were prepared of different w/w ratios (90/10, 80/20, 70/30, 60/40, and 50/50) through polymer dissolution in acetone (15% w/v). Cytocompatibility was analyzed through Presto Blue assays. Rheological properties of the colloidal gels were measured to determine shear‐thinning capabilities. Gels were then extruded through a custom‐built DIW printer. Space filling constructs of the gels were printed and subjected to thermomechanical characterization to measure shape fixity (Rf) and shape recovery (Rr) ratios through five successive shape memory cycles. The polymer‐ceramic composite gels exhibited shear‐thinning capabilities for extrusion through a nozzle for DIW. A significant increase in cellular viability was observed with the addition of β‐TCP particles within the polymer matrix relative to pure PLA. Shape memory effect in the printed constructs was repeatable up to 4 cycles followed by permanent deformation. While further research on scaffold macro‐/micro‐geometries, and engineered porosities are warranted, this proof‐of‐concept study suggested suitability of this polymer‐ceramic material and the DIW 3D printing workflow for the production of customized, patient specific constructs for bone tissue engineering.
Objectives
To characterize the mechanical and biological properties of three commercially available resins, which are currently used for provisional restorations and to compare them to an ...experimental resin intended for definitive fixed dental prostheses.
Materials and methods
Three commercially available resins: Crowntec (CT, Saremco), Temporary C&B (FL, Formlabs), C&B MFH (ND, Nextdent), and the experimental resin: Permanent Bridge (PB, Saremco) were printed and subjected to biaxial flexural strength test, finite element analysis, Weibull analysis, scanning electron microscopy, cell proliferation, immunohistochemistry and cytotoxicity assays. Samples from CT, PB, and ND were provided directly from the manufacturers ensuring ideal workflow. FL was printed using the workflow as recommended by the manufacturer, using a Formlabs 2 printer and their post‐processing units Form Wash and Form Cure.
Results
From the tested resins, PB yielded the best overall results in terms of mechanical properties. Cell proliferation and cytotoxicity did not show any significant differences among materials. PB showed higher values for probability of survival predictions (35%) when subjected to 250 MPa loads, whereas the other materials did not reach 10%.
Significance
Despite mechanical differences between the evaluated materials, the outcomes suggest that 3D printed provisional resins may be used in clinical settings, following the manufacturers indications. New materials intended for long‐term use, such as the PB resin, yielded higher mechanical properties compared to the other materials. Alternative printing and post‐processing methods have not yet been evaluated and should be avoided until further literature is available.
Clinical significance
3D printed resins for provisional restorations have become popular with the emergence of new technologies. In this study, we evaluated three different commercially available resins for provisional restorations and one new experimental resin. The results from this study indicate that commercially available resins could be used in clinical settings under certain conditions and limited periods of time. Following the manufacturers protocols is of paramount importance to not compromise these properties.
The bulk metallic glass (BMG), Pd79Ag3.5P6Si9.5Ge2, has a high fracture toughness and has been found to accommodate post-yield stress, unlike most other BMG. Moreover, due to its greater noble gas ...composition it has a intrinsic corrosion resistance, ideal for dental and orthopedic implants.
This present study aimed to evaluate the in vivo application of Pd79Ag3.5P6Si9.5Ge2 in a large translational sheep model to assess its efficacy to be utilized as an endosteal device.
Twelve implants in the form of cylindrical rods (3 mm in diameter) were produced through rapid quenching. Each sheep (n = 12) received one osteotomy in the mandibular region using rotary instrumentation, which was filled with Pd79Ag3.5P6Si9.5Ge2. After 6- and 24-weeks the animals were euthanized, and samples collected en bloc to conduct histomorphometric analysis. The degree of osseointegration were assessed through bone-to-implant contact (BIC).
All samples revealed favorable BIC along with with fibrous connective tissue layers at both 6- and 24-weeks. Bone along with interfacial remodeling was observed in proximity with the metallic glass surface at 6 weeks with higher degrees of bone organization being observed at the later healing time, 24 weeks.
