Anin vitrocomparison of possibly bioactive titanium implant surfaces

Polyether ether ketone coated with nanohydroxyapatite/graphene oxide composite promotes bioactivity and antibacterial activity at the surface of the material

Polyether ether ketone (PEEK) is considered an alternative material for manufacturing dental implants. However, PEEK lacks bioactivity and antibacterial action. In a series of experiments designed to enhance the surface properties of PEEK, we present a nanohydroxyapatite (nHA) and graphene oxide (GO) composite as a coating for PEEK-based dental implants to improve biological properties and antibacterial action. PEEK discs were polished, cleaned, and coated with the composite consisting of nHA particles doped with 0.75 wt% graphene oxide by a micro-emulsion technique according to patent US8,206,813. X-ray diffraction, field emission scanning electron microscopy-energy dispersive spectroscopy, and atomic force microscopy were utilized to characterize the composite coating. The wettability of the coated and non-coated samples was assessed by optical contact angle measurement. Antibacterial action of the composite coating was explored against S. aureus and E. coli and cytotoxicity determined utilizing osteoblast-like cells and gingival fibroblasts. The findings showed that the nHA/GO composite coating, approximately 1.3 μm thick, was homogenous with few micro-cracks and adhered to the PEEK surface. The surface roughness was reduced to 21.26 nm and the wettability was improved to 54.6⁰ after coating with the composite coating. Antibacterial activity was moderate, killing 99% of S. aureus and E. coli, with acceptable levels of cytotoxicity to mammalian osteoblast-like cells and gingival fibroblasts.

Bioactive calcium phosphate materials and applications in bone regeneration

BACKGROUND

Bone regeneration involves various complex biological processes. Many experiments have been performed using biomaterials in vivo and in vitro to promote and understand bone regeneration. Among the many biomaterials, calcium phosphates which exist in the natural bone have been conducted a number of studies because of its bone regenerative property. It can be directly contributed to bone regeneration process or assist in the use of other biomaterials. Therefore, it is widely used in many applications and has been continuously studied.

MAINBODY

Calcium phosphate has been widely used in bone regeneration applications because it shows osteoconductive and in some cases osteoinductive features. The release of calcium and phosphorus ions regulates the activation of osteoblasts and osteoclasts to facilitate bone regeneration. The control of surface properties and porosity of calcium phosphate affects cell/protein adhesion and growth and regulates bone mineral formation. Properties affecting bioactivity vary depending on the types of calcium phosphates such as HAP, TCP and can be utilized in various applications because of differences in ion release, solubility, stability, and mechanical strength. In order to make use of these properties, different calcium phosphates have been used together or mixed with other materials to complement their disadvantages and to highlight their advantages. Calcium phosphate has been utilized to improve bone regeneration in ways such as increasing osteoconductivity for bone ingrowth, enhancing osteoinductivity for bone mineralization with ion release control, and encapsulating drugs or growth factors.

CONCLUSION

Calcium phosphate has been used for bone regeneration in various forms such as coating, cement and scaffold based on its unique bioactive properties and bone regeneration effectiveness. Additionally, several studies have been actively carried out to improve the efficacy of calcium phosphate in combination with various healing agents. By summarizing the properties of calcium phosphate and its research direction, we hope that calcium phosphate can contribute to the clinical treatment approach for bone defect and disease.

Enhanced Bone Bonding to Nanotextured Implant Surfaces at a Short Healing Period: A Biomechanical Tensile Testing in the Rat Femur

PURPOSE

To compare the bone bonding capabilities of 2 different surface treatments at an early healing period. Titanium alloy (Ti6Al4V) custom-made rectangular plates (1.4 × 2.4 × 4 mm) were either dual acid etched (Ti6Al4V-DAE) or DAE/nanotextured blasted (Ti6Al4V-NTB).

MATERIALS AND METHODS

Implants were placed in the distal femurs of 10 Wistar rats and were allowed to heal for 9 days. After euthanasia, the bone immediately proximal and distal to the implant was removed to test the bone bonding force with a universal testing machine. Ultrastructure of the bone/implant interface was assessed by scanning electron microscopy.

