Blood and fibroblast responses to thermoset BisGMA-TEGDMA/glass fiber-reinforced composite implants in vitro.

OBJECTIVES: This in vitro study was designed to evaluate both blood and human gingival fibroblast responses on fiber-reinforced composite (FRC) aimed to be used as oral implant abutment material. MATERIAL AND METHODS: Two different types of substrates were investigated: (a) Plain polymer (BisGMA 50%-TEGDMA 50%) and (b) FRC. The average surface roughness (Ra) was measured using spinning-disk confocal microscope. The phase composition was identified using X-ray diffraction analyzer. The degree of monomer conversion (DC%) was determined using FTIR spectrometry. The blood response, including the blood-clotting ability and platelet adhesion morphology, was evaluated. Fibroblast cell responses were studied in cell culture environment using routine test conditions. RESULTS: The Ra of the substrates investigated was less than 0.1 µm with no signs of surface crystallization. The DC% was 89.1 ± 0.5%. The FRC substrates had a shorter clotting time and higher platelets activation state than plain polymer substrates. The FRC substrates showed higher (P < 0.01-0.001) amount of adhered cells than plain polymer substrates at all time points investigated. The strength of attachment was evaluated using serial trypsinization, the number of cells detached from FRC substrates was 59 ± 5%, whereas those detached from the plane polymer substrates was 70 ± 5%, indicating a stronger (P < 0.01) cell attachment on the FRC surfaces. Fibroblasts grew more efficiently on FRC than on plain polymer substrates, showing significantly higher (P < 0.01) cell metabolic activities throughout the experiment. CONCLUSIONS: The presence of E-glass fibers enhances blood and fibroblast responses on composite surfaces in vitro.

The Application of Organs-on-a-Chip in Dental, Oral, and Craniofacial Research.

The current development of microfluidics-based microphysiological systems (MPSs) will rapidly lead to a paradigm shift from traditional static 2-dimensional cell cultivation towards organized tissue culture within a dynamic cellular milieu. Especially organs-on-a-chip (OoCs) can very precisely re-create the mechanical and unique anatomical structures of the oral environment. This review provides an introduction to such technology, from commonly used chip materials and fabrication methods to the application of OoC in in vitro culture. OoCs are advantageous because of their small-scaled culture environment, the highly controlled dynamic experimental conditions, and the likeness to the in vivo structure. We specifically focus on current chip designs in dental, oral, and craniofacial (DOC) research. Also, future perspectives are discussed, like model standardization and the development of integrated platforms with advanced read-out functionality. By doing so, it will be possible for OoCs to serve as an alternative for animal testing and to develop highly predictive human models for clinical experiments and even personalized medicine.

Dynamic cell adhesion and migration on nanoscale grooved substrates.

Organised nanotopography mimicking the natural extracellular matrix can be used to control morphology, cell motility, and differentiation. However, it is still unknown how specific cell types react with specific patterns. Both initial adhesion and preferential cell migration may be important to initiate and increase cell locomotion and coverage with cells, and thus achieve an enhanced wound healing response around an implantable material. Therefore, the aim of this study was to evaluate how MC3T3-E1 osteoblast initial adhesion and directional migration are influenced by nanogrooves with pitches ranging from 150 nm up to 1000 nm. In this study, we used a multi-patterned substrate with five different groove patterns and a smooth area with either a concentric or radial orientation. Initial cell adhesion measurements after 10 s were performed using atomic force spectroscopy-assisted single-cell force spectroscopy, and demonstrated that nascent cell adhesion was highly induced by a 600 nm pitch and reduced by a 150 nm pitch. Addition of RGD peptide significantly reduced adhesion, indicating that integrins and cell adhesive proteins (e.g. fibronectin or vitronectin) are key factors in specific cell adhesion on nanogrooved substrates. Also, cell migration was highly dependent on the groove pitch; the highest directional migration parallel to the grooves was observed on a 600 nm pitch, whereas a 150 nm pitch restrained directional cell migration. From this study, we conclude that grooves with a pitch of 600 nm may be favourable to enhance fast wound closure, thereby promoting tissue regeneration.