The synthesized BMG, given its unique combination of toughness and strength, revealed potential to serve as an alternative to commonly used Ti alloys.
Periodontitis is a bacteria‐induced chronic inflammatory disease characterized by degradation of the supporting tissue and bone in the oral cavity. Treatment modalities seek to facilitate periodontal ...rehabilitation while simultaneously preventing further gingival tissue recession and potentially bone atrophy. The aim of this study was to compare two differently sourced membranes, a resorbable piscine collagen membrane and a porcine‐derived collagen membrane, in the repair of soft tissue defects utilizing a preclinical canine model. This in vivo component consisted of 10 beagles which were subjected to bilateral maxillary canine mucogingival flap defects, as well as bilateral soft tissue defects (or pouches) with no periodontal ligament damage in the mandibular canines. Defects received either a piscine‐derived dermal membrane, (Kerecis® Oral, Ísafjörður, Iceland) or porcine‐derived dermal membrane (Geistlich Mucograft®, Wolhusen, Switzerland) in a randomized fashion (to avoid site bias) and were allowed to heal for 30, 60, or 90 days. Statistical evaluation of tissue thickness was performed using general linear mixed model analysis of variance and least significant difference (LSD) post hoc analyses with fixed factors of time and membrane. Semi‐quantitative analysis employed for inflammation assessment was evaluated using a chi‐squared test along with a heteroscedastic t‐test and values were reported as mean and corresponding 95% confidence intervals. In both the mucogingival flap defects and soft tissue gingival pouches, no appreciable qualitative differences were observed in tissue healing between the membranes. Furthermore, no statistical differences were observed in the thickness measurements between piscine‐ and porcine‐derived membranes in the mucogingival flap defects (1.05 mm ±0.17 and 1.29 mm ±0.17, respectively p = .06) or soft tissue pouches (1.36 mm ±0.14 and 1.47 mm ±0.14, respectively p = .27), collapsed over time. Independent of membrane source (i.e., piscine or porcine), similar inflammatory responses were observed in both the maxilla and mandible at the three time points (p = .88 and p = .79, respectively). Histologic and histomorphometric evaluation results indicated that both membranes yielded equivalent tissue responses, remodeling dynamics and healing patterns for the mucogingival flap as well as the soft tissue gingival pouch defect models.
Hydrogels with long-term storage stability, controllable sustained-release properties, and biocompatibility have been garnering attention as carriers for drug/growth factor delivery in tissue ...engineering applications. Chitosan (CS)/Graphene Oxide (GO)/Hydroxyethyl cellulose (HEC)/β-glycerol phosphate (β-GP) hydrogel is capable of forming a 3D gel network at physiological temperature (37 °C), rendering it an excellent candidate for use as an injectable biomaterial. This work focused on an injectable thermo-responsive CS/GO/HEC/β-GP hydrogel, which was designed to deliver Atsttrin, an engineered derivative of a known chondrogenic and anti-inflammatory growth factor-like molecule progranulin. The combination of the CS/GO/HEC/β-GP hydrogel and Atsttrin provides a unique biochemical and biomechanical environment to enhance fracture healing. CS/GO/HEC/β-GP hydrogels with increased amounts of GO exhibited rapid sol-gel transition, higher viscosity, and sustained release of Atsttrin. In addition, these hydrogels exhibited a porous interconnected structure. The combination of Atsttrin and hydrogel successfully promoted chondrogenesis and osteogenesis of bone marrow mesenchymal stem cells (bmMSCs) in vitro. Furthermore, the work also presented in vivo evidence that injection of Atsttrin-loaded CS/GO/HEC/β-GP hydrogel stimulated diabetic fracture healing by simultaneously inhibiting inflammatory and stimulating cartilage regeneration and endochondral bone formation signaling pathways. Collectively, the developed injectable thermo-responsive CS/GO/HEC/βG-P hydrogel yielded to be minimally invasive, as well as capable of prolonged and sustained delivery of Atsttrin, for therapeutic application in impaired fracture healing, particularly diabetic fracture healing.