RESULTS

Ti6Al4V-NTB samples exhibited significantly greater bond strength than Ti6Al4V-DAE samples. Morphologically, the Ti6Al4V-NTB surfaces presented intimate interaction with bone, whereas little interaction between the Ti6Al4V-DAE surface and bone was observed.

CONCLUSION

The results of this study indicated a significant increase in bone bonding for the DAE/nanotextured blasted surface, which is suggested to be the outcome of the nanotexturing.

Hydroxyapatite–-Past, Present, and Future in Bone Regeneration

Hydroxyapatite (HA) is an essential element required for bone regeneration. Different forms of HA have been used for a long time. The essence of bone regeneration always revolves around the healthy underlying bone or it may be the surroundings that give enough strength. HA is well known for bone regeneration through conduction or by acting as a scaffold for filling of defects from ancient times, but emerging trends of osteoinductive property of HA are much promising for new bone regeneration. Emerging technology has made the dreams of clinicians to realize the use of HA in different forms for various regenerative purposes both in vivo and in vitro. The nanostructured calcium apatite plays an important role in the construction of calcified tissues. The nanostructured material has the ability to attach biological molecules such as proteins, which can be used as functional materials in many aspects, and the capability of synthesizing controlled structures of apatite to simulate the basic structure of bone and other calcified tissues. The process of regeneration requires a biomimetic and biocompatible nanostructured novel material. The nanostructured bioceramic particles are of interest in synthetic bone grafts and bone cements both injectable and controlled setting, so that such composites will reinforce the strength of bioceramics. Extensive research is being carried out for bone regeneration using nanotechnology. Artificial bone formation is not far from now. Nanotechnology has made many dreams come true. This paper gives comprehensive insights into the history and evolution with changing trends in the use of HA for various regenerative purposes.

Evaluation of bone healing on sandblasted and Acid etched implants coated with nanocrystalline hydroxyapatite: an in vivo study in rabbit femur

This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone.

The effect of hydroxyapatite nanocrystals on osseointegration of titanium implants: an in vivo rabbit study

Osseointegration is dependent on implant surface characteristics, including surface chemistry and topography. The presence of nanosized calcium phosphates on the implant surface is interesting to investigate since they affect both the nanotopography and surface chemistry, forming a bone mineral resembling surface. In this work, the osseointegration of titanium implants with and without the presence of hydroxyapatite (HA) nanocrystals has been evaluated in vivo. The integration was examined using removal torque measurements and real-time polymerase chain reaction (RT-PCR) analysis. The study was performed using two healing time points, 3 and 12 weeks. The results showed that the torque needed to remove the implants was insignificant between the non- and HA-coated implants, both at weeks 3 and 12. The RT-PCR, however, showed significant differences for osteoblast, osteoclast, and proinflammation markers when HA nanocrystals were present.

Osteogenesis-inducing calcium phosphate nanoparticle precursors applied to titanium surfaces

This study investigated the effects of the morphology and physicochemical properties of calcium phosphate (CaP) nanoparticles on osteogenesis. Two types of CaP nanoparticles were compared, namely amorphous calcium phosphate (ACP) nano-spheres (diameter: 9-13 nm) and poorly crystalline apatite (PCA) nano-needles (30-50 nm × 2-4 nm) that closely resemble bone apatite. CaP particles were spin-coated onto titanium discs and implants; they were evaluated in cultured mouse calvarial osteoblasts, as well as after implantation in rabbit femurs. A significant dependence of CaP coatings was observed in osteoblast-related gene expression (Runx2, Col1a1 and Spp1). Specifically, the PCA group presented an up-regulation of the osteospecific genes, while the ACP group suppressed the Runx2 and Col1a1 expression when compared to blank titanium substrates. Both the ACP and PCA groups presented a more than three-fold increase of calcium deposition, as suggested by Alizarin red staining. The removal torque results implied a slight tendency in favour of the PCA group. Different forms of CaP nanostructures presented different biologic differences; the obtained information can be used to optimize surface coatings on biomaterials.