Submicron-patterning of bulk titanium by nanoimprint lithography and reactive ion etching.

Nanopatterns on titanium may enhance endosseous implant biofunctionality. To enable biological studies to prove this hypothesis, we developed a scalable method of fabricating nanogrooved titanium substrates. We defined nanogrooves by nanoimprint lithography (NIL) and a subsequent pattern transfer to the surface of ASTM grade 2 bulk titanium applying a soft-mask for chlorine-based reactive ion etching (RIE). With respect to direct write lithographic techniques the method introduced here is fast and capable of delivering uniformly patterned areas of at least 4 cm(2). A dedicated silicon nanostamp process has been designed to generate the required thickness of the soft-mask for the NIL-RIE pattern transfer. Stamps with pitch sizes from 1000 nm down to 300 nm were fabricated using laser interference lithography (LIL) and deep cryogenic silicon RIE. Although silicon nanomachining was proven to produce smaller pitch sizes of 200 nm and 150 nm respectively, successful pattern transfer to titanium was only possible down to a pitch of 300 nm. Hence, the smallest nanogrooves have a width of 140 nm. An x-ray photoelectron spectroscopy study showed that only very few contaminations arise from the fabrication process and a cytotoxicity assay on the nanopatterned surfaces confirmed that the obtained nanogrooved titanium specimens are suitable for in vivo studies in implantology research.

Third-generation modular mandible endoprosthesis in Macaca fascicularis.

The aim of this study was to develop a third-generation modular mandible endoprosthesis that would experience less stress concentration at its stems compared to earlier generations, thereby minimizing micromotion and achieving long-term stability. In this three-piece modular design, different degrees of movement were incorporated between the endoprosthesis module interfaces. It was hypothesized that this unique feature would minimize stress concentration at the stems and hence promote osseointegration during the early phase of implantation. The endoprosthesis system was made of commercially pure grade 4 titanium, machined and surface-treated, then sterilized and implanted in segmental mandible defects of nine Macaca fascicularis. Clinical, radiological, histological, and histomorphometric evaluations were performed 4 months post-implantation. The endoprosthesis systems with a degree of movement incorporated, exhibited superior performance compared to the rigid system: 30.9-34.8 times higher percentage bone-implant contact (P< 0.0001) and 3.4-4.1 times higher percentage bone area (P<0.0001), with osseointegration noted at the posterior stems. However, fibrous tissue encapsulation was noted around the majority of the anterior stems in all groups. Although the degree of movement was favourable for improving bone healing and stability of the endoprosthesis system, more work needs to be done to investigate other strategies to further reduce loading on the endoprosthesis to achieve predictable osseointegration at the stems.

The influence of nanoscale topographical cues on initial osteoblast morphology and migration.

The natural environment of a living cell is not only organized on a micrometer, but also on a nanometer scale. Mimicking such a nanoscale topography in implantable biomaterials is critical to guide cellular behavior. Also, a correct positioning of cells on biomaterials is supposed to be very important for promoting wound healing and tissue regeneration. The exact mechanism by which nanotextures can control cellular behavior are thus far not well understood and it is thus far unknown how cells recognize and respond to certain surface patterns, whereas a directed response appears to be absent on other pattern types. Focal adhesions (FAs) are known to be involved in the process of specific pattern recognition and subsequent response by cells. In this study, we used a high throughput screening "Biochip" containing 40 different nanopatterns to evaluate the influence of several nanotopographical cues like depth, width, (an)isotropy and spacing (ridge-groove ratio) on osteoblast behavior. Microscopical analysis and time lapse imaging revealed that an isotropic topography did not alter cell morphology, but it highly induced cell motility. Cells cultured on anisotropic topographies on the other hand, were highly elongated and aligned. Time-lapse imaging revealed that cell motility is highly dependent on the ridge-groove ratio of anisotropic patterns. The highest motility was observed on grooves with a ratio of 1:3, whereas the lowest motility was observed on ratios of 1:1 and 3:1. FA measurements demonstrated that FA-length decreased with increasing motility. From the study it can be concluded that osteoblast behavior is tightly controlled by nanometer surface features.