Preparation of hydrogel solutions, the schematic crosslinking mechanism between the CS and HEC with GO, and a single dose injection of the materials at the fracture site immediately after inducing femur fracture in mouse closed gravity-induced fracture model. Display omitted
Bone tissue has the capacity to regenerate under healthy conditions, but complex cases like critically sized defects hinder natural bone regeneration, necessitating surgery, and use of a grafting ...material for rehabilitation. The field of bone tissue engineering (BTE) has pioneered ways to address such issues utilizing different biomaterials to create a platform for cell migration and tissue formation, leading to improved bone reconstruction. One such approach involves 3D‐printed patient‐specific scaffolds designed to aid in regeneration of boney defects. This study aimed to develop and characterize 3D printed scaffolds composed of type I collagen augmented with β‐tricalcium phosphate (COL/β‐TCP). A custom‐built direct inkjet write (DIW) printer was used to fabricate β‐TCP, COL, and COL/β‐TCP scaffolds using synthesized colloidal gels. After chemical crosslinking, the scaffolds were lyophilized and subjected to several characterization techniques, including light microscopy, scanning electron microscopy, and x‐ray diffraction to evaluate morphological and chemical properties. In vitro evaluation was performed using human osteoprogenitor cells to assess cytotoxicity and proliferative capacity of the different scaffold types. Characterization results confirmed the presence of β‐TCP in the 3D printed COL/β‐TCP scaffolds, which exhibited crystals that were attributed to β‐TCP due to the presence of calcium and phosphorus, detected through energy dispersive x‐ray spectroscopy. In vitro studies showed that the COL/β‐TCP scaffolds yielded more favorable results in terms of cell viability and proliferation compared to β‐TCP and COL scaffolds. The novel COL/β‐TCP scaffold constructs hold promise for improving BTE applications and may offer a superior environment for bone regeneration compared with conventional COL and β‐TCP scaffolds.
Non-resorbable dental barrier membranes entail the risk of dehiscence due to their smooth and functionally inert surfaces. Non-thermal plasma (NTP) treatment has been shown to increase the ...hydrophilicity of a biomaterials and could thereby enhance cellular adhesion. This study aimed to elucidate the role of allyl alcohol NTP treatment of poly(tetrafluoroethylene) in its cellular adhesion. The materials (non-treated PTFE membranes (NTMem) and NTP-treated PTFE membranes (PTMem)) were subjected to characterization using scanning electron microscopy (SEM), contact angle measurements, X-ray photoelectron spectroscopy (XPS), and electron spectroscopy for chemical analysis (ESCA). Cells were seeded upon the different membranes, and cellular adhesion was analyzed qualitatively and quantitatively using fluorescence labeling and a hemocytometer, respectively. PTMem exhibited higher surface energies and the incorporation of reactive functional groups. NTP altered the surface topography and chemistry of PTFE membranes, as seen through SEM, XPS and ESCA, with partial defluorination and polymer chain breakage. Fluorescence labeling indicated significantly higher cell populations on PTMem relative to its untreated counterparts (NTMem). The results of this study support the potential applicability of allyl alcohol NTP treatment for polymeric biomaterials such as PTFE—to increase cellular adhesion for use as dental barrier membranes.
Hypothesis
Injuries requiring resection of tissue followed by autogenous bone transfer may be prone to infection by Staphylococcus aureus, impeding recovery and increasing medical costs. For critical ...sized defects, the common approach to reconstruction is a tissue transfer procedure but is subject to limitations (e.g., donor site morbidity, cost, operating time). Utilizing beta tricalcium phosphate (β‐TCP) as bone grafting material augmented with silver (Ag), a custom graft may be 3D printed to overcome limitations and minimize potential infections.
Experiments
Scaffolds were 3D printed and augmented with Ag by external attack on the surface by silver nitrate (AgNO3) at varying concentrations (0.1, 1.0, 10% wt/wt of scaffold). The augmented scaffolds were evaluated utilizing X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP‐MS) to verify the presence of Ag and phosphate (PO4) groups followed by electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to gather information of chemical and physical properties. Preliminary biocompatibility and bactericidal capacity of the scaffolds were tested using human osteoprogenitor (hOP) cells and methicillin‐sensitive S. aureus strain, respectively.