Plasma treatment maintains surface energy of the implant surface and enhances osseointegration

The surface energy of the implant surface has an impact on osseointegration. In this study, 2 surfaces: nonwashed resorbable blasting media (NWRBM; control) and Ar-based nonthermal plasma 30 days (Plasma 30 days; experimental), were investigated with a focus on the surface energy. The surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and the chemistry by X-ray photoelectron spectroscopy (XPS). Five adult beagle dogs received 8 implants (n = 2 per surface, per tibia). After 2 weeks, the animals were euthanized, and half of the implants (n = 20) were removal torqued and the other half were histologically processed (n = 20). The bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated on the histologic sections. The XPS analysis showed peaks of C, Ca, O, and P for the control and experimental surfaces. While no significant difference was observed for BIC parameter (P > 0.75), a higher level for torque (P < 0.02) and BAFO parameter (P < 0.01) was observed for the experimental group. The surface elemental chemistry was modified by the plasma and lasted for 30 days after treatment resulting in improved biomechanical fixation and bone formation at 2 weeks compared to the control group.

Simplified drilling technique does not decrease dental implant osseointegration: a preliminary report

BACKGROUND

To date, some experimental studies have addressed the effect of bone drilling technique and sequence on dental implant osseointegration. In the present study, the authors hypothesize that there would be no differences in osseointegration when reducing the number of drills for osteotomy compared to the conventional drilling protocols.

METHODS

Seventy-two implants (diameters 3.75 mm and 4.2 mm; n = 36 for each diameter) were bilaterally placed in the tibia of 18 beagles for 1, 3, and 5 weeks. Half of the implants of each diameter were placed using a simplified drilling procedure (pilot and final drill), and the other half were placed using a conventional drilling procedure (all drills in sequence). The retrieved samples were subjected to histologic and histomorphometric evaluation.

RESULTS

Histology showed that new bone formed around the implant, and inflammation or bone resorption was not evident for both groups. Histomorphometrically, the simplified group presented significantly higher bone-to-implant contact and bone area fraction occupancy compared to the conventional group after 1 week; however, no differences were detected at 3 and 5 weeks.

CONCLUSION

Bone responses to the implant with the simplified protocol can be comparable to the conventional protocol.

Nano Hydroxyapatite-coated Implants Improve Bone Nanomechanical Properties

Nanostructure modification of dental implants has long been sought as a means to improve osseointegration through enhanced biomimicry of host structures. Several methods have been proposed and demonstrated for creating nanotopographic features; here we describe a nanoscale hydroxyapatite (HA)-coated implant surface and hypothesize that it will hasten osseointegration and improve its quality relative to that of non-coated implants. Twenty threaded titanium alloy implants, half prepared with a stable HA nanoparticle surface and half grit-blasted, acid-etched, and heat-treated (HT), were inserted into rabbit femurs. Pre-operatively, the implants were morphologically and topographically characterized. After 3 weeks of healing, the samples were retrieved for histomorphometry. The nanomechanical properties of the surrounding bone were evaluated by nanoindentation. While both implants revealed similar bone-to-implant contact, the nanoindentation demonstrated that the tissue quality was significantly enhanced around the HA-coated implants, validating the postulated hypothesis.

In vitro characterization and osteoblast responses to nanostructured photocatalytic TiO2 coated surfaces

The aims of the study were to characterize a nanostructured photoactive titanium dioxide (TiO(2)) coating and to compare the cellular response of human osteoblasts before and after ultraviolet (UV) irradiation of the coating. A specific nanostructured TiO(2) powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs, and was heat-treated thereafter. After topographical, chemical and photocatalytic property characterizations, human osteoblasts were cultured on the coated discs before and after UV irradiation. Cell morphology was evaluated by scanning electron microscopy (SEM), and cell viability was analysed by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. From the contact angle analysis, the wettability significantly improved after UV irradiation. The cultured cells were flattened with numerous elongated lammellipodia; however, no morphological differences were indicated between -UV and +UV surfaces. The MTT assay analysis showed that -UV surface presented significantly higher viability compared to the +UV surface except for one cell population group at 3h where there were no differences. The nanostructured photoactive TiO(2) surface improved its hydrophilicity by UV irradiation, however no enhancing effect in cell response was confirmed at the time tested compared to the non-irradiated surface.