A Novel Thermoresponsive Gel as a Potential Delivery System for Lipoxin.

The objective of this study was to evaluate a novel thermoresponsive polyisocyanopeptide (PIC)-based hydrogel as an injectable carrier for local drug delivery for periodontal applications. Three formulations of PIC gels, 0.2%, 0.5%, and 1% w/w, were prepared. As controls, commercially available poloxamer 407 (P407) gels of 20% and 26% w/w were used. Lipoxin A4 (LXA4), a proresolving drug, was suspended into the gel solutions. The systems were evaluated regarding dynamic mechanical properties, injectability and stability, release and bioactivity of LXA4, and cytocompatibility. Results showed that the gelation temperatures of PIC and P407 gels were around 13°C to 23°C. PIC gels were less viscous and mechanically weaker than P407 gels due to the low polymer concentrations. However, PIC gels kept gel integrity for at least 2 wk when incubated with phosphate-buffered saline, whereas P407 gels were disintegrated totally within 1 wk. LXA4 was chemically stable in both neutral and alkaline medium for over 1 mo. The release of LXA4 from either 1% PIC or 26% P407 gels depicted an initial burst release followed by a sustained release for around 4 d. The extent of burst release was negatively correlated to the polymer concentration. LXA4 remained bioactive after release from PIC gels. No cytotoxicity was observed for 1% PIC gel. However, 26% P407 inhibited periodontal ligament cell and gingival epithelial cell growth. In conclusion, the thermoresponsive PIC gel is a potential candidate for periodontal drug delivery.

[Bone substitutes, growth factors and distraction osteogenesis]. / Botsubstituten, groeifactoren en distractieosteogenese.

Up to the present time, bone transplants are commonly used to reconstruct bone defects. Recently, several bone substitutes have been suggested to overcome the disadvantages of the procedure of bone harvesting. However, research reveals that an autogenous bone graft is still the gold standard. To replicate the structure and function of natural bone, growth factors or even living, bone-forming cells can be added to enhance the formation of new bone. In that case, one speaks of cell-based tissue-substition. As an alternative distraction osteogenesis, a mechanical-based way of tissue engineering is suggested. In this procedure, tissue-generation takes place without the addition of external material. A combination of both tissue-substitution techniques, consisting of the addition of bone-replacement materials or growth factors during distraction osteogenesis, has also been evaluated in research on animals, although not with unequivocal results.

The threshold at which substrate nanogroove dimensions may influence fibroblast alignment and adhesion.

The differences in morphological behaviour between fibroblasts cultured on smooth and nanogrooved substrata (groove depth: 5-350 nm, width: 20-1000 nm) have been evaluated in vitro. The aim of the study was to clarify to what extent cell guidance occurs on increasingly smaller topographies. Pattern templates were made using electron beam lithography, and were subsequently replicated in polystyrene cell culture material using solvent casting. The replicates were investigated with atomic force microscopy (AFM). After seeding with fibroblasts, morphological characteristics were investigated using scanning electron microscopy (SEM) and light microscopy, in order to obtain qualitative and quantitative information on cell alignment. AFM revealed that the nanogroove/ridge widths were replicated perfectly, although at deeper levels the grooves became more concave. The smooth substrata had no distinguishable pattern other than a roughness amplitude of 1 nm. Interestingly, microscopy and image analysis showed that fibroblast after 4 h had adjusted their shape according to nanotopographical features down to cut-off values of 100 nm width and 75 nm depth. After 24 h culturing time, fibroblasts would even align themselves on groove depths as shallow as 35 nm. It appears depth is the most essential parameter in cellular alignment on groove patterns with a pitch ratio of 1:1. On the smooth substrata, cells always spread out in a random fashion. Analysis of variance (ANOVA) demonstrated that both main parameters, topography and culturing time, were significant. We conclude that fibroblast cells cultured on nanotopography experience a threshold feature size of 35 nm, below this value contact guidance does no longer exist.