Results
XRD, FTIR, ICP‐MS, TGA, and DSC confirmed presence of Ag and PO4 groups, whereas electron microscopy showed a decrease in Ca and an increase in Ag ions, decreasing Ca/P ratio with increasing surfactant concentrations. PrestoBlue assays yielded an increase in fluorescence cell counts among experimental groups with lower concentrations of Ag characterized by their characteristic trapezoidal shape whereas cytotoxicity was observed at higher concentrations. Similar observations were made with alkaline phosphatase assays. Antimicrobial evaluation showed reduced colony‐forming units (CFU) among all experimental groups when compared to 100% β‐TCP. β‐TCP scaffolds augmented with Ag ions facilitate antibacterial effects while promoting osteoblast adhesion and proliferation.
Bone regeneration remains a significant clinical challenge, often necessitating surgical approaches when healing bone defects and fracture nonunions. Within this context, the modulation of adenosine ...signaling pathways has emerged as a promising therapeutic option, encouraging osteoblast activation and tempering osteoclast differentiation. A literature review of the PubMed database with relevant keywords was conducted. The search criteria involved in vitro or in vivo models, with clear methodological descriptions. Only studies that included the use of indirect adenosine agonists, looking at the effects of bone regeneration, were considered relevant according to the eligibility criteria. A total of 29 articles were identified which met the inclusion and exclusion criteria, and they were reviewed to highlight the preclinical translation of adenosine agonists. While preclinical studies demonstrate the therapeutic potential of adenosine signaling in bone regeneration, its clinical application remains unrealized, underscoring the need for further clinical trials. To date, only large, preclinical animal models using indirect adenosine agonists have been successful in stimulating bone regeneration. The adenosine receptors (Asub.1, Asub.2A, Asub.2B, and Asub.3) stimulate various pathways, inducing different cellular responses. Specifically, indirect adenosine agonists act to increase the extracellular concentration of adenosine, subsequently agonizing the respective adenosine receptors. The agonism of each receptor is dependent on its expression on the cell surface, the extracellular concentration of adenosine, and its affinity for adenosine. This comprehensive review analyzed the multitude of indirect agonists currently being studied preclinically for bone regeneration, discussing the mechanisms of each agonist, their cellular responses in vitro, and their effects on bone formation in vivo.
The aim of this study was to evaluate the bone healing of tight‐fit implants placed in the maxilla and mandible of subjects compromised with metabolic syndrome (MS) and type‐2 Diabetes Mellitus ...(T2DM). Eighteen Göttingen minipigs were randomly distributed into three groups: (i) control (normal diet), (ii) MS (cafeteria diet for obesity induction), (iii) T2DM (cafeteria diet for obesity induction + Streptozotocin for T2DM induction). Maxillary and mandibular premolars and molar were extracted. After 8 weeks of healing, implants with progressive small buttress threads were placed, and allowed to integrate for 6 weeks after which the implant/bone blocks were retrieved for histological processing. Qualitative and quantitative histomorphometric analyses (percentage of bone‐to‐implant contact, %BIC, and bone area fraction occupancy within implant threads, %BAFO) were performed. The bone healing process around the implant occurred predominantly through interfacial remodeling with subsequent bone apposition. Data as a function of systemic condition yielded significantly higher %BIC and %BAFO values for healthy and MS relative to T2DM. Data as a function of maxilla and mandible did not yield significant differences for either %BIC and %BAFO. When considering both factors, healthy and MS subjects had %BIC and %BAFO trend towards higher values in the mandible relative to maxilla, whereas T2DM yielded higher %BIC and %BAFO in the maxilla relative to mandible. All systemic conditions presented comparable levels of %BIC and %BAFO in the maxilla; healthy and MS presented significantly higher %BIC and %BAFO relative to T2DM in the mandible. T2DM presented lower amounts of bone formation around implants relative to MS and healthy. Implants placed in the maxilla and in the mandible showed comparable amounts of bone in proximity to implants.