Bioactivity of nanostructure on titanium surface modified by chemical processing at room temperature

PURPOSE

Recently, there has been considerable interest in finding novel applications and functions for existing dental materials. We found that, at room temperature and atmospheric pressure, titanium oxide spontaneously generates nanostructures very similar to the "nanotubes" created by TiO(2) sputtering. The aim of this study was to evaluate the ability of this surface to affect the cellular osteogenic differentiation response.

METHODS

Titanium disks without and with a 'nanosheet' deposited on their surface were used as the control and test groups, respectively. Cell culture experiments were performed with SD rat bone marrow cells, which were seeded into microplate wells and cultured in media designed to induce osteogenic differentiation. We measured alkaline phosphatase (ALP) activity, osteocalcin (OCN) production, calcium deposition and Runx2 gene expression to assess the levels of differentiation.

RESULTS

After 14 and 21 days, cellular ALP activity was significantly higher in the test group than in the control group. After 28 days, cells in the test group also showed significantly more calcium deposition and OCN production than those in the control group. There was significantly different expression of Runx2 mRNA in the test group compared to the control group after 3 days of culture.

CONCLUSION

In conclusion, these data suggest that titanium implants modified by the application of nanostructures promote osteogenic differentiation, and may improve the biointegration of these implants into the alveolar bone.

The effect of a nanothickness coating on rough titanium substrate in the osteogenic properties of human bone cells

This study evaluated the effect of a bioactive ceramic coating, in the nanothickness range, onto a moderately rough surface on the osteogenic behavior of human bone cells. The cells were harvested from the mandibular mental region and were cultured over Ti-6Al-4V disks of different surfaces: as-machined (M), alumina-blasted/acid etched (AB/AE), and alumina-blasted/acid-etched + 300-500 nm thickness amorphous Ca- and P-based coating obtained by ion beam-assisted deposition (Nano). The culture was then evaluated regarding cell viability, adhesion, morphology, immunolocalization of osteopontin (OPN) and alkaline phosphatase (ALP). The results showed that the surface treatment did not interfere with cell viability. At 1 day, AB/AE and Nano showed higher adhesion than the M surface (p < 0.001). Higher adhesion was observed for the M than the Nano surface at 7 days (p < 0.005). The percentage of cells showing intracellular labeling for OPN at day 1 was significantly higher for the Nano compared to M surface (p < 0.03). The percentage of ALP intracellular labeling at 7 days was significantly higher for the AB/AE compared to the M surface (p < 0.0065); no differences were detected at 14 days. Our results suggest that the presence of a thin bioactive ceramic coating on a rough substrate did not favor the events related to in vitro osteogenesis. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

A nanodevice for rapid modulation of proliferation, apoptosis, invasive ability, and cytoskeletal reorganization in cultured cells

We have fabricated a nanodevice composed of a matrix of nine nanodot arrays with various dot sizes, ranging from a flat surface to 10 nm, 50 nm, 100 nm, and 200 nm arrays. HELA, C33A, ES2, PA-1, TOV-112D, TOV-21G, MG63, and NIH-3T3 cells were seeded onto the device and cultured for three days. To evaluate the size-dependent effect of nanodot arrays on cell growth, indices corresponding to cell proliferation, apoptosis, cell adhesion, and cytoskeletal organization were defined. VD50 is defined as the diameter of nanodots on which 50% of the cell population remains viable. AD50 is defined as the diameter of nanodots on which 50% of the cell population appears to have an apoptosis-like morphology. FD50 is the diameter of nanodots that promotes the formation of 50% of the focal adhesions compared to cells grown on a flat surface. CD50 is defined as the diameter of nanodots on which cells have half the amount of microfilament bundles compared to cells grown on a flat surface. We were able to distinguish between the invasive ability of HELA versus later-staged C33A cells. Ovarian cancer cell lines (ES2, PA-1, TOV-112D, and TOV-21G) also exhibited differential growth parameters that are associated with cell type, grade, and stage. Modulation of the growth of MG63 cells was also achieved. More broadly, we have established a platform that can be used to assess basic parameters of cell growth. A simplified fabrication process ensures mass production and lowers cost. According to our results, the device is capable of distinguishing among cancer cell lines at various stages and also provides basic design parameters for artificial implants. Our device will serve as a convenient and fast tool for tissue engineering and cancer treatment.