Macrophage behavior on multilayered DNA-coatings in vitro.

A pivotal factor to consider in the development of biomaterials and biomaterial coatings is the inflammatory response to these materials. The insertion of implants is followed by protein adsorption and subsequent interactions with cellular components of the biological surroundings, in which macrophages play a dominant role through the production of a myriad of signaling molecules. In view of this, the aims of the present study were to evaluate (i) gross protein adsorption to, and (ii) in vitro behavior of macrophages on novel biomaterial coatings, composed of poly-D-lysine (PDL) or poly(allylamine hydrochloride) (PAH) and DNA, and to compare these coatings with negative (noncoated glass) and positive controls (noncoated glass + LPS-stimulation). The results demonstrate that multilayered DNA-coatings do not affect gross protein adsorption compared to noncoated controls. Cell culture experiments showed that the attachment to, and viability and morphology of two types of macrophages cultured on multilayered DNA-coatings is comparable to noncoated controls. Still, macrophages repeatedly showed decreased secretion levels of the proinflammatory cytokine TNF-alpha on multilayered DNA-coatings, whereas no differences were observed in the secretion of IL-1beta, IL-10, and TGF-beta1. Appropriate animal studies are required to elucidate if these in vitro indications have clinical effects on the inflammatory and wound healing processes around implants.

Multilayered DNA coatings: in vitro bioactivity studies and effects on osteoblast-like cell behavior.

This study describes the effect of multilayered DNA coatings on (i) the formation of mineralized depositions from simulated body fluids (SBF); and (ii) osteoblast-like cell behavior with and without pretreatment in SBF. DNA coatings were generated using electrostatic self-assembly, with poly-d-lysine or poly(allylamine hydrochloride) as cationic polyelectrolytes, on titanium substrates. Coated substrates and non-coated controls were immersed in SBF with various compositions. The deposition of calcium phosphate was enhanced on multilayered DNA coatings as compared with non-coated controls, and was dependent on the type of cationic polyelectrolyte used in the build-up of the DNA coatings. Further analysis showed that the depositions consisted of carbonated apatite. Non-pretreated DNA coatings were found to have no effect on osteoblast-like cell behavior compared with titanium controls. On the other hand, SBF-pretreatment of DNA coatings affected the differentiation of osteoblast-like cells through an increased deposition of osteocalcin. The results of this study are indicative of the bone-bonding capacities of DNA coatings. Nevertheless, future animal experiments are required to provide conclusive evidence for the bioactivity of DNA coatings.

Repair of sheep long bone cortical defects filled with COLLOSS, COLLOSS E, OSSAPLAST, and fresh iliac crest autograft.

COLLOSS and COLLOSS E are osteoinductive bone void fillers consisting of bone collagen and noncollagenous proteins from bovine and equine bone, respectively. The aim of this study was to compare COLLOSS, COLLOSS E, iliac bone autograft, sintered beta tricalcium phosphate (beta-TCP; OSSAPLAST), and COLLOSS E plus OSSAPLAST. Materials were placed for 4, 8, or 24 weeks in 5-mm cortical bone defects in sheep long bones. Histological sections in a plane perpendicular to the long axis of the bone were used to measure the total repair area (original defect plus callus) and the area of bone within the total repair area. The incidence of defect union was also evaluated. At 4 and 8 weeks, defects treated with COLLOSS and COLLOSS E with or without OSSAPLAST had total repair and bone areas equivalent to autograft, and larger than OSSAPLAST-treated defects. At 8 weeks, the incidence of defect union was higher in defects treated with autograft or COLLOSS E plus OSSAPLAST than in untreated defects. At 24 weeks, the incidence of union was 100% in all treatment groups and 0% in untreated defects. The incidence of union was related to the degree of remodeling between 8 and 24 weeks. This was greater in all treated than nontreated defects. In conclusion, COLLOSS and COLLOSS E were equivalent to each other and to autograft, and superior to beta-TCP, in this study model.

Biological responses to multilayered DNA-coatings.

This study was performed to evaluate the basic biological response to deoxyribonucleic acid (DNA)-based coatings for soft tissue implants. To that end, in vitro experiments were used to study their cytocompatibility, and in vivo subcutaneous implantation studies with transponders in a rat model were performed to evaluate their histocompatibility. The DNA-based coatings were fabricated using the electrostatic self-assembly technique using cationic poly-D-lysine or poly-allylamine hydrochloride and anionic DNA. Noncoated substrates served as controls. In vitro, the behavior of primary rat dermal fibroblasts was assessed in terms of cell proliferation and morphology. Both types of multilayered DNA-coatings significantly increased rat dermal fibroblast proliferation without altering the morphological appearance of the cells. The tissue response to multilayered DNA-coatings was assessed using an in vivo rat model, in which transponders were inserted subcutaneously for 4 and 12 weeks. No macroscopic signs of inflammation or adverse tissue reactions were observed at implant retrieval. Histological analyses demonstrated a uniform tissue response to all types of implants. All implants were encapsulated in a fibrous tissue capsule without intervening inflammatory cells at the implant surface. Histomorphometrically, multilayered DNA-coatings induced fibrous tissue capsules with similar quality and thickness compared to noncoated controls. In addition, all fibrous tissue capsules showed similar expression of alpha-smooth muscle actin. This study demonstrates that multilayered DNA-coatings are cytocompatible and histocompatible, and justifies further research on their functionalization with biologically active compounds to modulate tissue responses.

A theranostic dental pulp capping agent with improved MRI and CT contrast and biological properties.

Different materials have been used for vital dental pulp treatment. Preferably a pulp capping agent should show appropriate biological performance, excellent handling properties, and a good imaging contrast. These features can be delivered into a single material through the combination of therapeutic and diagnostic agents (i.e. theranostic). Calcium phosphate based composites (CPCs) are potentially ideal candidate for pulp treatment, although poor imaging contrast and poor dentino-inductive properties are limiting their clinical use. In this study, a theranostic dental pulp capping agent was developed. First, imaging properties of the CPC were improved by using a core-shell structured dual contrast agent (csDCA) consisting of superparamagnetic iron oxide (SPIO) and colloidal gold, as MRI and CT contrast agent respectively. Second, biological properties were implemented by using a dentinogenic factor (i.e. bone morphogenetic protein 2, BMP-2). The obtained CPC/csDCA/BMP-2 composite was tested in vivo, as direct pulp capping agent, in a male Habsi goat incisor model. Our outcomes showed no relevant alteration of the handling and mechanical properties (e.g. setting time, injectability, and compressive strength) by the incorporation of csDCA particles. In vivo results proved MRI contrast enhancement up to 7weeks. Incisors treated with BMP-2 showed improved tertiary dentin deposition as well as faster cement degradation as measured by µCT assessment. In conclusion, the presented theranostic agent matches the imaging and regenerative requirements for pulp capping applications. STATEMENT OF SIGNIFICANCE: In this study, we combined diagnostic and therapeutic agents in order to developed a theranostic pulp capping agent with enhanced MRI and CT contrast and improved dentin regeneration ability. In our study we cover all the steps from material preparation, mechanical and in vitro characterization, to in vivo study in a goat dental model. To the best of our knowledge, this is the first time that a theranostic pulp capping material have been developed and tested in an in vivo animal model. Our promising results in term of imaging contrast enhancement and of induction of new dentin formation, open a new scenario in the development of innovative dental materials.

Functionalization of multilayered DNA-coatings with bone morphogenetic protein 2.

The focus of the present study was to functionalize multilayered DNA-coatings with the osteoinductive factor bone morphogenetic protein 2 (BMP-2) using different loading modalities. The multilayered DNA-coatings were built up from either poly-d-lysine (PDL) or poly(allylamine hydrochloride) (PAH) and DNA using electrostatic self-assembly (ESA). The amounts of BMP-2 loaded into the multilayered DNA-coatings and its subsequent release characteristics were determined using radiolabeled BMP-2. Additionally, the effect of BMP-2 functionalized multilayered DNA-coatings on the in vitro behavior of bone marrow-derived osteoblast-like cells was evaluated in terms of proliferation, differentiation, mineralization, and cell morphology. The results demonstrate the feasibility of multilayered DNA-coatings to be functionalized by embedding BMP-2 according to three different loading modalities: superficial (s), deep (d), and double-layer (dl). BMP-2 was incorporated proportionally into the multilayered DNA-coatings as: s+(4*d)=dl. All differently loaded multilayered DNA-coatings showed an initial burst release followed by an incremental sustained release of the remaining BMP-2. In vitro experiments demonstrated that the loaded factor remained biologically active, as an accelerated calcium deposition was observed on s- and dl-loaded multilayered DNA-coatings, without affecting cell proliferation. In contrast, d-loaded multilayered DNA-coatings influenced osteoblast-like cell behavior by decreasing the deposition of calcium.

Hydrodynamic compression of young and adult rat osteoblast-like cells on titanium fiber mesh.

Living bone cells are responsive to mechanical loading. Consequently, numerous in vitro models have been developed to examine the application of loading to cells. However, not all systems are suitable for the fibrous and porous three-dimensional materials, which are preferable for tissue repair purposes, or for the production of tissue engineering scaffolds. For three-dimensional applications, mechanical loading of cells with either fluid flow systems or hydrodynamic pressure systems has to be considered. Here, we aimed to evaluate the response of osteoblast-like cells to hydrodynamic compression, while growing in a three-dimensional titanium fiber mesh scaffolding material. For this purpose, a custom hydrodynamic compression chamber was built. Bone marrow cells were obtained from the femora of young (12-day-old) or old (1-year-old) rats, and precultured in the presence of dexamethasone and beta-glycerophosphate to achieve an osteoblast-like phenotype. Subsequently, cells were seeded onto the titanium mesh scaffolds, and subjected to hydrodynamic pressure, alternating between 0.3 to 5.0 MPa at 1 Hz, at 15-min intervals for a total of 60 min per day for up to 3 days. After pressurization, cell viability was checked. Afterward, DNA levels, alkaline phosphatase (ALP) activity, and extracellular calcium content were measured. Finally, all specimens were observed with scanning electron microscopy. Cell viability studies showed that the applied pressure was not harmful to the cells. Furthermore, we found that cells were able to detect the compression forces, because we did see evident effects on the cell numbers of the cells derived from old animals. However, there were no other changes in the cells under pressure. Finally, it was also noticeable that cells from old animals did not express ALP activity, but did show similar calcified extracellular matrix formation to the cells from young animals. In conclusion, the difference in DNA levels as reaction toward pressure, and the difference in ALP levels, suggest that the osteogenic properties of bone marrow-derived osteoblast-like cells are different with respect to the age of the donor.

The influence of the crystallinity of electrostatic spray deposition-derived coatings on osteoblast-like cell behavior, in vitro.

This article describes the influence of the crystallinity of carbonate apatite (CA) coatings on osteoblast-like cell behavior. Porous CA coatings were produced with electrostatic spray deposition (ESD), and subsequently, received heat treatments of 400, 500, or 700 degrees C to induce various coating crystallinities. As a result, an amorphous calcium phosphate (ACP), a crystalline CA (CCA), and a crystalline carbonated hydroxyapatite (CHA) structure were formed, respectively. Uncoated titanium substrates served as the control group. After seeding rat osteoblast-like cells, the initial cell attachment was similar between the groups, and approached 100% after 6 h. Between the various coatings, no differences were observed for proliferation, differentiation, or mineralization. However, proliferation of the osteoblast-like cells was lower on all coated substrates after longer culture periods, compared to the uncoated substrates, while at the same time differentiation was stimulated. Furthermore, after 8 and 16 days of incubation, scanning electron microscopy showed more signs of mineralization on coated substrates, compared to the uncoated substrates. In conclusion, porous ESD-derived CA coatings have a positive effect on the in vitro differentiation of osteoblast-like cells, compared to uncoated, as-machined titanium. However, this effect is not further enhanced by the degree of crystallinity of the ESD-derived CA coatings.

Cyto- and histocompatibility of multilayered DNA-coatings on titanium.

DNA-containing biomaterial coatings offer potential beneficial effects for both soft and hard tissue implants because of the structural properties of DNA. In the current study, the aim was to assess the in vitro cyto- and in vivo histocompatibility of multilayered DNA-coatings generated using the electrostatic self-assembly technique, with poly-D-lysine or poly(allylamine hydrochloride) as the cationic counterparts of anionic DNA. Multilayered DNA-coatings were fabricated on titanium substrates. Noncoated titanium substrates served as controls. In vitro experiments with rat primary dermal fibroblasts (RDF) assessing their viability were performed using a Live/Dead assay and an MTT-based assay. The presence of multilayered DNA-coatings did not affect RDF cell viability. On the other hand, an increased proliferation was demonstrated on both types of multilayered DNA-coatings. An in vivo rat model was used to study the soft tissue histocompatibility of subcutaneously inserted implants during implantation periods of 4 and 12 weeks. Light microscopic analysis revealed that all implants were surrounded by a fibrous capsule containing alpha-smooth muscle actin, and that the presence of a multilayered DNA-coating did not induce any adverse effects in terms of inflammation and wound healing. Histomorphometrically, no significant differences in capsule quality or thickness were observed dependent on multilayered DNA-coating or implantation period. The cyto- and histocompatibility of multilayered DNA-coatings demonstrated in this study allows their use and functionalization with appropriate compounds to modulate cell and tissue responses in dental and medical implantology.

Integrins as linker proteins between osteoblasts and bone replacing materials. A critical review.

The adhesion of osteoblasts to substrates is mediated through proteins that have adsorbed to the substrate, providing integrins on the cell membrane with ligands to connect to. The integrins regulate cell behavior through bi-directional signaling pathways. This critical review has the purpose to consider the research that has been performed with osteoblasts, integrins, and bone replacing materials. Until now, most research has been done to investigate the integrin expression of osteoblasts in culture during cellular adhesion. However, it remains difficult to draw general conclusions from this research. Nevertheless, it can be concluded that the used substrates and protein or peptide coatings can influence the integrin expression and cellular behavior. Additional research has to be done to fully understand all the parameters involved in integrin expression, the adhesion of cells to substrates, and the subsequent cellular behavior. For this purpose, model substrates are under development. The signaling pathway is receiving more and more attention, but for biomaterial purposes, too little consideration is paid to the translation of the in vitro results to the in vivo situation, and to practical applications.

The response of healing corneal epithelium to grooved polymer surfaces.

Corneal epithelial wounds heal rapidly by the inwards growth of tissue with a contracting wound front. A synthetic polymer lens to correct refractive error (an implantable contact lens) could be incorporated into the cornea using this wound healing process. Topographical cues on the polymer surface may facilitate epithelial tissue migration over the anterior device surface. Here, silicone discs with a defined surface geometry of parallel grooves (groove and ridge widths of 1, 2, 5 and 10 microm; groove depths of 1 and 5 microm) were implanted into corneas and maintained in organ culture. The nature and rate of epithelial tissue migration over the test surfaces was monitored for 8 days and evaluated using microscopy and histology. Irrespective of the pitch, deep groove geometries directed tissue migration laterally along the grooves but this prevented contraction of the wound front and retarded migration rates. No guidance occurred on any of the shallow groove geometries but these allowed inwards radial migration with a contracting wound front and supported migration rates equivalent to a flat surface. None of the geometries tested promoted tissue migration above a flat polymer surface and data suggested that parallel grooves may not be optimal for this application.